# What bits n bobs will I need?

Hey guys,

I’m going into this slightly unprepared so need some words of advice from the pros as to what to buy before I start tinkering… I have attached a pdf with a rough outline of my product idea (however it’s more of a general design than a construction document).

In a nutshell; the chairs need to heat up the closer they are to the ‘alpha chair’ and every so often a new alpha chair is selected and the process begins again.

On a small prototype scale the only way I can contemplate doing this is to use those usb mug warmers to heat the inside of the chairs. Can you directly power this type of usb using arduino or would you need to start tinkering with the circuitry in the heater?

I have been told that infra-red proximity detectors are a no-no so I am using a copper squares, 5x5 (check out pdf), to connect each chair to the mainframe. In essence, in this prototype; the squares act as the alpha and the orbiting beta chairs, not the chairs themselves, the chair objects are simply complete a circuit, tell the arduino they are active and facilitate the heat. In the pdf these squares are made from 2 triangles; a plus and a minus which connects to the relative conducting parts on the bottom of the chair.

SO! I hope you understand my concept. I’d welcome any criticisms or feedback and most certainly your analysis on what you think I might need to buy!

Thanks very much,
Regards,
Andy

tepid spec copy.pdf (99.1 KB)

how do you plan to power the heaters?

a) 'duino can't power them directly b) if the power is coming through the floor pads i would worry about large voltages or currents flowing where people are present c) power on-board the chair would solve that, but then you have the problem of power storage!

The power input required to power the heaters is 2.5W~DC 5V. I don't think it's enough to cause a shock but you have a good point. You could store a 9v in there with a hack... http://lifehacker.com/5397081/diy-9v-battery+powered-usb-charger As long as it lasts the few hours of the exhibition it's fine.

Andy

Will the chairs be self-powered and just get their on/off cue from the arduino? Do 1 wire comm's between chair & uno - all left triangles are signal, all right triangles are gnd. Each square has its own address (25 lines (Mega), or a couple of mux/demux chips), uno queries each by address & listens for response if a chair is on that spot, gives it the heat up command. Use some batteries like these that should last a while, http://www.mpja.com/prodinfo.asp?number=17280+BT http://www.mpja.com/prodinfo.asp?number=18899+BT

Arduino-clone with MOSFET PWM to control current to a heating pad on the seat?

CrossRoads: Will the chairs be self-powered and just get their on/off cue from the arduino?

Yes it sounds like a viable method like mmcp42 said but would the same principle not apply to receiving a shock from the bottom of the chair then as well?

Can you not have a broken circuit to the arduino from each square then when the chair is placed on the square it completes that individual circuit and sends the signal back to arduino that square x is active. Arduino could then command a switch connected to a power source to true and initiate power to that square.

By the way, thanks for the replies guys, saving my ass here, really appreciate it! Andy

I/O levels on the 1-wire interface are 0/5V, and low current, not enough to shock anything.