Automating a hob extractor

[Dave]

I'm about to fit a hob extractor and got to thinking it would be useful if it could turn itself on, possibly triggered by heat and/or humidity. Has anyone done this? what sensors did you use?

Dave

[Chip]

On Wed, 13 Jul 2005 23:45:54 +0000 (UTC),it is alleged that Dave spake thusly in uk.d-i-y:

My thought would be something akin to this:

have no clue what the wiring regulations would have to say about it though, or where to obtain one at a reasonable cost.

You'd also have to have a large time delay, like in the order of a minute or 2, to prevent the cycling of the hob thermostats from turning the hood on and off.

[BigWallop]

How about a thermostat inside the hood, above the cover. Something like a simple bi-metal strip switch fitted in line with the on off switch on the front of the hood would work I'd have thought.

[Brian Sharrock]

Why bother ... ? On mine it's switching a push button ON/OFF; Slow/Med/Fast. I frequently want the extractor fan ON (without the hob) to act as an room extractor - particularly when grilling 'stuff' utilising the oven's grill; or venting steam when using the steamer; or venting fumes when using sandwich toaster or fat-fryer. In other words having the extractor fan interlocked with the hob would be inconvenient. Besides ... if you can't remember to turn the device ON when you're presumably standing at the hob ... !

[Dave]

The idea isn't to interlock the extract and hob but to add an auto mode that would respond to anything that was happening in the kitchen, as well as what was happening just below it. There'd obviously still be the manual controls. Why bother? - it's for the other more members of the family who are more memory-challenged than me - I'm perfect, like most uk.d-i-y'ers ;-)

Dave

[fred]

No need to justify yourself mate, here goes:

If you just wanted something to come on when the cooker was in use then a simple bi-metal thermostat in the hood would probably do the job as the temperature there will rise pretty high and pretty quickly. The setting would need to be low enough to switch on quickly but high enough not to switch off as loads of (slightly cooler) air starts to rush past it when the fan comes on :-). Tolerance of capsule (safe) stats is high so you may find it difficult to get a happy balance of fan on vs fan off.

Also, this would not cover your late breaking requirement for the system to be sensitive to other activities in the kitchen. For that I reckon that a humidistat may suit better, as long as all your heat making activities create water vapour (cooking, ironing, heavy breathing etc). Here's one form TLC

, mounted unobtrusively in the room, say under a cabinet, close to the hob, I think that would do the job. Main issue is cost, that'll be 30quid with the vat but don't expect to find one cheaper, they are expensive.

Btw: Humidistats can be a bit of a PITA for running on, if your fan is a multispeed one, maybe dedicate the lowest speed switch position to the humidistat (connect in series) so it can be turned off.

[Brian Sharrock]

Alternatively .... : save yourself the thirty-odd quid (perhaps five-odd quid direct to Gordon Brown?) for the humidistat and/or thermostat and ... SPEAK SLOWLY AND CLEARLY to your memory-challenged others! "HOB ON! FAN ON!" Repeat as necessary until message gets through. Thirty Quid will buy a lot of D-I-Y thingies! :)

[fred]

In article , Brian Sharrock writes

I think you've suggested that already, I've no problem helping someone out who chooses to pamper themselves.