As some of you already know, I'm a big fan of ants and for one of my colony, I decided to make a heater. Today I will describe the current state of this device, however it's far from being finished. It uses a resistor that (as any other resistor) produce heat when current goes through it
Let's start from the theory, what should be the value of the resistor (resistor's max power and resistance) if it would be desirable to obtain as much power from USB as possible? The USB supplies always constant voltage (5V) and maximally it can supply 0.5A of current. The maximal power consumption of the device connected to the USB (a resistor in this case) is P=U*I = 5V*0.5A = 2.5W. From Ohm's law, R=U/I = 5V/0.5A = 10Ω.
I placed this resistor in gypsum form (created from matchbox, after it dried-out the paper was scratched out by using a knife).
Before even trying to connect it to the USB port, I verified if it works by using my lab power supply, it worked but I observed two negative things, the first one was the amount of power drained from power supply - was a bit too big, the second was that the heater heats itself way too much, it was too hot. That's why I plan to add some sort of PWM regulation to decrease power consumption, after that I think that it will be a quite useful gadget.