Recent content by bob_s

  1. bob_s

    help with LCD power

    MP, Here is some more data that you might be interested in. It has to do with power dissipation of the KTP package I'm using. The one inch square pcb copper improves the power dissipation greatly if done correctly. Take a look at page 6, I'm using a pattern similar to #4. If the power...
  2. bob_s

    help with LCD power

    Sorry MP, I have to disagree with you. I know from experience that this regulator will not work well with less than 8v. This is why my previous circuit provided 8v for it to regulate properly. With any less the regulator was not consistent. Besides the problem was I needed 12v for my circuit...
  3. bob_s

    help with LCD power

    MP, Thanks for the reply. However the problem has been solved (except for the imperial/metric problem :)) The regulator had gone into oscillation and required some filtering. Bob
  4. bob_s

    help with LCD power

    audioguru, The temp is 126F which is about 52C which works out to 52C/28C = 1.85W. That's pretty close to what we were looking for. Sorry about the confusion with the temperature unit. Thanks again. Bob
  5. bob_s

    help with LCD power

    audioguru, Thanks, you were right. It did need both 0.33uf and 0.1uf cap. Brought the temp down to 126 and stable. It must have been oscillatint. Thanks also for correcting me in my calculation. I'll try to remember that for next time. Bob
  6. bob_s

    help with LCD power

    I've been trying to power an LCD module using a UA78M05CKTPR regulator (power-flex package) but the regulator gets very hot. I measured it with a temperature probe and its more than 155F which is too high. The max operating temp is 150F and the recommended operating temp is 125F. The LCD LED...
  7. bob_s

    isolated motor feedback circuit

    This seems to be an impossible task. Trying to adjust for the wide range of CTR, loss of LED integrity and temperature changes. I seems to me that tranfering the information is still best done digitally and then converting it to an analog signal or a timed digital signal on the other side. So...
  8. bob_s

    isolated motor feedback circuit

    Ok that's sounds great! But how do I make an adjustable gain op amp circuit? Bob
  9. bob_s

    isolated motor feedback circuit

    Audioguru, I've found from experience that the motor requires an inrush of full current for at least 10ms to get started. I'll have to wait for the spec sheet on the motor until monday. I've managed to free up an analog channel for the sensing circuit and I am planning on using it to check...
  10. bob_s

    isolated motor feedback circuit

    Ok. Then the output is not a digital signal but rather an averaged DC output. This is not exactly what I was looking for. I only have a digital input available. Could I expect a cleaner signal if the drive signal was 20khz (50us)? Bob
  11. bob_s

    isolated motor feedback circuit

    Wow! Thanks you guys for all the help your giving me. I have a question in regards to frequency. I am driving the fet at 50khz and somewhere between 25 and 100% duty. I am using a PS2501 optocoupler. What kind of delay can I expect from input pulse to opto output? Bob
  12. bob_s

    isolated motor feedback circuit

    Ante, I've been busy dealing with another issue and have not been able to try this circuit out yet. Could you explain the theory of this circuit to me? Why you chose the values? What was your train of thought? I would like to understand the theory better before using this circuit. Thanks
  13. bob_s

    isolated motor feedback circuit

    Ok. So how do I set up the circuit? I am not that familiar with opamp circuits. Bob
  14. bob_s

    isolated motor feedback circuit

    I wouldn't want to have more than 1V drop. Less is better.
  15. bob_s

    isolated motor feedback circuit

    I already have motion feedback. Having current feedback as well gives me a better indication of what is happening (limit switch, obstruction, etc..).
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