I dare say we've all wasted expensive food at some time by forgetting to turn our skimmers off when we feed - or forgotten to turn the skimmer back on again and left it off all night!
Well, I've seen "push" switches that turn lights etc on and then turn themselves off automatically after a pre-set period of time, but is there a similar switch available (or is there a way they can be wired differently) so that I can turn the skimmer off when I feed and know that it will turn back on automatically after 10 - 15 minutes?
I've thought about using a time switch, but I can't always get to feed at regular times and I haven't heard too many good reports about autofeeders.
Any advice or suggestions will be greatly appreciated.
Not being waterproof is no a problem as I can site it in the shed - but can it be wired/programmed to be turned OFF and then turn back ON automatically after the set delay period, i.e. the reverse of the usual (and probably designed) use?
Oooops! Sorry Bob, I have re-read the spec and now I don't think it will do what you are asking.
There are a number of ways of achieving your goal but most include the use of complicated control hardware. The easiest way would to be to use a SPDT relay (Single pole, double throw). You would still need a timer circuit to energise the relay coil but this can be made quite easily for pennies if you've got some soldering skills? You could of course buy a pneumatic timer switch (the type you referred to earlier) and have that in front of the relay.
Would you be able to put in a low voltage supply in your shed?
If your still interested in following this up, I can probably give you more info over the weekend when I've got more time. I'll dig out a circuit diagram for a timer if you wish.
if having a soldering iron and experience of mending connections in kids' toys etc. is sufficient soldering skills, then we might be OK there.
However, timer circuits, relay coils and low voltage supplies all sound a bit complicated to me! but if you say it's easy and can be done for pennies, I'm up for learning something new! Any advice, circuit diagrams etc you're able to provide will be very much appreciated.
Not been on to much lately so only just read your thread.
Here's an option which should not cost you to much at all. In the past I have used a central heating timer to control a lighting circuit whilst away on holiday. You should be able to control more than one period of time without power to your pump.
Thanks for the reply, but I'm not trying to set up a standard timer with set (or randomly selected) on/off periods.
I want to be able to interupt the power supply to my skimmer pump (i.e. turn it off) at whatever time of day I can get out to feed my koi, and know that it will turn back on automatically after about 10 or 15 and minutes (when the koi have had time to eat the food).
To minimimise the length of my return pipe runs and maximise the turnover rate through my main filters, I have included my heater and UV on the return from the skimmer, so if I forget to turn the skimmer back on, I have no UV or heater
This is a basic "555" Timer IC configured as a "missing pulse detector" circuit (I include this info just in case you want to do some research - search for missing pulse detector and you'll get loads of info.) This is the circuit I was going to suggest originally and in this kit form should be easy enough to build. It also includes start & stop buttons so that you can interrupt the timing cycle should you wish, I doubt you'd buy all the bits for the £7.99 cost and if put it into a decent enclosure should look quite professional.
More info about the kit is available direct from Velleman website here:
Connect your pump through the normally closed contacts of the relay.
Connect the 12v supply for the relay coil through the timer output relay.
Now when you operate the timer the power relay coil will become energised and the contactor will switch to the normally open position ie breaking the circuit of the pump. It will remain like this during the timer cycle and then revert to the normally closed position thereby making the circuit to the pump.
Thanks very much for taking the trouble to search out and post the links - very much appreciated.
It all sounds a bit complicated but, hopefully, it will be a lot clearer when I've actually got all the bits of the kit in front of me!??
Anyway, we have a Maplins abouit 5 miles away in Luton and at £8 the kit looks a bargain and well worth trying - and if it works, I'll save the cost by not wasting so much food in no time at all!
Thanks again for your help and I'll let you know how I get on!
Let me know if you have any questions.......and don't forget - be careful when playing with the mains. Test the low voltage circuits properly before connecting the pump!
Carl, Doesn't Bob need a 12 volt supply? (Presume you need to add an appropriate transformer to his shopping list and would suggest you then need to draw him a diagram of how the relay, pcb and transformer all get wired into his pump circuit). Martin
Quite right Martin, a 12v supply would be required both for the PCB and for the power relay coil.
Sorry Bob, thought you'd infer this from the earlier post. A std 12v "wall wart" type transformer will be ok. You'll also need an enclosure (box) or boxes to put it all in.
I accept that this puts the cost up, but if your anything like me, you'll have loads of these things knocking around. You might also like to use these switches:
Once you get your pcb kit built and working let me know if you need any assistance on putting it all together. Wouldn't want to give it all away in one go would I? Besides by the time you've built the kit you'll have probably figured it out anyway!!
but is there a similar switch available (or is there a way they can be wired differently) so that I can turn the skimmer off when I feed and know that it will turn back on automatically after 10 - 15 minutes? 
Any advice, circuit diagrams etc you're able to provide will be very much appreciated.
