Need help with 555 circuit

Discussion in 'The Projects Forum' started by gunlocators, Dec 19, 2014.

  1. gunlocators

    Thread Starter New Member

    Dec 4, 2014
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    I have some 555 ICs and need to find a schematic for a circuit that will be on for 5 minutes and off for 5 minutes. Actually between 3-5 minutes is fine however the amount of time circuit is on should be very close if not the same as time off.

    this will run a relay on and off I have the relay and the 555 probably most if not all the other components however when I google 5 minute circuit I did not find anything using a 555 IC any help is appreciated.
     
  2. #12

    Expert

    Nov 30, 2010
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    Last edited: Dec 19, 2014
  3. KJ6EAD

    Senior Member

    Apr 30, 2011
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  4. MikeML

    AAC Fanatic!

    Oct 2, 2009
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    300sec is getting close to the upper limit for a 555. The R needs to be ~1meg, which can only supply about 2uA at the 555's trip point. C needs to be an electrolytic capacitor whose leakage is approaching 2 uA, so you get erratic or unreliable timing.

    I second the recommendation of using the CD4060.
     
  5. #12

    Expert

    Nov 30, 2010
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    Thanks, KJ6. I'm glad I didn't spend any time designing what he already has!
     
  6. gunlocators

    Thread Starter New Member

    Dec 4, 2014
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    So I have the schematic downloaded from Kris. However what if I do 180 seconds will the 555 be ok. I have some flexibilty on the time off and on I just need them to be close to the same time on as it is off. That too does not have to be exact but somewhere close would be nice. If thats possible I would rather go that route for now and get the project going while I order the CD4060 and wait for it to arrive.
     
  7. Alec_t

    AAC Fanatic!

    Sep 17, 2013
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    Anything beyond ~ 1min is dodgy with a 555 because of capacitor leakage (as Mike mentioned). If you are concerned about the on and off times being stable and as equal as possible you really should abandon the idea of using a 555.
     
  8. gunlocators

    Thread Starter New Member

    Dec 4, 2014
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    Well Here is what I did with 9volts in to the 555 if it does not last then I will go the CD4060 route. I ran the circuit for 2 hours and it seemed to cycle fine for now. Thank you for all the help. I wanted to try this seeing for now I had all the components on hand....

    [​IMG]
     
  9. Bernard

    AAC Fanatic!

    Aug 7, 2008
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    Do'nt forget to connect pin 4 to + supply, and add supressor diode across relay coil, cathode to + V side.
    Longest time period that I have used a 555 was 3 hours. 30 min, no sweat.
     
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