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Question about electrical components

  1. Jul 21, 2003 #1
    i was wondering if any one out their knew if their is a device which reduces amps and not voltage i need something that i can use to controll the amount of amps flowing.

    thanks everyone
  2. jcsd
  3. Jul 21, 2003 #2
    Maybe stick an op-amp in it?
  4. Jul 22, 2003 #3


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    zener diode
  5. Jul 22, 2003 #4
    As a former analog IC designer, I recommend the following quick and dirty cure-all.

    Put the current source in series with a resistor to ground. Take the voltage between these components and feed it into an inverting-configuration op-amp with unity gain. Follow this amplifier with a second inverting-configuration op-amp with unity gain. To modulate the attenuation of the current, change the value of the first resistor mentioned (the input resistor).

    Here is your controlling equation.

    Iout = (Rin / (Rin + R)) * In, where

    R = value of matched resistors used in first inverting-configuration op-amp, and

    Rin = input resistor.

    Last edited by a moderator: Jul 22, 2003
  6. Jul 22, 2003 #5


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    How many amps? How many volts? There may be a VERY simple way. I assume you are looking for a controllable current source as opposed to a voltage source. BTW, you really can't change one without changing the other. I don't know your expertise in electronics. The difference is whether the amperage is regulated to a constant value regardless of the type of load or if the voltage is regulated to a constant value regardless of the load. I'm rambling, I'll shut up now! Let me know the application though, it may be alot easier than you realize.
  7. Jul 22, 2003 #6
    volts and amps

    its a battery for a lawn mower its 12 volts with 9.9 amps
  8. Jul 22, 2003 #7


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    Still not sure what you are trying to do. Are you limiting charging current to the battery? Replacing the battery with something? What? Need more information before I can be of help to you.
  9. Jul 23, 2003 #8
    Re: volts and amps

    You should have mentioned this in the beginning. In this case, you don't need the fancy electronics I previously mentioned. You just need a current divider. You can make one by connecting your battery to two resistors connected in parallel. Ground the end of one resistor and feed the other end into your lawn mower. The same equation I previously gave you applies here. Just make sure that input resistance of your lawn mower is small compared to the resistance value of the resistors you use (< 10%).

  10. Jul 23, 2003 #9
    volts and amps

    im connecting the battery to something that runs on 12 volts dc and 500 milli amps and i dont want to break it because the battery has 9.9 amps so i want to reduce the amps, but the thing im hooking the battery up to can go up to 1 amp so i want to be abel to increase the amps when i need to by moving a dial or something
  11. Jul 23, 2003 #10


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    Ok, you are thoroughly confused on this. Electrical loads draw the amount of current required. A 12 volt source can have the capability to supply hundreds or thousands of amperes, but if a small load only requiring one amp is hooked to it nothing out of the ordinary happens. It will draw one amp even though the source is capable of much more. You would be wise to hook a 1 or 1.5 amp fuse in-line with whatever you are powering. BTW, what ARE you powering? Hope this helps.
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