CMOS 4001 Repeating Timer

[johnc]

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.

 

[Audioguru]

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.

 

[Chemelec]

15 Minutes is a Bit Long for this circuit also.

 

[73's de Edd]

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.

 

[Colin Mitchell]

Try just one 100k without any diodes

 

[Chemelec]

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.

 

[johnc]

I think a CD4060 oscillator/counter IC should be used for such long timings. Then an ordinary little non-polarized timing capacitor can be used.

That looks easier

 

[(*steve*)]

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.

 

[johnc]

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.

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

 

[johnc]

I gave up and went with an ATmega328 I had laying around.
It works nicely but it needs a few more additions.

 

[(*steve*)]

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.