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  • michaellawton commented on KaeptnBalu's instructable DIY Arduino Battery Spot Welder2 months ago
    DIY Arduino Battery Spot Welder

    That's the TVS diode. See the thread for more details.

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  • michaellawton commented on KaeptnBalu's instructable DIY Arduino Battery Spot Welder3 months ago
    DIY Arduino Battery Spot Welder

    I finished my spot welder today. Uses copper bus bars and avalanche protection mod. Lots more info in my build log which starts on page three of this thread: https://endless-sphere.com/forums/viewtopic.php?f=31&t=80315&p=1215403#p1215403

    The switching time of a few milliseconds will be too long - the total time it's on for may be less than that! You could try using the cheaper TC4424/MIC4424YN (available from AliExpress) or a single driver such as MCP1407 driving all of the fets.

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  • michaellawton commented on KaeptnBalu's instructable DIY Arduino Battery Spot Welder3 months ago
    DIY Arduino Battery Spot Welder

    I don't know where my last comment went, I replied to this a couple of days ago. I doubt the schottky would have failed. As far as I'm aware it is only there for reverse polarity protection. If it failed the spot welder probably wouldn't turn on.It sounds like the Arduino may be resetting.What power supply are you using? If your power is tripping or if you are directly using the 12V battery to power the spot welder it may cause these symptoms.

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  • michaellawton commented on KaeptnBalu's instructable DIY Arduino Battery Spot Welder3 months ago
    DIY Arduino Battery Spot Welder

    I doubt the schottky would have failed. As far as I'm aware it's only there for reverse polarity protection. If it failed it would probably be open circuit and the spot welder wouldn't turn on.There's a chance that the arduino could be reseting on every weld. Do you use a separate 12V supply for the spot welder? Any chance this could be tripping or resetting when driving the mosfets?It was me who replied about the avalanche protection diodes on endless-sphere. For some reason instructables takes a long time to email me notifications of comments on here.

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  • michaellawton commented on KaeptnBalu's instructable DIY Arduino Battery Spot Welder3 months ago
    DIY Arduino Battery Spot Welder

    And no, metal standoffs would create shorts.

    First, putting the battery that far away is not a good idea. When mosfets fail in this application it is because of inductive spikes. Wire inductance is proportional to it's length so it will cause bigger spikes.Your issue sounds a bit like a heat problem (possibly caused by inductive spikes) But if it was really doing exactly 20ms when you selected a different number it is most likely a software problem. That is because the max duration of 20ms is only defined in software, it has no relation to the hardware.I made quite a few changes to the software recently which is now merged into the main repository. You may want to test that out but I didn't notice any obvious bugs like you've described and I don't think I changed anything that would affect it.

    They are 11.6mm http://www.ebay.com/itm/172248383171?var=471069475076

    Note that the changes have been merged now, so just use the file from KaeptnBalu's GitHub

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  • michaellawton commented on KaeptnBalu's instructable DIY Arduino Battery Spot Welder3 months ago
    DIY Arduino Battery Spot Welder

    You don't have to use a 50kΩpot. Almost any linear pot that fits will work. For example even going down to 1kΩwill dissipate 0.025W which will probably be within specs. You could probably go up to at least 1MΩ without problems.

    Yes, even 500mA will be fine. high current needed by the gate drivers can be supplied by the capacitors.

    What did you use for probes?

    I spent a while improving the Arduino sketch. I have submitted a pull request but for now you can get it from here:https://github.com/MichaelLawton/Arduino_Spot_Weld...I have made lots of changes, but none to the features or operation of the spot welder. Mainly I have improved the display subroutine and the potentiometer reading.Most important changes: - Display code is now non-blocking. So pulse will happen as soon as switch is pressed, not a few hundred milliseconds later - Display updates immediately and shows ones place digit when adjusting pot"1" digit in tens place shows on left which is more readable - Hysteresis added to the potentiometer reading - Potentiometer midpoint shifted so 20 milliseconds gets 0.5/21 of a turn, the same as 1 millisecond - Display only flashes ...see more »I spent a while improving the Arduino sketch. I have submitted a pull request but for now you can get it from here:https://github.com/MichaelLawton/Arduino_Spot_Weld...I have made lots of changes, but none to the features or operation of the spot welder. Mainly I have improved the display subroutine and the potentiometer reading.Most important changes: - Display code is now non-blocking. So pulse will happen as soon as switch is pressed, not a few hundred milliseconds later - Display updates immediately and shows ones place digit when adjusting pot"1" digit in tens place shows on left which is more readable - Hysteresis added to the potentiometer reading - Potentiometer midpoint shifted so 20 milliseconds gets 0.5/21 of a turn, the same as 1 millisecond - Display only flashes when showing two digit number - LED stays on for 50ms after pulse - Cleaned up display blanking code

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  • michaellawton commented on KaeptnBalu's instructable DIY Arduino Battery Spot Welder3 months ago
    DIY Arduino Battery Spot Welder

    I've posted my Mouser project and other parts from eBay here: https://endless-sphere.com/forums/viewtopic.php?f=31&t=80315&p=1215403#p1215403

    I think it should work well as stainless steel is not very conductive.

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  • michaellawton commented on KaeptnBalu's instructable DIY Arduino Battery Spot Welder4 months ago
    DIY Arduino Battery Spot Welder

    Nope, that's AC—this is only for DC. For a MOT you can control the primary. Refer to http://www.avdweb.nl/tech-tips/spot-welder.html and http://www.avdweb.nl/arduino/hardware-interfacing/spot-welder-controller.html

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  • michaellawton commented on KaeptnBalu's instructable DIY Arduino Battery Spot Welder4 months ago
    DIY Arduino Battery Spot Welder

    Hi KaeptnBalu, I have a few questions:Is the mosfet driver model important? The MIC4424YN http://www.micross.com/pdf/micrel-smd-5962/MIC4424.pdf by Micrel (now owned by Microchip) is cheaper than the MCP14E10 and seems to be an earlier version of it. The rise and fall times are slightly better while the delay times and output resistances are slightly worse.What power rating do the resistors need to be?Can you confirm that the two pin header for the foot switch is 2.5mm not 2.54mm?I think there's a small mistake with the seven segment display. Each segment should have it's own resistor - having one resistor means that the current through each segment will be lower than it should be when more than one segment is on at a time.

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