Questions about Arduino spot welder controller

I mounted the electronics for the spot welder, I turned, but I always 220 V on output to the transformer. I checked and installed all components correctly.It has already happened a problem like this?
Thanks.

Kingmaury:
I mounted the electronics for the spot welder, I turned, but I always 220 V on output to the transformer. I checked and installed all components correctly.It has already happened a problem like this?
Thanks.

If you want to measure the output voltage, use a load.

Kingmaury:
I mounted the electronics for the spot welder, I turned, but I always 220 V on output to the transformer. I checked and installed all components correctly.It has already happened a problem like this?
Thanks.

You must load the output with a MOT, lamp, resistor etc.

Considering that each one of the two SCRs switch on for either the positive or negative mains half-waves which are 10ms long (assuming 50 Hz for the power mains) is there any reason why the minimum welding time cannot be set to 10 ms instead of 50 ms?

Maybe with a shorter welding time there will be no need for switching to the lower 400A current mode.

candido:
Considering that each one of the two SCRs switch on for either the positive or negative mains half-waves which are 10ms long (assuming 50 Hz for the power mains) is there any reason why the minimum welding time cannot be set to 10 ms instead of 50 ms?

Maybe with a shorter welding time there will be no need for switching to the lower 400A current mode.

The first weld controller that I have built had no synchronisation and therefore the weld time was not very accurate (+/-20ms) and the minimum weld time was set to 50ms because of reproducibility. For me this was fine. But with the synchronisation, the weld time is more accurate and a shorter weld time is possible, but I have not tested this. The weld times can be changed in the software easily.

Maybe with a shorter welding time there will be no need for switching to the lower 400A current mode.
I think that very short weld times are tricky, in some circumstances it may work, it should further be examined.

avandalen:
The first weld controller that I have built had no synchronisation and therefore the weld time was not very accurate (+/-20ms) and the minimum weld time was set to 50ms because of reproducibility. For me this was fine. But with the synchronisation, the weld time is more accurate and a shorter weld time is possible, but I have not tested this. The weld times can be changed in the software easily.

Maybe with a shorter welding time there will be no need for switching to the lower 400A current mode.
I think that very short weld times are tricky, in some circumstances it may work, it should further be examined.

OK, that makes sense, thanks.

Some capacitor discharge spot welders can use dual pulses where the first is a short pulse in the order of 10 ms and the second (after, say, a 10 ms pause) is a bit longer. It was in this context that I had asked the initial question.

As you say, this will require some investigation and testing. In theory the current from the capacitor discharge will be a decreasing exponential while the one from the transformer should be sinusoidal. These different waveforms will probably produce different welds.

If you detect the zero crossing point of the mains, you can use phase angle control to vary the current, and also vary the time of the weld.

You would need 2 thyristors, or a non zero crossing triac, to switch the AC. detect the zero cross point, for full power fire thyristors just after zero crossing, half power then wait 5mS.

Then to adjust the time repeat above for the required number of half cycles.

P.S. The current would be very spiky at lower currents.

You could rectify the output, then use a coil of welding cable as a choke, to get a more smooth DC output.

Or you could of course leave AC on, and use a 4 thyristor bridge to control the dc current. This is the way I would, and have done it, except using 6 thyristors for 3 phase welders.

Why do you use Arduino like controller? What is a reason for that? Would not it be possible to
just use ON/OFF switch? When the arms connect, the switch would make a
circuit and current will flow. Can you please explain the advantages of
using your controller?

Jane1:
Why do you use Arduino like controller? What is a reason for that? Would not it be possible to
just use ON/OFF switch? When the arms connect, the switch would make a
circuit and current will flow. Can you please explain the advantages of
using your controller?

It surely is possible to use a mechanical switch like a push button to do some spot welding but if reproducibility, consistency, reliability and welding quality are important then a micro-controller and solid state switching is probably the best way to achieve that.

Additionally, if doing battery tab spot welding then it is important to have a precise control of the amount of current/energy/heat used for the weld to avoid damaging the battery. A good overview is given in here:

http://www.macgregorsystems.com/app_note7_battery_pack_manufacture.pdf

Jane1:
Why do you use Arduino like controller? What is a reason for that? Would not it be possible to
just use ON/OFF switch? When the arms connect, the switch would make a
circuit and current will flow. Can you please explain the advantages of
using your controller?

With a mechanical switch you can't create short weld times which are required, 50ms, 100ms etc.

candido:
OK, that makes sense, thanks.

Some capacitor discharge spot welders can use dual pulses where the first is a short pulse in the order of 10 ms and the second (after, say, a 10 ms pause) is a bit longer. It was in this context that I had asked the initial question.

As you say, this will require some investigation and testing. In theory the current from the capacitor discharge will be a decreasing exponential while the one from the transformer should be sinusoidal. These different waveforms will probably produce different welds.

The weld-controller software creates a short pre-weld time of 50ms (see http://www.avdweb.nl/tech-tips/spot-welder.html). I will this info the the PCB site too.

Thank you for the link
Does it mean with your controller you can control current as you need?

I need to heat up a large soldering tip of size 45x20x1mm (lengthxheightxwidth).For this reason I also modified a micro oven transformer( to use a resistive heating).The secondary gives about 600A /2V. But when I shorted it , in a very few seconds, winding was very hot, so not possible to use. I need the soldering tip to be heated up so that it reaches a temperature about 200C, then I need to allow the temperature to drop to about 170C and after a minute or two, I need to increase the temperature to 200C again, wait about 15 sec then drop to those 170C ad so on.
It is not a problem to control the temperature, but my problem is the current that causes big heating of the secondary of the transformer.

Would be possible to use your controller for this project or how I should modified it?

Jane1:
Thank you for the link
Does it mean with your controller you can control current as you need?

I need to heat up a large soldering tip of size 45x20x1mm (lengthxheightxwidth).For this reason I also modified a micro oven transformer( to use a resistive heating).The secondary gives about 600A /2V. But when I shorted it , in a very few seconds, winding was very hot, so not possible to use. I need the soldering tip to be heated up so that it reaches a temperature about 200C, then I need to allow the temperature to drop to about 170C and after a minute or two, I need to increase the temperature to 200C again, wait about 15 sec then drop to those 170C ad so on.
It is not a problem to control the temperature, but my problem is the current that causes big heating of the secondary of the transformer.

Would be possible to use your controller for this project or how I should modified it?

My spot welder controller board can be used for all kinds of 230V / 120V power control but you need to find out yourselve and write the software yourselve, I can't help you with this.

@avandalen
Thank you for reply.
I can rewrite the software and buy the hardware from you but will it help to reduce the heating if I send pulses to the secondary? The secondary of my modified MOT gives about 600A /2V. But when I make it short , in a very few seconds, the secondary winding is very hot, so not possible to use( it could burn out).
Any spot welder is shorted for a very short time, but I need much longer time to be shorted.
So my question is: will pulses cut down the heating? Or how could I reduce heating and prevent transformer from burning?

P.S. I read about Pulsed Heat Soldering Power Supplies,( Reflow Soldering & Bonding Power Supplies | AMADA WELD TECH) does it mean that it uses pulses and not continuous current?( You have a link on your website to that amadamiyachi company too

Jane1:
@avandalen
Thank you for reply.
I can rewrite the software and buy the hardware from you but will it help to reduce the heating if I send pulses to the secondary? The secondary of my modified MOT gives about 600A /2V. But when I make it short , in a very few seconds, the secondary winding is very hot, so not possible to use( it could burn out).
Any spot welder is shorted for a very short time, but I need much longer time to be shorted.
So my question is: will pulses cut down the heating? Or how could I reduce heating and prevent transformer from burning?

P.S. I read about Pulsed Heat Soldering Power Supplies,( Reflow Soldering & Bonding Power Supplies | AMADA WELD TECH) does it mean that it uses pulses and not continuous current?( You have a link on your website to that amadamiyachi company too

On the ex-MOT I've rewound the maximum current I get (with secondary short circuited) is about the same as shown in Albert van Dalen's website, i.e. 1200A. If I use a 80mm x 4mm nail made of steel to short-circuit the secondary it melts in about 3 secs. In 3 secs there are 100 power mains half-waves (assuming 50 Hz).

Doing some quick calculations, the melting point of steel is about 1500C, so to achieve instead 200C in the same time we need 100/7.5 ~ 13 half-waves or about 4 or 5 half-waves/sec. This can easily be implemented using Albert's "Arduino spot welder controller", just needs some reprogramming of the C code shown in there.

To guarantee a more precise temperature control a thermocouple sensor can be used and interfaced into the Atmega MCU. The advantage of Pulse Heat Soldering is that the soldering tip heats up and cools down very fast, compared to a soldering iron, hence not much energy is wasted. A good description can be seen here:

@candido

Can you please let me know further details about your secondary winding? What wires did you use?What cross-sectional area ?

I do not understand this

In 3 secs there are 100 power mains half-waves (assuming 50 Hz).

But I think in 1 sec there are 50 waves. in 3 sec there are 3x50 =150 sec
Or am I wrong?
Thanks for feedback.

Jane1:
@candido

Can you please let me know further details about your secondary winding? What wires did you use?What cross-sectional area ?

I do not understand thisBut I think in 1 sec there are 50 waves. in 3 sec there are 3x50 =150 sec
Or am I wrong?
Thanks for feedback.

Sorry, I meant to say "In 3 secs there are 300 power mains half-waves (assuming 50 Hz)." This will then lead (to achieve 200C) to 300/7.5 = 40 half-waves/3 secs or about 13 or 14 half-waves/sec

Regarding the secondary widing, just google for "MOT rewinding", there are plenty of youtube videos showing how to do it.

Hello, I am rather interested in ordering one of your spot welder control boards. I am located in the US, but would like to purchase a few in the near future.

I was wondering if I could you could explain a few thing for me. What is the benefit of the zero-cross/ quarter hertz time circuit? Does this accomplish power factor correction? What kind of welding is most benefited by this method of control? I want to do both parallel electrode battery spot welding and opposing electrode sheet metal, along with possibly doing resistive to non-resistive spot welding for heater elements.

I already have a 1100 watt transformer wound and mounted with my setup, but was originally going to use a foot switch and power switch to control a relay on the mains. I decided that I might be better with an ssr/scr diode when I found your page.

That you for your time, and I will be anticipating your response. Have a good day.

Also after a bit of thinking I have an additional question to ask. When you look at the power side of this system, it is essentially a purely inductive/resistive load. When I disassembled the microwave that I stole the transformer core from, there was a rather large capacitor that looks to have been paired with the magnatron. This would make sense in terms of overall efficiency since the reactance of the capacitor would help to bring the power factor of the unit closer to a unity pf. Wouldn't it make sense to employ some sort of pf correction to this design?... It seems that if this was to be done, then the zero-cross/pulse time trigger would need to be rethought.

I was wondering if I could you could explain a few thing for me. What is the benefit of the zero-cross/ quarter hertz time circuit? Does this accomplish power factor correction? What kind of welding is most benefited by this method of control? I want to do both parallel electrode battery spot welding and opposing electrode sheet metal, along with possibly doing resistive to non-resistive spot welding for heater elements.

It is just for educing the weld transformer inrush current.

I already have a 1100 watt transformer wound and mounted with my setup, but was originally going to use a foot switch and power switch to control a relay on the mains. I decided that I might be better with an ssr/scr diode when I found your page.

You can't control weld times by a foot switch, weld times are sometimes just 50ms.

Also after a bit of thinking I have an additional question to ask. When you look at the power side of this system, it is essentially a purely inductive/resistive load. When I disassembled the microwave that I stole the transformer core from, there was a rather large capacitor that looks to have been paired with the magnatron. This would make sense in terms of overall efficiency since the reactance of the capacitor would help to bring the power factor of the unit closer to a unity pf. Wouldn't it make sense to employ some sort of pf correction to this design?... It seems that if this was to be done, then the zero-cross/pulse time trigger would need to be rethought.
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PFC doesn't make sense I think because the weld times are very short. The capacitor is a high voltage type and not designed for PFC.