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This circuit is Ideal for car use. It has ability to transform a mains adapter in to a charger . This one can be used to charge cellular phone, toys, portables, video batteries, MP3 players, ... and has selectable charge current. An LED is located in circuit to indicate charging. Can be built on a general purpose PCB or a veroboard.... [read more]

This is a single zone alarm - with independently adjustable Exit, Entry and Siren Cut-Off timers. When the alarm is activated its Siren will sound once - for up to 20-minutes. Then it will switch off and remain off. If you wish - you can use a mains power supply. But the extremely low standby current makes battery power a realistic option.... [read more]

The LED flasher circuits below operate on a single 1.5 volt battery. The circuit on the upper right uses the popular LM3909 LED flasher IC and requires only a timing capacitor and LED.... [read more]

This circuit is intended for alerting purposes after a certain time is elapsed. It is suitable for table games requiring a fixed time to answer a question, or to move a piece etc. In this view it's a modern substitute for the old sandglass. Useful also for time control when children are brushing teeth (at least two minutes!), or in the kitchen, and so on.... [read more]

This circuit uses an LM11 to form a voltage follower with 1G ohm input resistance built using standard resistor values. With the input disconnected, the input offset voltage is multiplied by the same factor as R2; but the added error is small because the offset voltage of the LM11 is so low. When the input is connected to a source less than 1G ohm, this error is reduced. For an ac-coupled input a second 10M resistor could be connected in series with the inverting input to virtually eliminate bias current error; bypassing it would give minimal noise.... [read more]

Ordinary LED flashers turn the LED on and off abruptly, which can get a little irritating after a while. The circuit shown here is more gentle on the eyes: the light intensity changes very slowly and sinusoidally, helping to generate a relaxed mood. The circuit shows a phase-shift oscillator with an adjustable current source at its output. The circuit is capable of driving two LEDs in series without affecting the current.... [read more]