Comments on: Measure a Bipolar Signal with an Arduino Board https://masteringelectronicsdesign.com/measure-a-bipolar-signal-with-an-arduino-board/ Electronics Design and Modeling with Emphasis on Analog Design Thu, 30 Mar 2023 01:19:33 +0000 hourly 1 By: Adrian S. Nastase https://masteringelectronicsdesign.com/measure-a-bipolar-signal-with-an-arduino-board/#comment-52462 Thu, 30 Mar 2023 01:19:33 +0000 http://MasteringElectronicsDesign.com/?p=1861#comment-52462 In reply to Anand Phadnis.

What you describe is a different circuit, in which R2 is connected to ground and it becomes you R5, and R3 connects to V3 which I do not have.

]]> By: Anand Phadnis https://masteringelectronicsdesign.com/measure-a-bipolar-signal-with-an-arduino-board/#comment-50409 Tue, 17 Jan 2023 11:49:25 +0000 http://MasteringElectronicsDesign.com/?p=1861#comment-50409 Hi Adrian,
Greetings. Good article. I may be wrong, but, I do believe that there could be an error in your circuit. You are missing a 10K resistor to ground node from the non-inverting input of the opamp. At least thats how classical summing amplifier configuration is depicted or thats how I remember it from my college days.
The classical equation for the o/p of the summing amplifier is as follows:
Vout = V1(R5/ (R1+R5))*G + V2*G – V3(R4/R3)
where I have assumed R5 to be a 10 K resistor from the non-inverting terminal of the opamp to circuit ground AND
where G = 1+ R4/R3
In your case since R5 is infinity then the equation reduces to
Vout = (V1 + V2) * G – V3(R4/R3)
Therefore what you refer to as the “Offset” its technical nomenclature happens to be the Pedestal voltage. This pedestal voltage in the above circuit is 2.5 V and when multiplied by the non-inverting gain of (1+ 10K/10K) = 2 will give you an effective pedestal voltage of 5V. Therefore the signal will swing not around +2.5V but around 5V.
Just my two cents.
Regards Anand

]]> By: Adrian S. Nastase https://masteringelectronicsdesign.com/measure-a-bipolar-signal-with-an-arduino-board/#comment-41615 Tue, 24 Oct 2017 04:00:11 +0000 http://MasteringElectronicsDesign.com/?p=1861#comment-41615 In reply to waleed-II.

Arduino is powered with a positive voltage. I do not see how you can measure a negative voltage with it. You need a buffer and that’s what this article is about.

]]> By: Adrian S. Nastase https://masteringelectronicsdesign.com/measure-a-bipolar-signal-with-an-arduino-board/#comment-41614 Tue, 24 Oct 2017 03:46:40 +0000 http://MasteringElectronicsDesign.com/?p=1861#comment-41614 In reply to alan.

1. As long as it is a 2.5V supply you do not need to modify the resistors.
2. An op amp cannot function without a power supply. The comment says that, for this particular circuit, you do not need the negative power supply. But you need the positive one.

]]> By: alan https://masteringelectronicsdesign.com/measure-a-bipolar-signal-with-an-arduino-board/#comment-41593 Fri, 20 Oct 2017 22:26:23 +0000 http://MasteringElectronicsDesign.com/?p=1861#comment-41593 Hi, thanks for the article – it’s very helpful. I just have a couple of questions:
1. If I use a buck voltage regulator to supply the 2.5V supply, do I need to modify the resistances at all?
2. In the first comment above you mention that for this specific example, the second voltage supply is not actually required; do you mean that the +v and -v feeding the op amp are not required?
Thanks!

]]> By: waleed-II https://masteringelectronicsdesign.com/measure-a-bipolar-signal-with-an-arduino-board/#comment-41580 Wed, 18 Oct 2017 23:25:58 +0000 http://MasteringElectronicsDesign.com/?p=1861#comment-41580 Why not just use the “Analog Input Reference” pin on the Arduino/AVR to cause its ADC
to read +2.5 to -2.5V and then scale the ADC input for whatever range you might want?
Seems too easy.

]]> By: Adrian S. Nastase https://masteringelectronicsdesign.com/measure-a-bipolar-signal-with-an-arduino-board/#comment-33932 Sat, 12 Mar 2016 17:02:30 +0000 http://MasteringElectronicsDesign.com/?p=1861#comment-33932 In reply to Dilhani.

Which diagrams are you referring to? There is just one figure in this article. To answer your question, you need to tell me more: What is the sensor signal amplitude? What is the sensor output resistance? What is the signal level expected at this circuit output?

]]> By: Dilhani https://masteringelectronicsdesign.com/measure-a-bipolar-signal-with-an-arduino-board/#comment-33893 Thu, 10 Mar 2016 06:56:01 +0000 http://MasteringElectronicsDesign.com/?p=1861#comment-33893 Hello,
I need to use a level shift cct to interface emg sensor and arduino. What is the best cct diagram from those two cct diagrams. this article was really helpful. thank you very much

]]> By: Adrian S. Nastase https://masteringelectronicsdesign.com/measure-a-bipolar-signal-with-an-arduino-board/#comment-28139 Sun, 27 Sep 2015 19:39:22 +0000 http://MasteringElectronicsDesign.com/?p=1861#comment-28139 In reply to David Dubins.

Assuming that your input and output voltage levels are the same as the ones in the article (input -2.5V to 2.5V, output 0 to 5V), you can use a voltage divider with two resistors. This will divide 5V in 2, for the 2.5V reference. However, these two resistors will change the ratio of R1 and R2. So you need to drop the value of R2 to take the divider resistors into consideration. So, if you use two 10kohm resistors for your divider, make R2 = 4.99kohm. All resistors should be at least 1%.

]]> By: David Dubins https://masteringelectronicsdesign.com/measure-a-bipolar-signal-with-an-arduino-board/#comment-28134 Sun, 27 Sep 2015 18:14:26 +0000 http://MasteringElectronicsDesign.com/?p=1861#comment-28134 In your example, I was wondering about the 2.5V shifting voltage. specifically, if I use a voltage splitter on the +5V Arduino power line with equal value resistors to get 2.5V, what values should I use? Does the summation where R1 and R2 lines meet require equal current from the 2.5V shift and the analog signal? I’m probably saying this wrong, but I’m really new to this. I was thinking 1K and 1K for the splitter. Thanks!

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