lm555 circuit to keep keyboard awake

Discussion in 'The Projects Forum' started by 1964Kyle, Mar 5, 2012.

  1. 1964Kyle

    Thread Starter New Member

    Mar 5, 2012
    3
    0
    Hi everyone,
    I built a lm555 timer circuit (attached) and purchased an NTE R42 relay

    http://www.google.com/url?sa=t&rct=...Hn9rwZ&usg=AFQjCNG0jecBfDzPQvwNKJZXaBjjs3axYg

    to connect to it. The purpose of this is to simulate the push of a button on my casio keyboard that auto-powers off every 6 minutes, in order to keep it awake. Would anybody help me understand where in the circuit to hook the relay up to and which terminals on the relay to connect to where?
    thanks,
    Kyle
     
  2. JDT

    Well-Known Member

    Feb 12, 2009
    658
    85
    Connect pin 3 on the relay to pin 3 on the 555. Pin 5 on the relay to pin 1 of the 555 (ground).

    According to the relay data sheet, the relay has an internal diode. But if it did not you would need to connect a diode in parallel with the relay coil with the cathode to pin 3.

    The relay contacts are pins 1 and 7.
     
  3. 1964Kyle

    Thread Starter New Member

    Mar 5, 2012
    3
    0
    Thanks very much! It worked when I connected the positive and negative terminal of a battery to it, would it work if I used the negative terminal of the power source on the keyboard to power it as opposed to the ground?
    sincerely,
    Kyle
     
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