USB heater for ant colonies

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.

USB sound card made from a broken USB headphones

If you have old USB headphones you can easily transform them to a USB sound. This card can be helpful during testing of home built devices connected to the speaker or microphone ports on the PC (for example A proof of concept of a simple sonar and Constructing a homemade microphone).

I used broken Audio 655 DSP headphones with working electronic inside. They have below features:

  • Powered from USB.
  • Stereo output.
  • Built-in microphone.
  • Mute/unmute switch.
  • Volume up/down switches.
  • Power on LED indicator.

Some of my current projects or what I will present here in the future

Yellow Tank

A simple tank robot based on prefabricated chassis.

Update (2015-05-20): Description of a board with the microchip and motor driver is available here.