Diagram Plus guide

Here is another simple circuit to mute the volume of Audio devices through simple touch. It exploits the action of the flip-flops in the timer IC 555 to reduce the volume of the Audio amplifier. IC NE555 is designed in the toggle mode. Its lower and upper comparator inputs are connected to the touch plates which can be membrane switches or two pieces of conducting plates. The inputs of comparators are stabilized through R1 and R2 to avoid floating.

When the touch plate connected to pin 2 is touched momentarily, output of IC1 goes high and T1 conducts. The centre tap of the volume control is connected to the collector of T1. So when T1 conducts current going to the amplifier drains through T1. This reduces the volume.IC1 remains latched in this position with LED on. When the touch plate connected to pin 6 is touched momentarily, output of IC1 goes low and T1 turns off. This restores the volume.

The modern mechanic switches are improved concerning of old technology. We need however many times to replacement some old switch or to check currents bigger than the durability of certain switches or simple we need something with modern appearance. For he and different reasons is essential the up circuit. It is simple in the manufacture and the materials that use they exist everywhere.

This circuit is based on the well known timer IC 555 (IC1), which drives a relay of which the contacts play the role of switch. The metal surfaces can have what form we want, but it should they are clean and near in the circuit. In order to it changes situation it suffices touch soft somebody from the two plates. Plate MP1 in order to the contacts of RL1 close [ON], or plate MP2 in order to the contacts of RL1 open [OFF]. The current that RL1 will check depended from his contacts. The Led D2 turns on when the switch they are in place ON and the contacts of RL1 closed. Two small pieces of metal can be used instead of MP1 – MP2. Because MP = Metal Plate.

Source : www.extremecircuits.net