Auto switch off device

[VictorDelta]

I wonder if anyone can help me with this? We have an electrical pump which runs an ornamental feature in the garden. For several reasons, it can easily be accidentally left on and it is only a matter of time before it runs dry and the pump burns out.

I would therefore like to power it via a simple device which will automatically power it off, say, about 4 hours after it is switched on. Does anyone know of anything on the market that will do this please? An ordinary time switch will not fit the bill as it will come back on after 24 hours (or whatever). I'm sure there must be a simple answer but so far it has eluded me!

Thanks,

V

 

[Steve]

http://www.screwfix.com/prods/34572/Electrical-Supplies/Timers/3-Wire-Push-Button-Timer

Up to 2 hour delay.

But this must be fixed to a backbox and wall.

 

[electronicsuk]

How about a PIR so it only runs when someone is around?

 

[VictorDelta]

Many thanks. Both very good ideas but neither will quite solve the problem. If only they made push button timers (or something similar) with a longer delay time...?

V

 

[brig001]

What about a normal mechanical plug in timer? Just put the pins in for switch off, say one at midday, one at 5pm and one at 10pm, then use the override on the side to switch it on. Not exactly what you want, but might be close enough.

 

[333rocky333]

You could use a delay off relay.
But you would need to put it in an enclosure and wire it in circuit.

 

[VictorDelta]

You could use a delay off relay.

Thanks. Do they make them to work with delays up to 4 hours or so? I've only seen ones that delay by a few minutes.

V

 

[timtheenchanter]

dont have the wiring diagram here, but you could use a relay and time clock, takes a bit of thinking about, but essentiall there is a push button in the system that needs to be pushed at the same time as the time clock is active to energise the relay.
This stops the relay re-energising when the power is returned via thew timeclock.

I have one on my battery charging system, means I know if power has been interrupted at any point when I havnt been there (this is critical as the batteries need to be fully charged.)

 

[ericmark]

There are timers but tend to be expensive. However a timer with pegs for switching on and off can have only off pegs active and would be much cheaper.
The other method is to run timer from itself with override button so as soon as it switches off it stops.
The special timers for the job are designed to be fitted in a panel and so not only do you need timer you also need enclosure. These
cost around £24+vat and will do what you want off delay 0 - 100 hours but as you can see not self contained.
Here they list 40 odd diffrent units but all seem to have same problem you would need to also by a box to mount it in.

 

[VictorDelta]

Thanks for all the suggestions. To keep the size down, I might investigate building something myself based on a small timer chip and mains relay.

V

PS The only other thought I had was whether anyone makes what I want as an electronic night light for children that, like a candle, goes out after a few hours...?

 

[Joe4542]

Bit like Steve had mentioned above, you could use one of these Immersion Timer , Easily overrated for a small pond pump, but with a simple press sets the power for 30, 60, 120 mins.
Dunno if that would be long enough for you tho?

Again would need to be mounted in a patress box etc.

EDIT : Or this one which is a bit cheaper...

 

[securespark]

http://www.screwfix.com/prods/34572/Electrical-Supplies/Timers/3-Wire-Push-Button-Timer

Up to 2 hour delay.

But this must be fixed to a backbox and wall.

This one better, surely?

http://www.screwfix.com/prods/39533/Electrical-Supplies/Timers/Outdoor-3-Wire-Touch-Timer

 

[LoveRocket]

How about a flowswitch on the output of the pump?

Have a momentary push switch wired in parallel with the flowswitch, you push this for a few seconds to start it, then once the water is flowing the pump is fed via the flowswitch. Pump runs dry, flowswitch opens, pump stops!

 

[VictorDelta]

Thanks for the further suggestions. I wonder why all the timers have a maximum time of 2 hours; I'm really looking for up to 4 hours if possible.

Flow switch - good idea but I want to be able to switch the pump on from inside the house if possible.

V

 

[slup]

What was wrong with ericmark's suggestion?

The timer he suggested does exactly what you want - just put it in a small DIN enclosure and connect a momentary switch to it.