New user with Cosmo 170 (SIP) and a headache

[BChild]

A lot of stuff that "nearly" made sense to me

Did I mention that electrickery wasn't my strong point?

But with no schematic, I can't suggest where in the circuit to put the resistor.
Robert

IF what I'm trying to do doesn't work as well as I hope or the 10 turns becomes tiresome I'll have a go at trying to get a schematic from SIP and resurect your points raised.

Thanks for all the inputs it's appreciated

 

[BChild]

10 Turn Potentiometer fitted

Problems - well the threaded section on the new one is not as long as the original - I had my suspicions but hoped I could get away with it - I did but I'm going to find one that's a better fit for a long term fix as it's the only thing that fixes the board to the front of the machine

Because of the short thread I couldn't use the 10 turn dial so I settled for just turning the shaft untill the counter version arrives

Having fitted it obviously I had to try it

two words

CHALK

&

CHEESE

It's so easy to trim the wire feed to get the sizzle - in fact my young apprentice trimed as I welded and you could really feel and hear the changes - no more switch like changes it was subtle and progressive and very very controlable..... We'd tried that with the old one but even touching the dial had such big effect it was impossible to adjust as you are going along - now you have such a range of adjustment that it's easy to trim it to a perfect point about half a turn is the difference between just right and to fast or too slow that equates to a 20th of a turn on the old pot

I can

 

[BChild]

I'm going to find one that's a better fit for a long term fix as it's the only thing that fixes the board to the front of the machine

Looks like my chances of finding one with a longer threaded section are slim at best - so I'll have to look at plan B - mounting pot on front of welder panel and having the circuit board spaced out behind it - I'll need to find another LED for the thermal overload indication as that will be too far from the front panel once the circuit board is moved back.

 

[BChild]

Well having got the welder performing as I wanted time to understand why

It's all about the math now...... If you don't like - just change channels

So the std Pot now removed and separated from the board gives me chance to actually measure the resistance at several points

Here's the profile of resistance v pot position

So not very linear in the extremes is obvious straight away

Raw data below

Pot Position - Ohms
000 --------- 2
005 --------- 3
010 --------- 22
015 --------- 122
020 --------- 253
025 --------- 392
030 --------- 550
035 --------- 687
040 --------- 837
045 --------- 956
050 --------- 1099
055 --------- 1223
060 --------- 1336
065 --------- 1480
070 --------- 1608
075 --------- 1757
080 --------- 1910
085 --------- 2007
090 --------- 2200
095 --------- 2250
100 --------- 2260

Below 20% of the avaliable range and above 95% of the avaliable range any movement results in little or no change

This isn't helped by the pot being a 1 turn but having an effective 0.75 of a turn operation range

Add in a wire speed range of 14 metres per sec and fit that into 0.75 of a turn and bottom line is every 10% increase on the dial results in approx 1.5metres per min added to the wire feed.

So when I was trying to weld 1.1mm steel with 0.8mm wire target wire speed was 2.2 metres per min and thats right in the slow area of the pot

Moving down to 0.6mm wire requires a target wire speed of 3.5 m/min so further away fromm the flat area of the curve but not exactly controllable on a pot that for 5% of the operational movement ramps up the wire speed by 0.75m/min even in the linear section of the dial and thats a large change

below is the data for wire speed v dial position

Wire Feed Speed - Mtrs / min
000 --------- 1.38
010 --------- 3.48
020 --------- 4.2
030 --------- 5.61
040 --------- 7.02
050 --------- 8.43
060 --------- 9.84
070 --------- 11.25
080 --------- 12.66
090 --------- 14.07
100 --------- 15.48

so thats where I conclude that with the original pot there was no way I was ever going to get a stable sizzle at the low end of the range

I think if I had trimmed the trim pot on the board to have no feed at all at zero it may have moved the start point up the scale a bit but bottom line it's still a very coase pot and little changes to setting result in large changes to wire speed

 

[BChild]

I think if I had trimmed the trim pot on the board to have no feed at all at zero it may have moved the start point up the scale a bit but bottom line it's still a very coase pot and little changes to setting result in large changes to wire speed

On reflection can I do that anyway - trim the internal pot to zero? so that at zero on the wire feed speed potentiometer nothing comes out but as soon as you start to turn it the wire starts to feed?

 

[aaronbassett]

just wondered if any one has thought about using a 24v speed controler from a scooter like this one on ebay for wire speed http://cgi.ebay.co.uk/24V-250-W-RAZ...3|66:2|65:12|39:1|240:1318|301:1|293:1|294:50

 

[BChild]

just wondered if any one has thought about using a 24v speed controler from a scooter like this one on ebay for wire speed http://cgi.ebay.co.uk/24V-250-W-RAZ...3|66:2|65:12|39:1|240:1318|301:1|293:1|294:50

Looks expensive compared to a transformer and a few too many wires for me

 

[BChild]

Anyway having got one of the items in my sticky mitts I've had a look for a larger one and this looks much better as it has a larger knob that will be easier to work with a gloved hand and also a 0-999 number indicator based on the 10 turn rotation

http://uk.rs-online.com/web/search/searchBrowseAction.html?method=getProduct&R=0811153

Picture looks like this

In black shouldn't look out of place on the front of the welder as far as add ons go?

Data sheet is here and that says knob size is 17mm diameter which is almost twice the size of the one I've already purchased

All dimensions on the link below

http://docs-europe.electrocomponents.com/webdocs/00ad/0900766b800ad527.pdf

It's Perfect - I can work it with gloved hand - the knob is a bearable size 10 turns = 999 it seems so should be really easy to note settings down and keep a table of settings that work as a ready reference

Just need to mount the pot on the front of the welder casing and mount the PCB that used to be held to the front of the welder by just the Pot!!!! away from the pot and one small hole to drill above the pot to locate the pin on the unit......

In the absense of any advice against it I'm going to have another go at the internal trim pot to drop the wire speed down to as close to zero as possible as the current wire speed right at the bottom of the range is still a bit quick for thin stuff!!

 

[GTG]

Schematics..

Hi Group
I'm new in this group. Have a SIP 150P.
Have done a mod to the feed control. Instead of using the existing relay to turn on and off the extra transformer, the transformer is turned on when power is turned on. To control the feed motor, i added a 12V 30A car relay, which is turning on the feed motor.
The reason for doing it that way is that the existing relay seems to work very hard already, and i dont want to add more load to it.
Have created a schematics of the circuit.
Where can i upload it ? To reduce it to 9.5 kb will make it unreadable.
I also have it in pdf.

 

[malcolm]

Which format did you try? Sounds like a bug if it's saying 9 kb is the maximum - should be 9 Mb for most formats. JPEG or GIF format should result in a decent size image. See the link below for how to upload images straight to the forum. PDFs and word documents won't work (viruses etc).

 

[GTG]

Well.. I did not try to upload a file. I did not read carefully.
It was 9Mb. not 9kb. Sorry for that.
But here i attach a jpg of the schematics.

 

[BillJ]

That's a nice schematic. I simply scanned mine from the manual...

I switched the low-voltage side too but I used a relay with a 240V coil driven from the primary of the welding transformer rather than a low-voltage coil on the secondary (it was what I had available). I also used a 24V DC regulated power supply instead of the transformer and bridge.

I used the normally-closed contact on the relay as a brake to reduce run-on when the trigger is released. This makes a big difference.

The schematic below is not for a 170 but the same principle applies.

It is possible to go as low as 100R on the trim-pot. In fact later SIP/Cosmo units use 100R. I fitted one to mine and it works well.

 

[BChild]

Guys where the hell were you earlier in the thread!!! Bottom of page 4 and start of page 4

Nice schematics and I may have to use the relay option as mine does run on fractionally

 

[R Kraft]

Guys where the hell were you earlier in the thread!!! Bottom of page 4 and start of page 4

Nice schematics and I may have to use the relay option as mine does run on fractionally

With a 24v transformer, the motor would tend to run faster and overrun somewhat.
At 120a output the motor normally would have had about 20v max. (24v/20v=+20%), through it and the pcb.
At 30a output about 15.5v max. (24v/15.5=+55%).
Has anyone measured the high/low speed voltages through the motor , before and after the transformer mod ?
Robert

 

[GTG]

BChild: On page 4 and 5, i was still annoying about the way it worked.
I had not found this page at that time. I read the tread, and found that there was someone who wanted the schematics. I had it already. Only needed to upload it.
I had to make the schematics from the pcb to find out how the circuit is working. It was an easy job to modify it when i knew the circuit.
The reason why there is no capacitor in the circuit, is that it works as a simple "pulse width regulator". It is better that way because the motor will get more torque than if the circuit has a cap, and you have to reduce the voltage. But you will loose some of the max speed. Not a problem as it is running fast enough anyway.

If you measure the voltage level after the rectifier, you will read somewhere between 17-20V DC.
Reason is that you are measuring middle value.

 

[BChild]

I'm not having a go at you, but I think it's important to know the potential REAL cost of these 'good value for money', 'they join metal together' type units is.

OK

SIP Cosmo 170 Costs (Inc modifications)

£152.00 Purchase cost BINB - "Old Stock" (included delivery)

£2.00 Wire Brace (1st mod to wire feed)

£4.70 Relay Bridge (2nd WFM Mod)
£21.10 Transformer (-----"------)
£10.00 Wire & Connectors (-----"------)

£29.00 Euro Torch Connector (3rd mod - Euro Torch)
£20.00 Gas Solenoid (-----"------)
£32.00 Euro Torch (-----"------)
£7.00 (Postage) (-----"------)

I'll add in the 10 turn pot and counter unit once it's all fixed properly

£277.80 Total

I haven't priced my time - not even sure how I would do that but I would guess I've spent several hours either modifying the welder or researching the how to side

Incidently I see on the SIP web site a very similar machine to mine can be purchased with a euro torch for £413.99 (RRP £708.56 )

http://www.sipuk.co.uk/tools/info_SIP25037.html

 

[Jaeger_S2k]

OK

SIP Cosmo 170 Costs (Inc modifications)

£152.00 Purchase cost BINB - "Old Stock" (included delivery)

£2.00 Wire Brace (1st mod to wire feed)

£4.70 Relay Bridge (2nd WFM Mod)
£21.10 Transformer (-----"------)
£10.00 Wire & Connectors (-----"------)

£29.00 Euro Torch Connector (3rd mod - Euro Torch)
£20.00 Gas Solenoid (-----"------)
£32.00 Euro Torch (-----"------)
£7.00 (Postage) (-----"------)

I'll add in the 10 turn pot and counter unit once it's all fixed properly

£277.80 Total

I haven't priced my time - not even sure how I would do that but I would guess I've spent several hours either modifying the welder or researching the how to side

Incidently I see on the SIP web site a very similar machine to mine can be purchased with a euro torch for £413.99 (RRP £708.56 )

http://www.sipuk.co.uk/tools/info_SIP25037.html

You'll be happy then?

I think you're estimate on time is, let's say, conservative I must have spent a couple of hours reading your interesting and compelling progress

Charging time, easy £25 per hour. First hour usually £35 each hour after £25.

I'd recon you've got easy 8 hours of tinkering, fiddling, coffee and biscuits, fitting, refitting, coffee and biscuits, writing, reading, coffee and biscuits, waiting! Fitting and failing, coffee and biscuits, refitting and testing etc.

It's a great result though, as many people don't cost their time into the equation so in that aspect a fine result.

Hope it prompts others to take little annoying idiosyncrasies of their machines and try to make them better, there are a lot of wire feed related issues with less expensive welders and as it's quite critical to success you're tenacity will I'm sure encourage others to do the same.

You know it could become the 'must have' welder, you should start buying them modifying and selling them on, get one over to TechnicalAl, Malcolm and others and ask for testimonials.

weldquip could be asking for exclusive distribution rights

well done that man!

 

[crankbuoy]

Hi all,

Long time lurker, first time poster.

Firstly, thanks to everyone who has contributed to this thread, it makes for fascinating reading.

I have a four year old Cosmo gas/gasless 225 purchased here in Oz.

I have completed the wire feed mod with great success and have got on with the transformer mod up to the bridge rectifier but have struck a snag-- when I make the connections to the feed motor and turn the machine on the wire feed immediately springs into life, so somehow I have managed to bypass the torch switch.

I have followed the photos in bump's thread with great diligence but no success. My unit is slightly different to those described here so I'm hoping somebody who's more familiar with the wiring can set me straight.

The schematic is:


The relay is not on the PCB but is mounted under the feed motor here:


This means of course, that the PCB is different:


This is a photo of the general arrangement before modification:


The green connector (D in the photo) appears to be same as all the others, the blue wire goes via a thermocouple to the trigger, the red wire goes to a tap on the main transformer, the white wire goes to the feed motor +ve and the black wire goes to the rectifier heat sink at A.

The feed motor -ve connects to the post at F.

The relay is fed from the connectors at B and the PCB is fed with 240v at C from the main 240v switch at E.

Once I connect the bridge rectifier to the feed motor and the black wire at A is when the problem starts.

Hope that's all clear and the photos are big enough.

Any help would be greatly appreciated.

TIA

 

[BChild]

I have completed the wire feed mod with great success and have got on with the transformer mod up to the bridge rectifier but have struck a snag-- when I make the connections to the feed motor and turn the machine on the wire feed immediately springs into life, so somehow I have managed to bypass the torch switch.

I think (an electrics are not my strong point) that you have connected to a permanent live rather than the torch switched live but your PCB is different to mine so I can't instantly identify which one you need - I'm sure someone will be along soon enough to help

Welcome anyway

 

[BillJ]

This is the reason why, when I posted my wire-feed modification, I posted a schematic rather than a procedure of the form (coined by another member) "cut the blue wire..."
There is no guarantee that even two of the same model are wired up the same since the design evolves over time. Trying to follow such a procedure without knowing for certain that it applies to your own welder may give undesirable or even dangerous results (since some of those wires carry mains voltage).

I think you will only be able to do this by following the schematic and identifying the wires from that, or by getting someone else here to do it, having first established that the welder they are working from is exactly the same (not sure how you would do that).

I'm not trying to be discouraging here, merely cautious. If in doubt, get someone who knows what they're doing to carry out the modification.

As BChild says, it does appear that you have connected the output of the bridge directly to the motor rather than to the controller PCB, which should then supply the motor.