narrow field of view sensor


New Member
Hi. The owner of a cafe has asked me to install heaters above tables that are placed outside the cafe on the sidewalk. There is a roof over the tables where the sensors can be located about 12 feet of the ground. He wants the heaters to come on when people sit at the tables - what sensors should be used? how could i avoid false activation of the sensors from hot air or people just walking past and not stopping at the tables?
My first take at this one is not a good automation project. Bound to have false triggers or no trigger. What if the folks sitting aren't jumping around? Heat goes off? Customer disatisfaction. I am thinking only weight detection (hard to implement seamlessly) would be accurate enough.
hi wild_riverz, welcome to CocoonTech!

I have to agree with David here. The only way I would suggest is just installing a controller and have the waiter activate it when serving the customers, and turn it off when the bill has been paid.
How bout an X10 Palm remote transmitter sending RF commands (from the waiter) to a relay that turns on the particular heating unit? H1 - H8 for eight seperate heaters / tables as example.
thanks for the feedback. i agree with your comments, there r no waiters at this cafe though. I was wondering if there are sensors that work in different ways to passive infra red- for example ultrasonic, .... how ever i think in the end staff will have to use a switches behind the counter probably via a timed contact.
How about a motion sensor mounted on the underside of each table, pointed down? If they aren't keeping their legs moving, they must not be cold.
Being a customer myself and often siting outside, I would recommend that you place a Timer switch at each table. The problem that I see with this is that some people may prefer to be cold and some may prefer to be hot. If you buy a timer for each one then you are giving your customer the option to turn on the heater for as long as the timer would allow.

You can probably find timers that have an On/Off switch also. This would keep your customers from having to force the timer in the wrong direction if they changed their mind. The waiters could offer to set the timer for the customer.

I don't think motion detectors would work well enough. I think if you allow the customer to control their comfort then they are garunteed to be happy with atleast that part of their experience and it gives them something to do while the waiter is getting their drinks and food. If you wanted to take it a step further and get fancy then I would use some table top touch screens with perhaps a few games.

My momma always said KISS! (Keep it Simple Stupid)
how about just turn heaters outside on during business hours when the temp is below a threshold? Inside override for on and off too? At least they'll be automatic and the above logic will save money over a fully manual system.