#340

3 роки тому

I often get questions about how to measure voltage with microcontrollers. We will look at this topic, at the quality of built-in and external Analog-to-digital converters, and I will show you some “secrets.”
In this video, we will:
- See how ADCs work
- Look at how we can determine the quality of ADCs
- Compare the ADCs of different microcontrollers with external chips
- Learn how to tweak the calculations to get the best out of any ADC
- See how we can extend the range of ADCs
- Discover some “hidden” things of Microcontrollers and their ADCs
- Look at different external boards and their usage
I am a proud Patreon of GreatScott!, Electroboom, Electronoobs, EEVblog, and others.
Links:
ESP32 dev board: s.click.aliexpress.com/e/_dZRlwBw
ESP32 Breakout: s.click.aliexpress.com/e/_dYPpD2c
ADS1115: s.click.aliexpress.com/e/_d9kxGU8
PCF8591: s.click.aliexpress.com/e/_dTanrOc
AD7705: s.click.aliexpress.com/e/_d6fDmrw
Nice looking ADC (AD7606): s.click.aliexpress.com/e/_dYHWm0A
Voltage reference: s.click.aliexpress.com/e/_d6N3GHc
Voltage Divider: www.ohmslawcalculator.com/volt...
ADC Theory: e2e.ti.com/blogs_/archives/b/...
DAC Theory: en.wikipedia.org/wiki/Digital...
The links above usually are affiliate links which support the channel (no additional cost for you).
Supporting Material and Blog Page: www.sensorsiot.org
Github: www.github.com/sensorsiot
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КОМЕНТАРІ: 681

@shenlong3879 3 роки тому

The external ADC at 2.5V didn't show 2.4994 as you say as per the reference but 2.4594 at 22:22 in the video.

@AndreasSpiess 3 роки тому

You are right. My mistake!

@projectmanager9116 3 роки тому

ukposts.info/have/v-deo/eXl9Z2yKbYShpXU.html awesone project

@tigerresearch2665 3 роки тому

yup. I felt a little spoofed. With that inaccuracy it seems that an external ADC isn't really that much better than a software-compensated ESP32 ADC. However, the precision of an external ADC could be interesting for scaled up projects: you are trading the extra costs for an ADC to skip the individual calibration process of each ESP32 ADC.

@leocurious9919 3 роки тому

@@tigerresearch2665 The external ADC only performs so bad due to his own "correction formula" that very likely only corrects errors on the analog end (aka from V_ref to the PGA inside the ADC). So it shows the correct value at this one point, but not anywhere else. One error that affects the analog end, which I would suspect here: High sampling rate -> low input impedance -> voltage drop Correcting ADC values in code like he does is not something anyone should do. The first step is to correct the hardware/setup! Let me compare that to a car that constantly steers to the left: Do you just "counter steer" to make it straight... or do you fix your car so it drives straight?

@matzke089 3 роки тому

Andreas Spiess So, the conclusion of the Video is wrong?

@L-36 3 роки тому

I am using an ESP32 to monitor the battery voltage on my boat and send an email if it gets too low. I found the measurements very noisy due to occasional glitches. My solution was to take 8 readings and ignore the largest and smallest and average the middle 6. I do this twice and average them. It is quite easy to do in the code as you just have to keep track of the largest and smallest measurements and subtract them from the sum and divide by 6. I found this better than longer averages so that I did not get multiple glitches in my sample period. The result is very stable and quite fast. I very much enjoy your videos I am a retired circuit designer. I designed test equipment for HP (Now Keysight) and things like cable modems in the early days. Now it is a hobby.

@AndreasSpiess 3 роки тому

Good idea because you can eliminate the far glitches. I did not investigate the distribution of the measured values, but maybe they have a pattern you break with your formula. I like my Keysight MSOX3045 ;-) Good products!

@L-36 3 роки тому

@@AndreasSpiess The distribution was not Gaussian. It was mostly correct values with a few outliers. It is actually a pretty standard way of filtering. There is even a name for it but I can't find it any longer. I learned it from a statistician who worked for me for a short time.

@bobblaine1437 3 роки тому

Thanks for this video! I've been puzzling over how to reduce the noise of a voltage reading for a project without losing responsiveness introduced by filtering. Based on your video, I switched over to an external ADC (ADS1115) and it solved the problem. Much appreciated!

@AndreasSpiess 3 роки тому

Glad I could help!

@y2ksw1 3 роки тому

For a very long time I paid my studies by building accurate DAC's for the growing digital industry. Making them precise is a science! 😊

@Scrogan 3 роки тому

Sounds neat, were they hand-matched R2R ladders? I always wonder why you can’t just buy R2R resistor networks in single packages, like a SIP10. Though these days I’d be tempted to just use a half-bridge and low-pass filter, like a good-old class-d amp.

@budward7846 3 роки тому

@@Scrogan Try www.digikey.com/products/en/resistors/resistor-networks-arrays/50?k=resistor+array&k=&pkeyword=resistor+array&sv=0&pv9=392120&sf=0&FV=-8%7C50&quantity=&ColumnSort=0&page=1&pageSize=100

@AndyPayne42 3 роки тому

Yup, I have a esp32 based ph/temp/ec meter I'm doing for hydroponics github.com/physiii/grow

@AndreasSpiess 3 роки тому

@y2ksw1: I can imagine that this is not trivial!

@y2ksw1 3 роки тому

James Barclay Yes, with my never patented fool proof method nobody ever thought about before. Pure science 😊

@ericon.7015 3 роки тому

I never get tired to watch your videos. I like the fact that you put your personal opinion in each fact. I understand better this way. Thank you

@AndreasSpiess 3 роки тому

Thank you for your nice words!

@agf9995 3 роки тому

Greetings from South Africa Andreas. Well done as usual! I am always surprised how much information you share with great clarity and structure in such a short video clip. When I learnt this stuff (long before internet), choices were fewer and one had to study the data sheets thoroughly (or copy somebody's example from Elektor, EE, ETI etc). Microcontrollers (with built in ADCs) only arrived later and choices were fewer - which was a blessing, because obsolescence took longer. Hobbyists today should be thankful that you share years of experience, crammed into a nutshell...and for free. Love your work and your very structured method of teaching (unlike my ADHD brain which likes to skip around). Best Regards, Allen.

@TannerFrisby 3 роки тому

Thanks for putting out such high-quality videos regularly!

@AndreasSpiess 3 роки тому

Glad you like them!

@juanramirezjardua2082 3 роки тому

Thanks Andreas for this interesting video. I've used ADC lots of times, and never had concerns about the quality of the conversion (noise reduction with average method). In a current project, getting feedback from the servo's potentiometers for a robotic arm, I've used a calibration table, but now I'm going to introduce your formulas. Thanks again, Juan.

@AndreasSpiess 3 роки тому

It depends on the desired accuracy. I compared, of course, with the data sheet.Calibration tables are good if the ADC is dependable wrong and not stochastically wrong...

@meclucas 3 роки тому

Very interesting video as always, thank you. Another benefit of using the ADS1115 is that the internal PGA can be configured to read a differential signal, this is very useful for measuring some sensors, although it also results in a slower data acquisition rate.

@AndreasSpiess 3 роки тому

True!

@sewingmachinesindetail 5 місяців тому

This trick can also be used in general by the Arduino by using two analog inputs connected to the signal direct and the signal amplified by a fixed op amp.

@consoleteam 3 роки тому

Thank you for the breadth of the experiments to help reinforce the lessons. Seeing how externally sourced ~5v can impact the readings was an "of course!" moment, since I'm used to using a good regulator versus an adjustable power supply for projects. Spotting things like how the radios on the chip may affect the ADC are very good clues. I'll investigate some of the external ADCs, since I'm thinking about a project that will use a mesh radio network and I had planned to use analog inputs as well... thanks again!

@AndreasSpiess 3 роки тому

Some distance to radios is never a bad thing ;-)

@Mr_Zisky 2 роки тому

Perfect! Thank you for this video! I am working on a project now with analog sensors and i learned everything I needed to!

@AndreasSpiess 2 роки тому

Glad it helped!

@dvohwinkel 3 роки тому

I like the fact that your opinions/observations are unfiltered. You just tell it like it is. "Subscribed"

@AndreasSpiess 3 роки тому

Welcome aboard the channel!

@TheDefpom 3 роки тому

If you tweak the adc settings in the ESP32 down to 10 bits, and some other changes, the noise and accuracy gets a LOT better, I’m not at my computer at the moment but I will post the code when I get a chance.

@augustinenwafor7673 3 роки тому

Please leave a link on your comment when you do. Thanks

@TheDefpom 3 роки тому

Augustine Nwafor - I posted the code in the comments, it’s here somewhere.

@skuashh 3 роки тому

Here is the code of the @@TheDefpom comment: "Here you go, here is the code to help get the ESP32 ADC to behave better: // configure ADC for getting battery voltage pinMode(VoltageSense, INPUT); // Battery Voltage Sense input analogSetPinAttenuation(VoltageSense, ADC_0db); // set the attenuator for the ADC to allow 1.1V input range analogSetWidth(11); // set the resolution width to be 2048 instead of the default 4096 to try and reduce noise analogReadResolution(11); // set the resolution to be 2048 instead of the default 4096 to try and reduce noise"

@raymondzhao9557 2 роки тому

@@skuashh cool， will try when i have a chance

@johnhutchens8970 3 роки тому

The ADS1115 is my favorite ADC for microcontrollers. I started using it when I moved over to 32bit microcontrollers, but needed a way to read 5V automotive sensors (using a Teensy 3.2). I had 4 sensors (an MPX5700AP pressure sensor, an NTC thermistor, an AEM Wideband oxygen sensor and a 0-100psi oil pressure sensor), the ADS1115 had 4 inputs, it was a match! I didn't have to average values to get a stable reading, like you said, the stability of the ADC is fantastic.

@AndreasSpiess 3 роки тому

Thank you for sharing your experience. This seems to be a perfect solution.

@tdtrecordsmusic 3 роки тому

This is such an important topic. I send a million thanks and encourage this topic. Getting signals INTO the computer is probably just as important as having the computer to begin with. This topic makes me consider re-writing all of computer science just to make an analog computer.

@AndreasSpiess 3 роки тому

You find analog computers if you google. They were used befor the cheap silicon

@peterpepo9232 3 роки тому

Thanks for this awesome intro to the ADCs! I'm going to measure voltage of my LiPo cell, so I know when to charge it :)

@AndreasSpiess 3 роки тому

I do this too for most of my battery operated nodes

@mahudson3547 3 роки тому

At 12.07, I love the way you dodge the 1023/1024 argument!

@AndreasSpiess 3 роки тому

I had enough discussions about that in my life. So I once used 1023 and once 65536

@TheRainHarvester 12 днів тому

@@AndreasSpiessWhy was there ever an argument? (1023/1023 =1) Just curious

@AndreasSpiess 11 днів тому

@@TheRainHarvester Because of the 0

@TheRainHarvester 9 днів тому

@@AndreasSpiess if you can measure the voltage at the high rail, you divide by 4095 so you get 1* vcc.

@jenskaa4044 3 роки тому

Nice video. Remember to consider the input impedance of the ADC, especially if you use high value resistors for a voltage divider in front.

@uwezimmermann5427 3 роки тому

since the input is in parallel to the low-side resistor of the voltage divider only its value really matters - well actually it is of course the parallel-combination of the upper and lower resistance in the voltage divider... And for the ATmega328 the input resistance of the ADC-channels is astonishingly high! I tested it with discharging a 1µF capacitor from 5 V to zero through a 100 MΩ resistor - it took about 15 minutes to discharge and the resulting curve indicates an input resistance beyond 1 GΩ.

@Scrogan 3 роки тому

Uwe Zimmermann I was going to ask what you used to measure that voltage, but I guess you were just using the ADC itself. I imagine most of the leakage current will be through the protection diodes, if it had none then it would be a real recipe for ESD. Which reminds me of a friend using his atmega ADC for measuring back-emf of a solenoid. Directly on the 12V half-bridge output that was powering the solenoid. With no extra diode or resistors. The arduino got really hot, but somehow the circuit actually worked.

@jenskaa4044 3 роки тому

@@uwezimmermann5427 I am not talking Any specific microprocesor. I had an adc in a low power circuit where I wanted to messure the battery voltage, here I used a resistor divider in 10 Mohm Range to avoid draning the battery. In this applikation the messured voltage was wrong due to current flowing into the mcu.

@chuxxsss 3 роки тому

Well done mate reminded me of train school 30 years ago. Keep up the good work Andreas. Have a wonderful week.

@AndreasSpiess 3 роки тому

Thanks, you too! And hope for gold ;-)

@NimaSajedi 3 роки тому

Another great tutorial. I enjoy my time watching your videos. Thanks for making such valuable content. 👍

@AndreasSpiess 3 роки тому

Glad you enjoy it!

@stevetobias4890 3 роки тому

Great video, I just bought some external voltage reference modules so great timing

@AndreasSpiess 3 роки тому

Perfect!

@SybrenAStuvel 3 роки тому

The AVR ATmega328p used in the Arduino, and other AVR chips, have a special sleep mode for ADC noise reduction. It keeps the ADC running, but stops all the digital processing. See the "ADC Noise Reduction Mode" in the datasheet. It could be that the external ADC chips appear better simply because they are physically further away from the running digital logic.

@Slutuppnu 3 роки тому

Interesting. I didn't know Arduino had a sleep mode.

@SybrenAStuvel 3 роки тому

@@Slutuppnu I don't know about the Arduino library, but with AVR-GCC you have fine-grained control over it. www.nongnu.org/avr-libc/user-manual/group__avr__sleep.html

@SybrenAStuvel 3 роки тому

PS: The Arduino IDE already uses AVR-GCC, so you can use the functions that I linked from Arduino projects as well.

@GISED_Link 3 роки тому

@@SybrenAStuvel is it worth it with a 10 bit adc ? (Atmega16A)

@rojirrim7298 3 роки тому

@@Slutuppnu Most AVR chips (the ones inside arduinos) don't have just one sleep mode but a few of them. It has (as has been said), an ADC noise reduction in which the CPU and some other digital parts of the chip are turned off in order to remove noise from the ADC signal; it has a CPU sleep mode that allows you to save a bit of power during delays or when waiting for a short timer to wake you up; and finally it has a deep sleep mode, in which the CPU, fast clock signal (either the internal fast oscillator or the external crystal oscillator), and most peripherals are turned off, except for the WatchDog Timer (low power timer) and a few more things like pin interrupt wakeups. This allows for very low power applications, in which you can put the chip to sleep and only use a few microamps of current, which for battery applications is really useful. For those types of applications, you have to take care and desolder all the LEDs on the board that you can't control, make sure to avoid using any LDOs onboard, etc.

@kwazar6725 3 роки тому

Reminds me of school and r2r ladder dacs. I get my fix of andreas every sunday. Lovely stuff.

@AndreasSpiess 3 роки тому

Glad you like the "stuff" !

@WacKEDmaN 3 роки тому

very nice info there Andreas, thanks, it will come in handy... id be interested in seeing an RTL-SDR ADC compaired to these MCU ADCs

@AndreasSpiess 3 роки тому

It is quite different. If I remember it has only 8 bits. But of course, it is faster.

@yezhang2947 3 роки тому

I didn't know the truth and tricks of ESP8266/ESP32. Another high quality video. Thank you!

@AndreasSpiess 3 роки тому

You are welcome!

@tonysfun 3 роки тому

I'm amazed every time I see your great videos!!! You are testing stuff that went true testing before manufacture, but you made it better - why isn't Arduino listening??? If Arduino and ESP's had better ADC, the cost would not be that much higher - right? But now we can use your recipe and suggestions! Thank you again Andreas. And wishing your finger to heal FASTER!

@AndreasSpiess 3 роки тому

I am sure they have their constrraints. Create chips for a few cents with 3 CPUs and Wi-Fi is for sure not easy.

@Timh-hx2le 3 роки тому

Thanks for this video, it's exactly that what I need for my project!!

@AndreasSpiess 3 роки тому

Glad I could help!

@klif_n 3 роки тому

How timely. I'm just trying to do this right now to monitor the voltage on a battery in my mailbox alerter. :). Thank you!

@AndreasSpiess 3 роки тому

For monitoring a battery the internal ADCs should be ok.

@Scrogan 3 роки тому

I was just about to buy an ADS1115, good timing!

@AndreasSpiess 3 роки тому

I hope you will like it!

@n.t.1243 3 роки тому

Watched already a lot of videos of your channel and at the beginning it was a lot of „häääää, versteh grad überhaupt nix“ but from one video to the next I start to understand what you are explaining us. Have to say that I am a totally new beginner. My goal is to measure the 2 12V Solar Batteries in the OFF-Grid garden of my parents in law. Tried a lot with the ADC from the ESP32 itself and as u mentioned it’s readings are just bullshit. Thank you for introducing the ADS1115 to me. I guess that will fix my measuring problem and can finally bring the project into production. As I am original from Vorarlberg and worked many years in Kanton SG I love to hear your swiss accent as it remembers me of that great time in my life! Electronic wise you are my personal hero ;-)

@AndreasSpiess 3 роки тому

For this purpose you probably could also use a INA226 as suggested by other commenters. And I am glad you learn something with each video. We all started as beginners in this field.

@B4x4 3 роки тому

Thank you for this great episode. Loved it.

@AndreasSpiess 3 роки тому

Glad you enjoyed it!

@B4x4 3 роки тому

@@AndreasSpiess hope you will make one about amp reading too. How to use shunt to read up to 50amp draw.

@noslackyak 3 роки тому

Seriously good video. Thanks man! Appreciate your hard work :)

@AndreasSpiess 3 роки тому

Glad you liked it!

@artiem5262 3 роки тому

Hints for those starting out -- for built-in ADCs, throw away the bottom bit as it's most likely useless anyway. You can average samples equal to a power of 2 by adding the integer values and doing a right shift -- for example add up 8 integer ADC samples and right shift 3, a useful trick when your microprocessor doesn't have a divide instruction! What's your signal bandwidth? Adding a single pole RC low pass filter in front of the ADC can help. And do not expect the input impedance of the ADC to be constant.

@AndreasSpiess 3 роки тому

Good idea. Thanks!

@TheBreadboardca 3 роки тому

Just got to the end, you covered off some of my earlier comments.. nice :), i will leave them there to hopeful help noobs to the ADC world and as a text reminder. Awesome video keep up the good work

@AndreasSpiess 3 роки тому

Cool, thanks

@Graham_Wideman 3 роки тому

23:35 Really freaky video compression artifact at 23:35 -- the RF connectors appear to randomly telescope in and out!

@shreyaskul 3 роки тому

Because they are not soldered in, he just put them on the PCB just to show the board. It's not a video artifact.

@Graham_Wideman 3 роки тому

@@shreyaskul Yes, on closer viewing, I think you're right. They seem to be rocking back and forth.

@AndreasSpiess 3 роки тому

Shreyas is right!

@shreyaskul 3 роки тому

@@AndreasSpiess Hey! Thanks for your comment. Can you share which IC you have used in your ADC board? That would be great :)

@billglass5160 7 місяців тому

You have confirmed my discovery. Thanks! Unfortunate that we have to rely on "small and casual" posts or trial&error methods to correctly use the esp32.

@AndreasSpiess 7 місяців тому

Fortunately, we have Google and the internet to share our learnings ;-)

@tszulpinedo757 3 роки тому

Están increíbles todos los detalles que enseñó profesor... 👌😎

@AndreasSpiess 3 роки тому

Gracias!

@vaishakhmonti 2 роки тому

Fantastic as always, Professor!

@AndreasSpiess 2 роки тому

Thank you!

@CaddyBlue 3 роки тому

Hi Andreas! Great video as always! One note about the ADS1115 is that it is actually a 15-bit signed differential ADC( AC !!! ), or 16-bit single-ended. Differential measurements offer more immunity from electromagnetic noise. This is useful when using long signal wires or operating in an electrically noisy environment. I have been using an ADS1115 to measure the amperage of our utility inlet with a sct-013. The fine art of accuracy I've seen is matching the sampling rate of the adc to the frequency of your local provider to sample the highs and lows of the sine wave as accurately as possible (50Hz here in ZA).

@AndreasSpiess 3 роки тому

You are right with differential measurements. Concerning 50Hz: You have to synchronize because the ADS1115 is slow. A diode and a RC filter probably would help to get DC out of AC

@CaddyBlue 3 роки тому

@@AndreasSpiess on the sct013 each 10A represents 1v. Thus getting Amperage readings are easy and safe with non invasive clamps. Only when it comes to the measurement of voltage, territory gets unsafe. I have opted for a 220v primary, 12v secondary to convert ac to DC proportionally followed with a voltage divider and capacitor. With both voltage and amperage the apparent usage can be calculated to identify power consumption patterns at home. I cannot thank you enough for the extensive and concise research you have given to this community! You inspire us!

@charlescoult 3 роки тому

Some of the best educational content out there!

@AndreasSpiess 3 роки тому

Thank you!

@JohnBoen 3 роки тому

Great timing. I'm building a flash joule heater, and need to measure the voltage of the supercapacitor before and after the flash... i was just going to use an arduino and not even think about it - because I didn't want to do the research. Thanks much! Edit: after watching, an ADS1115 or equiv is what I need.

@AndreasSpiess 3 роки тому

Hopefully it will work out for you!

@JohnBoen 3 роки тому

Yeah... thought this is a bit less effort. Welcome to reality :) . These 2.7v 500F rh2ings don't want to release their energy instantly. Damn physics...

@nmidu Рік тому

hey man, your secrets are the best! thanks for all this information . greeting from argentina amigo!

@AndreasSpiess Рік тому

Glad you like them!

@SolarWebsite 3 роки тому

Excellent video, thank you! A related interesting subject for a future video might be how to safely and accurately measure the voltages of a multi-cell battery. After a couple of evenings of googling I have found out that's not trivial.

@AndreasSpiess 3 роки тому

Thank you for the suggestioon.

@sylvainlazare1114 3 роки тому

Maybe thats what you are looking for lazarduinoads1115.blogspot.com/2020/03/voltmetre-de-precision-avec-arduino.html I have a 4 cells version on trial now facebook.com/photo.php?fbid=10220134681951223&set=pcb.1665059790308923&type=3&theater

@pfeerick 3 роки тому

The typical manner is to have the most negative connection coupled to ground of your circuit, and then have voltage dividers for each cell. For a 4 cell battery, you could either use four identical voltage dividers, or preferably have four different ones each tuned to voltage ranges for each of the series cells. For simplicity sake, if it were a 4 cell lithium battery, 5v, 10v, 15v and 20v would be good voltage divider ranges to use for monitoring each successive series cell and being the most accurate for each in turn. Being able to measure the individual cells would be nice, but as you suggest, its not trivial, as you would need to somehow keep changing the ground/negative 'reference' when measuring each cell.

@matzke089 3 роки тому

I thought it‘s really simple if you use an individual esp8266 for each cell. It‘s even scalable. What is wrong about that?

@SolarWebsite 3 роки тому

@@matzke089 That could work, yes, but has disadvantages: 1. Relatively expensive, especially for small batteries. 2. High power consumption, especially for small batteries. 3. Communication between the ESPs will have to be engineered carefully. 4. Generally complex and not elegant. A "brute force" solution, if you will. I like elegance and simplicity (the two usually go together).

@giuseppedanilovaccarella8026 3 роки тому

Thanks for another fantastic video. Just for curiosity, if I insert a delay(1) between each analogRead(A0), the measurements related to WeMos D1 Mini have more fluctuations than without it. Is this due to the capacitor in the Sample and Hold circuit that discharges faster by inserting delay(1)? It is evident within low serial baud rate. Thanks

@MarcoTedaldi 3 роки тому

Awesome. Thank you for the great content! Just my two cents: 1. I've had to learn the hard way, that many (all?) of the ADC that have a MUX only have a single S/H aufter the MUX. This leads to problems, when reading signals on different channels with very different voltages in quick succession. There is quite a bit of "crosstalk". It's really important to make sure that the inputs to such an ADC are low impedance. 2. When I do averaging on a uC, I do 2^n samles (8, 16, 32...1024) samples, add the read values up (make sure to prevent overflow) and just use shift for the division at the end. Especially on uC without an FPU this speeds the averaging up quite a bit.

@AndreasSpiess 3 роки тому

Good info. Thank you! I would have expected only one S/H, though, because it is usually part of the ADC.

@myselfremade 2 роки тому

@@AndreasSpiess I was wondering, if one wanted to, for example. Record two audio signals that are exactly synchronized, how could you synchronize two different ADC's to make sure they are sampling at the same time?

@TheRainHarvester 12 днів тому

@@myselfremadedid you ever find an answer?

@gotbadger 3 роки тому

Really insightful video thanks for posting!

@AndreasSpiess 3 роки тому

Glad it was helpful!

@drusha8791 3 роки тому

Nice! This is what i am looking for. Thanks andreas.

@AndreasSpiess 3 роки тому

Happy to help!

@Arrowtake 3 роки тому

Thanks Andreas, once again learned alot!

@AndreasSpiess 3 роки тому

Glad to hear that! Thank you.

@alexandern8671 3 роки тому

Another great video from a very competent presenter. Just a point for a possible misconception: there are two other ADC architectures in common use, namely pipelined and sigma-delta. The first tries to keep the number of parallel comparators required in check by converting the output of a comparator stage back to analogue using a DAC, subtracting this output from the original input, and feeding the result to another comparators' stage. Three stages are quite common with typically 4bits per stage; leaving aside the unavoidable latency the conversion takes one clock cycle like the comparators' ADC. This breaks for high resolutions because analog subtractions accumulate too much error. Then sigma-delta comes to the rescue where in fact a control system tries to get its 1 bit output bitstream average as close to the input as possible (its operating principle is not easy to understand in detail though); 24 bits and higher resolutions became possible. Successive approximation is favoured by the MCU manufacturers for a very simple reason - it requires a single analog comparator and an R-2R DAC - cheap, accurate and reproducible architecture that covers nearly all practical DAC needs. Moreover it can be difficult to find a standalone successive approximation ADC as most are either pipelined (higher sampling rates) or sigma-delta (for high, eg audio, resolution). Again for a typical maker these are too finer points but I wanted to make sure they are mentioned in the footnote. Thanks again Andreas for your work

@AndreasSpiess 3 роки тому

Thank you for your explanations. I always learn something from my viewers! As you saw I am more a user and not a specialist in this matter.

@brecomp 3 роки тому

Excellent video! Congratulations!

@AndreasSpiess 3 роки тому

Thank you very much!

@foxeskeeper3817 3 роки тому

Pretty useful, Mr.Spiess

@AndreasSpiess 3 роки тому

Glad you think so!

@mattsaxey529 3 роки тому

More helpful content. Thank You!

@AndreasSpiess 3 роки тому

You're welcome!

@PhG1961 3 роки тому

Fascinating and of course useful.

@AndreasSpiess 3 роки тому

Glad you think so!

@davesemmelink8964 3 роки тому

Thanks for another great video! In researching my gas sensor project, I came across a method people say improves the accuracy of the readings, though I don't really understand it. You apply this calculation to the reading on the ADC pin: volts = -0.000000000000016 * pow(reading,4) + 0.000000000118171 * pow(reading,3)- 0.000000301211691 * pow(reading,2)+ 0.001109019271794 * reading + 0.034143524634089; (Also note that there is a more efficient way to do this calculation (10x faster), but it yields a slightly different result, so I'm leaving the original one here.)

@davesemmelink8964 3 роки тому

For some reason the calculation got scrambled when I pasted it in to the comment - apparently having a "+" after a "-" gets interpreted as strike thru... Hopefully you can figure it out.

@AndreasSpiess 3 роки тому

Unfortunately I am no mathematician. Maybe another viewer can help out.

@davesemmelink8964 3 роки тому

@@AndreasSpiess I forget how I originally found the calculation, but if you Google "ESP32 ADC Polynomial" you will find a lot of people use it to make the values returned by the ADC more accurate. You noted that the ESP32 wasn't accurate, but apparently it can be improved with this technique. I'm happy with the results I'm getting, but my application doesn't need it to be extremely accurate.

@AntonioMartinez-xt7gg Рік тому

Impecable, como siempre Andreas

@AndreasSpiess Рік тому

:-)

@imtrue2132 3 роки тому

The ladder reminds of the Covox sound board, connected to the LPT (printer) output of any computers and the output is a analog mono-sound.

@gacherumburu9958 3 роки тому

Thanks for the info..👍

@correcthorsebatterystaple 3 роки тому

Nice, very informative!

@AndreasSpiess 3 роки тому

Thank you!

@aldebaranflash2663 3 роки тому

Danke, alles gut erklärt.

@AndreasSpiess 3 роки тому

Gern geschehen!

@leololdb3299 3 роки тому

I boosted the ADC sample rate of an Arduino UNO at around 30800 SPS for audio purposes, the sound wasn't really great but when I discovered I can use the 1.1V reference, it immediately made it way more accurate! The issue was that the input audio signal was so low it could only be heard in a single bit.

@AndreasSpiess 3 роки тому

You are right. The usage of the internal reference is shown in video #10

@Scrogan 3 роки тому

Neat video! I’d have liked it more if you went over the details of successive approximation registers, and how a delta-sigma ADC (or DAC) works, but maybe that’s outside the scope of this video. On the topic of ADCs and DACs, I’d be interested in a video on DSP algorithms being implemented in an arduino, be it for audio or for filtering out narrow-band noise. Also when you said that SDRs use these very high speed GHz ADCs, I don’t think they actually do. They use lower speed ADCs with mixers and tuneable local oscillators to generate the I and Q signals. Direct sampling SDRs are very rare. I’d also have mentioned the fact that the ADCs have a finite input impedance, so putting a network of resistors in front of one without buffering it after could cause some systematic error. Well, you often use an instrumentation amplifier there anyhow so maybe it’s not too useful of a tip.

@AndreasSpiess 3 роки тому

1. This channels is for makers, so the most important decision is what not to show. 2. I define SDR not only as "SDR receivers for the general public". I define them as "digitalize the signal and do the processing in software". So radar and many other applications fit my definition. 3. You are right with the input resistance. If you calibrate the readings I assume you can live witout an instrumentation amplifier for 10 or 12 bit resolution. For more precise applications you are right, of course

@GlennHamblin 3 роки тому

Great video. Perhaps in a future video you can explain sigma-delta (or delta-sigma sometimes) ADCs. I think they are pretty cool.

@AndreasSpiess 3 роки тому

I am not sure if this would be interesting for many people. Maybe more for a specialized channel...

@butsukete1806 3 роки тому

@@AndreasSpiess But two of the ADCs you linked to, ADS1115 and AD7705, are sigma-delta. They're quite common, especially if you're looking for cheap breakout boards.

@dl8cy 3 роки тому

thank you for such a lot work for that video

@AndreasSpiess 3 роки тому

You're very welcome! Yes, this one took quite some time.

@sagar73594 2 роки тому

Great Scott!

@AndreasSpiess 2 роки тому

@sagar73594 2 роки тому

@@AndreasSpiess Sir, I mean "Great Scott! - expressing surprise or amazement."

@m.s.3346 3 роки тому

very helpful video, thanks!

@AndreasSpiess 3 роки тому

You are welcome!

@brianhelterline4888 3 роки тому

Great video. One thing to note. If you use an external i2c ADC, you can not set up any sort of interrupt driving timing to collect sames in the background at a given rate since i2c does not work within a ISR. This leads to a bit of work to make sure loop() gets called at a reasonable rate.... Just something to be aware of.

@AndreasSpiess 3 роки тому

Good to know. Maybe you try a second RTOS task on the ESP32

@brianhelterline4888 3 роки тому

@@AndreasSpiess This was on the AVR architecture

@leozendo3500 3 роки тому

I have a similar adc module with just 2 16bit ADCs and 50Mhz sample rate. It's like 40usd on eBay. It would be incredible if you want to make a video about how to read data off these cracy fast parallel lanes. My primary goal was to reduce cost. I thought it would be interesting if we can dump all the ADC data straight into a ram with some hard logic, and read the ram with some cheap slow microcenter. Thus eliminating the need of fpga.

@rodrigoduarte501 3 роки тому

Very nice characterization fod ADC's.

@AndreasSpiess 3 роки тому

Thank you!

@ingenia-tec5194 2 роки тому

Thank you a lot. Very impressive :D Thanks for all the info. Excelent Video :D

@AndreasSpiess 2 роки тому

Glad it helped!

@BritishBeachcomber 3 роки тому

I spent much time working in Switzerland, but never heard an accent like yours ;)

@AndreasSpiess 3 роки тому

So it seems I am special :-)

@electronic7979 3 роки тому

Very helpful video.

@AndreasSpiess 3 роки тому

Glad you think so!

@michaelbruns473 3 роки тому

That was very enlightening, too bad my favorite MC ESP32 yielded such weak (lab) results - still plenty accurate though for many projects. Will look into the ADS1115. Dankeschön !

@AndreasSpiess 3 роки тому

I also use the internal ADC. If you know what you can expect, it is ok.

@marcosmaziero 3 роки тому

Very inspiring video. thank you

@AndreasSpiess 3 роки тому

Glad you enjoyed it!

@taranagnew436 3 роки тому

a quick suggestion: can you plz do a video about "more in-depth" of voltage dividers using resistors, trying to understand more about voltage dividers and how the work. thank-you and keep up the great content

@AndreasSpiess 3 роки тому

This is too basic. Just google and you will find a lot of stuff.

@JanJeronimus 3 роки тому

As always a verry interesting video. By the way it is also possible to do other things than averaging. E.g. dropping the spikes / outliers.

@ThijsVandenrijt 3 роки тому

To remove this kind of "shot noise", a median or percentile filter is a common and easy-to-implement method!

@gerleimarci 3 роки тому

Or simply use "Olympic average"

@AndreasSpiess 3 роки тому

@Jan. True. I just used this simple one, also to show the formula. Many people store all values and then create the average, which is not good in a MCU environment.

@zawilious Місяць тому

@@AndreasSpiess Can you plz explain how the averaging formula works ? And how you get the 3.09 number for correction you used for esp32 test

@sailingmarquise9742 3 роки тому

very good explanation

@AndreasSpiess 3 роки тому

Glad you think so!

@ThylUlenspiegel101 3 роки тому

Hi Andreas, great video. Any chance you've also looked into reading low voltage signals (in range 0-0.3V) and related challenges (noise introduced by amplification, etc?)

@AndreasSpiess 3 роки тому

No. As you write, this is more a topic of amplification than a topic of ADC.

@stefans9990 3 роки тому

I had to chuckle a little about the example of measuring a 24V Solar panel and then setting the range to 30V (around 13:23 in your video). A solar panel that you would use with 24V batteries in a real-world scenario would normally be a 72-Cell panel, which typically has an open circuit voltage around 45V @25ºC, and quite a bit higher when it gets really cold. I realise it was just an example in your video, but for anyone wanting to really measure a "24V Solar Panel", maybe increase that range in your resistor divider a little :-) As usual, thanks for an interesting Video Andreas - toll!

@TheAoab50 2 роки тому

Thanks for the video, I had a problem with the adc fluctuating reading with my arduino, I never knew that there are imperfections in these microchips. I wish you also compared an STM32 board like the black pill (STM32f411)

@AndreasSpiess 2 роки тому

I thought I did this in another video.

@kesor6 3 роки тому

Great timing! I just got ten sliding potentiometers and was wondering how to measure their values. Found another video that shows how by connecting all the value pins with a diode to a single analog input, the VCC pin on the potentiometers can be muxed using digital outputs one after another. Also thinking of using a GPIO extender chip like the PCF8575 for this, so I could measure about 16 analog values (slowly) using a single analog pin in the Arduino with pins left over. Will be a MIDI controller project, don’t need resolution or speed or accuracy all that much imho.

@AndreasSpiess 3 роки тому

You can buy analog MUX ICs like the 74HC4067

@bpcorner Рік тому

Thankyou Andreas. I just subscribed.

@AndreasSpiess Рік тому

Welcome onboard the channel!

@xDR1TeK 3 роки тому

Great video. Just for feedback, the first adc is called flash adc, flash for lightning speed. Another idea, adc chips are good for generating a binary value for raw signal within specifications, but the limitation often lies within the controller to manipulate the binary value to usable data. Often, the dilemma is within the controller's ability to manipulate double float values. Some controllers can only handle 8 byte floats. So calculating a thermocouple voltage becomes an inaccurate reading because of the float calculation errors. Not just thermocouples, even ntc resistors. So usually for such operations a good math library is needed to overcome these hurdles but capture rate of course would be at a disadvantage.

@AndreasSpiess 3 роки тому

True. Fortunately, The ESP32 has a floating point engine.

@xDR1TeK 3 роки тому

@@AndreasSpiess i'm using the 8266, moved all my heavy load to the STM32F103C8 due to power requirements. I like these ESP devices; however, I'm interested in another solution where they don't offer a flash.

@freepoet6737 3 роки тому

Nice comprehensive review, one question comes to my mind, is the ESP32-S2 any better than the ESP32?

@Sovvyy 3 роки тому

Notf sure overall, but the esp32s2 has a bit width of 13, compared to the esp32's 12 - which is significant. I don't think it's shown in the documentation yet? However idf alerts you to this when compiling and it can be seen in the respective header files (of course it works too!).

@cbm80amiga 3 роки тому

The same BS :)

@krukhlis 3 роки тому

@@Sovvyy It's just a marketing. I've tried this to monitor charge of the battery -- it's useless in the same way as regular ESP32 or ESP8266 that ESP32s2 should replace. Use only external battery controllers chips, internal ESP ADC is useless for such sensitive things. And what I hate the most with ESP -- this "filtering" formulas with magic numbers -- you need to adjust it for each and every chip. I never had any 2 chips in ESP32 or ESP8266 lines with the same ADC errors.

@MatthiasLeimbach 3 роки тому

Genau das brauche ich gerade, danke !!!!

@AndreasSpiess 3 роки тому

Bitte, gern geschehen!

@MatthiasLeimbach 3 роки тому

@@AndreasSpiess Klasse, ich möchte schon seit längerem die Spannungen meiner 24V PV-Inselanalge, die meine Garage incl. el. Torantrieb versorgt, monitoren. 2 Kanäle, für PV-Vin bis 50V, für Batterie bis 30V. Ein esp8266 (nodemcu) mit vorgeschaltetem Spannungsteiler hat dabei aber natürlich nur Mist ausgegeben. Die Anzeige sprang um mehrere Volt, die Werte waren also nicht zu gebrauchen. Jetzt ist auch mir klar warum. (ADC bescheiden, und WLAN an, zur Übertragung 🤦‍♂️🤷‍♂️) Habe mir gerade mal den ADS1115 aus Fernost bestellt. Dann sollten die Spannungen endlich sinnvolles ausgeben und ich bekomme mein Garagentor immer auf :-) Noch einmal ein großes Dankeschön!!!

@bm830810 3 роки тому

I think sigma delta ADC was also worth mentioning which is also used in ADS1115, maybe in future videos

@AndreasSpiess 3 роки тому

You are probably right. But the video was already very long :-(

@Jimmyng1968 3 роки тому

good lesson, thanks

@AndreasSpiess 3 роки тому

You are welcome!

@SantanderDiogenes 2 роки тому

Nice video!. When you are in the presence of glitches, one way to improve accuracy is to take a lot of measurements and calculate average. Then compare all samples with the calculated average. Take out all samples outside certain margin. Let say 10%. Then calculate the average again. You can continue to get better results. Also you can use statistic formulas as standard deviation to decide when your result is accurate enough.

@AndreasSpiess 2 роки тому

I agree you can reduce noise with those methods. Non-linearities will stay and unfortunately, the speed will decrease. But often, this does not matter.

@easthulk99 3 роки тому

Thank you for another knowledge session. I just bought sonoff power meter module and noticed the update value not that accurate. Maybe i need to do more reading on the usage. I just found you video #99. Three years ago....

@AndreasSpiess 3 роки тому

Some of those power meters are made for large currents and not very precise at low currents

@KnaufL 3 роки тому

Hey Andreas, what about splitting the digital and analog star ground connection point? I mean putting one before the other, or vice versa.

@uwezimmermann5427 3 роки тому

I have used the internal ADC of the ATtiny/ATmega in several scientific (aka "serious") projects - and they are up to the task when 10 bit resolution is enough. But you can loose a lot of the potential by not using a good design for the front-end outside the chip. The datasheet of the AVR series recommends to use a 10 µH inductor in series with the AVCC supply pin as well as the mandatory 100 nF decoupling capacitor. Using a star-ground is absolutely necessary if you have parts around which will draw significant current. However, while AVCC and VCC in the ATmega are separated inside the GND-pins are all connected to the same metal-layer going all around the chip. But for everything you have outside the chip, i.e. voltage divider, possibly an opamp, a split GND is almost mandatory.

@crazythunderchief 2 роки тому

Very nice video. One consideration though. The serial ADC will always need the same time independent of the measures voltage. As the comparator can only output "too high" or "too low" it can not detect that it hit the right voltage and finish early. It will always increment to the final / least significant bit. It can however be accelerated if you choose to reduce accuracy.

@AndreasSpiess 2 роки тому

Thank you for the additional information!

@bm830810 3 роки тому

I recommend using median filter for removing ESP32 ADC glitches, averaging is not good for this kind of noise

@valcob6617 3 роки тому

The formula @Andreas Spiess is using is not the usual average formula. He uses a so called filter with feed back and I don't know why he is calling it average but that one for sure is not just an average. And the second point when he says "when I use 10 samples or even 100 samples in that formula" .. those are not the actual samples. That number tells how much we should fed back to the initial value so basically to explain it we have an initial x=0.551 and in the loop he is calculating the next x by taking 99 parts of original x value (0.551) and adding 1 part of the new analogRead value thus it basically means we are just drifting to the left or right of the initial value and the amount of drift is expressed in the ratio we are using 1/10, 1/100, 1/1000 and so on parts of the new value mixed back to the initial one. Also this number will be the speed of conversion to the initial value so the higher value we use the slower is the speed and the more analog reads we need to go back to normal and at the same time the less is the chance to affect the final number by the new erroneous reading. Maybe @Andreas Spiess does not fully understand the formula he is using which I doubt but who knows maybe he can explain it in some further videos.

@bm830810 3 роки тому

@@valcob6617 This is a simple IIR filter (meaning the response never reaches steady state theoretically), its good for quick & dirty filtering

@bm830810 3 роки тому

@@valcob6617 Also the filter is prone to accumulating round off error for high filtering coefficients and my guess is this is why he gets 10% error on ESP32's ADC

@marceloap140 3 роки тому

Thanks from Brazil. 🇧🇷👍🏼

@AndreasSpiess 3 роки тому

You are welcome!

@klaushelmgens8403 3 роки тому

The ADS1115 is a good choice, BUT with my ESP-32 I had some trouble due to the fact that they was in the same casing and WiFi was enabled/used. The results was overlayed with lots of noise. The method of averageing takes to much time for my project. I need the result ASAP and the ADS1115 is anyway no the fastest. But I was able to solve the issue and I want to share this with you guys: First step was to build (3D Print) to boxes which fit in each other with a small gap. The outside of the small box got covered with a copper film. Afterwards I fit the small box in the big box. Why two boxes? Quit simple : isolation. The copper film I connected to ground. Inside the box I placed the ADS1115. For the cables I made small holes and the cable which is going to the probe is an coaxial. Problem solved. What I want to say by this is, that the interference of the RF signal has not to be underestimated!

@IchrisiI 3 роки тому

Hello, thanks for the in depth explanation!! Can you explain where is this float y = (x * 1023.0 / 331.0) ; coming from? In detail the term 1023.0/331.0 ... min19.45 also in min18.11 I do not understand the 5/497 :( many thanks for help

@vlastimilhajek6371 Рік тому

I don't understand this either. If x is a digital value, to calculate real voltage we need 1lsb voltage coef. Which is max_voltage/max_resolution. So, the proper formula seems to be: float y = x * 3.09/1023

@WistrelChianti 3 роки тому

Me at 16 mins: "ah... bugger" :D Had some "extensibility" ideas in mind for a project to potentially later hook some ADC2 pins up to some inputs... Still, good to know an I2C board is an option if I later want to do go that route and still use Wifi. Video wins just for that, but it had already won several times over for teaching me about how ADCs work!

@kmkessler 3 роки тому

I wish you would have released this video a couple of months ago. I struggled to get an ESP32 to read a thermistor, and I ened up having to generate a loop up table and do a linear extrapolation between the data points to get anything close to useful values out of the ADC. The STM32's have an HAL_ADCEx_Calibration_Start function to improve ADC accuracy. I've used it in the past, but only to read battery voltages where accuracy wasn't really important. Do you have any idea what that is doing(maybe building it's own LUT)?

@AndreasSpiess 3 роки тому

I never worked with STM32s, so I do not know.

@giorgioboiero 3 роки тому

A good alternative condidate could be the STM32 micros such as the Blue Pill (STM32F103) or the Black Pill (STM32F4x1) They could be programmed using Arduino or PlatformIO

@lorenzo.c 3 роки тому

Andreas, great video, very clear and useful. @11:43 you say that the analog reference voltage AREF is not available but it actually appears to be connected to a pin of the header named IOH (I have a genuine Arduino Uno and AREF is marked on the header)

@AndreasSpiess 3 роки тому

There is another commenter explaining the facts below

@lorenzo.c 3 роки тому

Thanks for replying. @@AndreasSpiess, do you mean Graham Wideman? I understood your sentence as "the pin of the microcontroller is not connected" but you meant that "the pin is not connected to an on-board voltage reference". Is that the case? I just bought a couple thermistors and an LM4040C41 and I'm going to use the Arduino to measure a couple temperatures. It would be nice if you showed how, even with a cheap and cheerful Arduino, it is possible to get fairly accurate measures when the signal is slow and the device (thermistor in my case) can be powered by the reference.

@AndreasSpiess 3 роки тому

It was Uwe Zimmermann : "available yes, connected to circuitry on the Arduino: no. But be careful, if you switch the ADC reference to the internal bandgap reference while connecting another voltage to AREF blows out the internal bandgap reference for good."

@nektariosbasdekis1123 2 роки тому

Hey Andreas. In the AD7606 module you saw at the end, the logic levels are 3,3 or 5 V? Thank you!

@AndreasSpiess 2 роки тому

It looks like 3.3 volt (see on the Aliexpress listing)

@asahajitdalui1962 3 роки тому

Thanks a lot .. A Quick question is there a 100 volt DC voltage Sensor ? or voltage divider is the only way out... Working on a raspberry pi based DC energy monitor wish you have something alike in pipeline... nicely declattered the fact of ADC 👌

@uwezimmermann5427 3 роки тому

The only way to go is a voltage divider in one or another form. Whether you build it yourself or anyone has built it and put it inside a module is the only difference. The "normal" cheap digital multimeters have a native voltage range of 200 mV - everything above is realized by means of voltage dividers combined into the fixed 10 MΩ input resistance.