Circuit converter from 1A down 10mA

Discussion in 'General Electronics Chat' started by phucodientu06, Jun 29, 2010.

  1. phucodientu06

    Thread Starter New Member

    Nov 24, 2009
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    hello everybody!
    I want schematic circuit converter current from 1A down 10mA
    please help me!
    thank you very much
     
  2. Dx3

    Member

    Jun 19, 2010
    87
    7
    You aren't making sense. Please try again.
     
  3. phucodientu06

    Thread Starter New Member

    Nov 24, 2009
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    Hi Dx3!
    I have the schematic power 24V/1A but I don't known decrease current from 1A to 10mA ->24v/10mA
    please help me!

    sorry English bad!
     
  4. retched

    AAC Fanatic!

    Dec 5, 2009
    5,201
    312
    Amperage is taken from a power supply, not given.

    If the power supply is CAPABLE of 1a, but the circuit only DRAWS 10ma, then no problem.

    Are you talking about 24vDC or AC?

    To limit the current that is drawn, use a resistor. A 2.4k ohm resistor will limit the circuit to 10ma.

    Are you using it for an LED?
     
    Last edited: Jun 30, 2010
  5. kingdano

    Member

    Apr 14, 2010
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    19
    do you want a regulated 10 mA 24V supply?
     
  6. Dx3

    Member

    Jun 19, 2010
    87
    7
    Sorry to disagree but...

    E = I R
    24 = .01 (2400)

    2400 ohms will allow .01 amps to flow.
     
  7. retched

    AAC Fanatic!

    Dec 5, 2009
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    Jeezuz.. I was only off by a little.. ;) (It was early...thats the only reason I can give for that OBVIOUS flub.)

    I have corrected the original post.
     
  8. phucodientu06

    Thread Starter New Member

    Nov 24, 2009
    9
    0
    Hi everybody!
    Thank you helped me
    I have the schematic power 24VDC/1A
    I want converter current from 1A to 10mA to use for sensor supply
    I hope everybody help me
     
  9. retched

    AAC Fanatic!

    Dec 5, 2009
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    The sensor only takes what it needs.

    2400 ohms will limit the current to 10ma.
     
  10. Ron H

    AAC Fanatic!

    Apr 14, 2005
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    Yeah, but if the load draws 5mA, the voltage across the load will only be 12V.
    Resistors are poor current limiters unless the normal output is unloaded.
     
    Last edited: Jul 1, 2010
  11. retched

    AAC Fanatic!

    Dec 5, 2009
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    True, Im having a hard time conveying the fact that the op doesn't need to 'dial down' the amperage rating of the power supply. The component will take what it needs.
     
  12. buckysparks

    New Member

    Mar 30, 2010
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    can you post link, part number or datasheet of the sensor you would like to power?
     
  13. phucodientu06

    Thread Starter New Member

    Nov 24, 2009
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    Hi everybody!
    below is datasheet sensor PT100
    can try use typical applications of L334?
     
  14. retched

    AAC Fanatic!

    Dec 5, 2009
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    The recommended excitation is 1mA not 10mA.

    Do you have a schematic on how you are using the device? What you are attaching it to to READ the thermocouple?

    Are you connecting this to a meter or to a microcontroller?
     
  15. Ron H

    AAC Fanatic!

    Apr 14, 2005
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    Did you mean LM334?
     
  16. buckysparks

    New Member

    Mar 30, 2010
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  17. phucodientu06

    Thread Starter New Member

    Nov 24, 2009
    9
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    Hi everybody!
    thank everybody help me!
    I don't have a schematic on using the device
    If you have a schematic on using the device then can you give me,please
     
  18. Potato Pudding

    Well-Known Member

    Jun 11, 2010
    684
    92
    Instrumentation engineering required?

    Your part is a type of Thermistor normally used for measuring cyogenic temperatures. Planning to send a sattelite into outer space and wanting to check the temperatures in the chassis, or if you need to make sure that a supercomputer bathed in liquid nitrogen is not overheating then these devices might be a good start.

    Looking at the performance graphs it seems to have a fairly level temperature sensitivity above about 90K of something around .35ohms/kelvin.

    Look for thermistor temperature measurement circuits. It will be used as part of a bridge or divider, as input sensed by an instrumentation op amp. There should be a callibration trimpot on the Op amp. The comparison reference and Op amp might use an oven to provide temperature stability.

    An Adc will convert the op amps amplified level to a digital signal and a microprocessor will need to be programmed with the device performance curve, especially under around 110K. The microprocesssor should use a lookup table or curve equation approximations and give you a temperature measurement based on the

    That is basically it. I don't think that is the answer you wanted but any circuit I could draw would be very general. It would be all about the calibrations and the programming.

    You could cut out the ADC and Microprocessor if you were happy using a coil meter across the Op Amp output to measure voltage.
     
  19. Ron H

    AAC Fanatic!

    Apr 14, 2005
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    Phucodientu06, as Potato Pudding suggested, tell us what you are trying to do. Then maybe we can help you.
     
  20. phucodientu06

    Thread Starter New Member

    Nov 24, 2009
    9
    0
    Hi everybody!
    Thank everybody help me!
    everybody look at circuit below
     
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