How to ground?

Thread Starter

cpleng7

Joined Dec 18, 2008
120
Currently I am worked out with single phase full wave bridge rectifier. I am using the microcontroller to control the 4 SCR bridge.

I want to ask is how to ground the part? now have 2 part, one is the controller part, with the voltage have step down using transformer to 9Vrms. since the SCR bridge rectifier is using the 240V and the optoisolator is used to isolate the 240V and 9V part. Should I ground all both of the part together? or I also need to isolate the ground part?
 

Georacer

Joined Nov 25, 2009
5,182
If the upper circuit was independand and worked alone, you wouldn't have to ground it. But if you want it to interface with other circuits, they should all have a common reference point and thererore, yes, that point should be grounded.
 

t06afre

Joined May 11, 2009
5,934
If the upper circuit was independand and worked alone, you wouldn't have to ground it. But if you want it to interface with other circuits, they should all have a common reference point and thererore, yes, that point should be grounded.
I do not agree. The OP use opto couplers. To achieve galvanic isolation, and keep the high voltage part isolated in respect to the low voltage control unit. So by all means do NOT apply ground to the point marked with a blue square. It is wrong and will make your circuit unsafe
 

Georacer

Joined Nov 25, 2009
5,182
I guess in high-power applications, where isolation is needed, your argument stands correct. But what I said isn't too different, since you don't need to "read" anything from a burning resistance (R11). I 'll agree though that I didn't put much emphasis on safety.

If however you needed to take readings from electronic devices on the heavy load, how would you proceed?
 

t06afre

Joined May 11, 2009
5,934
The correct thing here would be to have two reference points (grounds). Then measuring on the controller unit (low voltage). The reference point will naturally be the grounding point. On the high voltage part some other point that make sense. As I said In this circuit. A common ground point is not needed nor recommended
 

Thread Starter

cpleng7

Joined Dec 18, 2008
120
The correct thing here would be to have two reference points (grounds). Then measuring on the controller unit (low voltage). The reference point will naturally be the grounding point. On the high voltage part some other point that make sense. As I said In this circuit. A common ground point is not needed nor recommended

so should I create another ground point for the high voltage side, if I wanted to see the graph from R11?
 

t06afre

Joined May 11, 2009
5,934
so should I create another ground point for the high voltage side, if I wanted to see the graph from R11?
I do not use proteus. So I can not help you. But sure you can place a probe on each side on R11 and plot the difference. Or plot IR11*R11
 
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