Time-delayed switch-off pull switch

ISTR seeing one on MK's site. Couple of years ago I'd guess, so might not still be there. No idea where you'd get one. I've an 1/8th. DIN timer that I could put on the bathroom fan and, I hope, a diagram for wiring it so that it de-energises itself as well. That's why I put a 2-way pull switch on the fan. Circular tuit required.

They're used on lighting in corridors in some blocks of flats & HMOs. There are 2 types, pneumatic & electronic. Pneumatic are cheaper but a pain to adjust.

Or if you happen to be chucking out a microwave...

NT

Elkay 520A if you can find it

Owain

You can get momentary action pull switches. These can be user to trigger a delay timer.

Any switch can trigger a time delay relay.

Bill

Indeed it can, but if its latching, then there is some potential for confusion as to what is causing the device to run - i.e. is the switch still on, or is the timer just running on...

(depending on exact wiring configuration obviously).

I've seen push buttons that work this way, but not pull switches. Seems odd as really you just need a push switch upside down in effect! I guess they are meant for things like garden lights and fans. Brian

The ones used for lighting probably won't take the current. And they turn off after a few minutes. And you can't turn them off manually.

Relay

pneumatics go upto something like 30 minutes. The trouble is the slower you set them, the more borderline and unsable the mechanism becomes.

You can turn the relay off with a 2nd switch, or add a custom connection to the electronic timer switch to zero it. Or use a 2 gang switch to get there, albeit with a little more user complexity. You may want a simpler life of course.

NT

Thanks for the replies. There are only one or two pull switches with timed off facility that I can find on the Internet, and they are listed either as out of stock or discontinued. There certainly are modules available that are activated by momentary pull switches, but that would require modification to the existing wiring layout, much of which is not easily accessible. I was hoping for something that I could just replace the existing pull switch with. I'll think about it, but I suspect I'll just leave it as it is.

I suspect if the OP has a look through RS or CPC/Farnell he'll find a DIN timer that can toggle the output based on a momentary input plus only allow a max certain configurable run on time.

I've browsed before and there are a ridiculous number of timer devices with selectable logic diagrams.

As to the momentary pull - MK "disabled" alarm: White round base, white stub cord, red main cord. Throw the red cord away and replace with white. Looks the same. I have 3 - 2 for lighting where I'm triggering a hardwired input to a ZWave DIN module and one for a bathroom fan override.

Cheers, Tim

I think those are low voltage only, not 100% sure though.

NT

Yuk. For an electronic timer a momentary on-off-on rocker would be nicer, with one on triggering the timer and the other resetting it. I've done it for a cupboard light.

Can you get those in standard lightswitch format?

There ought to be timer modules able to be triggered by a standard light switch, but I don't know of them.

NT

Available as MK gridswitch modules, but make sure you are seated when you check the price.

I use simple momentary action switches for lighting. These go via a home automation system so I can program them to do whatever I want. Mostly, momentary operation simply toggles the light on and off, but the 'on' action also invokes a switch-off timer in some cases. For those which are also switched automatically by occupancy detectors, the 'off' action also disables the occupancy detection for a time limited period, thereby holding the light off in spite of the occupancy sensor.

There are stand-alone modules for creating a run-on fan, but they don't have any switch-off capability. Also, they can only handle a few tens of watts (tiny triac without any heatsink), so you'd need to add a relay.

yeah, making them not worth getting.

so not suitable. The Chinese are missing a trick. Build in PIR detection, a dancing flower, unwanted remote control colour changes & set default mode to flashing and you have a Chinese hit product.

NT

The pull switches? No, they are standard mains.

If anyone wants to do this, MK Grid have on-off-on rockers. I have a latching one for heating (auto-off-manualon). There are non latching versions available, usually aimed at roller blinds and garage doors.