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  1. Arouse1973

    Need help powering up 2 circuits on same battery

    You still might get greater than 800mA for a split second and this could cause the issue. It would also explain why it works with the single battery. A 2R resistor is a 2 Ohm. It might be decoupling problems, but without having the circuit here I can't tell. Link to a 1R resistor buy a few from...
  2. Arouse1973

    SMPS's with cascoded opto feedback

    Yes I think we were talking about different things which is what led to confusion, we were both right by the look of it but on different characteristics. How do you split quote, I wasn't being Lazy just could work it out. lol Thanks Adam
  3. Arouse1973

    Need help powering up 2 circuits on same battery

    I think I know what it might be, the USB power supply in the photo has two labels on them which look like the maximum current. The large servos peak current for a fraction of a second could be over this. The protection circuit within the power supply could be over sensitive to transients like...
  4. Arouse1973

    SMPS's with cascoded opto feedback

    Hi Steve I think it's just dawned on me what you are on about. I think I have confused matters, I was comparing the switch off time of both which would cause issues also. Which one will be a rise time and one will be a fall time. I'll do some more work also. The circuit you plan is the same...
  5. Arouse1973

    SMPS's with cascoded opto feedback

    Steve and Kris Apologies if I have upset you both. that was never the intention. I did do the experiment and yes I understand about the rise and fall timings, it's the slowest of either that would be the issue. Please if you have time do the experiment and you will see. I need to be less...
  6. Arouse1973

    Need help powering up 2 circuits on same battery

    Ah so the PWM is 5 volts going into the servo powered from 3.6V. This might be an issue. Also looking at the data the data sheet for the LM386 it says its output is set at half supply at rest. So this would indicate it might be used for controlling the power to the servo not the PWM signal. Try...
  7. Arouse1973

    Building a Frequency/Sound Generator

    Interesting schematic. Can you please explain the RX circuit a little. What's the purpose of the 100K pull up? Are these piezos of mini speakers? With no sound on the input is the transistor on all the time from the pull up. Do you need a pull down on the base to make sure it's off. Am I correct...
  8. Arouse1973

    Need help powering up 2 circuits on same battery

    Make sure you are not powering the servo from a lower voltage level than the processor is running and also make sure when you do this you are within the max voltage of the servo . This could cause current to go into the lower voltage battery from the PWM pin. I don't know the insides of the...
  9. Arouse1973

    Building a Frequency/Sound Generator

    Ok thank, I didn't know to what extent the OPs knowledge was, I thought being on a PCB would be a bit easier than assembling something on Varo board. thanks Adam
  10. Arouse1973

    SMPS's with cascoded opto feedback

    Ok this will probably be my last post on this subject, thank Christ I here you cry, as I would like to answer some of the others in more detail. The original post was to ask the question of what we thought was the better switching arrangement for an opto coupler used as a feedback element in a...
  11. Arouse1973

    SMPS's with cascoded opto feedback

    Hi Kris So what are you saying, physically connected to the base. What about the input of an audio amplifier which has a coupling cap between the input and the base. This then has no direct connection to the base. No signal current will flow through the capacitor, only displacement...
  12. Arouse1973

    SMPS's with cascoded opto feedback

    The photo-transistor is a three junction device BCE an LED is a two junction device so they are different. If you were talking about a photodiode then I would agree with almost everything you have said It does not use a field effect of anything it uses light which is an EM wave not an E wave. A...
  13. Arouse1973

    SMPS's with cascoded opto feedback

    Hey eem2am I have done a test using a 3 terminal NPN photo transistor BFX43. Connected up as what we will call CE with 100K as load, no base resistor the rise time was 12.8ms. Connected up as what we will call CC the fall time was 8.4ms. So if we forget about what we call the configuration...
  14. Arouse1973

    Building a Frequency/Sound Generator

    I found this unit and I wonder if you could modify it. It is only rated at 40Khz but might work. http://www.ebay.co.uk/itm/like/181262894185?limghlpsr=true&lpid=102&device=c&adtype=pla&crdt=0&ff3=1&ff11=ICEP3.0.0&ff12=67&ff13=80&ff14=102 What your planning is total achievable but you might...
  15. Arouse1973

    Need help powering up 2 circuits on same battery

    Hello What servo are you using? Even small RC servos can take several hundred mA of current to start up. Could it be the circuit board / USB power supply or regulator can't supply enough power and is shutting down. What supply voltage are you using for the servo. I don't know what the audio...
  16. Arouse1973

    SMPS's with cascoded opto feedback

    Yes Steve I did mention the use of a resistor to speed up the device and you will then see a marked change in the response of the rise time between the two. Is phase shift correct how you have used it? Phase shift is a shift in time between two signals. Should this be signal inversion...
  17. Arouse1973

    What exactly Is voltage drop and how Is It detected?

    Kris What a very detailed explanation as always. But I thought you said you should use the term in series with the battery not across the battery. Thanks Adam :)
  18. Arouse1973

    Repairing power supply of Ogawa Reflexology

    Good point Steve 1.3R to 3.8R but if he was measuring on continuity setting then the meter would probably buzz down as that low a value. Which maybe why he said shorted? Thanks Adam
  19. Arouse1973

    SMPS's with cascoded opto feedback

    Hi Steve If you connect up an Opto coupler correctly I am pretty sure you can have common emitter or common collector. Well all of the manufacturers think you can. I am not saying the attached circuit is correct, the user was asking what is better common collector or common emitter. The base...
  20. Arouse1973

    Repairing power supply of Ogawa Reflexology

    It should be short circuit. it's a 250mA PTC fuse. Thanks Adam
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