New user with Cosmo 170 (SIP) and a headache

[BChild]

just adding to this, almost gone to the wall thread.

pretty much gone to the wall indeed

to everyone thinking about this... do it properly fit a PWM controller, and a transformer... use the normal control circuitry to supply your brake switching relay. doing it this way you'll not suffer any variations on motor speed, you'll have precise control from the pot controlling the PWM circuit and thus wire speed. welding will become so much more relaible.

Plucking up the courage to do it.......

 

[furry1]

Points for persistence! Points also for the scirocco... I had a couple of them, good cars.
Still glad I got a decent cebora from fleabay, and flogged the SIP for nearly as much money.. You can get them to work, but it really is much easier to have a machine that works! Then you can spend time thinking up much crazier things to make! (there is a space somewhere near here, might be worth watching...)

 

[BChild]

Points for persistence! Points also for the scirocco... I had a couple of them, good cars.

It's an Opel Monza

I've just about reached the end of my patience with the SIP/Cosmo - I'll keep it as a small and portable spare and I'll try the final modifications to the wire feed circuit to improve the stability once I have a new replacement that works out of the box from day 1

Meantime I want to be welding not tearing down a welder and adding bits that I then need to learn how it's changed the welding characteristics.

So in nut shell the threads not dead yet but it's not got long to live

Still glad I got a decent cebora from fleabay, and flogged the SIP for nearly as much money.. You can get them to work, but it really is much easier to have a machine that works! Then you can spend time thinking up much crazier things to make! (there is a space somewhere near here, might be worth watching...)

I toyed with a few second hand welders on ebay - one from a forum user on here who purchased it for £67 with a few faults and fixed it up - it went for nearly £300 - and it still had some faults.....

I've decided to buy a Portamig 185 - it's a bit big size wise but so was the other choice the Parweld 171

 

[BChild]

Right while I've been waiting for a delivery I've been looking at how to fit the PWM unit

Std Disclaimer - Electrickery and me are not best buddies

So I want to use the modifications already fitted

Separate Wire Feed Transformer
Relay Brake
10 turn Pot and counter

It's all getting a bit tight for space in there and there are already some compromises made to the internals

I've looked at the std SIP PCB circuit board and to my untrained eyes (and simple mind) it looks like the motor control circuit is separate to the welding side - if it is I may be shortening the PCB as that would resolve most of my space and clearance issues

 

[BChild]

I'm now thinking that Pictures may help....... so i may have to wander off and take some

Oh and I know it's a one way trip but it's not much good now so how much worse can it be

 

[BChild]

OK rubbish pics

Back side of PCB

Everything ------> of the red line looks to be motor related

Front side of the PCB

Everything ------> of the red line looks to be motor related

 

[BillJ]

The first and second lines are not the same line
One should be a mirror-image of the other.

Anyway, the first line is wrong (it's upside-down) and the second one correct. You should be keeping the round black bridge rectifier.

Basically, ignore the top-side of the PCB and cut the line you have drawn (virtually) on the track-side.

That's the same board as is on my SIP 130T.

 

[fixit]

Sip 170 Pro overrun

If it is overrunning a little, maybe you will have to put a braking relay on the wire drive motor.
Robert

I was going to post a new thread then came upon this which is my problem. I have a sip 170 pro and a constant problem is overrun of the wire. A recent car restoration job where tacking is the order of the day means I'm wasting more wire with trimming than I'm welding. If I'm on max power and on meduim feed speed I can have 4" hanging out the torch to be trimmed.
Has anyone fitted a brake relay and did it solve your problem. I'm a electronics engineer at heart so this is simple for me to do but before I started I thought I would get a testimonial

 

[BChild]

I was going to post a new thread then came upon this which is my problem. I have a sip 170 pro and a constant problem is overrun of the wire. A recent car restoration job where tacking is the order of the day means I'm wasting more wire with trimming than I'm welding. If I'm on max power and on meduim feed speed I can have 4" hanging out the torch to be trimmed.
Has anyone fitted a brake relay and did it solve your problem. I'm a electronics engineer at heart so this is simple for me to do but before I started I thought I would get a testimonial

Yes and yes - I didn't have a problem with overrun of wire after I fitted the separate wire feed transformer but when I did the Euro torch conversion it became very obvious (less resistance to wire feed v previous hobby torch assembly I assumed but either way I was trimming more wire than using on thin metal technique)

 

[BChild]

The first and second lines are not the same line
One should be a mirror-image of the other.

Anyway, the first line is wrong (it's upside-down) and the second one correct. You should be keeping the round black bridge rectifier.

Doh - lousey paint skills

Basically, ignore the top-side of the PCB and cut the line you have drawn (virtually) on the track-side.

That's the same board as is on my SIP 130T.

Handy to know - not that I'm ever going to turn it back to std

 

[BillJ]

Has anyone fitted a brake relay and did it solve your problem.

Yes, and it did solve the problem:
http://www.mig-welding.co.uk/forum/showthread.php?t=11532

 

[BChild]

No turning back now

Bottom half of the SIP PCB is gone

PWM now installed and wired to the 10 turn pot (possibly running backwards but hey ho we'll find out when I fire it up after the rest of the wiring is done)

Now I have the headache that is wiring!!!

My current thoughts

The two wires that fed the motor via the Relay Brake from what was the std PCB I can hook up to the PWM +ve and -ve motor output feeds (if I get it wrong it'll just run in reverse so easy to correct that )

Where I'm stuck (although I might not be ) is the 24V feed to the PWM as it needs to be controlled same as the gas solenoid I fitted when I converted the machine to euro torch - in fact that's almost a plan! FLW!!!!!

Oh how I wish I paid more attention at school

 

[BChild]

Oh and Pictures now my camera is playing ball

So the PVW is tucked up in the corner - mounted on an insulator board fastened to the front panel

The cut down PCB is mounted in the original place (with the bottom cut off)

The red and white wires were in the green connector at the bottom of the PCB which used to feed the wire feed motor (pot controlled)

Just the power feed connections to the PWM to sort

 

[BChild]

Where I'm stuck (although I might not be ) is the 24V feed to the PWM as it needs to be controlled same as the gas solenoid I fitted when I converted the machine to euro torch - in fact that's almost a plan! FLW!!!!!

Oh how I wish I paid more attention at school

I should pay more attention to my own previous posts - Gas solenoid is 230V switched

I need a 24V switched so I'll have another look tonight

 

[BChild]

Meh went back to basics

Powered the PWM direct from the relay Bridge (the transformer is 240v switched)

Joined the motor to the motor terminals on the PWM and dropped the relay brake out of the circuit

It works - however a large fly landed in the ointment - my ten turn pot is a 2K - the PWM one removed and replaced with the fly leads to the PWM board is 10K

So I have a rather fast starting wire speed - having said that there is very little run on even flat out......

Off to look at RS on line

 

[BChild]

Off to look at RS on line

Exactly same size and spec except 10K ohms

Now that should fix that issue

Next I need to get my head around a relay brake back into the circuit (again) just in case like!!

 

[BChild]

I suppose the good news is

- I didn't blow the PWM up (my worst fear)

- I didn't make some huge miss calculation with cutting a huge chunk of the original PCB (well I could have missed a lot there - luckily BillJ gave me some good advice off and on thread - thanks Bill another beer I owe you)

- It works (it actually seems like it's given the motor some "grunt" certainly fires up with enthusiasm but as with all things SIP what you see isn't necessarily what you get in terms of overall result) Doesn't seem to slowly wind up speed wise but time will tell

- I wired the 10 turn pot up correctly first time so I can dispense with scotch lock joints (just in case) for the final install making it neater and more factory (there is a joke there too)

So RS order placed (be with me Thursday) and I'm going back a few pages now to make sense again of how the heck I'm going to wire up the relay brake (just in case I need it)

Might as well do a couple of other tidy up jobs inside the case

- shorten some over long wires added as part of a few previous mods

- tidy up the transformer fixings (bolts rather than temporary rivets now I've found the bolts I bought to do the job a year ago)

 

[BChild]

OK if you aren't sick of it - I'm surprised you aren't

Good news

So 10K Ohm 10 Turn pot arrived, fitted and now I have the full range of wire speeds from a hardly able to notice mm by mm (initially 039 on the counter with no wire installed) feed to an OMG (999 on the counter) flat out (It realy needs the relay brake on higher speeds so with a blank sheet of paper and a copy of an earlier post I'm getting my head round installing that)

However just doing a few subjective tests to see if the wire feed speed was stable with and without wire fitted (I just wanted to hear if the motor was changing speed when running) I noticed something weird happening

Old set up after a short while wire speed increased and needed to be knocked back constantly (never have bottomed out why and that's why I'm trying the PWM unit)

New set up appears to be having the opposite effect - after a various motor speed running tests to listen for any speed changes with no load/wire the "hardly able to notice mm by mm" setting needed 120 on the counter to get the drive wheel to turn

I don't yet know if that will be the same when wire is installed and welding commences but I thought I'd share and ask for some possible explaination

 

[shenion]

As the motor heats up, it will have more resistance. At very slow speeds, most power is dissipated as heat. Should be better at speed.

The SIP speed control will vary as the transistor heats up.

Still, you should be playing with that PortaMIG

 

[BChild]

As the motor heats up, it will have more resistance. At very slow speeds, most power is dissipated as heat. Should be better at speed.

OK so that explains the changes after the motor has been run for a while although it wasn't warm to touch - I checked

The SIP speed control will vary as the transistor heats up.

explaining the difference

So in the previous control system (SIP) the speed control changing as the transistor heats up was a greater change than the motor warming up reducing the speed.

Now I don't have any of the original circuit left the balance has swung the other way

Still, you should be playing with that PortaMIG

Yeah but if I started doing that this SIP would remain in bits forever parts being lost and eventually it would be thrown away