SIP 130 wire-feed power supply - alternative approach

[BillJ]

I recall posts about greasing gearboxes and bedding in the motor brushes in the past, might be worth a search, but that's getting silly.

I've done that with greasing the gearbox. Made no difference, really. Not done anything with bedding in the brushes. Is this done by disconnecting the motor from the gearbox and free-running it for a while? It's one of my remedies for dodgy Saab headlamp wiper motors. Running it in reverse too also helps.

One other mod that I'd almost forgotten about was to the reel spindle. I found the reel rather stiff to turn so I replaced the steel washer under the spring with a nylon one (which was also a tad thinner) and gave it a shot of silicone grease to lubricate it. Any other grease or oil would probably be OK. That made it a bit easier to turn. Maybe this is worth a try on yours?

Or make a spacer for the screw to lower the tension on the spring? Not tried that.

Can't believe the transformer would take a few seconds to fill with electricity.

I know what you mean, though. Neither can I.

However, I can imagine the addition of a big-ish capacitor might help if the motor is demanding more current than the transformer can provide during start-up. Then again, if my power-supply is rated at only 1.5A and it can get it going, then a 50VA (2A @ 24V) transformer should be able to cope. Or should it? I'll try to measure the current on mine over the weekend since I suspect the power supply can manage a bit of overcurrent for a short duration.

 

[R Kraft]

You might try measuring the voltage across the motor, at start up.
Robert

 

[BillJ]

You might try measuring the voltage across the motor, at start up.

I'll do both tomorrow - voltage and current at start-up. BChild should definitely measure the start-up voltage if he can and ideally current too.

 

[R Kraft]

Maybe also the resistance of the motor windings while stopped.
Does anyone know what model number the motor is on the SIPs ?
Robert

 

[BChild]

I'll do both tomorrow - voltage and current at start-up. BChild should definitely measure the start-up voltage if he can and ideally current too.

Right that was tommorrow I was gonna do that...............

Today I did it

Start up voltage 2.4 Volts (min wire speed)
Flat out voltage 24 volts (Max wire speed)
Set it at 10% of range and 4.8-5.0 Volts was the reading when stable but it started up around the 3 volt mark before climbing to the above figure - this is the speed variation I see in normal operation - definately less as you turn the wick up but I didn't buy the damn thing to weld girders!!!

Somewhere else I was asked about motor ID - The motor has absolutely no ID anywhere that I can see

Current is beyond my electrickery skills..... I'm sure someone explained how I just can't find the thread

 

[R Kraft]

To measure the current , you just take a wire loose that goes to the motor and test the current flow on the ma scale,probably the 200m scale.
Robert

 

[madkayaker]

or me3asure the resistance of the motor and use Ohms law to calculate the current

 

[R Kraft]

or me3asure the resistance of the motor and use Ohms law to calculate the current

Just measuring the resistance of the windings should give the stall current.
PM electric motors are a sort of dynamic resistance,based on the Q of the motors inductance, the resistance and the friction of the various components at different speeds.
So one needs to measure them while they are running.

 

[Charred fingers]

Has anyone done this mod at #1 on a gas/gasless Cosmo
as the PCB is wired differently

I assume tho' I am probably wrong not being an electronics expert
that CN5 on Bills diagram is a rectifier supplying a DC current to CN1,
On the diagram above CN5 isn't being powered directly from the transformer
but by a feed which appears to be linked to the torch which is switchable
depending on the mode being used.

 

[mechatronicsman]

Hi,
I have just completed a very similar modification on my SIP Migmate 150 DP Gas/Gasless welder which should be similar to your cosmo welder.

The difference between my and BillJs mod is that I use a 12V relay (as this was what I had in my parts bin), and that my welder is gas/gasless, so schematic is slightly different, identical to your cosmo welder.

Here is the schematic:

and a picture showing where to connect the 12V relay coil on the control PCB:

.

I have posted a full description of my mod on my homepage (www.hobbymechatronics.com), you will find all the details there. I could also add more info here if needed (but I am not fan of duplicating info, easier to have one source for modification if I later add details..

I also had problems with my gas-feed that was fixed by shaving of some plastics inside the torch trigger, also described on my homepage.

Bjorn
-----------------------------------
Mechatronicsman
www.hobbymechatronics.com

 

[R Kraft]

So you didn't use a resistor with the 12v relay ?
Robert

 

[mechatronicsman]

So you didn't use a resistor with the 12v relay ?
Robert

No. Note that it is NOT connected to 230V. It is connected to the relay on the controller PCB. The energizing voltage of the main relay on the controller PCB is 12V, so piggybacking the new extra-relay over the main relay terminals works well.

Bjorn
-----------------------------------
Mechatronicsman
www.hobbymechatronics.com

 

[R Kraft]

Ok i see, many of the boards that people are working on, have a 24v transformer to run the relay, that is why I asked.

 

[Wombat]

Thanks Mechatronicsman and BillJ for your contributions - I have done the power supply mod using a fully regulated 24 volt power supply (non-switchmode) I found in a box of transformers I bought on eBay for $15.

The motor starts low and speeds up evenly and is positively screaming by full dial( I will never have to take it past half way). I did some feed measurments and at half way on the dial I have approx 6 metres/minute , divide that half in approx thirds and I have 2 and 4 m/min respectively. I like the way the motor stops dead when the trigger is released too.

Didn't have time to try it welding - that's next weekend - have some car body work to do that will test it

Thanks again and I highly recommend the mod

 

[Wombat]

Works great - smooth welds. Next MOD will be the multi turn pot for speed control

 

[HysterBod]

Hi there,

I recently inherited a near as dammit brand new SIP mm 150 G/NG....

that's pretty much useless, so I had a look online for possible modifications to improve it's performance and before I knew it here I am.

I'd just like to say how great this thread is, and not being in the position to just fork out a few hundred £££ on a decent welder, I now know what I'll be getting up to in the garage this weekend.

again, great thread..great forum

thanks al
Darren

 

[signalsolution]

Mods PWM

Hi I've logged on to look for the wiring diagram for the 130 and found this very interesting thread. The mods described are interesting but are not the best way to deal with the motor drive. The circuit used to control the motor speed is a very inefficient DC set method. This method means that the available torque on turn on is proportional to the voltage. In modern motor control the norm is PWM (pulse width modulation) this uses a high frequency signal where you control the on time to control the motor speed. I will make a PWM controller for this one over the weekend and report back.. We are an electronic design company so nice and easy for me) BillM……..

 

[stuff to fix]

I dont think the problem with the welders is the available torque at the motor. The idea behind the original power supply is that the voltage is based on what is coming out of the welder, and the higher that is set, the faster the wire needs to run. So, power it directly from the weld supply and it will approximately adjust automatically.

The problem is the electronics they have used for doing this. I dont think it needs pwm, but if you are designing something that will work that way, it needs to adjust the basis speed of the motor according to the weld voltage setting. Then a fine control to tweak it, and ideally one which stays in pretty much the same position on every scale so everything is automatic and you do not need to change anything unless you are an advanced user or once you have got it right.

With a separate power supply, these guys are creating a different kind of speed control, which just has a dial and speed settings and you dial up what you want. I dont know which system an experienced welder prefers. The problem here is firstly the original design power supply isnt very stable (the welding output!), so replace it, but second the original power control isnt stable either. It was not designed as a DC controller but to control a fluctuating supply, and isnt brilliant even at that.

Now, what happens when you have the trigger depressed so the feed is running but you take the torch away from the work? Do some welders have a system to shut down wire feed when there is no arc?

 

[regcheeseman]

Thank you!

I had to register just to thank all the contributors to this forum.

I've a SIP migmate 150 turbo that I've had for about 12 years and it's never been that good.

I've been reading my way around the this forum and had a list of modification to try.

So I bought a new steel liner, swan neck, tip and shroud.

I made a brace for the ropey wire feed and fitted the new parts.

I had previous fitted a stronger front plate and a conduit gland to the front panel to support the torch and stop it drooping out of the front of the machine.

With the wiring guide from this forum I set about doing the power supply mod, I work in medical electronics and found a 24v 3.75A supply that would be ideal.

My PCB board was not exactly as per the diagram but I followed the wires and the four pin connector seemed the same. I connected it up with the relay as per the wiring diagram and hit the power.
The LED on the power supply lit up and the welder hummed into life and that was it, no relay working and no wire feed.
A correction to my wiring and the relay started to click as required but still no feed

I went over the wiring, over and over - tried a few different configurations before taking out the PCB, to see that tracks and resolve the circuit function from

scratch. Now I could see exactly what was required and wired it too suit....

still no feed -

desperation setting in I connected the power supply direct to the feed motor

Still nothing

21V at the power supply - but no wire feed.......arrrggghhh!!!!

Then I measured the voltage under load and the voltage dropped to 0 - I had picked up a duff power supply. I hooked up a 12V battery in place of the power supply and the wire feed worked fine.
Because of slight differences, my final wiring was a bit simplified over the original plan, but I now knew it would work if I could find a decent power supply, a quick scout about the house turned up an old dell laptop supply - 20V at 3.5A

I hardwired it into the welder - not pretty...

Result is that the welder is totally transformed - it now welds really nice, welding is a joy rather than a chore.
If anyone else has got one of these welders and thinks it's a bit iffy on the wire feed - do the mods, cannot recommend them highly enough.

Thank you! thank you! thank you!

 

[rtbcomp]

Thanks for the feedback, it's nice to know we're of some use!