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  1. dorke

    TLC5940 + TIP120

    The value calculated is Max for that resistor. You can use the 2.2K you do have;)
  2. dorke

    Digital potentiometer ?'s

    It would be easier if you could provide the voltages related to the resistances. Can you measure that? With that info a very simple "scaling " voltage amplifier can be designed.
  3. dorke

    Any cable TV experts?

    Welcome to EP. It is possible that an outage can damage different devices in different ways even though they are connected to the same surge protector. The reason being not all devices are equally sensitive nor are they equally protected internally. Don't immediately blame the Comcast box...
  4. dorke

    Flashlight Project Help

    O.K fine replace the IR module with this :
  5. dorke

    Flashlight Project Help

    WEcome to EP. Do you already have the IR receiver or need to get one? It is a simple circuit. you can use a 555 to create a single shot "off pulse". The trigger may be the IR receiver itself.
  6. dorke

    Speaker wiring

    Are all satellite speakers the same physical size? If there are, you can combine them any way you like. The center speakers are different ,therefore combining them would require a cross-over .
  7. dorke

    Signal acquisition circuit

    1. What frequencies do you expect to pass through capacitor C3? 2. What about biasing U3A as you did with U2A ?
  8. dorke

    using op amps in my circuit?!

    Why do you want to use an op. amp as a protection diode?Protection from what? Just use a diode! Op. Amps are amplifiers, they are used in very many ways. They can even create a "perfect diode" . They are often used as sensing devices and as error amps etc. in protection circuits.
  9. dorke

    Speaker wiring

    It is ok to mix, but take care that you don't drive the speakers above there rated RMS wattage. What are the power ratings of the different speakers ,what are their sizes and frequency ranges ?
  10. dorke

    Signal acquisition circuit

    Welcome to EP. Can you please post a full diagram of the circuit.
  11. dorke

    using op amps in my circuit?!

    Welcome to EP. No op.amp is needed for the on/off action. the simplest would be to use a relay driven by a BJT or Mosfet
  12. dorke

    TLC5940 + TIP120

    Yes ,you are correct. There is no Beta or VBEsat on the ULN2803A datasheet. But we do have Iin required and Vi(on). For 350mA collector current we have: Iin=350uA ,but can use a larger value of 500μA from the table. Vi(on)=3V so Rpullup max=(5-3)/500μA=4000 ohm ==>use a 3.9k or 3.3K
  13. dorke

    search for a Varistor replacement compatibility

    Probably a Chinese part. The black one is much larger ,where did you get it's specs , can you post a link to it?
  14. dorke

    search for a Varistor replacement compatibility

    Welcome to EP. From what equipment have you pulled it out?
  15. dorke

    Circuit design help needed

    I think I have misunderstood your question. You already have the full design and wont to have it in single IC. That is possible in several ways , It depends on the design size, is it digital only(without the battery charging), and most of all the quantities you are talking about.
  16. dorke

    TLC5940 + TIP120

    The TIP220 is an overkill for driving 0.5A current and less. I think you con do much better with a small Mosfet(like the BS170) then with a Darlington. even a ULN2803A 8xDarlington array is better ,it will save you space and cost.. The resistor value calculation is simple for the Darlington...
  17. dorke

    TLC5940 + TIP120

    Well, 1.First thing is this roll is 5 Meters and needs a 12V DC supply to work. That 12v is an external power supply connected only to the LED chain,it will supply the power not the TLC5940. 2. Using it with the TIP120 is the wrong way to go ,it is "reversed logic " . You are losing the most...
  18. dorke

    How i can retrieve and change firmware?

    Welcome to EP. You can not find it since it is internal to the big IC ,and most probably secured locked. What is written on U2 ?
  19. dorke

    2x 12 volt dc power supplies.

    What kind of memory device holds the setting? If you had used a "permanent memory device" like a FLASH , it would have solved your problem.
  20. dorke

    Oscillator

    Yes you are correct , It is smaller by a factor of 10. My bad, I should have written ±0.4% (49.8 Hz to 50.2 Hz) But still ,It may cause a noticeable clock error ,which can be easily eliminated with a crystal osc. Here is an interesting line frequency accuracy monitoring site.
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