h-bridge dc motor control circuit Reworked

[heathtech]

Reworked PCB

OK,

I reworked my Board with the changes proposed. For the sake of simplicity and minimal components, I went with the modified version of my original schematic (i.e. D flip flop in toggle mode) with Len and L. Chungs improvements rather than the more complicated flip flop using set and reset. I added Len's time delay and all of the RC filtering suggested by L. Chung as well as the use of the Schmitt trigger to couple several of the I/O's together. The circuit is working MUCH better without intermittent "skips" on the encoder. There does, however seem to be another problem that might be associated with the capacitor values or the capacitor series resistor values. I might need to speed up the charge/discharge rate by using smaller value resistors. This needs further testing to isolate the exact nature of the problem, so I will conduct tests and another completed schematic when I figure it out.

 

[eblc1388]

Tell us how long for the disc in the sensor slot to make one complete revolution.

 

[heathtech]

disc revolution

the speed of the motor is 1 revolution per 3 seconds or 20 rpm.

 

[eblc1388]

Re: disc revolution

the speed of the motor is 1 revolution per 3 seconds or 20 rpm.

Are you saying the present setup, if working correctly, the motor would change direction every 3 seconds?

If so, the RC timing is way too much. Reduce R6 from 10M to 4M7.

 

[heathtech]

reworked

I have revised and reworked the schematic....sorry it took so long to repost it. The circuit is working marvelously as I said before. Except, it takes a little while for it to line out. Meaning, it acts crazy the first 20-30 seconds, then it starts oscillating correctly. Could this be a problem in the delay circuit caps?

 

[heathtech]

Print

This file is a little big for the monitor, you may have to print it.

 

[eblc1388]

The circuit should work immediately upon power up. There is no timing components that would result in a 20-30 seconds delay.

One problem I saw is the power supply for the sensor. It was shown connected to +15V which if not a careless drawing error, would have already caused damage to the 40106 input already. Check this.

To troubleshoot your circuit, check +5V is healthy upon power up.

Measure the voltage of 40106 pin 12 & 10 immediately after power is applied to the whole circuit. If both voltage are high and remain high during the 30 second period, the motor would not turn.

If both are high, check whether Q and /Q levels are correct. Follow this line of reasoning. Report back any findings.

 

[ante]

Hi Heath,

I see you have done some improvements since we met in another forum. The problem now could be the small delay in the 78L05 which makes the 5V supply come on just a little later than the 15V. To eliminate this suspect try to feed the 78L05 from a battery so that the 5V is already present when the 15V is switched on.
:roll:

 

[heathtech]

AHA!

Ante, That makes a lot of sense. I'll try that! The problem goes away after several seconds, so it very well may be a delay issue on the 5v!