Thursday, October 7, 2010

Chapter 5 - Exercise 32 Update 4

A short update today - only a small bit of progress... let me explain.

First off, I've gotten over sharing my dumb mistakes with the world via this blog... when you decide to walk through a book and perform all the tasks/exercises/experiments and share your results, you've gotta expect to have the occasional embarassing moment. I've had plenty during my tour of Make: Electronics, and I'm not done yet...

So, here's what happened - take a look at the schematic for Experiment 32 (if you have the book)... see that 50K trimmer there and how the left side of the resistor isn't connected anywhere? That's not an error... but I thought it was! So, I just connected that end where it felt right.

And... of course... the video yesterday shows my results. So, after Mr. Platt explained this little techy bit to me, I pulled that wire and ran the circuit. The motor still spins, but THIS TIME the two microswitches, when pressed, stop the motor. Progress. But not fixed.

Pressing either of the microswitches is supposed to reverse the motor's spinning for a short period of time. But it doesn't. Instead, pressing a microswitch causes the relay to buzz LOUDLY and the motor does stop rotating... almost. If you hold down the microswitch, the motor appears to stop but in reality it still rotates in the original direction but VERY slowly... almost impossible to see. Oh, and the relay buzzes LOUDLY! Release the microswitch and the motor begins rotating in the original direction again.

So, don't connect the 50k trimmer on both ends... just the one shown in the figure. And if anyone has any ideas WHY my relay is buzzing AND why either microswitch doesn't cause a reversal in the motor spin, please let me know... I'm taking a step back to think about this for a bit.


  1. Any chance of a schematic again?

  2. I'll take a picture tonight and post it later.

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  4. Publishing your mistakes is what makes this blog interesting, if we wanted a flawless adventure through the book we could just read it ourselves, keep up the bad work!!

    Whenever I get a relay buzzing I quickly toss in a diode to act as a snubber, you put it in parallel with the relay magnetics but reverse biased.

    I've also (strangely enough) had success putting relays in series (not parallel) with my relay loads (perhaps this is what is called a clamper?) maybe try both.