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This is an enhanced version of the simple Garage/Shed Alarm. The Entry and Exit delays have been increased to about 30-seconds - and I've added a timed Siren cut-off and automatic Reset. I've also replaced the LED with an entry Buzzer. These enhancements mean that the new version will have a much wider application.... [read more]

A classic circuit of regulation of tone of three way, with which we can regulate low, mid and high frequencies, of acoustic signal. The boost/cut can be regulated in the range of ± 18 dB/oct. In the circuit the supply is ± 15V, but can be also supplied with alone supply + 9 until + 30... [read more]

Here's a power-on time delay relay circuit that takes advantage of the emitter/base breakdown voltage of an ordinary bi-polar transistor. The reverse connected emitter/base junction of a 2N3904 transistor is used as an 8 volt zener diode which creates a higher turn-on voltage for the Darlington connected transistor pair.... [read more]

This circuit could be used for replacing your manual volume control in a stereo amplifier. In this circuit, push-to-on switch SW1 controls the forward (volume increase) operation of both channels while a similar switch SW2 controls reverse (volume decrease) operation of both channels. A readily available IC from Dallas semiconductor, DS1669 is used here.... [read more]

This small transmitter uses a hartley type oscillator.... [read more]

This circuit of power supply, is very simple and easy to built, it can be assembled on a general-purpose PCB, finding its materials is very easy and cost-small. The output voltage is stabilized and is regulated in the region from 0V until + 15V dc, with biggest provided current 1 A. The regulation becomes with the P1. The Q1 is classic power transistor and it needs to be placed on a cool rib (Heatsink), when it works continuously in the region of biggest current it gets hot. The type of transformer is standard in the market.... [read more]