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  1. BobK

    Converting an electronic cooling fan to battery operated

    That looks like a pretty standard size cooling fan. Most of that type of fan run off DC, either 5V or 12V. Is there any reason you have to use that particualar fan to run off batteries when there are fans much more suitable for that use? Bob
  2. BobK

    2 Portable generators

    You do realize that the neutral and ground wires are connected together at the distribution panel. Bob
  3. BobK

    SCR series regulator

    If you are trying to get a regulated 48V a triac circiut is not going to do it. It will be much worse than an SMPS which starts with DC and uses a high frequency so the required inductors and capaciitors can be small. At 60 Hz, you would need at least 10000 ufd to smooth it. That is not...
  4. BobK

    Calculate Op Amp Gain

    The confusion is about whether we are talking about the gain of the opamp as being the gain from the input to the output pin of the opamp, or the gain of the entire circuit, which is from the input pin to the junction of R2 and R3. The two are obviously different. Bon
  5. BobK

    Lithium Ion 18650 cell capacity

    Discharge rate also affects the capacity. The stated capacity might actually be achieved only at a lower discharge rate. Bob
  6. BobK

    Digital potentiometer vs switch

    Switch: low cost, high power handling, operated by a finger. Digital potentiometer: High cost, low power, operated by a microcontroller. Pull up resistor: Very low cost. Needs nothing to operate it. What you propose is about like building a maglev train to carry you next door. Bob
  7. BobK

    Solar panels with 100W led

    Since you two are talking past each other... AG - He is shining his 100W LED on the solar panel and complaining that it produces only 6V. NVZN - The LED may be bright, but it is unlikely as bright as the noon sun. Bob
  8. BobK

    SCR series regulator

    Agree. If you are going to use an isolation transformer, why not a stepdown instead? Bob
  9. BobK

    Boost AC circuit

    Here is my calculation. 1/3 HP = 250 Watts 1/2 HP = 375Watts Total power = 625W Total current = 625 / 220 = 2.84A 1881 x 2 = 3762 feet. 12 AWG wire is 1.588 Ohms / 1000 ft R = 3.762 x 1.588 = 5.97 Ohms Voltage drop = 5.97 x 2.84 = 16.95 V Of course the motors are actually pulling more...
  10. BobK

    How to interface condenser MIC output converted to Infrared transmitter output

    That is the easy part. The same microcontroller/ computer that recgnized the spoken command can easily send the command sequencie over IR. Bob
  11. BobK

    Speakers clipping w/ TDA7492P

    If it is distorting only at very high loudness, then, by definition, the input is too high. Are you getting adequate loudness before it distorts? If so, 2 resisors for each channel will fix the problem. Bob
  12. BobK

    What transformer is this?

    What is the input to it? Bob
  13. BobK

    DC converter

    Or better yet, 8 or 12 with groups of 4 in series. Bob
  14. BobK

    What transformer is this?

    I have no idea either. What is it used for? Bob
  15. BobK

    Two-way 12V motor control using arduino and darlington?

    If you do go the way of a discrete H-bridge, be aware that you will also need a level translator for each of the high-side switches (PNPs). The complete circuit will require 6 transistors. Bob
  16. BobK

    How to interface condenser MIC output converted to Infrared transmitter output

    You are not making any sense. First you say only the transmitter is modified, then you talk about putting the voice on the IR LED. An unmodified receiver is not going to respond to voice over the IR input. I think what you are trying to do is this: 1. You have an existing remote control...
  17. BobK

    Two-way 12V motor control using arduino and darlington?

    Well, you can make an H bridge from 4 transistors. You need 2 NPN and 2 PNP or 2 N-channel and 2 P-channel. Bob
  18. BobK

    How to control 5v Relay with 2 way switch

    You can use a DPDT switch to exchange the NO and NC outputs of the relay before going to the lights. There may be a simpler solution, but this is what came to mind. Bob
  19. BobK

    DC converter

    3KW at 12V is 250A. This is not feasible. Try using 10 of those batteries. Bob
  20. BobK

    Speakers clipping w/ TDA7492P

    Are the speakers in a closed box when you are seeing this distortion? As AK said, the speakers themselves will hit their end of their range motion and distort if they are not properly loaded by an enclosure (without even producing that much sound). If the problem is simply that the input...
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