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  1. BobK

    Op Amp for speaker circuit

    Here is a circuit that will give you 1/4 W output to an 8 Ohm speaker from a 9V battery, using an LM324, 2N2222, 2N2907, and a few other components. Gain is set by the ratio of R8 to R4 (in this case 10). Showing input of 0.2V p-p 1000Hz sine wave with 2.0V p-p output. If you use 2 9V...
  2. BobK

    Op Amp for speaker circuit

    The LM324 is not capable of driving a speaker. Do you have and NPN and PNP transistors? You can add on a push-pull output stage to the LM324 to power a speaker at < 1Watt pretty easily. Bob
  3. BobK

    Reading data from ADC to PC through USB

    Then the ready-made hardware would be perfect for you. Bob
  4. BobK

    PV Cell application with an iverter op-amp.

    And do paint the room matte black so that it is not confused by reflected light. Bob
  5. BobK

    Photo-resist PCB help

    Success! It was NOT a problem with exposure, I did that exactly the same. I looks like it was a combination of underdevelopment, too little brushing and spent ferric chloride solution. I developed it to the point where I did last time, and I noticed that there was still a green tint over much...
  6. BobK

    Reading data from ADC to PC through USB

    Or, you can just buy a data acquisition product that does exactly what you want and includes PC side software for $29. http://www.dataq.com/products/startkit/di145.html?gclid=CLm26PyAsb4CFQEdOgodPGYAgA I have no experience with this product, it just happened to show up in my google search...
  7. BobK

    Toggle switch without the switch?

    Here is a simple circuit that does what I described. http://www.learningelectronics.net/circuits/momentary-switch-teamed-with-latching_03.html Bob
  8. BobK

    Toggle switch without the switch?

    Actually, I think this is what he wants: A momentary contact switch is used to alternate power from one device to another. I.e. push button and device 1 goes on device 2 goes off. Push again and device 2 goes on and device 1 goes off. I remember seeing a little board that drives a relay on...
  9. BobK

    microwave oven motor makes noise after couple hour of use

    It would not be surprising if a motor out of a microwave oven was not designed for continuous use. Bob
  10. BobK

    Do a variable AC, high-amp power supply exists?

    Yep, that was my point with my comment about having a lot of money. The requirements, as stated, were ridiculous. Bob
  11. BobK

    Laser Driver Troubleshooting?

    The white and orange appear to be plugged into the same node. Bob
  12. BobK

    Fiding "Voltage to Current" Converter

    This looks useful: http://www.linear.com/solutions/4475 Bob
  13. BobK

    Do a variable AC, high-amp power supply exists?

    Steve, These will not do. Perhaps you missed this line in the OP? - Change the output frequency ex. 10 - 100> Mhz. Bob
  14. BobK

    Transformer Voltage Amplifier

    You are right. I thought these were available, but they all seem to be controlled by a pot. Most likely, you could remove the pot and feed the control voltage to where the wiper was connected. This would work if the other two terminals of the pot are just connected to V+ and gnd. Bob
  15. BobK

    How do I build a Metal Detector?

    That was my point, the schematic in the OP shows 10MH. Bob
  16. BobK

    supplying AMC7135 with 12v

    You would be better off with a driver intended to take 12V. A boost driver would allow you to run the LEDs in series. You cannot run them in parallel and expect them to share current equally. In fact, they will not, and the one that takes the most will get hotter, which causes it to take more...
  17. BobK

    How do I build a Metal Detector?

    What kind of inductor are you using? If it has a ferrous core, then I don't see how it can work well as a metal detector. Metal detectors normally would use an air core inductor so that any metal nearby would disturb the magnetic field and drastically change the inductance. If you are using a...
  18. BobK

    Help for power regulation

    Sorry, but 25KA power supplies are out of my league. I am surprised that you are asking this in a hobbyist forum, since you clearly must be a very high-powered (pun intended) professional to be working with this kind of current. Bob
  19. BobK

    DC fan from car to run on battery power

    You would use the same kind of fuse that came with the fan. Bob
  20. BobK

    DC fan from car to run on battery power

    1. Correct. 2. Correct. In series the voltage adds. 10 1.2V batteries in series will give you 12V. 3. Wrong. The fuse is there to protect against a short, not overvoltage. 4. Yes, but be aware, batteries in series, the maH ratings do not add. I.e. the 10 1.2V batteries in series have the...
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