The current drain of the regulator is minute compared with that of, say, a 78L05: at an input voltage of 9 V and open-circuit output, it is just under 50 µA. The circuit consists of a straightforward...
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Monday, 28 October 2013
Electronic Torricelli Barometer
Although it does not have the same charm as real mercury barometers with long glass tubes on pieces of carved and polished wood, the Torricelli barometer discussed here is a functional equivalent and...
Sunday, 27 October 2013
Infrared Proximity Detector Alarm
This circuit can be built from readily available low-cost components, some of which may even be hiding in your junkbox! The indicated value of 22 Ω for resistor R1 causes an average current of about...
Saturday, 26 October 2013
Momentary Switch Teamed With Latching Relay
This circuit allows an SPST momentary pushbutton to act as a push-on push-off switch, using a DPDT latching (bi-stable) relay. It was originally intended to allow a single pushbutton switch on the dash...
Tuesday, 22 October 2013
Two-Cell LED Torch
It sometimes comes as a bit of a shock the first time you need to replace the batteries in an LED torch and find that they are not the usual supermarket grade alkaline batteries but in fact expensive...
Sunday, 20 October 2013
Cat And Dog Repellent
The electronic dog repellent circuit diagram below is a high output ultrasonic transmitter which is primarily intended to act as a dog and cat repeller, which can be used individuals to act as a deterrent...
Saturday, 19 October 2013
Simple NiCd Battery Charger
A simple NiCd charger can be built using ‘junk box’ components and an inexpensive LM317 or 78xx voltage regulator. Using a current limiter composed of R3 and a transistor, it can charge as many cells...
Tuesday, 15 October 2013
Car Interior Lights Delay
Most cars do not have delayed interior lights. The circuit presented can put this right. It switches the interior lights of a car on and off gradually. This makes it a lot easier, for instance, to find...
Friday, 11 October 2013
Compressor For Electret Microphone
The ‘FM Remote Control Receiver’ (available on this website in Infra-red circuits section) has a connector where an analogue output is made available. To make a simple intercom or P.A. system the associated...
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