SPDT Relay Help Please

Discussion in 'General Electronics Chat' started by race-team420, May 19, 2010.

  1. race-team420

    Thread Starter New Member

    Nov 25, 2009
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    Hey, I am having troubles with the top spdt relay in this circuit. I am trying to use a NPN inductive proximity sensor as a limit switch to control an actuator. The current wiring for the sensor is n/c. Any help trying to figure this sensor/relay problem is trumendusly appreciated.
     
  2. retched

    AAC Fanatic!

    Dec 5, 2009
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    What problem are you having?

    What is NOT happening that you are expecting?
     
  3. race-team420

    Thread Starter New Member

    Nov 25, 2009
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    What I am trying to achieve is when the SPDT switch is closed the actuator will extent until it reachs the proximity sensor then the contacts in the sensor open causing the actuator to stop. Then by reterning the SPDT switch to the original position to retract the actuator.

    The problem that I am having is the top relay is shorting out when the sensors switch is closed (has not sensed object) and then the sensor switch opens (senses object) then the relay stops chattering.

    I have connected the switch, proximity sensor, and the first relay (top one) exactly as shown on a breadboard and used a multimeter to test the output of the realy (30) and operated as wanted. As soon as i put it into the rest of the circuit the first relay starts to chatter.
     
  4. retched

    AAC Fanatic!

    Dec 5, 2009
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    Chattering sound like you are using the wrong voltage on the relay. Are you sure your relay is a 12v coil?

    What are you powering your circuit with? How many volts? amps? Battery? wallwart?

    You may be dropping too much voltage after adding more components in the circuit. There may not be enough to operate the relay coil.

    This is DC I suppose?
     
  5. race-team420

    Thread Starter New Member

    Nov 25, 2009
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    Im using a 12v battery charger for testing purposes so should have no problem powering this circuit
     
  6. retched

    AAC Fanatic!

    Dec 5, 2009
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    Well, not a problem with amperage.. but a single diode would drop your voltage to 10.8 and you will have a problem. Many relays have diodes built in across the coil.

    Do these?

    And are the relays ALL 12v relays?
     
  7. race-team420

    Thread Starter New Member

    Nov 25, 2009
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    Yea I am using all the same relays (all 12V). Attahed is the relays that im using. By looking at the diargam on the relay it doesnt have a built in diode. Is there a way I should go abouts to test to see if there is a diode across the coil?
     
  8. retched

    AAC Fanatic!

    Dec 5, 2009
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    No, they should be fine. Do you have everything connected per the schematic? Are you sure the pin outs of the transistor are correct?

    It seems the transistor is switching erratically and cutting the ground to the top relay causing chatter.
     
  9. race-team420

    Thread Starter New Member

    Nov 25, 2009
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    Yea the circuit is connected exactly as shown.... And the pin outs of the transistor are correct. If I was to use a PNP transisor so there is a negative voltage from the collector to pin 85, would this maybe solve my problem?
     
  10. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    Battery chargers are not made to power circuits like that.

    You would at least need a large electrolytic capacitor between the charger's outputs to keep the voltage somewhat stable.
     
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