Modding an optical trem circuit

[fastbreak78]

A while back I built an optical tremolo from Make magazine. Here's the schematic and concept:  http://makezine.com/projects/make-33/optical-tremolo-box/

The circuit's works, however, using a 3 volt battery pack, only about 1/2 of the speed knob is usable. The motor's not provided enough power on the lower speeds to turn. I plugged in a 9 volt wall wart, to see how that would work. The motor spins at a much higher velocity, so much so that the trem effect is difficult to notice on the upper range. I've done some research, and believe that changing the input voltage, to the motor, to either 4.5 volts or 6 volts would be the best fix. What would be the best way to do this? Any help would be greatly appreciated!

[armdnrdy]

Because of the motors current draw...I would use a voltage regulator.

It's kind of difficult to give advise without seeing a schematic. (I didn't see one in the link you provided)

[fastbreak78]

Whoops! Sorry about that. It's a bit harder to find under the link than I thought. It's under the pictures for step 9.

[Mark Hammer]

I think I have that issue.  In any event, I remember the project.

This is one of those don't-raise-the-bridge-lower-the-river things.  The challenge is that the disk spins far too fast at the supply voltage you have.  Now, the effect itself, is a function of how often the clear part on the disk passes between the light source and LDR.  The "how often" is a function of the diameter of the disk, where on the disk the clear spot is, and how many such clear spots there are on the disk.  The first link shows 3 clear spots on the disk, and a modest-diameter disk.  To compensate for a faster motor, you can make the disk bigger, and have a single clear spot, such that the clear spot passes between light source and LDR less frequently.

[Nasse]

Just watched version 2 vid last night

[fastbreak78]

At 9V, the motor is pretty loud, which the amp seems to be picking up. Also, fiscally it would make more sense to make an electronic fix, as it doesn't make much sense to spend $7 more on transparency paper, when a couple of resistors are less than a dollar.

I saw the improvements to the design they've made a couple days ago. I'm looking into building one of the redesigns, but for right now I'd like to finish up the project that I started. Thanks for the suggestion, though!

[PRR]

If you used the "1.5V-3V" motor, 9V will burn it out sooner or later.

> enough power on the lower speeds to turn.

There's friction in the motor. Because it is new, and cheap, and because sleeve bearings don't spin so good at very low speed.

Work a *small* amount of *thin* oil into the motor, where the shaft comes through bronze bearings. If you have nothing better, find the *transmission* dipstick in your car, use a toothpick to transfer a little ATF from the wet end of the stick to your motor bearings.

Run it at 3V all night long. I've seen brass bushings come down 100:1 in low-speed friction from extended running.

> I would use a voltage regulator

Agree, agree.

DC motor speed is nearly proportional to Voltage. Series resistance will starve the motor as friction rises at very low speed.

No real need for regulation, just *solid* variable voltage.

Get an old USB power supply. Maybe the charger for the cell-phone that fell in the toilet. Good-Will often has a pile of these. Cut the end and find PLUS 5V and MINUS 5V, know which is which.

Radio Shack parts. TIP120 has a metal tab, do NOT let this touch chassis or anything else, but do let it catch some air for cooling. Use nearest standard capacitor, any voltage (it might be 200V, that's fine).

http://i.imgur.com/Q1KPBSM.gif

[duck_arse]

I only glanced at the construction article. does it mention that the tremolo "waveshape" can be shaped by the shape of the interrupter dots? a different disk with different shaped dots, or a single disk with concentric dots of a shape and the ldr on a moveable arm makes the whole thing now too complex.

[fastbreak78]

PRR: I was wondering about that. I wasn't sure whether it would or not. I would've been quite frustrated if it had just stopped working one day. Thanks for the tip!

Would three-in-one oil do it? I have quite a bit of the stuff. Hm. Okay. I'll try that and see if that helps.

What's the difference between regulating voltage and solid variable voltage? Will this allow me to power off of a nine volt power supply, or would I still have to use my battery pack? Thanks again for all your help!

Duck: Moveable arm? I think one of us must be confused. Mine doesn't have a movable arm, instead using a spinning motor.

[fastbreak78]

Well, this past Sunday I added a dab of oil or two, and just let the thing spin. It seemed to loosen up the motor at least somewhat. Unfortunately I'm out of batteries at the moment, so I can't test it. Guess I'll be going out today and grabbing some.