Race car electronic circuit

Discussion in 'The Projects Forum' started by kayekit, Aug 7, 2014.

  1. kayekit

    Thread Starter New Member

    Aug 7, 2014
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    I am working with a Fab Lab to develop a workshop in which a toy car will be designed, 3d printed and raced with a built circuit.

    I need to design the electronic circuit, but it is not really an area of expertise for me.

    I have attached a circuit diagram for what i need but ill also describe it.

    [​IMG]


    I have a:

    2x 1.5v AAA batteries
    2x LED
    1x micro switch
    1x on on switch
    2x resistors
    1x motor - http://www.rapidonline.com/electrical-power/3v-12200-rpm-miniature-motor-37-0146


    • I plan to have the motor able to run on 2 settings high speed and low speed.
    • As the motor is 1.5v to 4.5v, i think this should be low- 1.6v and high- 3v
    • I want the led to run the same brightness on both high and low settings.
    • I can't for the life of me figure out the value of the resistors that i need to put in...

    Please help me figure out the resistors i need to get this working!!
    I do not have long before i need to order parts!

    It probably is not necessary, but if anyone knows a more elaborate but cheep way to do this then please let me know!
    It is for a workshop and i want them to have to think it through and take a wile to solder it together.
     
  2. mcgyvr

    AAC Fanatic!

    Oct 15, 2009
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  3. mcgyvr

    AAC Fanatic!

    Oct 15, 2009
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  4. kayekit

    Thread Starter New Member

    Aug 7, 2014
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    0
    Thanks for the responses, but none of them realy help me, I am using 2 aaa batterys in series.. just didn't explain it well as I thought my parts list would imply it.

    all I need it either 2 resistors to make the values I need across the motor, of a full circuit for a more complicated version of what I need to do.

    I know ohms law and how to use it, but for some reasons I can't get my multi meter to give me reliable readings... I also have no idea how to find the resistance of a motor, and the led resistances seem to change as the get warm.

    can anyone please just give me values that will work? Or an alternative circuit...
     
  5. djsfantasi

    AAC Fanatic!

    Apr 11, 2010
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    I believe mcgyvr has done just that. Although I'd duplicate the resistor/LED pair for your second light. What is wrong with his solution?
     
  6. mcgyvr

    AAC Fanatic!

    Oct 15, 2009
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    I don't know what the second LED is even for.. maybe "headlights" on the car.. Then yes just put another resistor/led in parallel with the other one.
     
  7. mcgyvr

    AAC Fanatic!

    Oct 15, 2009
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    LED's are diodes and not your typical resistive load.. They need to be fed a constant current which is what the resistor before the LED is doing. Without getting way over your head.. treat them like they don't have a resistance. They will take all the current available until they go up in smoke.
    The schematic I posted is the best way to accomplish your goal.
    Do you want it "more complicated" or something?
     
  8. ErnieM

    AAC Fanatic!

    Apr 24, 2011
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    Motors are even worse then LEDs in predicting the current, as (hopefully!) the majority of the current going thru the motor is being used to do useful work: make the car move.

    The only way I see to predict the reistors is to do some experiments. Full out at 3V is easy (no resistor), but the slow speed needs some work. Perhaps try connecting the motor to just one battery and see what current it draws, then use that value to compute a dropping resistor (R = 1.5V / current measured).

    That's a hard measurement to make, since to do it properly the car shold be in freely driving on it's motor.
     
    Last edited: Aug 8, 2014
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