Simple timer circuit wanted

Dtsteam

G Scale, Travel, Steam Boats, Mechanical Music
24 Oct 2009
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Preston
I am looking for a simple circuit to switch a relay on for 1-2 minutes then off for the same time and keep cycling. The relays I'm using are 12v miniature PCB ones. Any help would be appreciated.
 

gregh

electronics, computers and scratchbuilding
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Neil Robinson

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24 Oct 2009
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N W Leicestershire
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David, try the circuit below.
The supply should be about 12V DC.
The on time is adjusted by RV1 and the off by RV2. For the values quoted the theoretical max for each is approx 175 seconds and the minimum 23 seconds with 100 seconds about the mid point of the adjustment. The tolerance of the electrolytic C2 tends to be quite wide so the actual times can vary a bit. Also you may find that the first cycle is a little longer than subsequent ones.
7901aab9727c41a2a5065e5ea51ce03c.jpg


Edit, I see Greg had the same idea, it took me a while to do the drawing.
 

Philbahn

Registered
24 Oct 2009
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Swinton Manchester
Dtsteam said:
I am looking for a simple circuit to switch a relay on for 1-2 minutes then off for the same time and keep cycling. The relays I'm using are 12v miniature PCB ones. Any help would be appreciated.

David found this at maplins any good? MK111 Adjustable Timer with Relay Output[/h1] only £5.99

Order Code: VT27E
In Stock*
 

Dtsteam

G Scale, Travel, Steam Boats, Mechanical Music
24 Oct 2009
5,401
15
Preston
Thanks for your help guys - looking at the options, I'll probably dip my toe in the water and try some electronics - the maplin kit first, then one of the circuits. Especial respect to Neil for the drawing - clearly a fellow insomniac at work.
 

Neil Robinson

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24 Oct 2009
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N W Leicestershire
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Philbahn said:
found this at maplins any good? MK111 Adjustable Timer with Relay Output only £5.99
Order Code: VT27E
In Stock*

IMHO it may be O.K. but will need modification as according to Maplins "pulse time adjustable between 0.5 and 5s
Pause time adjustable between 2.5 and 60s"
I think David wants times of around 60s to 120s for both. The values in my diagram give an approximate range of 23s to175s.
 

Philbahn

Registered
24 Oct 2009
12,687
3
72
Swinton Manchester
Neil Robinson said:
Philbahn said:
found this at maplins any good? MK111 Adjustable Timer with Relay Output only £5.99
Order Code: VT27E
In Stock*

IMHO it may be O.K. but will need modification as according to Maplins "pulse time adjustable between 0.5 and 5s
Pause time adjustable between 2.5 and 60s"
I think David wants times of around 60s to 120s for both. The values in my diagram give an approximate range of 23s to175s.

Due respect Neil. Just thought it might be modifyable