555, dpdt question

Discussion in 'The Projects Forum' started by Tcg178, Aug 20, 2009.

  1. Tcg178

    Thread Starter Member

    Aug 15, 2009
    15
    0
    I posted once before and got great help, you guys rock. I'm still playing with the same project. I'm using a 555 wired according to the diagram A (Below) and using it with a Dpdt relay to try to control an actuator to go back and forth, up and down. So far, no luck. I think i am making a mistake in the relay wiring...if anyone can give me some more pointers i'd greatly appreciate it! Please excuse my bad diagram also, im not very good at putting them together.
     
  2. Tcg178

    Thread Starter Member

    Aug 15, 2009
    15
    0
    oh and R1 R2 are 10k, C1 is 100uf (35v). The relay is 12vdc 5a max 24vdc. The power supply is 3vdc 200ma
     
  3. pilko

    Active Member

    Dec 8, 2008
    213
    20
    The output and ground should be connected to the relay coil. Looks like the top two terminals are the coil . Verify by checking the ohms.
     
  4. jj_alukkas

    Well-Known Member

    Jan 8, 2009
    751
    5
    Disconnect the output pin 3 from the relay terminals and connect it to one end of the relay coil on the top. Then connect a wire from Vcc (+) to where you just disconnected the output pin 3 and give it to that position.
    Now take a connection from ground and give it to the other relay terminal. It will then work. To make your 555 safe, add a back EMF protection diode across the relay coils such that you wont short them.

    If it still doesnt work, you will need a driver transistor to drive the relay as it will be drawing larger currents than what 555 can handle.

    This ckt is similar, change the resistance values for what you need.

    [​IMG]
     
  5. Tcg178

    Thread Starter Member

    Aug 15, 2009
    15
    0
    Ok. I'll give that a try and reply with the results
     
    Last edited: Aug 20, 2009
  6. Tcg178

    Thread Starter Member

    Aug 15, 2009
    15
    0
    I now am having problems with the relay. The 555 circuit works well and i can even hear the relay clicking back and forth. I have tried as many combinations with the relay i can think of and i am still not getting any results. Once the power is applied the relay simply just clicks open and does not toggle. Any ideas?
     
  7. jj_alukkas

    Well-Known Member

    Jan 8, 2009
    751
    5
    If the relay is clicking back and forth exactly according to your timing, the the connection mistake is on the other part of the relay where you connected your motor.

    See this. I think you didnt understand how a relay works. And do the connections as I have drawn

    [​IMG]
     
  8. Tcg178

    Thread Starter Member

    Aug 15, 2009
    15
    0
    Ok, your diagram about the relay functions cleared up a lot of questions for me. So thank you. On the relay i am using the NC and NO positions are reversed (in a different position) so i thought this might be the problem. I dont know if this has a large impact on the way the relay will function or react. I wired it according to the diagram i posted. Now when i activate the circuit the actuator stays fully on in 1 position. Everyone has been really helpful so i really appreciate anyone taking the time to help with this project.
     
  9. Tcg178

    Thread Starter Member

    Aug 15, 2009
    15
    0
    I forgot to post the diagram, so here it is
     
  10. Heavydoody

    Active Member

    Jul 31, 2009
    140
    11
    The relay coil has no ground in this drawing and will thus be unable to energize (this is the pin which has no wire on it). I assume you have noticed that your relay no longer clicks? This is why your actuator remains in the direction wired to your normally closed pins.
     
  11. Heavydoody

    Active Member

    Jul 31, 2009
    140
    11
    Also, you should really add this suppression diode as recommended by JJ_alukkas. Hook the silver band up to the positive pin of the relay coil and the black side to the ground side of the coil.
     
  12. Tcg178

    Thread Starter Member

    Aug 15, 2009
    15
    0
    I added the Emf protection diode as is suggested and also added the ground wire to the other relay coil. Still getting the same reaction as before. Is it possible that the circuit isn't working because i have already damaged the relay?
     
  13. Tcg178

    Thread Starter Member

    Aug 15, 2009
    15
    0
    When i disconnect the circuit from the actuator, i can hear the relay clicking now. I'm confused though as to why adding the actuator would cause the relay to no longer function?
     
  14. CDRIVE

    Senior Member

    Jul 1, 2008
    2,223
    99
    Did anyone happen to catch what he said in his first post?

    Is your power supply really 3V or was that a typo? I'm also curious about what your actuator is and what its voltage and current requirements are. If it's a typical solenoid they are not a bipolarity device. IE, typical solenoids don't change direction of pull or push by changing its polarity. Also, if it's a 3V solenoid ( low R hi I ) I would guess that it sucks current like a shopvac sucks air. On the other hand I may be ( CYA ) misunderstanding your circuit function.;)

    FYI, I took this direction of probable cause because what you're describing sounds like a power supply that's being sucked down when you connect your actuator.
     
    Last edited: Aug 22, 2009
  15. Tcg178

    Thread Starter Member

    Aug 15, 2009
    15
    0
    I moved up now to a 9v 1.5a supply and it fixed the relay problem! The circuit is working perfectly. Now on to the next problem. lol

    The actuator motor will reverse when polarity is reversed. I need to come up with a way to give one stroke up and one stroke down. Meaning i need a way to give one pulse +/- and another -/+. I have another 555 and many other relays available. Any ideas?
     
  16. Heavydoody

    Active Member

    Jul 31, 2009
    140
    11
    I did notice that, but since the original thread specified a 12VDC source I suspected it was a typo.

    Also specified in the original thread as an automotive door lock actuator, which is basically a rack-and-pinion driven by a motor.

    Operating a 12 volt motor and relay off of three volts tends to do that. Of course, not grounding the relay coil conserves power. :D
     
  17. jj_alukkas

    Well-Known Member

    Jan 8, 2009
    751
    5
    Sorry, didn't get what you meant. The circuit described by you will give +/- during the time between 2 relay clicks and -/+ during the next. SO if you had connected a motor, it will rotate CW and CCW alternatively. Please explain what you need.
     
  18. CDRIVE

    Senior Member

    Jul 1, 2008
    2,223
    99
    A classic example of why not to split a thread.


    Funny!:D
     
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