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This is a medium range transmitter circuit diagram. This is also improved by changing the values of the resistor.... [read more]

A simple but less efficient methode of controlling a DC voltage is to use a voltage divider and transistor emitter follower configuration.... [read more]

This Keypad is suitable for the Modular Burglar Alarm. However, it has other applications. Pressing a single key will energize the relay. Entering the Four-Digit code of your choice will de-energize it.... [read more]

The purpose of this circuit is to animate shop-windows by means of a capacitive sensor placed behind a post-card-like banner.... [read more]

These are two - easy to build - relay-based alarms. You can use them to protect your motorcycle - but they have many more applications. If you use relays with 6-volt coils - they'll protect your "Classic Bike". Both alarms are very small. The completed boards occupy about half a cubic-inch - 8 cc. The standby current is zero - so they won't drain your battery.... [read more]

In the circuit, a quad voltage comparator (LM339) is used as a simple bar graph meter to indicate the charge condition of a 12 volt, lead acid battery. A 5 volt reference voltage is connected to each of the (+) inputs of the four comparators and the (-) inputs are connected to successive points along a voltage divider. The LEDs will illuminate when the voltage at the negative (-) input exceeds the reference voltage.... [read more]