Cool small Circuits

Posted on Feb 7, 2014

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

Cool small Circuits
Click here to download the full size of the above Circuit.

, 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. 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. 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...

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