Posted on Monday, May 23, 2011 • Category: RC Servo Motors
The USB-Servo is a device to control a servo via USB. A servo is a motorized device that is commonly used in remote controlled cars and planes. I built this device to activate a toy puppet. The puppet has a button on its bottom, if you press the button the puppet collapses. When the computer is able to press the button, I can use the puppet to signal information like someone's online-state in the Jabber-network: when my friend goes online, the puppet stands up, when he logs off it collapses.
Servos are connected with three-wire-cables. A red and a black one for the power, and a yellow one for the signal. Power has to be between 4.8 and 6 volts, so the 5 volts from the USB-port is in the range. The signal doesn't take much current, so you can connect it directly to the controller. The angle of the servo is controlled with pulse width modulation (PWM). It gets a signal of about 50Hz (one pulse every 20ms), the length of the pulse tells the servo the angle to adjust.
Posted on Tuesday, April 1, 2008 • Category: RC Servo Motors
Below you find the schematics of the servo-controller I use. It is based on the PIC 16F84A from Microchip. To obtain a good resolution, I use a version of 20 MHz. It's interfacing to the serial port with a rate of 38400 baud. The PIC is controlling 12 servos in parallel with a resolution of 240 steps over 90 degrees rotation.
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