Relay in place of motor

Discussion in 'General Electronics Chat' started by TexAvery, Nov 4, 2009.

  1. TexAvery

    Thread Starter Member

    Oct 7, 2009
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    Hi all!
    I am using/recycling a 555 timer circuit.
    This time it will drive a electronic relay. Relay data sheet link http://timwalker.cc/relay.pdf
    What components can I remove/not needed?
    My guess is IRF510 C4 & C5.
    [​IMG]
     
  2. SgtWookie

    Expert

    Jul 17, 2007
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    What are you planning on driving with the electronic relay?

    Do you want the timer to free-run (astable) or to be triggered by some kind of event?

    What is your desired on and off times?
     
  3. TexAvery

    Thread Starter Member

    Oct 7, 2009
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    The dual relay will be switching 6vac and 230vac. 100ma. each
    The PIR motion sensor triggers the 555 , which works fine now.
     
  4. SgtWookie

    Expert

    Jul 17, 2007
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    The electronic relay is rated for up to 200v @ 120mA.
    230VAC has a peak to peak voltage of about 326V.
    The 6v is OK, but the 230vac is not. You will exceed the ratings of the device.
     
  5. TexAvery

    Thread Starter Member

    Oct 7, 2009
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    Well then I will only switch the 6vac.
     
  6. SgtWookie

    Expert

    Jul 17, 2007
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    OK then.
    Your relay will take the place of the IRF510.
    R5 will need to be changed.
    The 555's high output is basically Vcc-1.3v under light load.
    The Vf of the LED in the switch averages 1.26v.
    That leaves 2.44v through which you want about 30mA current.

    An 82 Ohm resistor will work, if you are sourcing current to the diode in the relay.
    2.44v/82 Ohms = 29.7mA

    Everything else is still needed.

    If you wish, you can reduce C2 to 220uF and increase R2 & R3 to 100k, and R4 to 1 Meg. The timing will remain the same, but the cap will be much smaller.
     
  7. TexAvery

    Thread Starter Member

    Oct 7, 2009
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    will I need C4?
     
  8. SgtWookie

    Expert

    Jul 17, 2007
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    C4 needs to be 220uF for the 555 timer alone.
    I don't know what load you're powering. If it's a motor or the like, you'll probably need a cap that large.
     
  9. Wendy

    Moderator

    Mar 24, 2008
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    What you need is a SSR, they are pretty common, and will cost around $10-20. I used to get mine from Omega (the temperature control company). They can be rated for 230VAC at 10Amps, and use extremely low current to drive them. Basically they are optically coupled triacs, so they are extremely safe, you can eliminate the output transistor and resistor and drive them from the 555 directly (basically you're driving a LED circuit).

    ******

    Here is an example of one...

    http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=CC1540-ND

    [​IMG]
     
    Last edited: Nov 4, 2009
  10. SgtWookie

    Expert

    Jul 17, 2007
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    Interesting, Bill.
    Just checked the specs on that particular unit in the datasheet top of page 9, left column; load range is 150mA to 10A. I'm afraid that if his load is under 150mA, it might not work for him.

    Link to datasheet: http://www.crydom.com/en/Tech/crydom_us.pdf
    Maybe one of these instead: http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=CC1341-ND
    PF240D25, 60mA-25A current range, 3-15v DC control voltage, PCB mount (4-pin SIP), under $27.

    Or if the load won't exceed 3A, maybe one of these:
    http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=CC1334-ND
    ASPF240D3, 100mA-3A current range, 4v-10vdc control range, 15mA, PCB mount (4-pin SIP), under $15.
     
  11. Wendy

    Moderator

    Mar 24, 2008
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    Over the years I've accumulated several used models (I have nothing against used). They come in all sizes and ratings, and are extremely easy to use.

    The first unit I showed was a bit more expensive than I had planned, you can get them a lot cheaper.
     
  12. TexAvery

    Thread Starter Member

    Oct 7, 2009
    58
    0
    Most posts just fade away with no final photos, so here ya go.
    Here is my compleated project. The relay is used to power on the CRT from a PIR sensor. Thanks for the help!
    [​IMG]
     
  13. VoodooMojo

    Active Member

    Nov 28, 2009
    503
    53
    Spectacular!!
     
  14. SgtWookie

    Expert

    Jul 17, 2007
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    Now that is cool! :cool:

    Great job!
     
  15. Wendy

    Moderator

    Mar 24, 2008
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    Ditto. Love the box.
     
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