Need advice building new TIG foot control

[fatty Jr]

Hello.

I will cut to the chase. I need to build a tig foot control for my migatronic ac/dc tig unit. I have contacted the manufacturers who have sent me the diagram for their foot control and would like someone to view the diagram and basicly verify what components I need to use where etc.

Would also like to have this listed somewhere as I know a few people have asked about this about this machine and normally end up paying vast amounts of money for a simple piece of kit.

Here's the info i got.



The foot pedal it's self has 2 plugs on it (as shown in pic) one plug is for turning the arc on and off (M2) and the variable part which is on M1. Also shown on the pedal is two potentiometers



Other info sent by manufactuer is regarding setup the plug for use when robotic welding, but give the info for what pins supplies or takes what

View attachment remote-connections.pdf

I hope you can see all the attachments and can help me verify components

 

[OLIVE2222]

Well, the circuit is quite basic.
The main problem however is to list a product for which you don't own the rights.
The "vast" payed amount include the engineering cost, the storage cost, the cost linked to legal aspects and warranty... not only the parts cost!

 

[fatty Jr]

Well, the circuit is quite basic.
The main problem however is to list a product for which you don't own the rights.
The "vast" payed amount include the engineering cost, the storage cost, the cost linked to legal aspects and warranty... not only the parts cost!

I have spoken to migatronic about this and listing the diagram is NOT a problem because this it classed as obsolete technology.

Specifically asked about listing it up for this very purpose.

thanks for your time

 

[jpanhalt]

Not quite sure what you mean by"verify" what components you need. I suspect the answer is all of them.

Do you have a foot control to compare with what you are making? The control on mine (Miller synchro circa 1984) looks a little more streamlined than what you show, but the functions are the same. By that I mean, there is clearly a "start" feeling to the pedal, and once there is an arc, you have current control. Constructing the mechanical part may be the greater challenge, particularly the coupling of the potentiometers to the pedal.

As for posting, I suspect a site related to DIY welding might be most appropriate. There are rumors circulating that Yahoo groups may disappear or have serious barriers erected for access to or indexing of attachments, files, and so forth. It may not be indexed by Google. So, you may want to look at Google groups and blogs as an alternative.

John

 

[fatty Jr]

Hello jpan,

I do have a big alloy foot control from my old boc (rebranded murex) transtig that I planned to repurpose for my migatronic.

I spoke to a few companies about this and they said the internals are totally different and would need to buy a purpose made foot control ( me thinks they just wanted me to spend the $$$$) The mechanical side shouldn't be a problem as built all sorts of stuff before.

I am just not 100% sure on the electronics side. I find it easier to talk to someone about it until it sinks in.

I have made a list of the components I think will need

D1 = 1N4003 diode
R1 = 1k 1.5w resistor
R2 = 47 resistor
C1 = 470u capacitor (electrolytic)
C2 = 470u capacitor (electrolytic)
C3 = 100N capacitor
C4 = 100N capacitor
C5 = 33n capacitor
P1 = 1k potentiometer
P2 = 10k potentiometer
P3 = 1k potentiometer
P4 = 100 Variable resistor
Z1 (think it's a z) = 12u zener diode (not sure what a 12u zener looks like)

The initial trigger to fire the machine up is started by a simple on/off switch which is controlled off the 6 pin square plug Then the heat output is controlled off the variable parts on the foot control.

I am assuming that P4 controls the initial slope in on the arc. P1 and P3 control the minimium (P1) amp and maximium (P3) amp output with P2 being controlled by the foot to give variable control between P1 and P3. You set P1 and P3 with the knobs shown in the picture of the pedal.

I hope that makes sense. If i am wrong, I would be grateful if you would steer me in the correct direction.

 

[OLIVE2222]

OK so.
On the components side ensure that capacitors voltage rating are adapted.
Must be at least 25V for C1 and C2. potentiometers must be ruggeds as the connectors and yes mechanical side will be a bit challenging. Guitar volume pedal can maybe be re purposed.

Olivier

 

[jpanhalt]

My comment on mechanical was specifically directed at how to attach the potentiometer(s) to the pedal. I agree with your assignments for P1-P4. On my machine HF on/off is controlled by the pedal. When you mention a switch, I suspect you mean a switch whose action is integrated into the pedal action. A separate switch, while workable, might be a bit cumbersome to deal with in all situations..

Z1 is a zener diode as you surmise. It will look just like a regular diode.

John

 

[fatty Jr]

I thank you both for your replies.

My basic reason for doing this foot switch as I have had some operations on my hands recently and using the hand switch has been made uncomfortable to say the least.

The switch would be integrated into the foot pedal with a simple lever/roller switch or something.

I will get this old heavy foot pedal out I have and see what's inside

 

[fatty Jr]

Been reviewing my information and wondering if the zener diode (Z1) is 12v not 12u. Can't make my mind up what size diode to use.

G pin is supplying 24volts. A pin has an input range from 0 to +10v.

so it is used exactly like a voltage regulator like i found on wikipedia



This arrangement and voltage would make sense.

 

[jpanhalt]

That is correct. The zener is 12V. I probably saw the 12u, but interpreted it as 12V.

Zeners start conducting at their design voltage. Thus, at 12V, that zener starts conducting. There is always an upstream resistor (presumably R1). As the current increases due to conduction by the zener, the voltage drop across the resistor increases. Thus, you have voltage regulation.

John

 

[fatty Jr]

That is correct. The zener is 12V. I probably saw the 12u, but interpreted it as 12V.

Zeners start conducting at their design voltage. Thus, at 12V, that zener starts conducting. There is always an upstream resistor (presumably R1). As the current increases due to conduction by the zener, the voltage drop across the resistor increases. Thus, you have voltage regulation.

John

Thanks again

Just trying to work backwards now on what wattage the zener need to be.

24v input through to a 1k ohm 1.5w resistor and then to a 12v zener which should then supply a 0 to 10v reference through to the potentiometers at the end of the circuit

Can I get away with putting a 1.3w zener without having to worry to much about burning anything out?

 

[OLIVE2222]

Please note that the DC input will be around 17V the 24 volts AC being half wave rectified.
With the 1K resistor the zener current will be low so the zener power dissipation, 400-500mW type will already be OK

Olivier