Help with a Triac circuit please

[dar7ren]

Hi all,
This is my first post though occassionally I read most interesting posts.
I need to build a 1-35Amp (max voltage 35v) constant current source for Anodising Alluminium purposes. I have experimented with PWM on the DC side etc but on small loads <0.5R the circuits did not give adeqaute results.

Now I am trying to use an induvtive type dimmer and add feedback to control current in the load.

I have found a circuit (attached) from ST datasheets that looks interesting. (www.st.com/stonline/products/literature/an/3566.pdf )
However I need some help in reading the circuit. It is a Power variation circuit for arc welding transformer using Pulse train to trigger Triac. Particularly I cannot figure out how the bridge in the primary side is configured???

Any help is welcome. I am an electronics tech specialising in TV repairs.

thanks.

 

[RussMartin]

Perhaps a different approach could be had by using the Atmel U2008B:

https://www.electro-tech-online.com/custompdfs/2008/08/doc4712.pdf

 

[em2006]

The bridge is placed on the seconday side of the transfomer.
Is an error in the drawing. To correct, we must rotate the bridge 90 degree.
For your application, the configuration and corrections you can seee in attach.

Note: it is not a constant current source.
It is a voltage source.

 

[dar7ren]

Thanks for your reply RussMartin and em2006.
Dear RussMartin, I need to check more about this chip as I have read that it is not suitable for inductive loads such as transformers. But defenitely worth a try.

Thanks em2006 for your suggestions. I have amended drawing and would like if you take a look at it. I cannot understand the operation of the bridge config in the primary side, though it should provide a pulse train.

I have included a current transformer on the secondary windings to measure I flow through the 'load'. Then amplify,and rectify this feedback signal. Ultimately compare with a reference voltage. The comparator output should increase/decrease the isolated resistance which is to be used to control the firing of the triac. Hope i am close to my requirements

 

[RussMartin]

U2008b

I need to check more about this chip as I have read that it is not suitable for inductive loads such as transformers. But defenitely worth a try.

It is intended primarily as an AC motor control device. I've worked with it in some other applications. It is the successor to the obsolete TEA1007 and also to the U208B. A few years ago I saw a circuit using the TEA1007 in a do-it-yourself EasyWelder, but I can no longer find the link.

You would not need to use the chip and its circuit to drive the transformer; it will operate at AC voltages down to about 24 volts, so you would use it on the secondary side of the transformer, driving a bridge rectifier directly. There would be no control circuit on the primary side.

 

[dar7ren]

Yes you are right.
However I chose to work on the primary side to work with smaller currents. To recall the secondary triac/mosfet/transistor to be used must handle at max 35Amps. I think it is easier to control the primary with a tenth of the current though voltage levels are much higher. What do you think!

In anadosing experiments, I have seen that the resistance of the liquid varies with time depending on the surface area of the material. Typically from 15Ohms down to less than 0.1Ohms.

 

[em2006]

... It is the successor to the obsolete TEA1007 and also to the U208B. A few years ago I saw a circuit using the TEA1007 in a do-it-yourself EasyWelder...

Thanks, RussMartin, you helped me to clarify an old schematic using an unknown IC, a schematic from an user to another forum.
Now I'm sure, it is TEA1007.

 

[Eric911]

Hi, Dar7ren.

Did you figure out the project of constant current source? Pls advice. I met same issue with you, may i discuss with you? thanks for you reply.

Hi all,
This is my first post though occassionally I read most interesting posts.
I need to build a 1-35Amp (max voltage 35v) constant current source for Anodising Alluminium purposes. I have experimented with PWM on the DC side etc but on small loads <0.5R the circuits did not give adeqaute results.

Now I am trying to use an induvtive type dimmer and add feedback to control current in the load.

I have found a circuit (attached) from ST datasheets that looks interesting. (www.st.com/stonline/products/literature/an/3566.pdf )
However I need some help in reading the circuit. It is a Power variation circuit for arc welding transformer using Pulse train to trigger Triac. Particularly I cannot figure out how the bridge in the primary side is configured???

Any help is welcome. I am an electronics tech specialising in TV repairs.

thanks.