6-hour timer. Can someone help me?

[Electric Rain]

I've been googling for a while now, but I can't find anything. I need to find/build a circuit that will send out a quick (.5 second or so) 12V pulse, with enough current to drive a standard relay, every 6 hours. That's:

6 hours off
.5 seconds on
6 hours off
.5 seconds on
and so on...

Needless to say, a simple 555 can't handle it. So, if someone can help me design such a circuit, I'd really appreciate it. If someone can find it on the net, I'd appreciate even more. If someone could design one themselves for me, well, that would just be splendidly awesome. Thanks a lot.

Rain

 

[Nigel Goodwin]

I've been googling for a while now, but I can't find anything. I need to find/build a circuit that will send out a quick (.5 second or so) 12V pulse, with enough current to drive a standard relay, every 6 hours. That's:

6 hours off
.5 seconds on
6 hours off
.5 seconds on
and so on...

Needless to say, a simple 555 can't handle it. So, if someone can help me design such a circuit, I'd really appreciate it. If someone can find it on the net, I'd appreciate even more. If someone could design one themselves for me, well, that would just be splendidly awesome. Thanks a lot.

Another application for a PIC :lol:

 

[Misterbenn]

Yeah use a PIC, its the simplest way of doing it.

however if you need to do this with hardware for some reason,
use a 555 set as a Astable, with frequency of 0.2Hz (5 seconds for one oscilation)
then use a frequency divider :
in 6 hours there are 60*60*6 seconds
divide by 5 to get the amount of oscilations = 4320
so if you use a 'divide by 'n' counter' set at 4320 with the 555 clocking it, you should get a 5 second pulse every 6 hours.

programable divide by 'N' counter ..... HCT 4059

 

[Sebi]

4541 also a good choice.

 

[Electric Rain]

Another application for a PIC :lol:

You and your PICs... :lol: You always did tell me to use a PIC for like... everything. Problem is, I've never used them. So, therefore, I don't have a programmer, and I have no programming skills. So I'll have to take the hardware approach.

Yeah use a PIC, its the simplest way of doing it.

however if you need to do this with hardware for some reason,
use a 555 set as a Astable, with frequency of 0.2Hz (5 seconds for one oscilation)
then use a frequency divider :
in 6 hours there are 60*60*6 seconds
divide by 5 to get the amount of oscilations = 4320
so if you use a 'divide by 'n' counter' set at 4320 with the 555 clocking it, you should get a 5 second pulse every 6 hours.

programable divide by 'N' counter ..... HCT 4059

Alright. That sounds good. I'll probably have some questions I'll have to ask, so I'll be coming back here. Also, that 5 seconds is assuming that the 555 is in a 100% duty cycle, right? I didn't know you could do that. :?:

Rain

 

[audioguru]

The CD4541 is very easy. It has a built-in oscillator. It resets its counters when the supply voltage is applied. It works on any supply voltage between 3V and 15V.

The HCT4059 needs an external oscillator like a 555. It needs to have its counters reset after the supply voltage is applied. Its max supply voltage is 6V but the min supply voltage for a 555 is 4.5V so both will probably need a voltage regulator.

Your choice. :lol:

 

[Jay.slovak]

Another application for a PIC :lol:

You and your PICs... :lol: You always did tell me to use a PIC for like... everything. Problem is, I've never used them. So, therefore, I don't have a programmer, and I have no programming skills. So I'll have to take the hardware approach.

Yeah use a PIC, its the simplest way of doing it.

however if you need to do this with hardware for some reason,
use a 555 set as a Astable, with frequency of 0.2Hz (5 seconds for one oscilation)
then use a frequency divider :
in 6 hours there are 60*60*6 seconds
divide by 5 to get the amount of oscilations = 4320
so if you use a 'divide by 'n' counter' set at 4320 with the 555 clocking it, you should get a 5 second pulse every 6 hours.

programable divide by 'N' counter ..... HCT 4059

Alright. That sounds good. I'll probably have some questions I'll have to ask, so I'll be coming back here. Also, that 5 seconds is assuming that the 555 is in a 100% duty cycle, right? I didn't know you could do that. :?:

Rain

Actually I share Nigels passion for PICs, because they can solve many problems really simple (one chip sollution rocks). :lol:

 

[williB]

Rain is that .5 seconds or 5 seconds ..??

 

[ljcox]

The 4020, 4040 & 4060 series of CMOS ICs are suitable for your purpose.

To generate the 0.5 sec or 5 sec pulse, use a monostable triggered by the last stage of the counter. You will need to set the oscillator frequency and the number of counter stages to give you a 6 hour period (ie. 3 hour low & 3 hour high). The monostable will trigger on either the positive or negative edge thus giving a pulse every 6 hour.

Search this forum for terms such as counter, timer, 4040, etc. I think you will find plenty.

Len

 

[audioguru]

Hi Len,
The CD4020 and CD4040 don't have built-in oscillators so forget about using them for this application.
The CD4060 is too old because the CD4541 does its job much better.

I think a "Mickey Mouse" pair of diodes used as an AND gate can feed a transistor as an output driver. :lol:

 

[ljcox]

G'day again Audio,
I don't have any data on the 4541 so I must download it.

The reason I suggested a Mono rather than diode gating is because - given the delay is 6 hour, the gating would be complex and the ratio of 6 hour to 0.5 sec (or 5 sec) is probably not a binary multiple.

Also, recent experience with diode gates and these counters (ie. using a diode gate to reset the counter at a particular point) was messy because of the diode charge/discharge currents. So I did a PIC solution (Nigel please note).

However, given that the output is to drive a relay, then decoding spikes due to the diodes would not matter.

Len

 

[audioguru]

Hi Len,
The CD4541 doesn't even need a diodes AND gate. Just set it to give an output after 6 hours and after an RC delay, have its output reset it.

The CD4541 also lets you choose whether its output goes high or low at the timeout duration.

 

[Electric Rain]

It's 0.5 seconds. Or less. It only needs to be enough time to latch a "self latching" relay. The attached schematic is what I need the timer for. (I know, I know, I don't have a resistor on the LEDs or any other little details like that, but this schematic is only for testing purposes. The program I'm using only handles digital parts, in the way I want to simulate them, anyway.) As you can see, the timer doesn't need to be on for long. As I said before, just long enough to latch that relay. Thanks for the help everyone.

Rain

 

[ljcox]

The timing is not critiacl then, anything greater than 20 ms would suffice. Thus a diode gate arrangement would do.

Len

 

[mmrtik]

can you describe the circuit with cd4541 in more detail please !?