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Recent content by sdmays

  1. sdmays

    Isolated 3.3V to 5V 100mA design

    1000V, 1500V, 1500VAC,...really depends on the UL classification you are shooting for. I've seen UL hipot voltages from 500VAC to over 2000VAC. For voltages greater than 50V, the hipot voltage is typically 1000VAC + 2 X Rated Voltage (again, depending on the Standard to which you are trying to...
  2. sdmays

    Isolated 3.3V to 5V 100mA design

    ItSmoked, "Perhaps the TV was up too high and you miss interpreted" what hrc said the circuit wants/needs :). hrc wants/needs a circuit that will give 5V @ 100mA out from a 3.3V input source and that will have up to 1500V isolation between input and output.
  3. sdmays

    light dimmer save energy?

    My dad has been a self taught electronics technician since he was a teenager. He was fixing transistor radios since he was 13. In fact both of my grandfathers were electronics fix-its, but nowhere near at the same level as my dad. A lot of people may not think much of him, but I have always...
  4. sdmays

    Isolated 3.3V to 5V 100mA design

    Yeah, like my second paragraph... Martek Power, C&D Technologies, International Power Sources, Unfortunately, my experience with one of these isolated DC-DC converter solutions resulted in about 100mV of noise riding on my 5V rail.
  5. sdmays

    light dimmer save energy?

    Sorta Back to the second original question loosely regarding the operation of light dimmers (some light dimmers, anyway); when I was a kid my dad told me the white knob controlled a variable capacitor. At the time I had no idea what the heck he was talking about, but now, I presume the variable...
  6. sdmays

    Isolated 3.3V to 5V 100mA design

    You could always design an inverter using only enough secondary turns on the output for 5V. Zetex has some App notes showing how to design an inverter using their medium power BJT's. Have you considered using PCB mounted isolated DC-DC power supplies? The isolation of such an animal (if you...
  7. sdmays

    Can portions of code for a PIC16F877 be used in a PIC12F683?

    ...and, of course, #define statements available in a header file or at the top of the code are always good for making code portability from micro to micro much more convenient - all you have to do is copy the code from micro to micro and update the #define statements...
  8. sdmays

    In-Circuit Testing of a Diode

    I would assume the actual current the DMM supplies varies from DMM to DMM, etc...In my experience, the diode voltage is usually slightly lower than what you might expect. A DMM I use at work supplies about 16uA if I remember correctly (measured it with a second DMM).
  9. sdmays

    In-Circuit Testing of a Diode

    To add to itsmoked's post, verifying the diode in the forward biased direction (should read some small voltage 0.7V to 2 or 3 volts) will be accurate as long as there are no components connected in parrallel to the diode (atypical case). Verifying the diode in the reversed biased direction...
  10. sdmays

    can multiple PWMs be controlled simultaneously by one PIC?

    If you are referring to using the actual PWM peripheral of a given PIC product, then you will be limited. If, instead, you use a timer interrupt and handle each PWM output individually within the ISR (for example), you should be able to have as many PWM channels as you have available I/O. In...
  11. sdmays

    Switch lifetime at a capacitive load

    nbucska, are you saying across the input of your circuit you have a 1,000uF cap and you are wondering if this capacitive load would affect the contact life with the surge current associated with DC input voltage source suddenly applied to an otherwise discharged cap? I suppose there is a chance...
  12. sdmays

    Hi-Pot Testing Control Panels

    Yes, that is true...back to the question regarding agency listing. During my days working for a custom automated test equipment outfit we never had any kind of agency listing and we never hipotted anything. Amongst many other things, our equipment was responsible for controlling a hi-pot...
  13. sdmays

    Hi-Pot Testing Control Panels

    Is this for some agency listing? If so, then you would just have to become familiar enough with the applicable standard, etc... The most common hi-potting scenario with which I am familiar is hi-potting between all the wires tied together and the control panels. If all the wires are tied...
  14. sdmays

    PWMing a PWM signal

    I think limiting the ON and OFF time of the BJT's is something to consider, but there are some additional circuits you can use to absorb the extra energy from the inductor. I have been told BJT's are more 'forgiving' when it comes to voltage spikes than MOSFETs, and, as you mentioned above, the...
  15. sdmays

    PWMing a PWM signal

    With a DC-DC converter, the current is, of course, maintained at a fairly constant value by the inductor. If the load is suddenly removed, the inductor current will have nowhere to go (therefore the inductor voltage climbs without bounds). You will have to carefully watch for the outcome of...
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