How to use a dimmer controller on a transformer

[sam_sam_sam]

I need to build current controller for a transformer on a battery spot welder
Does anyone have any good idea on how I can do this

The TRIAC that was used in this unit was a ( BCR30AM ) but think that this TRIAC is not big enough for the transformer that they used

Here is the data sheet for it

https://cdn.badcaps-static.com/pdfs/...bd578d1bbf.pdf

The photos are below

I have a few of these TRIAC ( BTA100-800B ) would it be possible to use these to control a transformer

Here is the data sheet for this device

https://cdn.badcaps-static.com/pdfs/...980f798e70.pdf

[budm]

Re: How to use a dimmer controller on a transformer

Are you trying to use Lamp dimmer to control Transformer which is Inductive load, not resistive load like the lamp?

[sam_sam_sam]

Re: How to use a dimmer controller on a transformer

Are you trying to use Lamp dimmer to control Transformer which is Inductive load, not resistive load like the lamp?

I would like like to control the transformer like you control a light bulb the same idea if this is possible

[budm]

Re: How to use a dimmer controller on a transformer

http://www.lutron.com/en-US/Educatio...ingBasics.aspx
https://cdn.badcaps-static.com/pdfs/...1a0242ccd3.pdf
What does the spec of your existing dimmer indicate about inductive load?
How much power are you trying to get?

[Curious.George]

Re: How to use a dimmer controller on a transformer

I need to build current controller for a transformer on a battery spot welder
Does anyone have any good idea on how I can do this

What exactly are you expecting to get from your efforts?

Is the transformer being operated as a voltage device or as a current device?

Are you trying to design a circuit or repair/upgrade an existing one?

[budm]

Re: How to use a dimmer controller on a transformer

It sounds like he is trying to spot weld the metal tab to the battery.

[sam_sam_sam]

Re: How to use a dimmer controller on a transformer

It sounds like he is trying to spot weld the metal tab to the battery.

You are correct

I did some testing on this device that is in the photo below

[sam_sam_sam]

Re: How to use a dimmer controller on a transformer

Here are the results of the testing of this device

https://www.ebay.com/itm/10000W-SCR-...-/252538426028

--Voltage: AC 110- 220V
--Maximum Power: 10000W (connected resistive load,220VAC)
--Voltage Regulation: AC 10V to 220VAC
--Dimensions: 130MMx 60MMx 47MM
--Rated current：25A MAX 45A
--for Electric furnace, water heater, lamps, small motor, electric iron etc.

The device is for 220 volts so I had mod it for 110 volts

There is a 4.7 k-ohm resistor next the Diac I had add another 4.7 k-ohm on top of one that was there because I was not getting full power out the transformer <——- which works great

But I going to pull both of those 4.7 k-ohm resistors out and put in a 5 k-ohm pot in it place
so I can fine tune the voltage going to the Diac so I can limit the triac’s current to 20 amps

This transformer might be 30 amps hook straight to the main power outlet
I have not tried it yet I do not have any 30 amp outlet in my house or shed in shed I could wire one for 30 amp but I do not think I need it to be that high amperage any way




What is nice about this timer is that it 100 of a second it is very hard to find a timer like this

I am also going to be using this type of timer the one I have is a little different but I might change to this one

Digital Sestos Twin timer Relay Time Delay Relay 110v Count Switch B2E-2R-22

https://www.ebay.com/itm/Digital-Ses...IAAOSwbF1aQ1ud



This is how I am going to do this

I going to use the n/open contacts on the timer to control the power going to the Diac to the pot control on the triac controller

On the timer there is a pause function button that stops the timer I going use the foot switch to reactive the timer or maybe something a little different I have not worked this part out yet

I also have a temperature controller that I going to use for as a fan controller and alarm on the transformer



I have this battery spot welder that the controller when bad I can get a replace controller board
for $28.00 plus $16.00 for shipping I going order one for the exact same battery spot welder that just bought a month ago

The problem with these battery spot welders is that the transformers are not same in every unit for some reason I have bought two of the exact same model at different times one last year and one month ago

This one where the controller board went bad the lights would dim when I would hit button to weld

The new one does not do this but it does not get a hot of a weld as older one does

Some time you need the extra power with thicker metal tabbing

[sam_sam_sam]

Re: How to use a dimmer controller on a transformer

I will post more as this project moves forward

I also recap the timer controller now this was real fun

It has two boards on it one has the switching power supply and timer components and the other board has relay and some other components

But there is very little space between the two boards and there is ribbon type connector between the two boards I had removed this ribbon cable connectors to get to all of the caps

The caps that were in were cap brands that I have not seen before

It had a 5 volt and 12 volt power supply rails in it

It looks like this timer controller is well made

What real fun that was

[Curious.George]

Re: How to use a dimmer controller on a transformer

It sounds like he is trying to spot weld the metal tab to the battery.

Yes, I got that from his posts.

But, what I don't see is the role of the transformer in the circuit.

I would imagine a "spot-welder" (having never designed one) would store a user-defined amount of charge in <something> and then dump that charge, on command into a short-circuit (the two electrodes).

So, I would envision this as a big, low ESR capacitor that is charged to some voltage (user adjustable -- sets the total amount of charge that you're eventually going to deliver to the "load"). Once "prime", it is then discharged through a transformer, the output of which is the shorted electrodes.

Thus, you are using the transformer for current amplification (as the output is a short circuit, there is no voltage to be "gained" )

[sam_sam_sam]

Re: How to use a dimmer controller on a transformer

Yes, I got that from his posts.

But, what I don't see is the role of the transformer in the circuit.

I would imagine a "spot-welder" (having never designed one) would store a user-defined amount of charge in <something> and then dump that charge, on command into a short-circuit (the two electrodes).

So, I would envision this as a big, low ESR capacitor that is charged to some voltage (user adjustable -- sets the total amount of charge that you're eventually going to deliver to the "load"). Once "prime", it is then discharged through a transformer, the output of which is the shorted electrodes.

Thus, you are using the transformer for current amplification (as the output is a short circuit, there is no voltage to be "gained" )

Yes you are shorting the secondary winding when welding the battery tabs

I would like to make a capacitor discharge battery spot welder but here is my

******BIG********

problem is finding the right SCR for this job and of course I would like have a SCR a lot bigger than what I need and I also need a circuit to control this SCR

I have the transformer
I have the capacitors
I have the timer controller
I have the spot welder setup

I just need the SCR
I just need the control circuit for the SCR ( to control the amount of) current output to the load ( which is a short circuit to welding pins )

I have google this before

“How to build a capacitor discharge battery spot welder “


a few times before but I have not had very much success in finding what I am looking for

I have found a few examples before but what I do not like with some of these is that the control circuit does not control the transformer it leaves it powered when it is in the discharge cycle

I do not like this approach for this reasons

One if something goes wrong with the SCR then you have BIG short circuit on the transformer

The other BIG problem I have with most of the other approaches I have seen is there is no control of the discharge current


So if I could over come these few really big problem I would build one today

[Curious.George]

Re: How to use a dimmer controller on a transformer

I would like to make a capacitor discharge battery spot welder but here is my BIG problem is finding the right SCR for this job and of course I would like have a SCR a lot bigger than what I need and I also need a circuit to control this SCR.

8<

I just need the SCR
I just need the control circuit for the SCR ( to control the amount of) current output to the load ( which is a short circuit to welding pins )

Isn't that sort of like saying "I just need the turkey to make Thanksgiving dinner?"

I have found a few examples before but what I do not like with some of these is that the control circuit does not control the transformer it leaves it powered when it is in the discharge cycle

8<

One if something goes wrong with the SCR then you have BIG short circuit on the transformer

This is only a problem if the transformer's output impedance is low. So, don't let it be!

The other BIG problem I have with most of the other approaches I have seen is there is no control of the discharge current

You control it indirectly -- by controlling how much CHARGE you store in the capacitor BEFORE you dump it into the "load".

CV=It

C is a constant that you set at design/build time. V is an "adjustable constant" that the user sets just before making a weld. I will be (indirectly) defined by the material being welded and how good the connection your electrodes make to it (i.e., how good a short circuit you can form) AND the characteristics of the transformer's secondary. All that is left is the time it takes for the current to fall to zero -- which varies based on the previous sentence.

If your welds are too cold, you increase the amount of charge with which you "pre-fill" the capacitor. If they are too hot, you decrease the amount of charge. [You can never do anything for the welds you've already made; what's done is done]

The problem with this approach is that it relies on you being able to repeatably "connect" the electrodes to the material (consistency).

[sam_sam_sam]

Re: How to use a dimmer controller on a transformer

The problem with this approach is that it relies on you being able to repeatably "connect" the electrodes to the material (consistency).

I agree with you on this part

This is a big part of the problem is how to control this part connecting the electrodes to the tabbing to the battery

But the other problem to over come is the consistency with the charging of capacitors

[Curious.George]

Re: How to use a dimmer controller on a transformer

But the other problem to over come is the consistency with the charging of capacitors

C is a constant (defined by the rating of the cap). V is an adjustable constant (defined by the circuit that "fills" the cap with charge).

C may vary over time (age) and/or temperature (but, I imagine you will almost always be using the welder at the same general ambient temperature).

So, how well can you sense V? Millivolts? Microvolts?

[sam_sam_sam]

Re: How to use a dimmer controller on a transformer

Like I said earlier I still need to have a SCR big enough to handle 500. Amp or more that would work at about 6 volts or so I do not want to use a contactor to dump the charge from the capacitors

I could control the transformer from the triac controller that I talk about earlier

When I put all the parts together

Triac controller
Timer
The battery spot welder transformer assembly

Then I will see how well the triac controller works welding battery tabs because if it works the way I think it will

Then I may answer to how t control the current powering up the transformer to charge the capacitor bank

Because the capacitors that I have are rated for 10 volts DC the out on the transformer is at maximum 3.2 amps before the current reaches 15 amps

I will have to do some real testing to see if this is going to work or this is a bad idea that went up in smoke