rfranzk Posted August 11, 2005 Report Share Posted August 11, 2005 I am interested in buliding a micro spot welder for assembling battery packs and or other small items. Has anyone seen plans for one of these??? Quote Link to comment Share on other sites More sharing options...
ante Posted August 11, 2005 Report Share Posted August 11, 2005 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! ??? Quote Link to comment Share on other sites More sharing options...
rfranzk Posted September 7, 2005 Author Report Share Posted September 7, 2005 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. Quote Link to comment Share on other sites More sharing options...
ante Posted September 7, 2005 Report Share Posted September 7, 2005 What and where did you find some examples in your research? I am not sure you can or even need to control the voltage. The voltage is not interesting, only the current. Quote Link to comment Share on other sites More sharing options...
rfranzk Posted September 10, 2005 Author Report Share Posted September 10, 2005 Hi Ante Found another site with hopeful access to good schematics at roborific.com. This appears to be just what I am lookng for and is microcontrolled for accuracy and safety. Take a look. Thanks for your interest so far. rfranzk Quote Link to comment Share on other sites More sharing options...
ante Posted September 10, 2005 Report Share Posted September 10, 2005 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) Quote Link to comment Share on other sites More sharing options...
rfranzk Posted September 12, 2005 Author Report Share Posted September 12, 2005 HI ANTE: What would be your suggestions?? Would you try to use a transformer setup to achieve higher current?? Thanks rfranzk Quote Link to comment Share on other sites More sharing options...
ante Posted September 12, 2005 Report Share Posted September 12, 2005 Hi rfranzk,Are you sure you need DC for the job, it is much more complicated to achieve than an AC circuit? 30000A, :o 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.htmhttp://users.frii.com/katana/spotweld.htmlhttp://www.rhunt.f9.co.uk/Electronics/Spot_Welder/Spot_Welder_Page1.htmhttp://www.sas.org/E-Bulletin/2003-10-31/labNotesAS/body.htmlJust some thoughts! 8) Quote Link to comment Share on other sites More sharing options...
rfranzk Posted September 15, 2005 Author Report Share Posted September 15, 2005 Hi Ante, Quote Link to comment Share on other sites More sharing options...
ante Posted September 16, 2005 Report Share Posted September 16, 2005 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 Quote Link to comment Share on other sites More sharing options...
rfranzk Posted September 16, 2005 Author Report Share Posted September 16, 2005 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. Quote Link to comment Share on other sites More sharing options...
ante Posted September 17, 2005 Report Share Posted September 17, 2005 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. Quote Link to comment Share on other sites More sharing options...
rfranzk Posted November 9, 2005 Author Report Share Posted November 9, 2005 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 Quote Link to comment Share on other sites More sharing options...
ante Posted November 9, 2005 Report Share Posted November 9, 2005 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. ;) Quote Link to comment Share on other sites More sharing options...
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