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what eBay welder?
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Nick
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LOL, Use an Arudino and hook the torch control to the appendage of your choice!

Do you let the backing gas flow all the time during a welding session or do you have it controlled by a solenoid? I found a reasonably cheap solenoid to daisychain off the main solenoid so I don't forget to manually turn on the backing gas.
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Post Sat Dec 26, 2015 1:51 pm 
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maddox



Joined: 21 Dec 2006
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Solenoids galore Nick, I have a boatload of old Festo 1/8" 5/2's.

I hate it to find an empty bottle when I forgot to close the bottle valve.

Another thing I was thinking about.

On the appendage remark. It would get annoying , an amp rise every time my mind wanders to Babeth....

Post Sat Dec 26, 2015 2:13 pm 
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Nick
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Laughing The last time I went to a factory with welding bays, they were ALL covered in centerfolds so your controller idea has probably already been done. I saw a pistol grip accessory for welding torches that had trigger control for HF start and current. It looked rather awkward but shows there is interest in different controllers.

What I'd like is a heads-up display of the welding current in my helmet.
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Post Sat Dec 26, 2015 2:32 pm 
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maddox



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Further idea's.

Backing gas, I wonder how strong the relais controlling the solenoid in the welder is. If it can handle 2 or 3 solenoids, then post-gas-flow from several diffusors covering the welds is just making some extra "output ports".

For Ti, working in a kind of open top box can help, as argon is heavier than air.


Nick, that heads up display is a very handy tool to get a feel for the welder itself.
I learned that the Chinese welders I have use hobby amps.
The 250 from the old one is more like 210 on a Kemppi or simular.
But a simple 3 digit LCD will do the job too. Only to get the data to it without a wire.

Post Sun Dec 27, 2015 11:19 am 
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Spockie-Tech
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I was reading about current control options a while back when I got my welder, but Ive since discovered that its not really that critical for DC-only steel welding, so I havent followed it up yet.

Since steel doesnt conduct heat that well, you just sort of hang around a bit longer if you need more heat in a spot or are just starting, and speed up your movements once the piece gradually warms all over.

But for those welding Alu and maybe Ti (I know nothing about that), more current control would probably be nice, and foot pedals would suck for anything except sitting-comfortably-at-the-bench work, so I was thinking of something like this..

http://weldingweb.com/showthread.php?79951-TIG-remote-DIY-config-ideas&p=4071881#post4071881

A problem occurs with the HF start, you have to filter out, or ignore spikes and average readings, or it goes bonkers when the HF kicks in, but it looks promising, I like the idea of fingertip pressure control, seems like it would be very intuitive. not melting fast enough ? push harder on the button ! Smile


For a hud current display, the optics for readable numerals would probably be the hard part. Since you will be focussed on the weld pool, refocussing to read numbers might be eye-straining.

Perhaps a bargraph (LED, Nixie, whatever) horizontally on the low edge of your Field of View would be better ? then you dont have to "read" digital numerals, just "be aware" of the length of the bargraph, and you can just feed a low analog voltage to an LM3914 chip. Just a thought anyway.
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Post Sun Dec 27, 2015 1:11 pm 
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Nick
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I was just thinking about backing gas - my bots have a number of Tee joints and I am thinking about making some diffuser boxes with cut-outs as shown below:



The diffusers would go underneath and behind the tee joint to cover the surfaces not being welded. This 25mm tube is possibly a bit small for the job but 30 to 38mm tube would more than cover the HAZ.

Making a wireless current display should be possible without too much hacking of the welder. Reading the three digit display will take 10 digital in pins of a micro. De-multiplexing the display needs a couple of nested loops and a look-up table. There are a number of serial Bluetooth modules around - I have never used one but there is heaps of demo code. The helmet end is much simpler; read the serial output from the bluetooth module and drive a 3 digit display.

The display would be very handy while learning and for repeatability. I was trying out aluminium welding with the foot pedal and there was a really small sweet-spot between too cold and burning a hole. Once I had the current dialled in the welds looked great, but if I went too hot, there was no saving the weld.
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Post Sun Dec 27, 2015 1:16 pm 
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Glen
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The foot pedal is handy as you can hammer the current to full to get things going fast and taper off slowly towards to avoid melting a hole in the edge of the plate. Definitely not essential but i tend to use mine more often than not now cause it's much faster for doing lots of welding.

Dunno about the worth of an easy to see current readout, I just set the dial roughly where it works and go from there, Totally superfluous with the foot pedal attached. It's very obvious whether you have enough or not enough heat as soon as the weld pool is formed and you adjust it either with travel speed as said (to a degree ofc) or more current via footpedal.

Question though Brett - I modified a guitar pedal to replace the huge monstrosity the 200p tig came with and was thinking of making it wireless, reckon hacking the guts of a hobbyking 2.4ghz radio + reciever in both the welder and pedal might work? Been meaning to give it a go for a while now, wonder if the noise would make it useless.


quote:
I was trying out aluminium welding with the foot pedal and there was a really small sweet-spot between too cold and burning a hole. Once I had the current dialled in the welds looked great, but if I went too hot, there was no saving the weld.


Aluminium is no fun lol, Alot of the time it looks like the pool isn't there when it is which can make it seem like that. Did you wire brush it, acetone the part etc.
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Post Sun Dec 27, 2015 1:33 pm 
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Nick
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I was actually liking aluminium welding more than steel - the parts welded very nicely once I had the current right and seeing the puddle & dipping the filler was easy for me. The only real problem was learning to back off the current as the parts heated up and that's just down to lack of experience. I didn't clean the parts particularly well, just a quick wire brush and a wipe with isopropyl alcohol.
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Post Sun Dec 27, 2015 2:25 pm 
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maddox



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On the wireless pedal, if you get there , make 2 of 'm.


But the guitar pedal idea, thanks, that's easy enough to find.

Post Sun Dec 27, 2015 2:28 pm 
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Spockie-Tech
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quote:
Originally posted by Glen:
Question though Brett - I modified a guitar pedal to replace the huge monstrosity the 200p tig came with and was thinking of making it wireless, reckon hacking the guts of a hobbyking 2.4ghz radio + reciever in both the welder and pedal might work? Been meaning to give it a go for a while now, wonder if the noise would make it useless.


As we all know, 2.4Ghz radios are fairly resistant to noise (compared to the early PPM/PCM radios), but I dont know about 200amps of pulsed welding current with HF Start as well. It might work, might not.

Good news is, its easy to test prior to making it. Plug your Tx in, put a servo on the Rx and weld away. See if the servo failsafes or jitters. Move the leads around a bit, drap them over the Tx/Rx and so on. If it holds steady, you should be right.

You could add some noise filtering code in the Rx side.

The TX side will be easy.. you just replace a Tx Stick potentiometer with the pedal pot. But on the Rx side, youre going to need something (micro probably) to convert the PPM servo output from the RX into an analog voltage or a variable resistance. Measure the PPM with a micro, PWM an output ("analogout"). Cap/resistor filter the PWM output and drive a fet to convert to resistance maybe.

Then on the Rx side, you could do some code to ignore spurious errors. I forget what the receiver/servo frame rate is.. 15-50 per second ? so if you get any values that are miles different to the present rolling average, just ignore them.. something like that should handle spike noise if the receiver *mostly works and doesnt just simply go completely deaf the moment the arc strikes
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Post Sun Dec 27, 2015 3:05 pm 
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Nick
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Couldn't you just turn the original pot from the foot pedal with a servo? It misses out on the software noise rejection, but would be the simplest to build.
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Post Sun Dec 27, 2015 3:18 pm 
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Spockie-Tech
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Count on an Electronic Engineer to think of the tech details and overlook the simple Smile

I think in one of Isaac Asimov's Robot stories he said something about "If you want a doorstop, use a robot with a thick foot"

Good thinking.

Along those lines, I thought I was pretty clever a few weeks ago, using a "Gyro" Electric Screwdriver (one of those ones that senses how far you tilt/twist it to vary the speed) to turn a nut in the center of the wheels on my micro lathe as a simple form of auto-feed. Worked *really well, intuitively adjustable slow constant speed with lots of torque Smile
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Post Sun Dec 27, 2015 5:06 pm 
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Nick
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@ Brett: Titanium has even lower conductivity than steel; in my fusion welding test I didn't need variable current at all.

That hand-held current control is interesting but overly complicated. This commercial unit just replicates the pot from the foot pedal:





It looks suspiciously like an R/C pistol radio with a linear slider in place of the trigger.
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Post Sun Dec 27, 2015 5:27 pm 
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maddox



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Just did a piece with the Pulse mode of the El Cheapie Giant. Welding 0.8mm sheet to 3.2mm is just easy now.

Set on slow pulse, 90A, aim for the thicker piece, create a puddle, feed it a dab of filler in the high amp pulse, and move on to the next dab.

Fast and easy.

Post Sun Jan 03, 2016 9:40 am 
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GregCravens



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As we all know, 2.4Ghz radios are fairly resistant to noise.You could add some noise filtering code in the Rx side.
The TX side will be easy.. you just replace a Tx Stick potentiometer with the pedal pot. But on the Rx side, youre going to need something (micro probably) to convert the PPM servo output from the RX into an analog voltage or a variable resistance. Measure the PPM with a micro, PWM an output ("analogout"). Cap/resistor filter the PWM output and drive a fet to convert to resistance maybe.

Post Thu Apr 14, 2016 3:41 am 
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