Welder control circuit

tcmtech

Joined Nov 4, 2013
2,868
Solar uses a delayed phase angle firing type voltage regulation system. It's basically just a light dimmer circuit with voltage feedback circuit that keeps your output voltage stable as the load currents change.

As for the output the choke is for smoothing out the DC power and giving the welding arc stability.
 
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tcmtech

Joined Nov 4, 2013
2,868
It would be nice if the attachments were in a common format that can be opened with most any basic software. :rolleyes:

I know I would consider being more helpful if I could see the schematics. ;)
 

MaxHeadRoom

Joined Jul 18, 2013
19,186
I opened it up in AutoCad but it is a board layout rather than a circuit schematic which makes it very hard to decifer without putting a great deal of time in.
Max.
 

Thread Starter

hoader

Joined Mar 27, 2015
29
I opened it up in AutoCad but it is a board layout rather than a circuit schematic which makes it very hard to decifer without putting a great deal of time in.
Max.
Hi there:
How do I put this file in a different file format and what is it called? I have tried to trace the circuit to recreate a schematic but not all connections are clear. Some traces are so close to pads that I cannot tell if there is an electrical connection without de-soldering the components. My guess is the problem lies near the beginning of the circuit since all outputs are full on. Before the quad logic gate and quad comparator.

I have figured out from research and earlier posts from you guys. Either the solid state relay controls heat by pulse width allowing from a fraction of the sine wave to the full wave for high heat, or rapid pulses so the welder is powered a fraction of the time to no off pulses for high heat. The first circuit would have some form of zero voltage crossing detection.

I also don't know what kind of motor is on the wire feeder. Is it a plain DC motor or stepper motor. I have never seen a driver for a stepper motor of that size. If it is a plain DC motor, is it receiving pulses or a gradual voltage ramp to vary the speed?

The only other output from this board is to the gas solenoid valve. Even I should be able to figure this one out. I will try to start at the relay and work backwards to draw a schematic.

hoader
 

tcmtech

Joined Nov 4, 2013
2,868
I also don't know what kind of motor is on the wire feeder. Is it a plain DC motor or stepper motor. I have never seen a driver for a stepper motor of that size. If it is a plain DC motor, is it receiving pulses or a gradual voltage ramp to vary the speed?
More than likely it's just a common brush type DC motor and gearbox very similar to the type used in automotive windshield wiper drives.

Solar is well known for building their stuff as cheap as possible with the most common and cheap as possible parts they can get so the odds of them using a larger and fairly expensive stepper motor and driver circuit Vs a cheap Chinese knockoff of an already cheap mass produced windshield wiper drive unit would be what I suspect got used in your welder.
 

Thread Starter

hoader

Joined Mar 27, 2015
29
Hay Guys, I got lucky!

I called the company that deals with Solar welders and they sent me a fax of the schematic of the circuit board. I found much of the writing small and difficult to read. Zooming in on the document made the small marks into big blobs. I spent a lot of time copying the schematic in cad. Most of that time spent figuring out the junction labels by tracing that part of the circuit on my board. There are a couple slight differences from the schematic and my circuit board For example, there is an extra diode on the board and resister #31 is replaced with jumper wire W13. The output of the board are still full on even when the input signal (wires) are disconnected. I figure you will want me to take voltage measurements at various points in the circuit. Just tell me where and I will take the readings.

Thanks hoader

P.S. Did the 2 files get uploaded?
 

Attachments

tcmtech

Joined Nov 4, 2013
2,868
So do you make it a point on purpose to have your attachments in formats that are unopenable by the average person using common software? :rolleyes:
 

MaxHeadRoom

Joined Jul 18, 2013
19,186
Also you went back to DWG instead of DXF, I read the last DXF but your DWG will not even work on my convertor, which usually is no problem.
Max.
 

Thread Starter

hoader

Joined Mar 27, 2015
29
tcmtech and Maxheadroom, That is just one of many silly mistakes I made. I used open office to make to BOM for the circuit board. It had an option to save in text but still had an extension I was not familiar with. I'll try .RFT but I doubt it will keep things in columns. Is there a way to delete those 2 useless files?
 

Attachments

Thread Starter

hoader

Joined Mar 27, 2015
29
Hi there:

I tried to follow the circuit drawing and measure voltages at those components. Easier said than done. The drawing I made of the schematic from the prints have a couple mistakes , ex. 2 diode 16s and 14s. I couldn't read the numbers on the print of some of the resistors. There is a diode on the board not shown in the schematic and a couple components on the schematic that are not on the board. I connected the board to an auto-transformer set to 25 volts rms The voltage on each side of R5 is 15v and 5v at the zener diode. I connected the heat and wire speed pots to the board and made measurements from there and worked towards the outputs. The pins to the gun trigger was disconnected or open and the outputs should have been low.

Start with IC3 comparator - LM319N: Pins 1 and 2 output are square wave 5 volts p-p. Changing the pots changes the pulse width. Pin 4, 5 and 6 (-2 in & +2 in -1 in) were both saw-tooth waves about 3 volts p-p. Pin 7 (+1 in) showed 2 volts dc. Pin 8 (-3 in) was 0 volts. Pin 9 (+3 in) had 20 volt full wave rectification. Pin n10 and 11 and 13 (-4 in & +4 in 4 out) were 0 volts. Pin 14 (3 out) had a 7 volt saw-tooth wave.

IC2 Quad-Nand Gate – CD4093: Pin 7, 0 volts and pin 14 was +15 volts. Pins 1,2,3,5,6,19,11 had 4 volts dc plus a 1 volt square wave. Pins 8,11,13 had a 5 volt square wave. Pins 4 & 9 were 0 volts. Pin 12 was 4 volts dc plus about 9.5 volt p-p ac ripple.

IC1 Driver ULN2004A: Pin 1,2,5 had 3 volts DC plus 1 volt square wave. Pin 4,6,8,12,14,15,16 had 0 volts. Pin 3 and 7 was 12 volts dc. Pins 11 and 13 were 15 volts dc. Pin 9 was 27 volts. Now I got into some trouble. Pin 10 seemed to be inconsistent. Not having all the right tools sucks. I got the probe shorted between pin 9 and 10 and the chip exploded. A couple of the measurements listed above was after the fire works. The output from J5 has 30 volts going to the wire feeder and the SS relay. The solenoid valve has 15 volts.

All the frequencies of waves mentioned above are roughly 100 Hz. The chip that had originally burned was a PNP part of a darlington pair transistors and has been replaced.

Have you been able to open the BOM for the list of components used in that board? Have you been able to view the original print? I need some hints as where to go from here. The board is operating full bore regardless of the trigger, heat setting or wire speed setting. The trigger appears to go to both IC1 (pins 1 and 2) and IC2 (pin 2). What should the voltage be at those input pins and at the output pins?


Hoader
 

tcmtech

Joined Nov 4, 2013
2,868
The most common failure with those boards is one or more of the IC's but now that you have blown one up I would suggest replacing all of them together.

Also while doing so I would recomend putting IC sockets in so you can just pop the chips out and plug new ones in next time it fries.
 
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