This is not just another dimmer circuit. The improved design of this dimmer circuit enables its triac to be triggered with lower
voltage values. Normally, the triggering voltage of a triac is around 70V. In some applications though, it is desirable to use a lower voltage in
triggering the triac. A trick is used to achieve this effect in this circuit: the addition of the components R1,C1 and P1. Due to this, the trigger value can be pulled down to around 35V.
Construct the circuit and put it in a highly insulating box. Remember, the circuit is working with 220 volts! For P2 use a special potentiometer with a plastic shaft.
After constructing the circuit, check all wirings and isolations again before you plug it in the power line.
Turn the pot P2 first to its leftmost position. Then plug the load (bulb, electric drill, motor, etc.) before you plug the dimmer into the power line.
Pot P1 must be set in such a way that the lamp or the drill machine will almost start even though speed control P2 is at its leftmost position.
There are lots of practical applications for this circuit. One typical application is controlling the speed of an ordinary electric drill machine.
It can also be used to control the speed of a sewing machine, or the electric motor in a model boat, etc.
Parts Placement Layout
External Wiring Layout
Electronic Circuits volume 1.0 - Circuit Nr. 25
The complete data of the electronic circuit described above can be found in the following book and is available from Amazon.com.
Click on the image to view the book.