I thought the pin out would be helpful. With it a second pedal could be made with the pulse built into it. Still think it could be done with two pots, voltage dividers. The high one set by the pedal position, the low one manually.

Quote,^ "a pulse is a pulse of higher current." Think that is backward. The pulse is the low current. The high current is the welding current, it pulses to a lower current to control the heat.

I never liked the pulse myself. A lot of guy's use it as a crutch, instead of learning how to weld correctly. As a way to try and get the "stack of dimes" weld bead.

i am certain the pulse is pulsing up, not down. did you watch Jody's video in the link i posted?

if i were to adjust duty-cycle to more than 50%, then the pulse at the tip of tungsten would seem like it was pulsing down.

 

Go back and watch the video, at around 1min 30sec. If the pulse was to the high(welding) current you would only get a short weld time.

You do realize that the beads he shows were done on an automatic welding lathe with no filler rod, don't you? You won't get that effect in the bead by hand with filler. That still comes from proper technique.

 

Go back and watch the video, at around 1min 30sec. If the pulse was to the high(welding) current you would only get a short weld time.

You do realize that the beads he shows were done on an automatic welding lathe with no filler rod, don't you? You won't get that effect in the bead by hand with filler. That still comes from proper technique.

the bright light pulses are up, but, i found in some other forums that the pulsing they use is 50% duty cycle, which is neither up or down.

yes, he's on a lathe table, i know.
with adjustable duty cycle from 10-90%, 10-49% will be high current pulsing, 51-90% will be low current pulsing, etc. the benefits of pulsing are not just for bead looks, etc. i honestly dont know what the benefits are of say pulsing up or down, but i will find out, etc.

 

this is what i have come up with thus far. i have an existing circuit for the +5v so i left that part out. C1-C8 are just cap values to achieve my desired frequencies, etc.

U1 is actually a dual opto (quad fet) with some decent electrical characteristics. the on/off times of 0.8/0.1ms can accommodate my max switching rate of 200Hz, but it means there will be 0.7ms on every cycle where the wiper will look like infinite ohms, not sure what effect this will have on the machine. but it looks like with led in the 10-20mA range the on/off times can be just under 0.2ms

anyone see any issues with this? i will need to get these parts, breadboard it up, and then put it on my dual channel scope.

 

Please post your results, good or bad. Personally don't think it is going to work, but I've been wrong many times before. And before trying it on your machine, make sure new control boards are still available.

Your machine is expecting a certain voltage from the pedal to control the current out put. Just make sure you don't go past the level that's acceptable to the control board. If you do the magic smoke in the board will excape. Good luck!

 

Please post your results, good or bad. Personally don't think it is going to work, but I've been wrong many times before. And before trying it on your machine, make sure new control boards are still available.

Your machine is expecting a certain voltage from the pedal to control the current out put. Just make sure you don't go past the level that's acceptable to the control board. If you do the magic smoke in the board will excape. Good luck!

shortbus,
the exact reason why i am using opto's, my controller will be 100% isolated from the machine. the machine perhaps uses the pedal pot to create a ref voltage on the wiper pin, but as i noted before, the start position (min current) and max position (max current) of the pedal has the wiper on one side of the pot at start, and then fully to the other side at full pedal. i am not feeding the machine any voltage or current via the amph connector pins, all i am doing is simulating the pedal pot using a 10k resistor and moving the wiper from one side to the other with opto's.

the unknown right now is at min start current, when the pedal 1st turns the machine on, from a circuit perspective, is what side of the pot the wiper is. i know physically what side its on, but from the electrical perspective i dont. this however is a easy fix, would just need to swap the non-wiper pins on the opto's, etc.

 

I'm really not trying to be a smart a$$ with you just trying to help you out. If you look again at the block/wiring diagram in the manual it pretty much tells you every thing. It shows the amp connector pin out and what the pedal does.

1. There is a pot and a switch. When the pedal is depressed first the switch makes. It turns on the control circuit and the high frequency if your using it.

2. The pot then gets a voltage from the machine and feeds back a smaller voltage that the control board uses to set the output. The voltage from the pot wiper is this voltage. The only thing the ohm value of the pot does is set this voltage. If you put too high of voltage back to the control board.... magic smoke is let out.

If I was doing this for myself, I would measure the voltage going out to the pedal pot. Then measure the voltage going back to the control board/machine as the pedal is pushed. This will tell you what the control board is expecting, voltage wise. The max output of the electrode is controlled on the front panel, the pedal only allows from the start current to the max panel setting.

Then for the pulses you need to give the wiper pin, a voltage above the start voltage for low pulse. And the max pedal voltage for the high pulse. "Flipping the terminals" as you call it isn't going to do it. Sorry, just the way it is.

You said in an earlier post that a 555 timer is the same as a flip-flop. First time I ever heard any one say that. Even though it has a f/f in it it doesn't make it one. The only way I know of getting the two different voltages to the control board is going to take some logic gates and a more involved circuit than your thinking right now. Know I shouldn't worry but hate to see you blow up a perfectly good welder.

 

shortbus,
there's no schematic that shows any machine circuitry, so saying the pot is used to feed a voltage to the machine via the wiper is not a good statement imho.

i already gave the pot example of ABC where B is the wiper, AC is 10k, at start AB was 10k, and at full pedal BC was zero. how is this not simply moving the wiper from one side to the other??

i dont want to feed the machine any voltage or any current, thus the use of the opto's.

the 555 is a flip-flop with features.

 

There is no schematic, but knowing what the pedal does is a start. And looking at he pedal schematic and amp pin out tells a lot. It's there if you know what your looking at. Sorry that you don't want help.

 

There is no schematic, but knowing what the pedal does is a start. And looking at he pedal schematic and amp pin out tells a lot. It's there if you know what your looking at. Sorry that you don't want help.

i dont see where you are helping, sorry.

i have the pedal schematic, and i posted how the pedal works in one of my early posts. knowing how the pedal works doesnt tell us anything on how the machine uses the pedal pot, etc. and even if it was a simple voltage divider i dont want to feed the machine anything from my controller, etc.

if you have some advice on the opto's i have chosen, then please share your thoughts....

 

If you were to use a meter on the pins of the connector on the machine, pretty sure you will find there is a voltage coming from pins, C, B, G and D. And ground being pins A, E and H. Pin F will be a varying voltage when the pedal is pressed.

Your description of how the pedal works is wrong. If you meter the ohms from the A terminal to the wiper as the pedal is moved, you will see that the ohms change as the pedal is pressed. This is how it is supposed to work. Connect a voltage to one side of the pedal A or C and the opposite side to ground, and meter the wiper B and you will see the voltage change. This is how the pedal works.

Using optos to connect resistors to the machine will do nothing, unless the pedal voltage coming from the machine is involved. You need a complete circuit, basic electronics. A reference voltage comes from the machine, a varying voltage goes back to the machine. This is how the pedal works.

You said earlier to watch the video. Have you gone back and watched it? Pulse isn't going between full on and full off. He says something very similar in the video. The pulse only drops around 20% of the current. Not 100%.

You need something more than a 555 to do this. A 555 has only two outputs, a plus voltage and ground. To get the varying voltage to the controller in the machine, a 555 and optos will not do it. The optos, like the 555, only have two outputs on or off.

I have tried to help. But when the one your helping has already made up his mind, how can you help? Here is a link to the EASB service manual, but you have to register at the site to get it. http://www.allbookez.com/esab-service-manual/

 

the fet's in the opto's are the items completing the circuit in the machine. i will bridge (connect) pins E & GD with a 10k (just as the pedal pot does), and then the fet's in opto's will move the wiper F using PWM. the circuit will be E-GD (the 10k), and then E-F or F-GD via PWM control.

so as much as you dont see the fet's in the opto's completing any circuits, they are, but the circuit(s) are inside the machine, not my controller. the 555 is the PWM control that drives the opto's.

and yes, the diff in current on each end of the pulse can be set, my machine has a start(% of max) and max setting, thus those two settings will set the diff of the pulse, etc. example, max=100A and start=10%, this means there is 90A diff and the low side will be 10A and the high side 100A. i could then adjust start=50%, thus only a 50A diff, low 50A and high 100A. i could then adjust it to 90% start, thus just a 10A diff, low 90A and high 100A.

i dont understand why you keep wanting me to feed a voltage into the machine.

 

I added a pulser several years ago to a Miller 180SD TIG.
http://www.mwdropbox.com/dropbox/
Go down to files labeled "TIG Pulser...". One .txt, one .gif, and four .jpg's. I have my PCB files in ExpressPCB format.

I had discussed it on a couple of forums. Someone responded that a "company" had taken the design and was selling it. They had switched the position of a control and the indicator LEDs, but otherwise looked exactly the same. Their website disappeared after a very short time.

Ken

 

I added a pulser several years ago to a Miller 180SD TIG.
http://www.mwdropbox.com/dropbox/
Go down to files labeled "TIG Pulser...". One .txt, one .gif, and four .jpg's. I have my PCB files in ExpressPCB format.

I had discussed it on a couple of forums. Someone responded that a "company" had taken the design and was selling it. They had switched the position of a control and the indicator LEDs, but otherwise looked exactly the same. Their website disappeared after a very short time.

Ken

impressive. i am not wanting to integrate the pedal w/ pulser. mine will just be static hi/low settings from the welder using the switch for on/off. i am making mine much smaller to fit into a Hammond 1455C801BK.

my final schematic will not be posted, and i encapsulate all my stuff using MG 2part black encapsulating epoxy. i have been in this type of rodeo before, so i know how others might want to get in on the action.

 

i might go to this PWM setup, having that "analog" ability for freq adjustment might be a benefit (not sure), but it means adding a few more components. i guess i'll need to breadboard both and scope their characteristics, etc.

 

Thanks Ken. This is what I've been trying to get across in the thread. It's more than "flipping terminals".

 

Thanks Ken. This is what I've been trying to get across in the thread. It's more than "flipping terminals".

in Ken's schematic the pulsing is an overlay to the pedal, which is not what i am trying to do. when i get it running i will come back to this thread....

 

1st stage testing completed. the opto driver works good. i havent scoped it yet for switching. next up is the comparator.

edit: comparator is all wired up, need to hit the 7556 next.

and here's a learning tip. when your meter (a Fluke multi in my case) doesnt seem to measure what you expect it to, dont dismiss the meter as being the culprit. today i found my Fluke's small 650mA fuse was blown and it wasnt reading current. i took out a backup meter to verify that my circuit was good, etc.

 

all, i ran functional tests today hooked to my esab machine, and voila, works awesome !!!! and best of all, the module is 100% isolated from the machine.

thanks to everyone that helped answer my questions. now i have a boat load of weldors emailing me to buy it

 

I have a question on your "invention". If your not using a/the pedal, how do you trigger the welder on to start the arc? Or is it live and pulsing all the time the main switch is on? If the latter, that could make for some exciting electrode changes.