DIY Scanning Disk TV - Page 2 - Videokarma.org TV - Video

mbates14 · #16 08-22-2005, 08:45 PM

Basically itll lock the frame, and then roll, and lock as suddenly as it rolls, and keeps doing that. maybe the PLL is working now, and trying to lock onto noise, who knows.

Hey, its got more life now than what it did.

yagosaga · #17 08-23-2005, 02:12 AM

Quote:

Originally Posted by mbates14

Basically itll lock the frame, and then roll, and lock as suddenly as it rolls, and keeps doing that. maybe the PLL is working now, and trying to lock onto noise, who knows. Hey, its got more life now than what it did.

It is morning here in Europe and I have had no morning coffee, so forgive me my bad English.
It is the same trouble I had. In the first attemps I measured the opto fork output with a microampere meter to see whether it works or not. And when it works the next problem was to adjust the motor drive in such a way that one can control the motor speed. You can do it with changing the resistor values.
Resistor at pin 13 replace with 100K. The next resistor, connected with the speed control poti determines the basic speed of the motor. Take a lower value and you have an improved speed control range. I have experimented with values between 20K and 100K. You have to find out what works best. It is stupid and boring work, but I know no better way.
A paper Nipkow disk is not the best solution. For a more stable Nipkow disk, you can use a blank cover CD. Print the attached picture on a piece of paper with your printer (paper should not be diffuse). Sting the holes with a needle, cut the disk out of the paper and put it on a CD with some glu. Take a motor from an old CD-ROM drive and you can drive the disk with the CD-ROM motor. But note that the CD motor needs a very low voltage, if the motor runs too fast, add a resistor (20 - 100 Ohms) parallel to the motor.

mbates14 · #18 08-23-2005, 01:12 PM

Already done that. I used the speed pot to slow down the motor right where it almost holds. And then I hooked the sync back up.

Like I said before, it tries to lock, and as soon as it does, the motor gets another kick from the pll and it looses lock. and itll try to lock again, and when it does, it gets another kick from the pll. hmmm.

is this because I had to switch the syncs for it to work? because remember, if I switch it back like in the schematic, it will fail to operate, and drives the mosfet into saturation, thus running the motor full speed.

mbates14 · #19 08-23-2005, 01:16 PM

that one is already at 100k. I didnt have a 147, so i used a 100.

p.s. its cardboard, not paper. And all my cdroms I have are stepper motors, not two wire motors.

besides, wouldnt I have to have a microscope to see it?

yagosaga · #20 08-23-2005, 03:48 PM

Quote:

Originally Posted by mbates14

And all my cdroms I have are stepper motors, not two wire motors.

Perhaps this could be the reason why the motor looses lock. I had experimented with CD-ROM drive motors and the 4046, and this doesn't work, so I use a D.C. control with manual sync. Perhaps you get a better result if you insert a high wattage low Ohm resistor parallel to your motor.

Quote:

Originally Posted by mbates14

besides, wouldnt I have to have a microscope to see it?

I think, a magnifying glass is enough. But a better way might be to order a 12 inch Nipkow disk from Peter Yanczer. The picture is appr. 1" x 0.6" which is sufficient for direct view.

mbates14 · #21 08-23-2005, 04:01 PM

im using a carboard disc, and a cassette motor.

yagosaga · #22 08-23-2005, 04:06 PM

Quote:

Originally Posted by mbates14

im using a carboard disc, and a cassette motor.

With a belt drive?

mbates14 · #23 08-23-2005, 04:15 PM

no, dont have any hubs or anything.

I worked with what I had. Carboard secured right at the shaft.

old_tv_nut · #24 08-23-2005, 04:36 PM

I have been trying to follow what you have been doing, and I don't see where you connected the two grounds. Did you do that? If so, you should next see if the circuit has enough range to get to the right speed.

When you block the fork, it should appear to the PLL that the disk is too slow, hence the circuit should run up to maximum speed. On the other hand, if the gate of the MOSFET is grounded temporarily, the motor should slow way down or stop.

I also think the connections of pins 3 and 14 are correct in the schematic - if the disk is slow (test by blocking the fork), the output on pin 13 should go high, turn on the MOSFET, and make the motor run fast.

It does not matter if the input pulses are wide or narrow, since this phase detector detects pulse edges. So, you should be able to use either polarity of fork signal, as long as it swings from zero to twelve volts. However, the edges should be fairly clean and quick rise/fall time.

mbates14 · #25 08-23-2005, 05:22 PM

if I block the fork, nothing happens, but the motor no longer gets its "kick"

if i unblock the fork, itll try to sync again.

mbates14 · #26 08-23-2005, 05:27 PM

its only got a 2vP from the fork

mbates14 · #27 08-23-2005, 08:53 PM

ok, I ran some more tests.

With the sync backwards, as we know, it tries to work.

Now, If i bring the optical fork closer, it speeds off. So, I switched the sync inputs back to normal. The disk went full speed.

So, I made the fork closer together, like i did before, and still nothing. no signs of speeding down. I got them so close, it was scraping the disk. I got a good strong signal from the fork too.

So, i moved the syncs back the other way, and it started to work again, and like I said if i move the fork, it speeds up. I move it back it works fine. But no accurate sync. hmmmmm. sooooo confuzzled.

mbates14 · #28 08-23-2005, 09:31 PM

its workin now.

It only works if its connected backwards, I also put a filter on the fork output.

So, its trying its damndest to stay locked. Itll lock the frame, when the frame just starts to fall, the PLL kicks it, but the motor overshoots, and itll loose lock for a split second, and slowly fall into place.

If i blow on the disc to slow it down, almost immidiatly after I blow on it, it kicks the frame back into place.

so, its working I think.

old_tv_nut · #29 08-24-2005, 04:08 PM

If you block the fork, what do you mean by "nothing happens" - does it speed up, slow down, or keep constant speed? It *should* speed up, since it is getting information that indicates the disc has stopped. If it doesn't speed up, there is some problem with not having enough control range and/or not having speed trim set correctly (or possibly other circuit errors, of course). Then, when the fork pulses are applied to the chip, it should slow down and eventually lock. If you have a spare chip, you might consider substituting it. It is possible to blow out some chips if you disconnect the power supply from the chip but still have full voltages on the input pins (which I think you said you tried once).

mbates14 · #30 08-24-2005, 04:23 PM

but its working now.

but it only works right when I have the speed pot set right. If i speed it up or down with the pot, it wont lock.

oddly, but surely. I got this PLL chip from radioshack when they used to carry them. They dont anymore.

itll work, if I intensionally slow the disk down, it locks the frame right back in place. But has a tendency to get a spik from the sync pulse, and overshoot it. (frame starts rolling upwards.

More or less, i have line lock, but not so much frame lock. I covered one of the holes btw.

if i cover the fork, nothing happens, but it wont sync any more, when the frame starts to roll backwards, itll just keep on doing it.

but thats when the signals are switched than from the schematic.

If i switch them back, the motor speeds all the way up. never slows down. Even if I bring the fork closes together. Still dont matter. It only works when backwards.