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  #21  
Old 01-01-2018, 05:07 PM
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MetalWolf MetalWolf is offline
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i will get it later i have to go to his house and get the contactors he will give me after that i will get back with all required info may be a couple days as he is out doing calls and don't get in till late.

ill see if i have one around here too please bare with

Thanks...........Randall
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  #22  
Old 01-01-2018, 06:11 PM
BukitCase BukitCase is offline
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Here's the manual for the 240 HF spot welder

https://manuals.harborfreight.com/ma...1999/61206.pdf

There's even a "schematic" on page 14; if it's REALLY that simple, your plan may work - apparently YOU are the "timer".

If your intent is to go "mass production" though, keep in mind that it's typical HF stuff and has a duty cycle of 5 seconds out of 10.

the switch is on the INPUT (duh) which is rated 16 amps @ 240 - so I wouldn't use less than a 25 amp rated switch (or your limit switch and a contactor, more likely) and I'd look for a snubber for across the switch (contactor terminals) since it's switching an inductive load... Steve
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  #23  
Old 01-01-2018, 08:49 PM
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Quote:
Originally Posted by BukitCase View Post
Here's the manual for the 240 HF spot welder

https://manuals.harborfreight.com/ma...1999/61206.pdf

There's even a "schematic" on page 14; if it's REALLY that simple, your plan may work - apparently YOU are the "timer".

If your intent is to go "mass production" though, keep in mind that it's typical HF stuff and has a duty cycle of 5 seconds out of 10.

the switch is on the INPUT (duh) which is rated 16 amps @ 240 - so I wouldn't use less than a 25 amp rated switch (or your limit switch and a contactor, more likely) and I'd look for a snubber for across the switch (contactor terminals) since it's switching an inductive load... Steve
That is the spot welder i am using
i pulled the original switch and relocated it below to mechanically work with the foot pedal.

My concerns are original switch will not hold up I do not intend on using it for mass fabrication work, Its just for odd and end spot weld where i need them on minor repair stuff is all and yes the used is the Timer only takes 3 - 6 seconds to make a weld.
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  #24  
Old 01-02-2018, 05:29 AM
Riverr1 Riverr1 is offline
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This may be a stupid question but how does a limit switch work? With automotive relays there are ones that work while activated like with power windows but when all the way up or down they deactivate or when the switch is released. Then there are relays like those used for fuel pump emergency cutoffs or multiple battery systems. They power a switch and then shut off regardless of input. These relays created some problems with cycling in the early days of ECU's. A common example was if a wireless door lock was used when a door was open and the engine running. When the engine was shut off the cycling relationship between the door lock and an antitheft device was out of sync. Unlock the doors with the remote and the alarm went off. The under-hood light was similar. Turn off the engine with the hood open and then close the hood, the alarm went off.

With a limit switch, what's in control? The switch or the relay? With the welder having the switch and a relay what would the cycling sequence be? With ECU's, the programming controls most of this. I assume no programming is involved with a home spot welder. Again, I hope I'm making sense and sorry if this is ignorant or stupid. I'm no electrician.
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  #25  
Old 01-02-2018, 07:32 AM
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MetalWolf MetalWolf is offline
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Quote:
Originally Posted by BukitCase View Post
Here's the manual for the 240 HF spot welder

https://manuals.harborfreight.com/ma...1999/61206.pdf

There's even a "schematic" on page 14; if it's REALLY that simple, your plan may work - apparently YOU are the "timer".

If your intent is to go "mass production" though, keep in mind that it's typical HF stuff and has a duty cycle of 5 seconds out of 10.

the switch is on the INPUT (duh) which is rated 16 amps @ 240 - so I wouldn't use less than a 25 amp rated switch (or your limit switch and a contactor, more likely) and I'd look for a snubber for across the switch (contactor terminals) since it's switching an inductive load... Steve
I'm thinking now i may have made this more complicated in my own head
after thinking about it using the limit switch with basic square D contactor and energizer coil should work.

using a limit switch rated for the amps would be more ideal for the application but heck here is where it went wrong..

In being cheap and not wanting to fork out a lot of money, so it will now cost more to use the limit switch i have

Not thinking i found some limit switches for 2 bucks ea. shipped. but did not consider the amp load only looking at voltage

so what i think i will need to do is use the square D contactor with a 24v coil to engage the contactor coil to support the load using the limit switch to actuate load power to the spot welder....

this is probably why my brother got frustrated with me as the way i explain something most times with me is the basic idea in my head is rite but when i try to verbally express what's in my head don't come out the same way like putting them on paper most times don't work out either so again i may have just complicated it and started second guessing my self.

it sort of like this i draw something in my head and just do it, It usually comes out as i see it, But try to put it on paper or verbally express it usually a lost cause other than a scribble note/drawing no one understands but me.

So basically i have it figured out and "Appreciate all of you guys" for pointing out the need for the contactor.

once its done ill update the spot welder build with pics.

Thanks A bunch guys
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  #26  
Old 01-02-2018, 12:15 PM
BukitCase BukitCase is offline
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MW, sounds like you're on top of it; just keep in mind that there's 24 volt DC and 24 volt AC - and coils DO know the difference - if you use DC on an AC rated coil you will burn it up because the "steady state" current does NOT get "bucked" (resisted, sorta) by the inductive part of the coil. Just read the labels on stuff and give it what it's rated for and you'll be fine...

Riverr1 - "With a limit switch, what's in control? The switch or the relay? With the welder having the switch and a relay what would the cycling sequence be?"

What's in control (or lack of it) is the DESIGNER - "dumb" components are just that; a switch is just a switch, some relays are more complex in that some can be "pulsed" and will change state each pulse... but something as simple as that spot welder just needs to turn ON when the foot switch (limit switch in this case) is stepped on, and OFF when it's NOT.

In DC circuits WITHOUT any computerized stuff, the designer can also use diodes to help with "decision-making" - one polarity can operate a device while the opposite will NOT, etc -

In ANY case, the system is ONLY as good as the DESIGNER, computers or NO computers - if the designer doesn't correctly figure out ALL of the possible combinations of inputs to the system and allow only the ones that are OK, then he hasn't done his job and the device may not work correctly under ALL scenarios... Steve
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  #27  
Old 01-02-2018, 11:01 PM
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MetalWolf MetalWolf is offline
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Quote:
Originally Posted by BukitCase View Post
MW, sounds like you're on top of it; just keep in mind that there's 24 volt DC and 24 volt AC - and coils DO know the difference - if you use DC on an AC rated coil you will burn it up because the "steady state" current does NOT get "bucked" (resisted, sorta) by the inductive part of the coil. Just read the labels on stuff and give it what it's rated for and you'll be fine...

Riverr1 - "With a limit switch, what's in control? The switch or the relay? With the welder having the switch and a relay what would the cycling sequence be?"

What's in control (or lack of it) is the DESIGNER - "dumb" components are just that; a switch is just a switch, some relays are more complex in that some can be "pulsed" and will change state each pulse... but something as simple as that spot welder just needs to turn ON when the foot switch (limit switch in this case) is stepped on, and OFF when it's NOT.

In DC circuits WITHOUT any computerized stuff, the designer can also use diodes to help with "decision-making" - one polarity can operate a device while the opposite will NOT, etc -

In ANY case, the system is ONLY as good as the DESIGNER, computers or NO computers - if the designer doesn't correctly figure out ALL of the possible combinations of inputs to the system and allow only the ones that are OK, then he hasn't done his job and the device may not work correctly under ALL scenarios... Steve
So here are the components I have come up with....
Just have one question should i use the limit switch in line to brake the 24v to cut power and to activate power...?
Click image for larger version

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do nothing." -Edmund Burke-
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  #28  
Old 01-03-2018, 08:21 AM
Lew Hartswick Lew Hartswick is offline
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There is a new one on me. But I suppose the GD lawyers had something to do with it. two different size QC terminals on the pri. of the xformer.
...lew...
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  #29  
Old 01-03-2018, 08:40 AM
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digger doug digger doug is offline
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If your going down this road with a relay, might as well add a timer.
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  #30  
Old 01-03-2018, 09:23 AM
Riverr1 Riverr1 is offline
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Quote:
Originally Posted by BukitCase View Post
MW, sounds like you're on top of it; just keep in mind that there's 24 volt DC and 24 volt AC - and coils DO know the difference - if you use DC on an AC rated coil you will burn it up because the "steady state" current does NOT get "bucked" (resisted, sorta) by the inductive part of the coil. Just read the labels on stuff and give it what it's rated for and you'll be fine...

Riverr1 - "With a limit switch, what's in control? The switch or the relay? With the welder having the switch and a relay what would the cycling sequence be?"

What's in control (or lack of it) is the DESIGNER - "dumb" components are just that; a switch is just a switch, some relays are more complex in that some can be "pulsed" and will change state each pulse... but something as simple as that spot welder just needs to turn ON when the foot switch (limit switch in this case) is stepped on, and OFF when it's NOT.

In DC circuits WITHOUT any computerized stuff, the designer can also use diodes to help with "decision-making" - one polarity can operate a device while the opposite will NOT, etc -

In ANY case, the system is ONLY as good as the DESIGNER, computers or NO computers - if the designer doesn't correctly figure out ALL of the possible combinations of inputs to the system and allow only the ones that are OK, then he hasn't done his job and the device may not work correctly under ALL scenarios... Steve
Steve,

Thank you for the response. As I said, I'm no electrician but I'm interested in what MW is trying to solve and I'm just trying to learn something about this.

A system being only as good as the designer is conventional wisdom but with more than 35 years around industry I'd have to say it was rare that any finished system except the most basic systems, in the end were completely "as designed."

I've seen limit switches on part transfer systems that prevent a transfer if the "tail" (not sure of what else to call it) is not depressed. I've seen switches that operate as a "kill switch," and that's all they do. Doesn't matter what happens with the "tail" once it is activated. This condition was corrected by cycling the system from a control panel, digital or analog. I've seen limit switches that were in QC test systems that would send parts forward or back in to a process depending on test results. Etc.

I've always thought like this, a switch that continues a process only while the "tail" is depressed is a different kind, type or style of switch from one that kills a system or process regardless of "tail" motion after the switch is activated. From what I've read here, what I've always thought about the operation of the switches has been wrong because none of these potential operation issues were asked about MW's switches. The information shared with MW is that a limit switch is just a switch and the process the switch controls is separate from the switch, digital or analog. The only decision or condition selectable in the switch is if it opens or closes a circuit and maybe timing.

Do I have it right now? The switch has nothing to do with the logic of a circuit except open or closed.
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