I can't get a voltage reading when my meter is connected to the 12VDC power supply output and the black probe is connected to either the 110VAC neutral or it's ground. Does that mean that the 12VDC is not going to ground in either case ? I believe the 110VAC to 12VDC power supply has it's -V pin ultimately connected to the 110VAC neutral.

In this circuit, I want to connect only the coils discharge to either the 110V's neutral or ground. The reason for this is when the coil is pulsed with 400VDC, the kick back voltage will be very high and (+). I am concerned that the high (+) voltage might back up in the circuit's grounding and damage circuit components. One other thing. If I should I connect the coil's discharge to the 110V ground, which is attached to both the power supply and the metal box that will hold all the components, should I expect a wake up call every time the coil pulses via the metal box ?

Components:
Power Supply; 110VDC to 12VDC 12.5A, 150W
ZVS capacitor charger circuit set to deliver 400VDC
Electrolytic Capacitor; 500V 100uF to be charged to 400V
555 timer; Astable, 1Hz, High = 15ms
Optocoupler; CPC1788
Coil; 18g wire, 2.5mH

 

Typically the DC power is isolated. You'll read it like it were a battery; with one pole ( + ) and one ( - ) in reference to each other. Niether will read anything to an AC lead.

 

Does that mean that the 12VDC is not going to ground in either case ?

This would appear to be the case.

I believe the 110VAC to 12VDC power supply has it's -V pin ultimately connected to the 110VAC neutral.

That isn't what your measurements are telling you.

You can connect the ground from the output to neutral or ground for your 110VAC. If you're in the US, neutral and earth ground are bonded at the power panel, so they can be treated as being the same potential for most purposes.

EDIT: As @MaxHeadRoom mentioned, you should use earth ground.

 

You should never bond the circuit common to neutral, if you want ground reference, use the earth ground conductor.
Per NEC/CEC code.
Max.

 

You should never bond the circuit common to neutral, if you want ground reference, use the earth ground conductor.
Per NEC/CEC code.
Max.

Thank you.

By connecting the coil discharge to the 110V ground, which is also grounding the metal box, is there any problem personally contacting the box while the circuit is operating ?

 

Connecting the circuit to the same earth ground as the box should normally prevent any problems of coming in contact with the metal box.
Max.

 

is there any problem personally contacting the box while the circuit is operating ?

That's what usually prevents you from getting shocked.

 

Thank you all.