Detecting welding arc

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I'm thinking of building a device that is triggered by the welding arc. One obvious way of doing this would be with UV sensors, like auto-dark helmets, but I'd rather do something like an inductive lead wrapped around the welding lead, or, heck, maybe even a DINSE Y-pigtail with a huge resistor in it that prevents most of the welding current from getting to the device--although I think that would be overkill, and that there is probably a simpler way to do it.Can anybody help point me in a direction that would work? I know that inductive sensing works great with AC current, but I think it's a little more complicated with DC. Then again, if all I want to do is sense the presence of the current, and not measure e.g. voltage/amperage, maybe that will still work.I'm being cagey about what the device is, because, although it is probably stupid and useless and nothing will come of it, maybe it will be my one-in-a-million idea (like the Ten Foot Drill Bit) that will make me RICH RICH RICH! Everlast PA160-STH... and that's about it!
Reply:So far, I have found this:http://en.wikipedia.org/wiki/Sensors...ontact_sensorsBut it seems to be way over what I'm looking for. I guess I'm wondering if anybody knows of any existing products that do this, that I could study for examples. Other than autodark hoods, obviously. The reason I don't like the UV sensor method is that it has false positives (fluorescent lights and such) and requires line-of-sight to the arc. These are not ideal conditions for my device.Everlast PA160-STH... and that's about it!
Reply:A Electromagnetic Arc Sensorwww.georgesplasmacuttershop.comPlasma Cutter and Welder Sales and Repairs--Ebay storeTec.Mo. Dealer Consumables for the PT and IPT torch's
Reply:The OC welding voltage will drop to the welding voltage,when you strike an arc.
Reply:My miller digital elite welding hood has X-mode in which it senses the magnet pulse of the arc when struck and darkensBacked my CATMA over your CARMA oops clusmy me  What would SATAN do ?? Miller Trailblazer 302 AirPakMiller Digital Elite  Optrel Welding HatArcair K4000Suitcase 12RC / 12 VSHypertherm PM-45Rage 3 sawRusty old Truck
Reply:Now I've found this, which, again, is way overkill, but is in the right vein.http://www.lincolnelectric.com/en-us...roduct=K3019-1Everlast PA160-STH... and that's about it!
Reply:Originally Posted by BlueweldersThe OC welding voltage will drop to the welding voltage,when you strike an arc.
Reply:Why don't you wire directly off the wire feed or gas solenoid. Those should only be hot when an arc is on.  Unless you are talking about stick.   I would imagine there are photocells with a sensitivity adjustment on them. Check McMaster Carr.
Reply:Originally Posted by killdozerd11My miller digital elite welding hood has X-mode in which it senses the magnet pulse of the arc when struck and darkens
Reply:Originally Posted by blackbartWhy don't you wire directly off the wire feed or gas solenoid. Those should only be hot when an arc is on.  Unless you are talking about stick.
Reply:Just use the whole lens and have a light detector through the lens, like the emitter and receiver off of a computer mouse.
Reply:For voltage-reading, do you think it'd be fair to say that a threshold of about 35 volts would work? My impression is that most welders have an OCV of around 60-80, and a welding voltage of around 25-35, with CC sources typically being closer to 30 at most, and CV sources going a bit higher. But I don't know as much about CV; do really hot MIG processes go above that? The highest I've ever heard of is a big old dual-shield wire that was run at something like 32 volts.Everlast PA160-STH... and that's about it!
Reply:the first auto-dark helmut I bought for the shop back around 1980 had a wired input that you hooked to the contactor on a mig machine.miller thunderbolt 250vlincoln square wave tig 175 prolincoln idealarc mig sp250everlast tig 210EXTeverlast power plasma 50chicago electric (hf) 130 tig/90 arcchicago electric 90 amp flux wire3 sets oxy/acet
Reply:I don't know how many amps you want to go to, 25v is around 220a if I remember correctly.
Reply:I thought the miller elite already used this technology..Sal
Reply:Originally Posted by BlueweldersJust use the whole lens and have a light detector through the lens, like the emitter and receiver off of a computer mouse.
Reply:Hall effect sensor?  Current transformer?http://en.wikipedia.org/wiki/Hall_effect_sensor"USMCPOP" First-born son: KIA  Iraq 1/26/05Syncrowave 250 w/ Coolmate 3Dialarc 250, Idealarc 250SP-175 +Firepower TIG 160S (gave the TA 161 STL to the son)Lincwelder AC180C (1952)Victor & Smith O/A torchesMiller spot welder
Reply:Originally Posted by joshuabardwellThat's clever. Would it work in the dark, though? You'd need an emitter, I think.
Reply:Originally Posted by OldendumHall effect sensor?  Current transformer?http://en.wikipedia.org/wiki/Hall_effect_sensor
Reply:There is a special kind of current sensor called a current detector (I think) which is just what you're looking for. They do not make a signal proportional to current, just an output, or contact closure, when the current exceeds the set threshold. Try automationdirect.com - Grainger might have them too.JohnA few weldersA lot of hammersA whole lot of C-clamps
Reply:The simplest is a magnetic switch. Like the ones used in door alarms.If you need a switch that carries more current, Lincoln uses them in the LN 9 feeders and a lot of their older engine drives. Look up the LN 9 feeder code 9100 part number S12334-45.A switch in a tube that get strapped to the weld lead. Have one customer that uses this plus an hour meter to measure arc time for his workers. reads the meter at the start of each shift.seen them placed along the lead, across the lead and with a steel plate.
Reply:Dadgum it. I just realized that watching for a drop from OCV to welding voltage may only work on a CC machine. What happens to the voltage across a CV machine's leads when you start the arc? Is it the same whether there's an arc or not?Everlast PA160-STH... and that's about it!
Reply:Originally Posted by ccawgcThe simplest is a magnetic switch. Like the ones used in door alarms. If you need a switch that carries more current, Lincoln uses them in the LN 9 feeders and a lot of their older engine drives. Look up the LN 9 feeder code 9100 part number S12334-45. A switch in a tube that get strapped to the weld lead. Have one customer that uses this plus an hour meter to measure arc time for his workers. reads the meter at the start of each shift. seen them placed along the lead, across the lead and with a steel plate.
Reply:All of the welders that I am familiar with whether CC or CV, have a OC voltage that is higher than the welding voltage.
Reply:Originally Posted by BlueweldersAll of the welders that I am familiar with whether CC or CV, have a OC voltage that is higher than the welding voltage.Originally Posted by joshuabardwellSo far, I have found this:http://en.wikipedia.org/wiki/Sensors...ontact_sensorsBut it seems to be way over what I'm looking for. I guess I'm wondering if anybody knows of any existing products that do this, that I could study for examples. Other than autodark hoods, obviously. The reason I don't like the UV sensor method is that it has false positives (fluorescent lights and such) and requires line-of-sight to the arc. These are not ideal conditions for my device.
Reply:Originally Posted by joshuabardwellCan you give me a little better explanation of what you're talking about? What activates the switch when it is strapped to the welding lead?
Reply:Delay is no problem. I can handle that as long as I can figure out the sensor. I'll look into it.Everlast PA160-STH... and that's about it!
Reply:Near as I can tell, the door sensors are either reed switches or Hall effect sensors. I'm not sure these work on DC.Everlast PA160-STH... and that's about it!
Reply:Photocell to detect the flash of the arc.Hall effect current sensor to detect welding current.Both require amplifier circuits to drive a relay."The reason we are here is that we are not all there"SA 200Idealarc TM 300 300MM 200MM 25130a SpoolgunPrecision Tig 375Invertec V350 ProSC-32 CS 12 Wire FeederOxweld/Purox O/AArcAirHypertherm Powermax 85LN25
Reply:Simple DC current indicator using a reed switch:http://discovercircuits.com/H-Corner/high-DC.htmSimple AC current indicator:http://discovercircuits.com/dc-mag/Issue_dec10/pg-7.htmHere's a commercial 100A indicator - $12.http://www.automationdirect.com/adc/...rent_Indicator"USMCPOP" First-born son: KIA  Iraq 1/26/05Syncrowave 250 w/ Coolmate 3Dialarc 250, Idealarc 250SP-175 +Firepower TIG 160S (gave the TA 161 STL to the son)Lincwelder AC180C (1952)Victor & Smith O/A torchesMiller spot welder
Reply:you can purchase both/either AC and DC current sensorsExperience is something you get right after you need it
Reply:So, I've read up a little more on Hall effect sensors, reed switches, and current transformers, and it is looking like if I want to detect both AC and DC current, I'm going to need two separate sensors, one for AC (current transformer) and one for DC (Hall effect or reed switch). Detecting the change of voltage between OCV and arc voltage would be pretty reliable, I think, but would require a DINSE pigtail. The more I think about it, the more it seems like a UV sensor is the way to go, despite its potential issues.Last edited by joshuabardwell; 08-05-2013 at 11:01 AM.Everlast PA160-STH... and that's about it!
Reply:There are bi-directional sensors based on Hall Effect that can be used for AC/DC.http://www.panucatt.com/product_p/cs-45al.htmhttp://www.amploc.com/escor/CS100and.htmYou could use a rather small capacity sensor by making a plug adapter that has a smaller wire shunt in parallel."USMCPOP" First-born son: KIA  Iraq 1/26/05Syncrowave 250 w/ Coolmate 3Dialarc 250, Idealarc 250SP-175 +Firepower TIG 160S (gave the TA 161 STL to the son)Lincwelder AC180C (1952)Victor & Smith O/A torchesMiller spot welder
Reply:A hall effect current sensor can sense both DC and AC currents. The hall effect is really just one part of the device. The hall effect sensor senses the flux in the core element. There must also be another coil driven with a secondary device. Essentially, the secondary coil is driven such that it cancels the flux from the device being sensed and the hall effect sensor always reads the net flux in the core to be zero. Then you monitor how much current that it took to accomplish that with the secondary coil, which tells you how much current is flowing through depending on the turns ratio. Current transformers are ONLY for AC. DC current through them will eventually saturate their core and the reading will drop to zero (depending on the core inductance and the sense resistor you use). If you are planning to sense tig current, the HF arc start could pose big problems. Essentially all external sensing elements are going to have to get very close to the current path, which will have very high voltages on them during arc start.. If you could get inside the welder, that'd be different.Hah, actually, that could be your solution. You could detect the HF arc start to know the arc is about to come on.Last edited by Zmechanic; 08-05-2013 at 01:59 PM.
Reply:Originally Posted by ZmechanicIf you are planning to sense tig current, the HF arc start could pose big problems. Essentially all external sensing elements are going to have to get very close to the current path, which will have very high voltages on them during arc start.. If you could get inside the welder, that'd be different.
Reply:Go to Lincoln's web site. look up owners manual IM626.The Lincoln mobiflex fume extractor has a work light and arc sensor That might be adaptable for your use. Reed switches are used to detect DC current and CT or current transformers can be used with AC current.Hall effect systems can measure both AC and DC.One way to avoid having to add bandpass filters is to pick a detection point  behind the ones already built into the welder. Send Me a PM. If I knew a little more about what you are trying to do, Might be able to point you in the right direction.
Reply:Hey, Josh.First, don't get your hopes up about out selling the 10FtDrillBit!Now, I'm no expert but I am wondering if you could use a Normally Open relay with your ground somehow? I believe with a little study, you could easily switch on whatever device you want. That eliminates having to use a sensor that might be blocked and you could easily move to any other welder.Still thinking we might get together this fall. I'll let you know.Last edited by wb4rt; 08-06-2013 at 12:39 PM.Burt _____________________Miller Syncrowave 250Millermatic 211Miller 375 Plasma Cutter Hobart Handler 12010FtDrillBit.com
Reply:Burt,Can you give me any more details on how the NO relay might work? I'm still not clear. Being a relay, at least it wouldn't pass the welding current over to the "device" in question, so that problem would be solved. Still pondering how HF might come into play.The only thing I've got so far this fall is my sister's wedding on Sep. 7 and another event the 3rd weekend in October. Hope our schedules align!Everlast PA160-STH... and that's about it!
Reply:Well, Joshua, somebody smarter and better trained than me would give you a complete answer.With my limited ham radio and southern engineering background, I would try to see if I could reliably read a DC and/or AC range maybe between the welding table and a ground or the ground lead and the table. I'm sure a real welder could tell you what range and how to measure it. But if you have a AC/DC voltage range and find a NO relay that would work with that input and your required circuit output, seems to me you would be in business. So a Normally Open relay (NO) Single-Pole, Single-Throw (SPST), would have an open circuit until that voltage range is sensed and it would close the relay (switch). Then your circuit would be closed at the contacts and turn on whatever mystery device you have. See this site: http://www.galco.com/comp/prod/relay.htm for more information on relays. Make sure you understand I don't know that this will work, but I believe that is what I would try to do. Of course you could use the gas solenoid to trigger a relay pretty easily, too.Ok, now all you sparkys can tell me why that won't work or tell Joshua how to make it work. Seems like a good science project to me.Last edited by wb4rt; 08-06-2013 at 03:17 PM.Burt _____________________Miller Syncrowave 250Millermatic 211Miller 375 Plasma Cutter Hobart Handler 12010FtDrillBit.com
Reply:Originally Posted by wb4rtOf course you could use the gas solenoid to trigger a relay pretty easily, too.