Adding Digital Generators to an Old Analogue TIG Welder

[chy_farm]

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Set up a couple of digital generators to my old analogue TIG welder this spring, in an attempt to optimize its wave forms of welding current, to help my self when I make some butt-welding to thinner aluminium sheets.

[chy_farm]

Here showing my old TIG welder;


The digital unit above is set up on the front panel;

[chy_farm]

Several logic-chips are placed on a small additional board, and is placed on the main circuit board of the welder;

[chy_farm]

The default setting only provides the minimum duty ratio of welding pulse as 12.5%
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but I wanted smaller duty as small as down to 1.0% for each welding pulse frequency,
showing one sample I got after this retrofit;
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[chy_farm]

This old welder has a pulse-range from nearly 0.5Hz up to 500Hz done by analogue frequency generator by default. This old set-up of analogue pulse is not replaced with the new, it can be used if I want.

One of the features I love is that this new set-up can provide higher pulse frequency from 500Hz up to 900Hz, which I found useful in welding thinner steel sheet.
The arc sometimes wonders when the welding amperage is set low, like 30A for welding current and 5A for base current.

But I feel like this problem has nearly gone since I added this new digital generator by applying DC welding pulse frequency higher than 750Hz;
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with this frequency the arc shows somewhat better stability to the aimed point.

[chy_farm]

Below is a default wave form of Alternative Current welding, aluminium for example, showing the minus peak as 45A besides overshoot.
Output power is set to 50A for welding;

This shows the real welding power is a tad lower than the setting value.

Here is another wave form attained with the same setting but the output power was set to 30A;

[chy_farm]

Now I'm going to replace the rectangular wave forms of the both sides (of plus and minus domains), with a couple of pulses of arbitrary frequencies given by this new addition;


Replaced the rectangular wave with 650Hz pulses, setting power 150A for welding.


also with 700Hz pulses, setting power 170A.

[chy_farm]

As far the schematic, I am thinking of asking a buddy who guides me to attain this job with a lot of information on welding machines if he gives me permission to open his schematic design of this unit.

[chy_farm]

As far the schematic, I am thinking of asking a buddy who guides me to attain this job with a lot of information on welding machines if he gives me permission to open his schematic design of this unit.

This buddy gave me OK to open his schematics on this project, will compile a bit and post here soon.
(Note he says the schematics are only for Hitachi's welder, version name 'ADGP' and some series after this. )

[chy_farm]

This buddy gave me OK to open his schematics on this project, will compile a bit and post here soon.
(Note he says the schematics are only for Hitachi's welder, version name 'ADGP' and some series after this. )

This schematic is just for Hitachi's TIG welder, ADGP series. Hope you can apply this for yours thanks.
Chy