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ttl question

Discussion in 'General Electronics Discussion' started by flemingmike, Nov 10, 2012.

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  1. flemingmike

    flemingmike

    4
    0
    Nov 10, 2012
    hi all,
    so im trying to understand more about ttl. i have a chip that i am able to send a ttl signal to. im now trying to take that ttl signal and turn on 1 of 2 leds based on which signal it recieves.

    i have searched the internet for days and cannot seem to find any information to help me understand this process more.

    is anyone able to explain a little better to me?

    thanks!
     
  2. john monks

    john monks

    693
    1
    Mar 9, 2012
    Yes. You should do just fine using red LED's and a 100ohm or 270ohm resistor in series.
    What you need to do to be more precise is to look up the datasheet of the TTL chip and the LED you intend to use. A small red led typically runs at 1.6 volts @ 20ma and the TTL chip typically puts out about 4 volts in the high state. So you can calculate the resistor more precisely from there.
     
  3. flemingmike

    flemingmike

    4
    0
    Nov 10, 2012
    ok, maybe i should skip the led step then. i was going to use that as my first step.

    my final goal is to control a motor. both forward and reverse.
    i have a seperate power source that can run the motor, so i believe i just want to use the ttl signal to trigger 1 of 2 relays depending on the signal. once the relay is triggered, my motor will run off the second source of power.

    how would you recommend i go about translating the ttl signal to determine which relay to trigger?
     
  4. john monks

    john monks

    693
    1
    Mar 9, 2012
    Personally I would use relays capable of handling the load current of the motors and using CMOS power transistors to drive the coils of the relays. I might use IRF820's and I would use protection diodes across the coils of the relays. I might use two single pole double through relays.

    If you want you could post a schematic of what you're considering and I can see if it looks ok.
     
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