Hi, I am a beginner with electronics , I am very keen to learn and understand various motor speed controllers.
The attached pictures shows a pcb from a foot controller for a pendant style drill.I have a number of these boards which do not work and would like to try and troubleshoot the reasons.
I can understand how a chip controls the on/off to the gate on the thyristor , although I am unable to see how the gate is controlled on this pcb.

I would very much like any help in explaining how this style of AC output speed control works ,

Ps -I have not really posted much in forums before , I hope it’s all comlient etc.

 

The BTA16 is a triac not an SCR. It is like an SCR but it can conduct in both directions. This is a phase angle speed controller. If the triac is triggered just after the zero crossing point then it will give out maximum power. If it triggers at the crest of the waveform (90 degrees if we call the zero crossing zero degrees.) then the output power will be about half. So the later it fires in the waveform the lower the output power and therfore the speed of the motor. The same happens on the other half of the cycle. (180 degrees to 360 degrees.) I think the fact that it is not isolated from the mains means that is a topic that is not allowed on this forum. I will let one of the moderators decide.

Les.

 

I think the fact that it is not isolated from the mains means that is a topic that is not allowed on this forum. I will let one of the moderators decide.
Les.

There seems to have been plenty of mains SCR/Triac controller threads, also T.M. controllers apply to this.
Max.