Electronics and circuitry

Discussion in 'FAQs' started by Woodie, Apr 23, 2001.

  1. Woodie

    Woodie Active Member

    Andy, (and others that may be able to help)
    I notice you seem pretty clued up on electronics. capacitors etc and especially the 555 timer chip. I've put together a PWM controller kit that drive the engines fine. However a reason why I did this is to get a few more electonic facilities for the engines (before moving to DCC) which I understands works using PWM at the individual engine level, rather than the layout itself.

    Problem:
    I also put together a kit that generates realistic deisel sound and the module sits inside the engine. It uses the back EMF voltage generated by the motor to determine the sound level (ie idle, revving etc) The circuit looks for the back EMF feeback AC voltage generated by the motor, in between the DC pulses generated by the PWM controller. However, I cannot seem to get it to work. The sound is fine however does not alter when the PWM controller is varied. It does not make any difference whether the engine is on the track or not. I believe there may be a problem with the controller as there is a diode that filters the back EMF out so as not to damage the controller. Could this also effect the sound generator so it would not pick up the back EMF? Mulit meter testing does detect back EMF AC voltage across the tracks.
    I can post the circuit diagrams if that would assist, but not sure how to include them in a post. Any ideas?

    Thanks,

    TOOT!
  2. kf4jqd

    kf4jqd Active Member

    Woodie:

    This is a big problem with digital electronics and A.C. There is a couple of solutions to try.

    1.Make sure the brushes on the motor are clean. If they are not. They can cause arching. And the sound module will pick it up.

    2."Dirt" A.C. Actually all A.C. is considered "dirty". To fix this try an electrolic capasitor across the power terminals. Make sure the voltage rating of the capasitor is higher the the highest voltage sent to the loco. Make sure the polatity is correct. If these are not met, BOOOOOM!!! The capasitor will explode! [​IMG]

    3.Try some diodes or bridge rectifiers. This will help too. [​IMG]

    Woodie, I think the best solution is using a bridge rectifer at the AC. On the output of the rectifer is DC. Put the capasitor there. This should solve your problem. [​IMG]

    Andy

    Good luck
  3. Woodie

    Woodie Active Member

    Andy,

    I notice you just replied. Kewl. Thanks. From my limited electronics knowledge, I think there is a bridge rectifier in the circuit. Can I email you the circuit diagrams for your opinion please? Would be good. I'd post them in here but not sure how to do it yet. Hope you can help.

    Thanks,

    TOOT!
  4. Woodie

    Woodie Active Member

    Andy, When you say a capacitor across the terminals, do you mean the controller/track/engine. suppose it makes no difference if it is any of these where it is placed, however the enigne I used does not have one, but a new Lima engine I have does a a capacitor across the motor terminals. I have not tried the circuit with this newer engine. The engine I was using was realitively new. (2 months old).
    Thanks,

    TOOT!
  5. kf4jqd

    kf4jqd Active Member

    Woodie:

    Give me your email address. I will send you a simple diagram.

    Andy
    kf4jqd@pcpros.net

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