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Protect your expensive batteries from discharge damage with this mini-sized electronic cutout switch. It uses virtually no power and can be built to suit a wide range of battery voltages. Main Features Disconnects load at preset battery voltage Automatically reconnects load when battery recharged Ultra-low power consumption (<20ma) Miniature size 10A maximum rating Suitable for use with 4.8-12.5V batteries Transient voltage protection (optional) Suitable for use in... Cars, boats & caravans Security systems Emergency lighting Small solar installations Camera battery packs Many other low-power applications Picture of the project: Back in May 2002, we (Silicon Chip) presented the "Battery Guardian", a project designed specifically for protecting 12V car batteries from over-discharge. This unit has proven to be very popular and is still available from kit suppliers. This new design does not supersede the Battery Guardian – at least not when it comes to 12V car batteries....

This circuit uses an NE555 timer IC, some LEDs, a couple of piezo buzzers and a few other components to produce audio-visual effects as per your requirement. The timer NE555 and its equivalents are widely used for all sorts of audio and visual indications, such as door alarms. But the sound produced by these circuits may not be always pleasant to hear, or the light produced may not be visually appealing. With this circuit you can get different audio-visual effects. Here we use LEDs for visual indication and buzzers for audible alarms as they require relatively low current to operate. By simply connecting some resistors and capacitors to NE555 we can obtain some interesting visual and audible effects as described here. Circuit and working Fig. 1 shows the circuit of the versatile audio-visual alarm which is built around timer NE555 (IC1), LEDs, buzzers and some resistors and capacitors. Resistors R1 and R2 and capacitor C1 determine the frequency of the LEDs’ blinking. The frequency is ...