trahanc

Got it. This is my last set of questions, promise. (1) What purpose does the audio amplifier serve here? I went to Radio Shack and could not find it's specs. It doesnt appear to be a step-up or step-down. (2) How do I know the voltage/current output of my computer speakers. I know the speakers are 3 Watt RMS and 6 Watt System Power, and I think the two speakers are 8 OHM. Ok, I'm done. Thanks audioguru for all your help. -C

It really sucks that this was such a crappy circuit. Especially since it is the only one for this purpose I have found online after hours of searching. I will replace the transistors with your advised. I found this full wave rectifier at Radio shack http://www.radioshack.com/product/index.jsp?productId=2062581&cp=&kw=full+wave+rectifier&parentPage=search I suppose a capacitor would work as a filter. I assume I should use one with a voltage rating of at least the circuit power supply. Any clue as to what capacitance I should use? I also assume the rectifyer and capacitor should be in circuit before the transistors. Thankyou infinitely for your support here, AND if you ever have any 'stupid' quantum physics questions, please write me ... I owe you lol ;D -C Much appreciation for your help.

Wow, thanks so much for the warm invite and quick reply. And thankyou for going to the site and checking out this particular circuit. So, if I understand your reply well enough (I am an electronic novice), you mean to say that (1) I first need a stronger feed transistor (as opposed to the MPS2907), one that (2) can feed a more powerful transistor (as opposed to the TIP31). I need (1) because the output from the computer speaker is too weak. SO, any suggestions as to a pair of transistors that may fit my bill? >The circuit has a single rectifier diode, so the motor is powered for a max of >only half the total time. As far as the single diode rectifier, I'm not sure that I really need something more than this, as this circuit need only be a crude driver. It would be something interesting to test though. >The circuit doesn't have a filter, so the motor hums with the music. wow, I thought the hum was from the motor trying to push against the jaw resistance, but not having enough current to move it. Thanks for the tidbit. :) Thanks Again, Corey

Hello All, I write here because I am just about to give up. My project was as follows: I want to control a hobby DC motor (with a stall current draw of about 3A) with an audio signal coming from a pair of powered computer speakers. I am a super Halloween fan, and my hopes are to operate a jaw mechanism in this manner. I know servo controllers are normally used here, but I want to hack into Walmart's toys and use the already constructed jaw mechanism. Recently, I found this website http://home.rica.net/jimk/projects/servo/index.htm , which got me really excited. SO, I build the circuit and tried it out. It did, in fact, work, but only for one of my walmart toys ... the one with the lightest jaw (less load - it draws only 0.5A at stall). The others only hummed with an intensity proportional to the music. So, I emailed this guy, but recieved no reply. So, I write here in hopes that someone will help me in either altering the above circuit (and confirming my diagnosis), or just as easy, constructing a completely new circuit. Any help is greatly appreciated. Thanks, Corey