FREE
circuits!
Recently added diagrams and projects
November 30, 2010
This circuit uses the Holtek HT2884 IC to produce 8 different sound effects. [more]
November 30, 2010
This circuit takes an ordinary loudspeaker and allows it to be used in reverse, as a microphone. [more]
November 30, 2010
You are asking how to connect up some lights so that when the phone rings, they flash. This is very useful in a situation were there is lots of noise and it is impossable to... [more]
November 26, 2010
This nifty sound level meter is a perfect one chip replacement for the standard analog meters. It is completely solid state and will never wear out. The whole circuit is based on the LM3915 audio... [more]
November 26, 2010
This circuit should only be used with the solenoid type chime doorbells, the electronic type that play tunes will not work here. [more]
November 26, 2010
This digital volume control has no pot to wear out and introduces almost no noise in the circuit. Instead, the volume is controlled by pressing UP and DOWN buttons. This simple circuit would be a... [more]
November 26, 2010
This sensitive sound operated switch can be used with a dynamic microphone insert as above, or be used with an electret (ECM) microphone. If an ECM is used then R1 (shown dotted) will need to... [more]
November 26, 2010
After buying the processor, monitor, and printer, I wasn't willing to spring for a set of speakers too. After going "soundless", I decided to add speakers. Of course, this was the perfect excuse warm up... [more]
November 25, 2010
There are a number of npn transistors that will oscillate in the audio range when reverse biased. Minimum supply voltage is 7V for low power transistors such as BC109, BC238 and 2N2222A, it becomes 12V... [more]
November 25, 2010
This circuit enables you to test quartz resonators at the range values from 32kHz to 24MHz. Confirmation of good state of quartz resonator is done by diode signalling LED and acoustic signal [more]
All posts