The QT113 is a capacitance touch sensor. Unlike many touch sensors, it does not rely on AC line voltage to be present in the room. Instead, it detects the change in capacitance the closeness of your body produces. A 2" square sensor plate can detect the closeness of your finger from several inches away. It will detect a finger even through plastic, glass or brick. The larger the metal sensor plate, the more the distance it will detect. The sensor plate can be as thin as a wire or as large as a metal door screen.
Using the circuit above will detect proximity with the output going low when your finger is close or touching. To toggle the output, turning it on when you touch the plate once, and then turning it off when you touch it again--tie pin 3 and 4 to ground. The DC output will directly drive an LED or can go to an input of a microcontroller.
Up to a point, the larger the value of the capacitor, the larger the detection distance. If you want to detect only at the front of a sensor plate, you can add a backing plate. 1/32" to 1/16" double-sided copper printed circuit board makes a good front and back plate.
The QT line of sensors come in larger ICs with as many as 8 sensors on a chip.
Audio Amplifier
Here is a simple audio amplifier that will amplify various audio inputs. This amp will amplify an output pin from a Picaxe or other microcontroller to provide beeps, sound effects, or tunes. In this configuration, it has the maximum gain of 20.
Two motor Driver
This motor controller can control two motors forward and reverse with speed control. They can be controlled together or independently. It is ideal for smaller Robots. By putting pins A-D high or low in different combinations, forward or reverse is effected. Sending a pulse width modulated signal to two of the pins creates the speed control.
Each motor can run at up to 600ma and 36 Volts. Pins 4,5,12, and 13 are the ground pins which provide the heat sink for the IC. If you run this controller near the maximum ratings, you should solder these pins to some kind of external heat sink.
Adjustable Voltage Regulator
This makes a good power supply that will run off a 12 volt car battery. It will provide up to 1.5 amps of power. If you use it at 1 amp or more, you should heat sink the LM317. For some circuits, like motor power or simple circuits like blinkys, the capacitors can be eliminated.
If you only need 100ma maximum, you can use the smaller LM317L.
NE555P Timer
This timer will go from less than a second to around 10 minutes. The higher the value of the resistor and capacitor, the longer the time.
Servo Controller
This servo controller is handy for testing servos. Use some care, as turning the potentiometer too far in either direction can strain and damage some servos.
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