nbtv sync problem

[mhaznedar]

I built the circuit.(in the attached file)
But when i give the voltage motor begins to run(to its max speed so the sync not
happens).I doesn't waits the nbtv signal.Is it normal?If it is not can you tell
me my probable mistake.
I checked the circuit several times and used exactly the same components

[Harry Dalek]

My advice would be not all motors are the same so the circuit works with its motor, what ever you are using needs to be slowed down by the sounds of it ,i would put an lm317 variable voltage regular just for the mosfet driving the motor part of the circuit , with voltage control of the motor you should be able to now adjust the motors speed so the pulses can take over to control the motor the other control pot on the mosfet will fine tune it .

[DrZarkov]

Another problem could be the opto-fork: If you are using separate LED/phototransistors, try to change the distance. For example with the type from the club-shop the distance must be more or less exactly 8 mm to work properly. If it's more than a centimeter or less than half a centimeter it will not work at all.

[mhaznedar]

Can you show that in the circuit?

[mhaznedar]

Hello again

Can you Show me how i will put lm317 in the schema?

Thank you very much for YouTube helps.

[Harry Dalek]

[quote="mhaznedar"]Hello again

Can you Show me how i will put lm317 in the schema?

Thank you very much for YouTube helps.[/quote

https://www.youtube.com/watch?v=F-ahtojVl4M

Adjusting the motors power supply via this you should be able to get it in control ,

But before you even try this check there is no short circuit to your gate of the mosfet i have not tried it with a mostfet but same circuit with a bipolar shorting it to ground it will just make the motor run full speed so check you have not made a mistake before trying something else like this add on circuit .

[Steve Anderson]

Gents, in most cases you can ignore the (I adj x R2) term, it makes very little difference in practice. So it simply becomes:-

Vout = 1.25 x (1+ (R2/R1))

Use an E12 resistor for R2 instead of the E24 value of 240 Ohms, I generally use 220 Ohms, it's not critical at all. Plug that into the formula above.

Note that if you plan to use a metal chassis or other grounded item as a heatsink you'll need to insulate the heatsink tab of the LM317 as it's also the output of the device. The same applies to the negative version, the LM337 - but note the pinning is different.

Steve A.

[semuenter]

Hi Mhaznedhar:
Looking at the schematic, I think the motor driver works like this. The speed control pot adjusts the drive voltage to the gate of the MOSFET which drives the motor so that it spins the disk at approximately the speed you want. The NBTV frame rate of 12.5Hz means that you should adjust the pot so the disk spins at about 750 RPM. There is some inherent feedback to this speed control. As the motor spins faster, the motor's back EMF lowers the voltage on the speed control pot which lowers the gate voltage to slow the motor down. If something like frictional drag slows the motor down, the reduced back EMF raises the gate voltage to increase the motor speed.

The 4046 PLL uses the edge sensitive phase detector to add or subtract voltage from the MOSFET gate drive to speed up or slow down the motor around the operating point set by the speed control pot. When the opto fork pulses are aligned with the frame sync pulses, the output on pin 13 of the 4046 is high impedance which doesn't affect the motor speed. If the opto fork pulses are lagging behind the sync pulses, the 4046 outputs a train of positive pulses to raise the gate voltage of the MOSFET to drive the motor faster. Likewise, leading pulses from the opto fork cause the 4046 to output a train of negative pulses to slow the motor down.

To adjust the circuit, I would disconnect the 147K resistor from pin 13 of the 4046. You should then be able to use the speed control pot to adjust the free running motor speed anywhere between full blast and dead stop. Adjust the pot so the speed is set close to 750 RPM. Next, I would confirm that there is sufficient speed control from the 4046 to synchronize the disk. With the one lead of the 147K resistor still disconnected from pin 13 of the 4046, short this resistor lead to ground. This should slow the motor down a bit. Likewise, when you connect this lead to +12V the motor should speed up a bit. These slow and fast speeds should bracket the final desired speed of 750 RPM. If that works, reconnect the 147K resistor to pin 13 and you should be good to go. Even with no video input signal, the motor should be spinning.

I hope this helps.

Steve