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  1. BobK

    ELECTROMAGNETS

    Do you understand how an electric motor works? It uses electromagets and sometimes permanaent magnets to provide the force. But the magnets must be turned on and off in synchronization with the movement, otherwise, when they hit the closest approach they will just stop. You seem to want to...
  2. BobK

    Newbie question

    Think about it. What would cause the capacitor to change from charging to discharging? Since there is no change in the circuit, there is nothing to trigger that change. You need at least a switch to initiate that change. If the switch could be controlled electronically, i.e. charge until...
  3. BobK

    Connecting small wind turbines in series possible?

    Don't bother with summing op amps, they are for signals, nor for power. I am not sure what GG is thinking in mentioning them. Bob
  4. BobK

    Is this possible?

    He is saying that all you have to do is: 1. Obtain funding for your project 2. Design it. 3. Build it. 4. Accomplish changes to the laws to allow flying cars. Bob
  5. BobK

    Light detection

    An IR detector, the type used in remotes (38KHz) could be built into the flashlight such that it turns off if it sees the IR signal. Then an IR emitter could be put in the area where the flashlight should turn off. Bob
  6. BobK

    What can i do with Quartz Crystals?

    I see a book coming "101 Uses for a Dead Crystal" Bob
  7. BobK

    What can i do with Quartz Crystals?

    Yes, but building a rail gun to launch the crystal would be more fun. Bob
  8. BobK

    understanding Ferrite Rings

    I still think you should try my suggestion from post 11. I would like to know if it works! Bob
  9. BobK

    Transistor Resistor Help please

    That transistor is overkill for lighting a few LEDs, but you could use it anyway. This is a darlington transistor, which has two transistors connected together in a way to achieve very high gain. To determine the base resistor accurately, you would need to know the gain (beta) of the...
  10. BobK

    Relay configure trouble

    Either I, or everyone else on this thread is misunderstaning the question. As I understand it, He has a 12V source which is powering the coil of a relay (no Idea what the relay is connected to). He has no other source of 12V. He want to run a motor from that 12V source whenever the relay is...
  11. BobK

    Using transistors to control an AC voltage

    A transistor is not good for controlling AC. Use a triac. And if the AC is mains voltage, use an opto-isolated triac. Or just get a dimmer switch for a couple of bucks, which is the same thing. Bob
  12. BobK

    What can i do with Quartz Crystals?

    Electro123, Do you ever read any of the responses? Bob
  13. BobK

    Protection from reverse polarity

    You really don't understand what I am saying. The situation right now. The OP has + and - power supply leads that he is not sure how to connect to the PCB. The sitution after inserting a bridge on the power supply: The OP has + and - power supply leads that he is not sure how to connect...
  14. BobK

    Lead Compensator Design

    Have you noticed that there is a homework help sub-forum? Bob
  15. BobK

    AV Receiver help

    Umm. You don't connect an input from the receiver to a speaker. That would be an output. I think you better look at it again. Bob
  16. BobK

    Protection from reverse polarity

    Yes, and that is a fine practice. If there was a bridge designed into the PCB then he could not connect it incorrectly. But the problem the OP is asking about is how he can protect against connecting the wrong leads to the PCB. If he can connect the wrong leads coming out of the power...
  17. BobK

    24VAC power supply question about VA spec

    The fact that they specified a power supply to less than a specified wattage is totally bizarre. Any normal circuit will draw as much power as it needs, and therefore you would NEVER specify that a power supply must supply less than specific wattage, only that it would supply greater or equal...
  18. BobK

    Back EMF in Solenoid

    What makes do you think that? Bob
  19. BobK

    Bush Tv (CRT) having horizontal lines on the top half of TV

    I would say it has a vertical sync problem. Not that that is going to help any. Bob
  20. BobK

    Protection from reverse polarity

    How does that help at all? Right now, has a positive lead and ground lead that he needs to connect to the pcb correctly. After he builds a bridge, he has a positive and ground lead that he has to connect to the pcb correctly. Nothing has changed except that more possible mistakes are...
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