Hi rfranzk,
I have seen a circuit for this app, but unfortunately I can’t find it right now! If I do I’ll let you know. What I can remember from it was; they used a microwave oven transformer and some big diodes as a rectifier. The heater winding (low voltage) was used and rectified and then there where some timers and stuff! I will try to find it if I only could remember where to look! ???
I have seen a circuit for this app, but unfortunately I can’t find it right now! If I do I’ll let you know. What I can remember from it was; they used a microwave oven transformer and some big diodes as a rectifier. The heater winding (low voltage) was used and rectified and then there where some timers and stuff! I will try to find it if I only could remember where to look! ???
I have done a little more research on this potential project and the ones I've seen appear to charge and discharge capacitors of up to 1 to 2 farads. I'm curious whether the discharge is directly to the piece of work or whether it is discharged into a step down transformer??? Also curious about how voltage can be controlled with this type of system. ANY Help would be greatly appreciated.
Hi rfranzk,
I checked out the link, it’s an interesting circuit but will it work for your application? I am not saying there is a problem with the circuit (because I have not built and tested it) but I would not have built it that way. 8)
I checked out the link, it’s an interesting circuit but will it work for your application? I am not saying there is a problem with the circuit (because I have not built and tested it) but I would not have built it that way. 8)
Hi rfranzk,
Are you sure you need DC for the job, it is much more complicated to achieve than an AC circuit? 30000A,
can you get this from a cap which exists? We are talking ultra low ESR caps and the current must be conducted to the welding point in some way. Most caps will probably not even survive many spots under these conditions. Will the duration of the pulse be long enough to melt the target sheets? If you concentrate the spot by making your “points” thinner they will be melting instead. I think using AC makes it possible to use lower current and adjusting the time and pressure instead.
It is possible to control a transformer from it’s primary side with a zero cross phototriac optocoupler and a big triac. This way you can experiment with the number of mains cycles you need for each kind of job you like to perform. The pressure is another important factor to experiment with.
Some more info:
http://www.5bears.com/welder.htm
http://users.frii.com/katana/spotweld.html
http://www.rhunt.f9.co.uk/Electronics/Spot_Welder/Spot_Welder_Page1.htm
http://www.sas.org/E-Bulletin/2003-10-31/labNotesAS/body.html
Just some thoughts! 8)
Are you sure you need DC for the job, it is much more complicated to achieve than an AC circuit? 30000A,
can you get this from a cap which exists? We are talking ultra low ESR caps and the current must be conducted to the welding point in some way. Most caps will probably not even survive many spots under these conditions. Will the duration of the pulse be long enough to melt the target sheets? If you concentrate the spot by making your “points” thinner they will be melting instead. I think using AC makes it possible to use lower current and adjusting the time and pressure instead. It is possible to control a transformer from it’s primary side with a zero cross phototriac optocoupler and a big triac. This way you can experiment with the number of mains cycles you need for each kind of job you like to perform. The pressure is another important factor to experiment with.
Some more info:
http://www.5bears.com/welder.htm
http://users.frii.com/katana/spotweld.html
http://www.rhunt.f9.co.uk/Electronics/Spot_Welder/Spot_Welder_Page1.htm
http://www.sas.org/E-Bulletin/2003-10-31/labNotesAS/body.html
Just some thoughts! 8)
Hi rfranzk,
I would like to see some pictures of your project, especially the wiring from the transformer to the tips and the tips. Four feet wire even 8 gauge will be a resistor at these currents, have you measured the drop across each wire under load conditions? Have you tested tungsten or hard copper tips or any alloy in between? Have you tried different contact area size for the tips? The solide state relay you are using, does it have zero cross firing?
Sorry, that was a lot of questions! ;D
I would like to see some pictures of your project, especially the wiring from the transformer to the tips and the tips. Four feet wire even 8 gauge will be a resistor at these currents, have you measured the drop across each wire under load conditions? Have you tested tungsten or hard copper tips or any alloy in between? Have you tried different contact area size for the tips? The solide state relay you are using, does it have zero cross firing?
Sorry, that was a lot of questions! ;D
Hi Ante,
I have not measured voltage drops. Good idea !! I have tried brass, aluminum and copper contacts. I have tried different tip and contact areas and shapes.
I have some tungsten contacts I can try. Havn't yet.
I will have to dig up a digital camera to send photos.
I do not know what you mean about the solid state relay zero crossfire??
The one shot timer and relay circuit are isolated and powered with 12v dc from a battery pack.
I will check voltage drops and get back. I suspect this is an issue but also feel that contact pressure could be a problem with this arrangement.
Thanks rfranzk.
I have not measured voltage drops. Good idea !! I have tried brass, aluminum and copper contacts. I have tried different tip and contact areas and shapes.
I have some tungsten contacts I can try. Havn't yet.
I will have to dig up a digital camera to send photos.
I do not know what you mean about the solid state relay zero crossfire??
The one shot timer and relay circuit are isolated and powered with 12v dc from a battery pack.
I will check voltage drops and get back. I suspect this is an issue but also feel that contact pressure could be a problem with this arrangement.
Thanks rfranzk.
Hi rfranzk,
The zero cross firing is when the device (a solid state relay in this case) detects the zero crossing point of the mains sinusoidal wave and “fires” the relay at this (0V) point .
Yes the contact pressure and the positioning of the tips is also important factors.
The zero cross firing is when the device (a solid state relay in this case) detects the zero crossing point of the mains sinusoidal wave and “fires” the relay at this (0V) point .
Yes the contact pressure and the positioning of the tips is also important factors.
Hi Ante!!
I have been distracted lately. Moved and some other stuff and still don't have internet service at my home. I did complete a capacitive discharge welder with an adjustable power supply (just completed) a 2 farad audio capacitor and large triac to trigger the discharge. Works well for my intended purpose. I am also experimenting with another transformer recently aquired at a farm auction. Will send photos of project and weld results when possible.
Thanks for your help
rfranzk
I have been distracted lately. Moved and some other stuff and still don't have internet service at my home. I did complete a capacitive discharge welder with an adjustable power supply (just completed) a 2 farad audio capacitor and large triac to trigger the discharge. Works well for my intended purpose. I am also experimenting with another transformer recently aquired at a farm auction. Will send photos of project and weld results when possible.
Thanks for your help
rfranzk
Hi rfranzk,
It’s good to know that you didn’t zap yourself experimenting with your spot welder! ;D Yes, some pictures would be interesting and I also like to know about your choice of caps and for instance the recharge time and current for such caps.
It’s good to know that you didn’t zap yourself experimenting with your spot welder! ;D Yes, some pictures would be interesting and I also like to know about your choice of caps and for instance the recharge time and current for such caps.
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