Ht12e/d input output logic question

Discussion in 'Wireless & RF Design' started by Archaeus, Sep 19, 2016.

  1. Archaeus

    Thread Starter New Member

    Sep 10, 2016
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    Good day. I'm currently in the soldering phase of an RF circuit designed to operate an l293d motor chip. On the breadboard I managed to get it to work, but after soldering (and checking for shorts) I am not getting proper high/low signals sent through the encoder/decoder from 2 2p2t switches to the motor driver chip. The only variable I can think of is that in soldering, I put the positive leads from the switches to the 9v rail instead of the 5v regulator chip like I did on the breadboard. The data sheet says this is still within operating range for the encoder. Would a difference in voltage sent to the encoder data pins effect the transmitter signal to the decoder and out to the motor chip? As far as I know, they just operate on logic high/low signal. Thanks for any help.

    There are a few errors in his designs, but it' configured like this
    http://www.instructables.com/id/homemade-rc-car/
     
  2. Archaeus

    Thread Starter New Member

    Sep 10, 2016
    12
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    I changed the switches from his design to output from the commons with alternating positive/negative in the closed positions for reversable polarity. Rest of schematics are identical.
     
  3. AlbertHall

    Well-Known Member

    Jun 4, 2014
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    Is the encoder supply pin also at 9V or is it still fed from 5V?
    If the pins have been connected to 9V but the chip VDD is at 5V this is not good and may damage the chip.
     
  4. Archaeus

    Thread Starter New Member

    Sep 10, 2016
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    Yeah I just read that on the data sheet... Allowing is vdd+0.3v. The chip is 5v regulated. I didnt run the switches for very long, but I know it doesn't take much. Might have fried the protective diodes. Any ideas to test it other than taking voltage readings at the motor chip inputs to see if high/low is alternating? Thanks for the reply.
     
  5. AlbertHall

    Well-Known Member

    Jun 4, 2014
    1,893
    375
    Connect the pins to the correct voltage and see what happens at the output pin of the encoder. If you measure the voltage there then it should rise from zero to something like 2.5V.
     
  6. Archaeus

    Thread Starter New Member

    Sep 10, 2016
    12
    0
    Thanks friend. Appreciate the help.
     
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