Projects by members > Dynodon

My 8XA circuit

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Dynodon:
Here's a picture of the pulses going to my cell with the 8XA circuit.
What do you guys think? Does it look close?
Don

sebosfato:
good work! pretty much like mine...

Steve:
You are tricking us again, Don Gable.... ;)
That wave looks too perfect... :D

Steve

kickbackemf:
Hey guys, where is the probe connected to produce the waveform that you show?  much obliged?

kb

Dynodon:
No tricks Steve.That is the wave form taken right at my cell on the positive side.
I'm using my frequency generator to send pulses into a 7404 hex inverter,through a 220 ohm resistor.That then goes to the opto coupler.
Then the opto pulses the gate on the scr.

The output of the scr goes into my chokes of 300 turns of 25 gauge wire on a pair of "U" cores.The voltage comes from a full rectified variac.This is exactly as Stans schematic.

Now the key point to make here is how you hook up your scope and the frequency you pulse the gate at.Very simple to do.

First thing you need to know is that those unipolar pulses are the 120hz pulses coming from the rectified variac.The frequency you need to pulse the gate at must be lower than 120hz.If you pulse the gate higher than 120 hz,then you will be just adding pulses onto the 120 hz pulses.Then it will just create fuzzy 120 hz pulses.

The gating pulses are just turning off the 120 hz pulses from the variac.Then you see the wave form I show.

Now the most important thing you need to do is isolate the scopes ground from the variac.You can't hook up a scope probe ground to the variac,because it will short out the variac.

To do this I had to use a isolated transformer.It's just a 1:1 ratio.But I had to modify the transformers earth ground.I removed the ground from the units case and seperated the ground from the recepticle as well.If you have any ground from your scope probe going to earth ground,it will short out.Once the grounds are isolated,you will then see the same signal I have.

Now you might be able to get away with cutting off the ground lug and the scopes power cord and get the same effect,I don't know.But once you remove the short problem,then you can hook right across the cell with the probe and ground,and get a perfect signal.

Don