On 10/08/2012 03:18 PM, Shane Hathaway wrote: > Ok, it seems like you want 2 op-amps wired as comparators. One op amp > decides whether to move the motor forward, the other decides whether to > move it backward. (You can get multiple op-amps on a chip, so this > doesn't increase the parts count.) You'll have to calibrate the circuit > so that the op amps don't activate simultaneously. > > To keep things simple, let's say each op amp drives a DPST (or DPDT) > relay. That solves your voltage issue: it isolates the control circuit > from the motors, so you can apply reverse voltage to the motors. You > can also use a voltage regulator in case the supply is too noisy.
Good to know I'm on the right track. I was thinking along these very lines in fact just when I noticed your e-mail. > Each op amp should perform a slightly different comparison. When you > want the middle position, the op amp that controls forward movement > should compare the motor sense voltage with a voltage slightly lower > than the control voltage, while the other op amp compares the motor > sense voltage with a voltage slightly higher than the control voltage. > You can adjust the voltages using resistor-based voltage dividers. > > Does that make sense? The comparator circuit on this page is a good > reference: > > http://www.swarthmore.edu/NatSci/echeeve1/Class/e72/E72L2/Lab2%28OpAmp%29.html Absolutely makes sense! This is the track I'm heading down. Thank you very much for your thoughts on this. I knew there had to be a relatively easy way of accomplishing this. Michael /* PLUG: http://plug.org, #utah on irc.freenode.net Unsubscribe: http://plug.org/mailman/options/plug Don't fear the penguin. */
