Timer

[cdmtdm]

Hey Guys , i need to find a digital timer ,i can program to come on every 30 minutes for 30 seconds (or 1 min) it has no load only control circuit , it will be a 24/7 thing .. any ideas how i can solve this ?

[thomasteve]

RS components may have something suitable :

http://thailand.rs-online.com/web/c/automation-control-gear/timers-counters/

[cdmtdm]

ok appreciate it that is a great website , will call them tomorrow .... hard to decipher exactly which one will do , narrowed done to three that will do less than a minute , what concerns me is the amount of starts , many are limited to 8 stop/starts ...

cheers

[thomasteve]

ok appreciate it that is a great website , will call them tomorrow .... hard to decipher exactly which one will do , narrowed done to three that will do less than a minute , what concerns me is the amount of starts , many are limited to 8 stop/starts ...

cheers

Probably a lot cheaper to build a simple repeating circuit yourself from a few components, such as one of these examples :

http://www.zen22142.zen.co.uk/ronj/rt.html

http://www.zen22142.zen.co.uk/ronj/rt7.html

[Crossy]

+1 ^^^ although I would use a 555, far fewer components needed.

How accurate do the timings need to be, is 'digital' really necessary?

[thomasteve]

+1 ^^^ although I would use a 555, far fewer components needed.

How accurate do the timings need to be, is 'digital' really necessary?

I agree - it's the standard workhorse IC for timing circuits and first appeared over 40 years ago !!

A low power CMOS version is also available and you will surely find something suitable by Googling '555 timing circuits'.

[cdmtdm]

+1 ^^^ although I would use a 555, far fewer components needed.

How accurate do the timings need to be, is 'digital' really necessary?

hi crossy , no digital not necessary , as far as times go my only requirement is to have it come on every 30 minutes for 30 seconds or 1 minute if it has to be ...every hour of the day ....

[Crossy]

If you don't feel confident to make something with a 555 (requires soldering and stripboard) you can do it with a couple of readily available Omron timers from this range http://www.ia.omron.com/data_pdf/data_sheet/h3y_dsheet_csm92.pdf

Our local electrical emporium carries these timers in various times and voltages, 3-400 Baht each with sockets.

The circuit :-

How it works:-

For 220V operation:-

K1 is Omron H3Y-2 220VAC 60 min - set to 30 min
K2 is Omron H3Y-2 220VAC 120 sec - set to 30 sec

For other supplies use the relevant voltage timers.
.
1. Power applied to circuit
2. K2 receives power via NC contact of K1(K1 is unpowered)
3. Load is powered by the NC contact of K2
4. 30 seconds later K2 times out
5. Power is removed from Load
6. K1 receives power via NO contact of K2
7. 30 mins later K1 times out
8. Power is removed from K2

9. Power is removed from K1
10. Load receives power via NC contact of K2
11. Go to step 2.

.

[cdmtdm]

thats perfect Crossy , i can do that will start to gather gear ..

Cheers

[Crossy]

Out of interest, what's the application?

Please be aware I've not built or simulated that design, it's simple enough that I'm 99.9% certain it will perform as intended.

Don't forget to fuse the supply

[cdmtdm]

i have a drum filter on my fish tanks and it screens the water to 90 micron , the machine has a floatless level control ( 3 probes ) however to reach the level required by the level control is way to high for my water levels... so i use it now on plug in timer but its only good for 4 hrs ... i cannot lower the probes they are in built in the machine

[Crossy]

Some posts removed so bangkruatsteve doesn't look too much of a plonker

[cdmtdm]

Hi Crossy , any chance u can re do the diagram for me ? i have come up with a better energy efficient method , i will instal a float ( the std three wire ) unit that just dangles in the water and makes contact when the water gets to high or too low ,

what i need the unit to do, is when the water in the sump drops below my set height , it starts the drum filter and for the timer to then run for 30 to 45 seconds ... this wil rotate the drum filter and water flow continues as normal , the sump fills up and when it gets low again the same process happens , cheers