CD4060 Timer circuit - resetting when relay turns on.

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gregmcc

Member

• Mar 17, 2012

• #1

I build this timer circuit which works but I've run into a problem.
What I want to do is have the circuit pulse a relay every 60 mins - the relay must turn on for a few seconds (say 5) and then off again.

Using the above circuit the the relay stays on for quite a few minutes - which is right as the chip is a counter. I need to wait for pin 3 to go low again.

I was thinking there must be someone to mod this, so when pin 3 goes high it turns on the relay and then using another circuit I do a reset on pin 12?

Am I missing something or is there an easier way?

 

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ljcox

Well-Known Member

• Mar 18, 2012

• #2

You're on the right track.

You could design gating so the relay is operated for 5 sec, then gating to generate a reset pulse.

Another way would be to set the oscillator frequency so the counter reaches its maximum count at 1 Hour then goe to zero.

Use the negative going edge of the last counter stage to trigger a monostable that operates the relay for about 5 sec.

 

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colin55

Well-Known Member

• Mar 18, 2012

• #3

Take R6 to pin 3 and change the value of R6 and C2.

 

alec_t

Well-Known Member

Most Helpful Member

• Mar 18, 2012

• #4

Here's what I'd do. This circuit mod, with the R2 and C1 changes, makes the counter reach its max count every hour. When pin 3 goes high the added C and R cause a brief pulse to set a latch made from two NOR gates. The Q6 output at pin 4 resets the latch after about 7 secs (or you could reset it after 3.5 secs using pin 5 instead of pin4). The latch, when set, drives the transistor via R3 to energise the relay.

 

Last edited: Mar 18, 2012

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colin55

Well-Known Member

• Mar 18, 2012

• #5

You don't need any additional components.


Take R6 to pin 3 and change the value of R6 and C2.

 

alec_t

Well-Known Member

Most Helpful Member

• Mar 18, 2012

• #6

@colin55
Please explain how is that going to give a ~5 sec 'on' time very hour?

Edit: Ah, sussed it now. Good suggestion, colin55. R6 lower end connects to pin 3 instead of to ground. R6 = 750k and C2 = 10uF seems to work, assuming the 4060 tolerates a very slow rise-time on its reset pin. That slow rise time might lead to a weakly-defined end-point for the 5 sec period. Perhaps the OP will be happy with that?

 

Last edited: Mar 18, 2012

ericgibbs

Well-Known Member

Most Helpful Member

• Mar 18, 2012

• #7

hi alec,
I dont think I posted this LTS 4060 earlier for you, but just in case in helps.
Keep the the 4060 hierarchical and the asc's in the same folder.

E.

 

alec_t

Well-Known Member

Most Helpful Member

• Mar 18, 2012

• #8

Thanks Eric. I did a sim using a 4020 model; but the 4060 makes life easier

 

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gregmcc

Member

• Mar 18, 2012

• #9

Thanks for the help guys - the R6/C2 change did the trick. Its about 3 secs - I could play with the R/C values but its close enough and works great.

 

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ljcox

Well-Known Member

• Mar 18, 2012

• #10

This is how I would do it.

The 4093 is a Quad NAND gate Schmitt Trigger.

U2a, b & c generate a pulse of about 5 sec at the trailing edge of the Q14 signal, ie. after 1 Hour.

Since U1d would otherwise be unused, it can be used to generate a "Reset at Switch on" pulse to reset the counter when the power is first turned on.

The RC method in the original circuit is a crude way to do it.

It is a high pass filter, so it will pass any noise & extraneous pulses (should they occur on the supply line) to the counter reset.

The reset input to U1 (R) is pin 12.

 

Last edited: Mar 18, 2012