Muscle sensing servo: testing, operating & troubleshooting – Free preview!

Questions

  • 3

    Lightningie

    Hello!

    Has anyone here on the forum had any trouble with, and perhaps a solution to, not getting enough voltage supplied to the servo motor? It seems my amplifier circuit IS amplifying (as indicated by my multi-meter), just not enough, I think. I tried tuning the gain, like Mr. Juby said to, and yet it doesn’t seem to have any/enough of an effect.. If anyone has any thoughts on this, please let me know!

    Thanks!
    Lightningie

    • Ian Juby

      Hey Lightningie – I’m confused, what exactly is the servo doing or not doing?

      Ian

    • Lightningie

      Attachment

      Hi again,

      The motor appears to respond to the 555 timers: I can hear the ticking, it completely swivels to one side, and it turns to a specific position with my pot when I disconnect the timers circuit from the op-amp circuit, and change some part values to match that of the servo controller circuit.

      It doesn’t seem like my amplification circuit’s signal is getting to the servo, even though the signal from the op-amp seems to be amplifying my muscle’s voltage by 1 volt or so (if I’m testing for it correctly – one multi-meter lead on ground and the other on pin 14?), I don’t see any response from my motor… Based on the values from the circuit diagram, how high would the voltage coming from the op-amp circuit have to be in order for the motor to respond, typically?
      I attached a picture for you to view, if it helps.

      Thank you so much for your help!
      Lightningie

    • Lightningie

      I got it to work! The problem was that I was using a 0.01 uf capacitor instead of a 0.1 uf for the 555 timer! After switching the capacitors, everything worked! I messed up on the value because I didn’t do the conversion from picofarads to microfarads correctly…

      Sorry about the mix up!
      Thanks again!
      Lightningie

      • Ian Juby

        Oh I see! Okay, cool – glad you got it to work! That’s a seriously cool circuit. It was a lot of work to build, but I really had a lot of fun with it. I’m trying to figure out how to do biofeedback for a project in a later course – we’ll see how that goes. 🙂

        Ian

  • 2

    Lightningie

    Hello!

    I watched the lesson video, and noticed that the capacitors you use on your breadboard, although I cannot see the values on them, appear to be larger value capacitors than what is indicated by the schematic: the capacitors that are the same size as the 2200, 1000, and 2.2 uf capacitors (the black ones at least) that I received in my kit. Could you help me understand this? Did you, if I am correct, find that using larger capacitors helped the circuit work better?

    Thank you! I am very much enjoying the course!
    Lightningie

    • Ian Juby

      Hola!
      Ya, the size will vary wildly – for the videos I was often just using capacitors and parts I had kicking around. They were most likely not the same parts in your kit. Further to that, I’ve seen capacitor size be alllll over the map – 1 uf caps as big as 100uf caps. I’ve got some supercaps I just got in the mail – 100 FARADS (100 million uf) and I’ve had 300uf capacitors as physically big as those ones. The voltage is a big factor in the size because it affects the thickness of the insulators for example.
      The physical size of the capacitor has no bearing on its performance. Only its capacitance – and even a very small difference in capacitance can have a huge impact on how it performs.

      Ian

    • Lightningie

      Thanks! Thanks for helping me understand how capacitors work, too!

      Lightningie