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  1. BobK

    Help needed (Solar Lamp Circuit)

    The easiest way to make a constant current source is to use an LM317 or similar adjustable voltage regulator. See figure 26 in this datasheet. http://www.onsemi.com/pub_link/Collateral/LM317-D.PDF Bob
  2. BobK

    Water Detector Circuit W/Relay

    Yes, virtual caning for anyone who does not comply. Bob
  3. BobK

    transformer inductance 16000H??

    16000H sounds a little high. How did you measure it? The ratio is correct though: the square of the ratio of the windings. Bob
  4. BobK

    Is it safe to connect line level to lo Z mic jack on audio interface?

    If you have a line input, and you need 2 line inputs, just make the world's simplest mixer. 2 10K resistors, one side to each input signal the other side to the signal side of the input, all 3 grounds connected together. Bob
  5. BobK

    Water Detector Circuit W/Relay

    Except that this schematic was linked to and probably changed at the linked site. Bob
  6. BobK

    Sensor Based Tracking

    You have two optical (IR probably) sensors, with a wall between them. If the wall is pointing exactly at the beacon, both sensors see it, if it is a little off, only one sensor sees it, and you know which way to turn. If neither sees it, you rotate until one does see it. Bob
  7. BobK

    Low frequency Amplifer

    Not necessarily, the way it is shown, it will have negative feedback to stabilize the bias. Otherwise, an emitter resistor is needed. Edited to add: I don't think you get anything like 200mV out of an electret mic, more like 5mV. And an electret mic needs a power connection, if it is not...
  8. BobK

    Water Detector Circuit W/Relay

    You have apparently changed your diagram twice from when you first posted. You should not do this, as anyone coming back to the thread will be confused (at least I was). If you make a change, post it as a new circuit and link to it in the a new post, and tell us what you have done. You have...
  9. BobK

    Can I do this with 2 Mosfets, LEDs in series.

    Okay, now I cam confused, I looked back at your other thread, and it seems you want one or the other lit, not both, but then why in series? Please tell us what states you actually want. Bob
  10. BobK

    How to not hear Mylie Cyrus when I am playing guitar?

    I feel your pain. Bob
  11. BobK

    Can I do this with 2 Mosfets, LEDs in series.

    I think the question is how to control, from the micro whether 1 or 2 LEDs are on, with the LEDs in series. You can wire them in series, then wire an N channel MOSFET in parallel around the one nearest to ground. Turn that MOSFET on, and only 1 LED lights, off and both light. Caveat: if...
  12. BobK

    What component can alter electric flow if there is a voltage applied.

    Two MOSFETs will work. They can be found already wired together in a CMOS inverter. However, you better put some resistors in series with the LEDS. and if you use a single inverter, you would have to wire one LED to ground and the other to V+. Bob
  13. BobK

    MOSFET terminology

    I would not use a MOSFET in that application, and certainly not an P channel one. I would use an NPN bipolar transistor. The reason I would not use a MOSFET is because even the so called logic level ones typically require more than 3.3V on the gate. The reason I would not use a p-channel...
  14. BobK

    Low frequency Amplifer

    One transistor is unlikely to get you from an electret mic to a speaker. Show us your circuit. Bob
  15. BobK

    Lm317 help?

    If you 12V is regulated you could dispense with the regulator and use an additional resistor on each pot (between the pot and 12V) to drop the voltage across the pot to 10V. For a 10K pot, the resistor would be 2K. Bob
  16. BobK

    Lm317 help?

    One regulator is good for all four. Bob
  17. BobK

    programming help!!!!

    No. There should be no difference between those two statements. Are you sure you did not change something else? It would help if we could see the code that checks the ALM array and outputs to ports driving the LEDs. Bob
  18. BobK

    two week lightbulb

    It might be better then, to rig a switch so that the light comes on when the box is opened. Bob
  19. BobK

    Lm317 help?

    Yes, you can run 4 10K pots from a single 10V supply. The current is miminal: V = I R 10 = I * 10000 10/10000 = I = 1ma So 4ma total. This is a very small current. If you are using a 12V supply, you could use a low dropout 10V regulator. Here is one that would work...
  20. BobK

    Lm317 help?

    A potentiometer is a 3 terminal device. You connect one side to ground, and other to 10V and then the center terminal will vary from 0 to 10V as you turn the pot. To size the pot you have to know the impedance of the input. You can measure this by applying 10V and measuring the current in...
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