Questions about curve tracer

Discussion in 'General Electronics Chat' started by lokeycmos, Aug 23, 2012.

  1. lokeycmos

    Thread Starter Active Member

    Apr 3, 2009
    432
    7
    hello fellow enthusiasts! i have a couple questions about a curve tracer circuit also known as "octopus". i found a similar transformer but with different voltages i will be selecting via a rotory switch. the voltages are: 3, 4.5, 6, 9, and 12. the transformer i found is rated for 300ma. my question is about the current limiting resistor and pot. im trying to figure out what the maximum amount of current i should use so i can find the appropriate resistor/pot combination. with the schematic using my transformer with the 12 volt tap and a 560 ohm resistor its only putting out 21ma. im not sure if this is sufficient or not or if i should use a smaller resistor to put out a little more current.the reason im asking is because i want to make this device as general purpose, and universal as possible. any help or advice would be appreciated.
     
  2. ErnieM

    AAC Fanatic!

    Apr 24, 2011
    7,392
    1,606
    If every conceivable device you intend to test requires at most 21 mA then you are good to go. If not, then you should come up with a different approach.

    I wouldn't even think of using this scheme as there is no simple way to measure the current in any sort of calibrated way.
     
  3. lokeycmos

    Thread Starter Active Member

    Apr 3, 2009
    432
    7
    thats what im asking. what would be a reasonable amount of current. i can just change the value of the resistor. this 'octopus' schematic has been around for a very long time. from what ive read, its tried and tested.
     
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