Hobby Projects - Insulation tester, LED Circuits, Meters.

Saturday, May 21, 2011

Step Down Capacitor - No Heat

Sometime in the eighties, I had to change a blind timer design due to non-availability of a component. A high resistance relay 600 ohm coil was not in supply, 150E was available. The Power to timer was derived from a resistor, I put a 0.47uF 630V and it Worked !. This design of mine, deriving a low voltage from a capacitor shown on right adaptation became popular. I used a 0.47uF 440V AC or 630V DC Plastic Capacitor.

Schematics of delabs: Mains Voltage Indicator

This circuit has been drawn from my memory and i have not tried it out again, just see if it is ok and then try. You should use the fuse of 100mA a slow blow if you want but it is very important. This circuit has to be enclosed in a plastic sealed enclosure to avoid contact.

Mains Voltage Indicator with a LED

Mains Voltage LED Indicator

Mains Current Indicator with a LED

You should use the fuse of 1A a slow blow if you want but it is very important. You can design the shunt R3 and Fuse rating as required by your load. Note that this circuit is to be put in series with the load like an ammeter. If you put it across the supply like a voltmeter it will fuse out or burn out. This circuit has to be enclosed in a plastic sealed enclosure to avoid contact.

Mains Current LED Indicator