Diy tig pedal - Help Needed !

[Premiershipman]

Hi Matt, that light doesnt appear to be on the front panel of the Basic Plus model that I have.

The foot pedal works as if I press the microswitch, the gas starts and the arc engages no problem and when I release it (2T mode) the arc goes off and the gas goes through post flow and off.

Its just a matter of the potentiometer not affecting the amps at all when I rotate it even though it shoes ohms decreasing/increasing when I test with a multimeter.

And looking at the diagram there is nothing else apart from the 8 wires to connect (1&2 for microswitch which works fine, 3,4&5 for the pot and 6,7&8 joined together prob to 'engage' foot pedal mode).

Just frustrating that I am so close to getting it working but still not there !

Thanks

Shady

 

[Premiershipman]

Looked fully in the manual and I will check tonight as the basic plus says that a decimal point will appear in the display on the right if a remote control unit (foot pedal) is connected correctly.

Shady

 

[Wedg1e]

I appreciate that the Lorch is using a membrane keypad for control, but on my TIG the current control is a pot.. So when you use the pedal, you set the front panel pot. for the max current you want and then the pedal varies the output from zero up to that preset current.
I assume the Lorch must have something similar otherwise the pedal would give you the full span of output which wouldn't be very controllable!

 

[matt1978]

I appreciate that the Lorch is using a membrane keypad for control, but on my TIG the current control is a pot.. So when you use the pedal, you set the front panel pot. for the max current you want and then the pedal varies the output from zero up to that preset current.
I assume the Lorch must have something similar otherwise the pedal would give you the full span of output which wouldn't be very controllable!

Yes, its the same, what ever current is set on the front panel is the maximum amperage that you will get when the pedal is fully pressed down.

So if you set 50 amps on the front panel, you only get 50 amps when pedal is all the way to the floor regardless of the maximum potential current available from the machine.

 

[Premiershipman]

Doesnt seem that way - you tend to set the welding current on the unit and thats it - there is no additional setting on the pedal it just varies the amps via the internal pot.

I would guess that it would initiate arc, upslope and then go to the amperage set on the display when the pedal is fully depressed.

*** Matt beat me to it !!

 

[matt1978]

I would guess that it would initiate arc, upslope and then go to the amperage set on the display when the pedal is fully depressed.

Apart from the Upslope part, there is no Up/Down Slope in operation when used on a FootPedal because its all controlled via the Footpedal.

 

[Premiershipman]

Cheers matt, will let you know if the decimal lights up with the footpedal when i try tonight.

Shady

 

[Premiershipman]

Well the right hand decimal lights up when I engage the foot pedal, so the machine knows there is a foot pedal attached.

The potentiometer works fine when the machine is off (increasing/decreasing), but when I power the lorch up the potentiometer seems to become disabled and does not function - no decreases or increases in resistance.

Can't see what I am missing ?! Very frustrating !

Shady

 

[AndyStobbs]

Is there an initial state for the pot to be in at the moment of initiating the arc?

 

[Premiershipman]

Tried both ends of the pot rotation, basically it seems to become disabled as soon as the welder is powered up.

 

[AndyStobbs]

How have you configured it though, is your pot expected to be at some a certain resistance rather than max/min.
I'm not a welder person so I'm just fishing here.

 

[Premiershipman]

The pot is a 100K and you set the amps on the welder then the pedal controls the amps up to the value set on the welder.

Just it seems to disable the pot when turned on !

 

[AndyStobbs]

Is it meant to work as a variable resistor or a potential divider?

 

[Premiershipman]

It's not particularly clear on the diagrams but I would guess as a variable resistor.

However the port on the back of the welder has 10 pins available and only 8 pins are marked on the wiring schematic, still not sure if there is something I am missing.

 

[Premiershipman]

Quick question but would the wattage value of the potentiometer affect function ?

The wiring diagram specifies a 2W potentiometer but I think the pot that I have in it is only 1/2 watt.

If that's the case could there be a control signal that is more than 1/2 a watt which then renders the pot disabled as it requires 2 Watts ?

 

[AndyStobbs]

unlikely, thats not an ideal start but its reffering to how much heat the pot can dissapate due to the power going through it.
can you measure voltage at pins 3,4 and 5 wrt. each other and to dc negative?

 

[Premiershipman]

I did wonder if there would be any effect given that its only about 1 watt of difference.

I only had a small amount of time to measure this morning and will look to investigate more this evening after all the halloween festivities.

 

[shenion]

The wattage won't matter. It would be 0.00025 watts used at 100k. A 2W pot would be more durable over a 1/2W (both electrically and physically.)

Are you sure it is supposed to be 100k? 50k or 10k seem more common. Should probably work though as it is a voltage divider setup.

 

[Premiershipman]

It is supposed to be 100K as per the schematic - it just seems that the potentiometer is not becoming 'active' when the welder is turned on it just seems to be disabled.

 

[derekm]

its not clear that pin 4 is the wiper or the pot is causing the porblem
to determine if pot connections
connect each wire to the other by a 50k resistor
to form a triangle.
you should then get current to the torch regardless. if not it isnt the pot connections
to determine which is the wiper
half the resistance of one of the resistors, if the current does not change then neither of terminals it is connected to is the wiper.
in other words the wiper is the one not connected to the resistor you just changed.