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  1. BobK

    thermostat circuit counter

    I did some more research and I find that thermostat circuits, at least in the US, work on 24VAC as I guessed. If this is what you have, search for "24VAC hour meter" and "24VAC counter" to find appropriate ones. With these you would just wire the two terminals to the R and W wires of your...
  2. BobK

    thermostat circuit counter

    The counter that I pointed to, one of many available, has a 10V to 80V DC input. Do you know what voltage is on the two wires from the thermostat when it is on and when it is off? Also AC or DC. If have a funny feeling that they are 24V AC. If so a simple circuit would deal with it or you...
  3. BobK

    My amplifier hums whenever no input is connected

    If C7/C8 and C9/C10 are the only filtering on the + and - 24V supplies, then they need to be a lot bigger. Can you show the power supply circuit? Bob
  4. BobK

    thermostat circuit counter

    Hi brad, and welcome to the forum. What you are looking for is a run time meter, or hour meter. Here is an example of an inexpensive one: http://www.zoro.com/i/G1689721/?utm_source=google_shopping&utm_medium=cpc&utm_campaign=Google_Shopping_Feed&kpid=G1689721&gclid=CNKB0Kma68ECFcJQ7AodfUYAjg Bob
  5. BobK

    Replacing Ni-Cd with Ni-MH in solar light?

    No it is the cylindrical kind. I guess LiFePO4 may be the correct designation for them. Bob
  6. BobK

    Faulty Laptop Charger - 0.7mm

    Lifting the trace is likely to happen when you remove the old one. Do you have a hot air soldering tool? These are much better for removing surface mount components. Bob
  7. BobK

    question about gain of an op-amp

    Those resistors are too low, they would load the output too much. Multiply them by 10. Bob
  8. BobK

    Replacing Ni-Cd with Ni-MH in solar light?

    I guess we got the luxury model, we have some that have a LiPo. They work better than the previous ones we had. Though I have had to repair 2 of the 4 (one failed resistor, one bad solder connection) Bob
  9. BobK

    Intel Galileo 1 unidentified component half-broken

    Here are links to the two crystals used: ECS ECS-250-18-23A-EN-TR http://www.mouser.com/ds/2/122/ecx-64a_ecx-64cr-6514.pdf Epson FC-255 32.7680K-A0 http://www.eea.epson.com/portal/pls/portal/docs/1/1697497.PDF The sizes are different, so you should be able to tell which it is by...
  10. BobK

    help eliminating oscillation in circuit

    That amplifier has a gain of 500 (50K / 100). The gain margin listed for that amplifier is 29 dB. I am not at all sure what gain margin means, but I think it means that using negative feedback to get more than 29 dB of gain make the amplifier unstable. Your gain of 500 is 54 dB. So, the...
  11. BobK

    Do I need to put resistors between Arduino outputs and H-bridge + some theory

    Both the high input current and the low input current could be important. But, you are not likely to find a logic input that requires anything near the current that your Arduino can put out. Digital signals are 1 or 0 if they are within pre-defined boundaries defined by the logic family. For...
  12. BobK

    Replacing Ni-Cd with Ni-MH in solar light?

    The voltage and charging characteristics of NiCd and NiMH are quite similar. Solar lights are using trickle charging, so using NiMH should work just fine. Bob
  13. BobK

    Using all four amplifiers in an LM324

    If you want low voltage (5V or less) opamps that operate from rail to rail, Microchip has a great selection. Bob
  14. BobK

    Learning Electronics, need help with my noob circuit

    A Joule thief on steroids! Bob
  15. BobK

    Motor question

    Ah, found an image. It has a board with a connector with 24V 24V GND GND F/R ACC DEC MFG I would interpret F/R as forward / reverse ACC as accelerate DEC as decelerate MFG no idea, but probably speed feedback. I would guess it is a a brushless DC motor with integrated controller. Bob
  16. BobK

    Lego Block Detection on Baseplate for Musical Project

    I think the camera based approach would be much more interesting. No need for special LEGOs at all. Bob
  17. BobK

    MOSFET

    Yes, I am referring to your second example, which is pretty much the universally used symbol now. The distinction of the arrow being on the source or body is not one that I knew about, I only know that for an NPN transistor the arrows points out and for the NMOS transistor it points in, which...
  18. BobK

    Variac .

    Actually I prefer fuzzy devices because you are less likely to cut your finger on them when installing them. Bob
  19. BobK

    MOSFET

    No only that, but they put the arrows on the source in the opposite direction that they are on a BJT emiiter. Whoever designed the MOSFET terminology and symbols was evil. Bob
  20. BobK

    Using all four amplifiers in an LM324

    The 5mV figure I have is for the typical one with the FET amp. You need a gain of about 200 to get it to line level. Bob
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