I got bored one day, and decided to work with chris benham on a color wheel monitor project. i got the circuit completed and working.

the hardest part of the whole project was the motor control servo. but i decided to write a program for a CPU, and i have full control.


What do you think?

http://img525.imageshack.us/my.php?image=dsc00402el0.jpg

http://img175.imageshack.us/my.php?image=dsc00403nu4.jpg

http://img158.imageshack.us/my.php?image=dsc00404mn3.jpg

Nice! What is the scanning rate? Presume it's running from the computer VGA output? How big is it?

Really nice job. It's interesting to see an Elenco put to such 'practical' use!:thmbsp:

I think that's pretty damn cool!!! I just wouldn't try traveling through any airports with that case... :no:

its 640x480 at 60hz. the flicker is horrible, but my monitor wont go past 60hz becuase the horizontal rate it cant handle.

also the most interesting thing about this project is i have the motor control servo running in a processor, with custom control code. all PWM.


the first MOSFET controls the motor current, (which is un-needed, so i disconnected it). and the second mosfet is the PWM controller output.

basically it has a wide lock range. dont have to adjust gain, or anything. just power it on and it locks.

i can change the refresh rate to 80hz, and itll lock it without touching anytrhing. except you cant read whats on the display, becuase it cant support it.

I used PWM for my mechanical TV with similar results - no adjustments needed, just pulls in to whatever the incoming video is. However, supplying pulsed current to the DC motor does make it buzz/hum. How's yours noise-wise?

cant hear anything. i have it set about 50khz.

Real nice work Mike. With school and all how did you find the time?
Richard.

im out of school now. been out since december.

WOW, Time does fly when you get old. Shoot me a PM or email so I can catch up.
Richard.

cant hear anything. i have it set about 50khz.

AHA. My mechanical set runs at 400 Hz, convenient becuase it's the line scan rate. - makes the motor whine.

ah you made a PWM controller for a nipkow? or something like that.

i thought about that, but i never did do that becuase i wasnt as fluent in processors.

processors makes it really nice. all you need is a mosfet, an opto-coupler to upstep 5V to about 9v to fully-on the mosfet, a chip and thats it. no resistors, capacitors, or nothing. single chip motor control . :music:

Yes a PWM for the scanning disk - however, done with 555 timers instead of a microcontroller.

555 timers and a phase comparator? use the voltage output to control the duty cycle?

details here:

http://www.bretl.com/mechtvprogress2/mechtvprogress2.htm

[QUOTE=mbates14;1289849]

"the hardest part of the whole project was the motor control servo."

Very good color. I hadn't been able to look at any of the picrtures you sent me because I can't get an .rar files program to work on my PC.

The servo for my set has to be the hardest thing I've ever built too.

Congratulations!
Cliff

the only issue i have is when i first turn it on, the loop oscillates from the disc inertia until it stabilizes. it zooms off to full speed, then drops back down to below normal speed, then speeds up past normal speed then eventually locks in. almost like a "ring" effect of the rising edge of a square pulse.

as the battery discharges, itll jump a color frame or two, and it has to lock back in. only takes sec. dont have a 12V 7amp power supply to run the motor. LOL.

Does it also oscillate in phase if you disturb it slightly? It is possible to have the wrong or right loop gain for either speed or phase or both depending on how your algorithm works. In the circuit for the mechanical TV, a 4044 "type II" phase/frequency detector is used. While the type II 4044 phase detector is very linear for phase, it is nearly "bang-bang" for frequency, resulting in an oscillation when the speed is first pulling in, but then becoming very stable for small phase perturbations.

it sorta bounces back and forth until the disk inertia balances out. once it does, its good to go.