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Op Amp 02 Workshop

Adapting sensors to an Arduino. This is a hands-on workshop.

Silicon diodes have a handy feature. Using a constant current, the voltage drop across a forward biased silicon diode drops by about 2mV per degree Celsius and are good over a wide range from cryogenic temperatures to around 200 to 250C.

However, that is on an offset voltage of about 600mV at room temperature, and only covers about 200mV from 0 to 100C. With an Arduino Uno analog input mapped from 0-5V a 1024 bits, that is about 4.9mV per bit, which is about 2.5C per bit, or only about 41 bits of resolution from 0 to 100C!

We'll use an Op Amp to remove the offset and amplify the signal to match an Uno or Nano's input. Or with one resistor change, any other Arduino.

There is a $5 charge for Nonmembers, free for members in good standing of OlyMEGA. A kit of parts will be available for an additional charge if you wish to build along, protoboard (white plug in board) extra.

Many other sensors have an offset and a small output signal. Gas detectors, strain gauges, etc. With minor changes, this same circuit can adapt their output to get the best resolution.

An Arduino is required if you wish to put this to the test. OlyMEGA has Unos available for purchase. We will be programming Arduinos to read and display at the next workshop.

I strongly recommend downloading the PDF of the 2nd edition of Op Amps for Everyone:

Or buy the latest 4th edition on Amazon. Don't forget to go to the OlyMEGA page first and click on the Amazon Associate link, then OlyMEGA gets 4% while you pay the same price.

Please join the OlyMEGA forum to help me choose a project or projects that will be offered at a later session.

Join or login to comment.

  • Polymorph

    OK, I'm NOT changing it again. I WILL be teaching this class tonight.

    In addition, I'll also be teaching a lesson called "Perfect is the enemy of good enough".

    July 24, 2013

  • Polymorph­ changed the date and time from Wednesday, July 31, 2013 at 7:00 PM to Wednesday, July 24, 2013 at 7:00 PM

    July 24, 2013

  • Polymorph

    I'm -very- sorry to do this again, I've had to push it back a week.

    July 23, 2013

  • Polymorph­ changed the date and time from Wednesday, July 24, 2013 at 7:00 PM to Wednesday, July 31, 2013 at 7:00 PM

    July 23, 2013

  • Polymorph

    Since I've had no responses about a kit of parts, I am going to focus on simulating this in LTSpice. I will have one on a whiteboard, and I'll make the schematic and kit of parts available.

    I'd also like to gauge interest in making a PCB for this project. A few resistor substitutions can make it good for level shifting other sensors.

    Download LTSpice here:

    July 23, 2013

  • Polymorph

    I have had an emergency and so have rescheduled this event to Wedn July 24th. I am very sorry for any inconvenience this may cause.

    July 17, 2013

  • Polymorph­ changed the date and time from Wednesday, July 17, 2013 at 7:00 PM to Wednesday, July 24, 2013 at 7:00 PM

    July 17, 2013

  • Polymorph

    There may be some protoboards to borrow around the space.

    An optional kit of parts will be $10, in addition to the $5 charge for nonmembers. Please let me know how many of you want one. You'll also need a protoboard and Arduino Uno or Nano, although other Arduino models should work, it should have a 3.3V regulated power output.

    July 16, 2013

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