How to make one device start and stop when another device does the same? - Page 1
Forum section: electronics / projects

author: drummerdimitri
author_rank: Frequent Contributor
timestamp: November 19, 2020, 10:17:15 am
content: I'd like to build a simple circuit that allows my welding fume extractor to start or stop when my welding machine starts or stops for the sake of convenience.Got the inspiration from another model that has this option, however the fume extractor I am considering purchasing does not have this option.What they use is some device that attaches to the welding cable which is most probably some kind of current sensing/hall effect sensor that is then connected to the welder via a cable.Wouldn't it be a simple project to make a similar device? I would need to be able to control the trigger threshold with an electronics circuit that could interpret the current or lack thereof to then command a relay to turn on or off, sending or cutting out the power to the fume extractor while its main switch is in the on position.Maybe such a device already exists in which case I would just purchase it instead of attempting to find a solution to this problem.

author: rvalente
author_rank: Frequent Contributor
timestamp: November 19, 2020, 11:42:38 am
content: What kind of welder is yours? If is a TIG/MIG or anything with a trigger/pedal just sense this trigger and add a TOFF electrical timer, when the trigger goes high the fume extractor turns on, when the trigger goes off the timer waits a few min and turn off.

author: drummerdimitri
author_rank: Frequent Contributor
timestamp: November 19, 2020, 12:26:43 pm
content: Quote from: rvalente on November 19, 2020, 11:42:38 amI have both but since TIG does not generate any smoke, I will mostly be using it with my Stick and MIG welder.What do you mean by "sense this trigger"? Going to need much more than that to make anything out of it.

author: rvalente
author_rank: Frequent Contributor
timestamp: November 19, 2020, 10:08:12 pm
content: Maybe I'm not following, but I imagine this workflow.Begin of you working day, arrive at company and turn on the welder, great.When you start to weld you want the fume extractor to run, when you stop to weld the fume extractor will keep running a little longer.After some time not welding, the fume extractor stops, right?

author: rvalente
author_rank: Frequent Contributor
timestamp: November 19, 2020, 10:09:16 pm
content: To sense the TIG or MIG is welding just get the trigger/pedal signal as start.For the stick, sense the voltage, when it drops you know its welding.

author: S. Petrukhin
author_rank: Super Contributor
timestamp: November 19, 2020, 11:30:31 pm
content: You can use a light sensor. The light from welding is very large. It is possible to use a ready-made night light switch, for example, covering its sensitive part with a dark film in several layers to adjust the operation.

author: rvalente
author_rank: Frequent Contributor
timestamp: November 20, 2020, 12:37:14 am
content: Quote from: S. Petrukhin on November 19, 2020, 11:30:31 pmTIG arcs are not that bright (thankfully) but for MIG and stick, yes, definetelyAnother simple idea, a few turns of wire over the welder cable + shunt resistor (you've just made yourself a current transformer) and a 555 timer and a relay.

author: Doctorandus_P
author_rank: Super Contributor
timestamp: November 20, 2020, 03:01:01 pm
content: Or use a master-slave switch.These are standard devices that monitor the current to a socket and switch a relay if the current goes over an (often adjustable) threshold.

author: drummerdimitri
author_rank: Frequent Contributor
timestamp: November 20, 2020, 03:37:48 pm
content: Quote from: Doctorandus_P on November 20, 2020, 03:01:01 pmSeems like an elegant solution to my problem thanks!

author: rvalente
author_rank: Frequent Contributor
timestamp: November 20, 2020, 03:44:06 pm
content: Google "Siemens current sensing relay"