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CMOS 4001 Repeating Timer

Discussion in 'General Electronics Discussion' started by johnc, Nov 25, 2016.

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  1. johnc

    johnc

    4
    0
    Nov 25, 2016
    Hello All,

    I was hoping someone would be able to assist with development of this circuit I am trying to replicate on a breadboard as a test
    http://www.zen22142.zen.co.uk/ronj/rt2s.html

    I have attached a photo but it will probably be too hard to see anything of use on it.

    Basically, it doesn't really do anything. Occasionally touching components, or moving my hand around it can turn it on and off. So I have something floating although I don't think that explains why it's not cycling itself.

    One difference is that I had to go with the two 1000uf caps back to back as I couldn't get a non-polar one at the required rating.

    Does anyone have any pointers as to what I can look for to figure out what is going on?

    I am also open to any other circuit suggestions. I'm after switching on a relay for 30 seconds every 15 minutes. I looked at 555 timer but the advice seems to be it's not really suited for longer timeframes.

    Edit: I found one issue. It no longer turns on and off from touching it. It just stays constantly on now though.

    [​IMG]
     

    Attached Files:

    Last edited by a moderator: Nov 25, 2016
  2. Audioguru

    Audioguru

    3,082
    691
    Sep 24, 2016
    Get rid of the breadboard with messy wires all over the place and possibly intermittent contacts and build the circuit soldered neatly on stripboard (Veroboard) exactly as shown.

    You might have zapped the IC with static electricity from you touching it.
     
  3. Chemelec

    Chemelec

    291
    47
    Jul 12, 2016
    15 Minutes is a Bit Long for this circuit also.
     
  4. 73's de Edd

    73's de Edd

    3,039
    1,286
    Aug 21, 2015
    Try much much lower values of C1 to initially get the operational speed faster, to visually confirm that the circuit is actually working.
    Seems like that required capacitance is / will be having excessive leakage,as to even think of that loooooong of a timing interval.
    Then . . . . I also see no variable resistors being used on the board for setting the timing ratio.
     
  5. Colin Mitchell

    Colin Mitchell

    1,417
    313
    Aug 31, 2014
    Try just one 100k without any diodes
     
    Last edited by a moderator: Nov 25, 2016
  6. Chemelec

    Chemelec

    291
    47
    Jul 12, 2016
    Two 1000's in series Makes 500uF.
    Definitely CLOSE ENOUGH to 470uF.
    But Leakage on these Caps can be a Problem!

    Even Better would be CD4541.
     
  7. johnc

    johnc

    4
    0
    Nov 25, 2016
    That looks easier
     
  8. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,473
    2,818
    Jan 21, 2010
    Check the resource we have on long duration timers.

    What you want to do is extremely difficult with a single RC delay.

    These days a microcontroller would be the simplest solution, but (as I think has been suggested) a combination of timers and counters is also probably viable.
     
  9. johnc

    johnc

    4
    0
    Nov 25, 2016
    I was trying to keep it simple by not using a microcontroller, but I think I have ended up making it harder.
    I am a programmer so I find Arduino and Raspberry Pi easy for these sorts of things, but I thought this would be simple.

    I picked up a CD4060 so I will give that a try, but I think I will have to end up going with a microcontroller. ( edit: ugh, I just found out that they gave me the wrong one. I asked for a 4060, they gave me a 4026 )

    This could be an easier option for me. But the question is can the on and off time periods be set independently.
    I already have one of these but the on and off time is identical.

    http://archive.siliconchip.com.au/cms/A_111920/article.html

    [​IMG]
     
    Last edited: Nov 26, 2016
  10. johnc

    johnc

    4
    0
    Nov 25, 2016
    I gave up and went with an ATmega328 I had laying around.
    It works nicely but it needs a few more additions.
     

    Attached Files:

    Last edited: Nov 26, 2016
  11. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,473
    2,818
    Jan 21, 2010
    You can eliminate the crystal and the capacitors by using the internal 8MHz oscillator. Essentially you just have a bare chip. There's also the picaxe which is available in an 8 pin device and is programmable in basic.
     
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