Roland Alden
New Member
I want to detect cooking on a cooktop/stove so that a circuit can automatically turn on the fan of an overhead ventilation hood. I have looked at heat detectors and smoke detectors made for fire detection and find they are not sensitive enough. They are cleverly designed to not be fooled by the rate of rise from a stove or steam or even the smoke coming off cooking food. In spite of the fact that everyone in the smoke alarm industry says don't install a smoke alarm in the kitchen, I find them to be relatively immune to cooking smoke. I have looked at HVAC thermostat type controls thinking a probe inside the hood and another probe away from the cooktop but up on the ceiling might work. A comparator would fire if the difference between the two probes was > n and the hotter probe was the one in the cooktop/chimmney. However, no HVAC thermostat actually can do that comparison; they have different ideas about what to do with what they are measuring. I have also looked at motion detectors and maybe PIR detectors but the commercially available ones are 1) very wide angle and would trigger even if someone were just in the kitchen and not cooking; and 2) are designed to not be fooled by heat that is not in motion. Preceisly wrong for detecting a pot on a stove coming to a boil. I have thought about detecting that the stove is "on" by installing either a flow meter on the gas line or draw on the AC line. This would work except for the fact that I need the detection location to be up on the ceiling and not down on the floor because of wiring limitations. I could go with wireless I guess. However just turning on the stove and then having the fan start is not as good as actually waiting until some significant amount of heat/smoke starts to rise. If you are just boiling a cup of water it might be annoying to have the fan come on the moment you hit the on switch. There are some solutions I could hack together with some fancy laboratory sensor units feeding data to a computer but these are all overkill / too expensive. All I need to do is close a dry contact relay up on the roof. Any ideas?
Last edited: