Sunday, July 29, 2012

1.3-12V Small Variable Power Supply

This is a small variable power supply delivers adjustable output voltage of 1.3v-12v. The current output determined by R3. With current setting (see part list), it will deliver current output about 1A.

Sunday, June 3, 2012

220V Light-Operated On/Off Switch

220V Light-Operated On/Off Switch circuit diagram

This schematic diagram is a light-operated, remote-controlled solidstate switch circuit to handle lamp. While in darkness, the resistance of Light Dependent Resistor (LDR) is extremely hight, it shoots up to megohm range. As a result, the triac isn't going to have gate drive and therefore it doesn't conduct.

Friday, April 20, 2012

Gold Detector Schematic

Gold Detector Schematic circuit diagram

Here the very simple and easy build gold detector circuit. The circuit capable to sense gold or metal or coins from a distance of about 20cm, depending on the size of the object to detect.

The circuit oscillates at about 140kHz and a harmonic of this frequency is detected by an AM radio. You can simply tune the radio receiver until a squeal is detected.