Pulsed DC Square Wave Circuit.

This is an involved circuit and some of the parts seem to be elusive. Firstly I would like to check to see if this circuit can be achieved and whether or not the parts can be updated and reconfigured better. I am an enthusiast(novice) any help would be really appreciated. Thanks in advance, for the membership and any help surrounding this posting. Find the image attached.

The circuit is a fully-developed versatile driver for the electrodes (arc welder, I guess). All the components are popular.

It is versatile because you can vary the frequency and duty cycle to the electrodes.

If you wish, you can experiment with just the 555 timer IC driving the mosfet. There are easy ways to adjust the frequency and duty cycle, without a need for the 741 op amp, or the 4069 inverter (6 on one chip).

I have not used the mosfet driver IC. An expert here might have better advice about that than I would give.

this circuit uses switches to vary capacitance and resistance (rc time for 555)

cant we use variable pot and variable capacitor?

ec_nisarg said:

this circuit uses switches to vary capacitance and resistance (rc time for 555)

cant we use variable pot and variable capacitor?

Click to expand...

Yes there are variable pots, but you might have trouble finding a variable cap with a large enough range.

About the best you can do is try a cap in one of the middle values.
If you need a lower frequency then try a greater value cap. Etc.

See this website for ideas about how to use a 555, change duty cycle, etc.

**broken link removed**

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ec_nisarg said:

this circuit uses switches to vary capacitance and resistance (rc time for 555)

cant we use variable pot and variable capacitor?

Click to expand...

Yes there are variable pots, but you might have trouble finding a variable cap with a large enough range.

About the best you can do is try a cap in one of the middle values.
If you need a lower frequency then try a greater value cap. Etc.

See this website for ideas about how to use a 555, change duty cycle, etc.

http://home.cogeco.ca/~rpaisley4/LM555.html

Thanks, I have trimming potentiometers 2k and 20k, Designing the circuit with a variable capacitor? what kind of range would be best? and thanks guys

FullFromFlight said:

Thanks, I have trimming potentiometers 2k and 20k, Designing the circuit with a variable capacitor? what kind of range would be best? and thanks guys

Click to expand...

The dip switches in the schematic are a convenient way to switch in different capacitors.

I think you'll want to have a way to change the frequency (or duty cycle) of the arc welder, to allow it to handle different metal thicknesses, electrode diameters, etc.

No one can predict what frequency and duty cycle you'll use most often. That is why the schematic provides a wide range of selection, among 4 capacitors.
And then the potentiometer (frequency) adjust.
And another potentiometer ('throttle') adjust.

I have not done 12V DC welding but I have done AC welding with a big unit. I know how easy it is to vaporize sheet metal. By having a wide range of adjustment you could be able to do light jobs, more easily than with a plain 12VDC battery.