need help, for a 15min repeat on &off

[frosty]

Hi, I'm new to this froum. I need a repeat timer 15min. on and 15 off. with a 9v relay. I have a circuit for a 4060b that I can build. but the problem being is that its not accurate. from what I readed, the timer will lose time or gain. so that being, I can use a 32,768 quartz crystal for accuracy, so I would think that I would have to use two 4060 to make it work,I have the diag for just the crystal hook up the but not the rest. Thank you

 

[k7elp60]

Does the time have to be exactly 15min on and 15min off? With one 4060 as an oscillator divider and then another 4060 as just a divider you could get 17min on and 17min off.

 

[eblc1388]

I can use a 32,768 quartz crystal for accuracy, so I would think that I would have to use two 4060 to make it work,I have the diag for just the crystal hook up the but not the rest.

That would be a bit difficult. Let me explain:

When you connects a 32.768KHz crystal to the 4060, you'll get 2Hz(Q14), 4Hz(Q13), 8Hz(Q12) then 32Hz(Q10) from its output. Note that the 16Hz is missing because the designer has choose to miss out Q11 on the 4060 chip.

Naturally you would connect this low frequency to the clocking input of another 4060 and try to decode the counts (900 seconds in your case) you have wanted. Now this missing Q11 output will continue to haunt you because one would need this output in order to correctly decode 900, regardless whether one is using 2Hz, 4Hz or 8Hz. 32Hz is too high to decode for 900 seconds.

The solution is simple. Don't use 4060 but use a 4040 for the second counter instead because it has all the output stages available upto Q12.

That my personal view maybe someone can work out a clever solution that requires only two 4060s.

 

[frosty]

15min timer

I don,t care what kind of ic I use as long it works. I would need a diagram any help on that. Thank you

 

[Pommie]

Your lucky as 900 is 1110000100 in binary and so you just need to AND together Q9,Q8,Q7 and Q2 and use that to reset the counter.

Mike.

 

[frosty]

thank you, is this accurate or do I still need the quartz crystal in the circuit??? how would I hook up the other and together?? I don't know much on electronics.?

 

[frosty]

Yes' the 15 min. repeat timer has to be accurate,and I need a relay with it. So the crystal needs to be hooked up. If anybody has a schematic, that would be very help full. I don't know to much on electronics I just do alot of reading to find things out, I know how to make pc broads now just by reading and find how to do it. I'm not to good in the math part, but I'm trying. I already made some pwm units. Also finding the on and off times of the timer I don't understand, does any one know of some softewear were you just plug in the on and off time that is need for the timer, that will gave you the size of the cap. and resiter.

 

[blueroomelectronics]

If it's accuracy you want than a crystal is almost a must.

 

[Diver300]

Rubidium oscillator?

GPS frequency standard?

Mains frequency division?

Rubidium oscillators are far too expensive for amateur use. However, GPS receivers aren't expensive and mains frequency division is very cheap and has good long term accuracy.