Years ago, there were countdown timeswitches, a bit like a kitchen pinger timer, which you wound up to as many hours as you wanted and the appliance was then on for that time (immersion heater was a typical appliance). Looking for something similar for someone. Needs to go up to 8 hours (or near). I can find ones that do 45 minutes, but not 8 hours. Anyone seen one?
This one has a count down, but not sure how loong for - do you have a local Screwfix where you can go and look at one?
On 26 Nov 2008 13:17:57 GMT someone who may be snipped-for-privacy@cucumber.demon.co.uk (Andrew Gabriel) wrote this:-
Not up to 8 hours. Horstmann, do ones that go up to ISTR 4 hours (can't be bothered to check) and may do longer runs.
The few old fashioned ones I have seen went for an hour or two, not eight hours.
Have a look on here;
whatever you want.
Don.
Dunno about commercial ones. But the ol' U6047 chip was ideal for this - basically designed for car heated rear window timing. Could be triggered in a variety of ways including at power on, wide range from 4 sec to 20 hours, and could drive a meaty relay directly.
It's obsolete but I have some left. There's probably a near equivalent.
Screwfix have complex digital plug in timers on offer at the moment for =A32.49 which seem to have a 99 hour count down - at least I've just taken one up to 30 hours. Don't know if they are on the website but they are in the Edinburgh shop.
Rob
Having given the key info, I'm now going to hijack the thread ans ask a similar question about digital timers.
We have an old one that is becoming unreliable on the battery contacts; it's main asset is that unlike everyone I have seen since, it reverts automatically to program if you switch it to manual - ie you just press the ON button and it will then go OFF at the set automatic time. This is a great boon for the bed electric blanket if you want to go to bed early. All current ones I've checked just stay ON once switched there.
Rob
Our old tumble drier has something like that. You wind it up, and then when power is applied to the tumble drier it starts counting down. This was compatible with an external time switch which just allowed the tumble drier to run at off peak periods.
The timer on the tumble drier as broken, and I can't get a replacement. All the modern tumble driers have a start button and are thus incompatible with an external time switch, though some driers do have a delay start.
Does it have to be mechancical with user variable amount of ON?
No
Yes, but doesn't need high resolution (1 hour would do, half hour would be better).
That looks very useful.
It's still available from Digikey for £2475 for 4000 of them ;-)
I have a couple of Micromark MM9539 plug-in timers which behave as you wish. They appear to have been succeeded by the MM9578 which look the same and have the same specification. I cannot vouch for them behaving in the same way as regards manual override but you might be able to find online a user manual.
I guess it also needs to be "user friendly" not a couple of tiny tweaky switches on the front of a 1 unit wide DIN module then, they come in all manner of variations.
Maybe one has a simple external method of altering the triggered period? Like an ordinary pot but is there requirement for feedback to the user of how long is left to run whicg a pot wouldn't do? Requirement to cancel early could be met with an "off" button next to the "on" one.
Take an ordinary rotary 24hr timer, put an 'off' pin in it, and remark the dial hours to count down to the off pin instead of counting up.
NT
Actually, that would probably be OK, providing it's simple (such as press a button once for each 30 minute period you want). There's already a complex way to do it -- looking for something simpler.
Yes. Dave's rear heater IC would do the job nicely, if it was still available in quantities < 4000.
Very - it also has the ability to toggle on and off, so useful for other things as well as a timer.
Well I could do with some more. ;-)
TLC do them as immersion heater timers. Up to 1 hour or 2 hours, but not 8.
RS (and anywhere industrial, maybe even TLC) have them, but it's rack- mount and you'll need to box it, and possibly add a contactor for the current.
Look for two brand names Intermatic and Leviton. They specialise in all sorts of timed control and timed switching products. They have websites, so you should fine them ok.
You'd presumably need feedback so you know what it set it to. Starts getting complicated...
Someone mentioned a time switch and setting an off peg. I have that, a modified motorised plugin timer with the live feed to the motor taken after the switch so it stops when it switches off. Just rotate the dial to the required position and of it goes for that period of time. Remark the scale and you have 15m to 23h 45m easyly settable.
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