JP spot-welder, FET-switched, timed adj. pulse
- Thread starter okashira
- Start date
pguk
100 W
Geekineer said:
I have the same question at the moment with my own design. I'm leaning towards using more capable FETs. I have been using same FETs as you, 24 volt rated, 6 in parallel, 1324 FET (surface mounted) with the 1407 driver. Testing this weekend resulted in an exlploded FET. I have scope shots showing 27 volts hammering the FETs at every turn off event. I installed the flyback diode which improved things marginally - time spent at 27 V decreased a little. Okashira's scope shots show over 30 volts. He seems to have succeeded getting Drain - Source voltage at turn off under 24 volts using 2 diodes, (he talks about avalanche, but I think he means Drain to Source voltage at turn off). Might it not be easier to just accept that this is what is happening and go with larger FETs which will tolerate higher avalanche current and are rated for over 30 volts?
Edit: member Quokka reports that he is able to weld copper using 8 of IRF1405. These are rated for 55 volts.
pguk
100 W
I have drain side current coming in from left hand side (of a single row of 6 FETs), and going out of the source side from right hand side. I use a single gate resistor to equalise gate current. One thing I didn't do was to match my batch of 25 FETs into groups of close turn on times. Perhaps the one which failed had an earlier turn on time than the others - it was the 2nd one in from the right hand side.
On my layout I have 6 82 ohm resistets fanned out from the 1407 driver chip.....large ground planes and alum bus bars used for source and and drain on double sided pcb......weak link is source connections on fet....I try to fatten it with solder and larger pad to ground plane
Overclocker
10 kW
works great. thanks riba2233
pguk
100 W
riba2233 said:
Not according to Texaspyro on here. He built a large welder and is something of a coding wizz, and has posted some working principles which I wanted to take advantage of. https://endless-sphere.com/forums/viewtopic.php?f=2&t=2633&start=575.
"In order to keep the currents balanced through paralleled mosfets, you need to drive them with the same source... no independent drivers, no independent gate resistors. It also helps to match the mosfet gate threshold voltages. For all the gory details see: http://www.irf.com/technical-info/appnotes/para.pdf . If your eyes gloss over easily... don't bother... it's rather heavy going."
Myself - of course I didn't bother with the gory details, but I took the advice from a guy who built a more powerful system than we are working with here
Edit: it seems this is not good advice.
See Geekineer's post further on next page of this thread, plus IRF app note AN-941 says "It is common knowledge that paralleled MOSFETs must have individual gate resistors"shr00m said:
Sorry but no idea, I'm still fighting with the disease and it's serious.
pguk said:Not according to Texaspyro on here. He has built an amazing welder and is something of a welding/coding wizz, and has posted some working principles which I wanted to take full advantage of. https://endless-sphere.com/forums/viewtopic.php?f=2&t=2633&start=575.
"In order to keep the currents balanced through paralleled mosfets, you need to drive them with the same source... no independent drivers, no independent gate resistors. It also helps to match the mosfet gate threshold voltages. For all the gory details see: http://www.irf.com/technical-info/appnotes/para.pdf . If your eyes gloss over easily... don't bother... it's rather heavy going."
Myself - of course I didn't bother with the gory details, but I took the advice from a guy who built a more powerful system than we are working with here
Ok, that's great for you! You can ask him why your mosfets blew in that case.
Mammalian04
100 kW
riba2233 said:
Riba, I'm very sorry to hear this. We knew you were struggling with some health issues but I don't think most of us knew severity. Your ES brethren are rooting for your recovery.
All the best to you during this trying time.
markz
100 TW
.
Hi guys I was able to get the files for these loaded to osh park.shr00m said:
http://www.instructables.com/id/DIY-Arduino-Battery-Spot-Welder/step3/Populating-the-PCBs-and-adding-wires/
So any of you who want to order a set of 3 boards here is the link.
https://oshpark.com/shared_projects/cT1nnc6l[/quote]
I am working on finding the BOM and when I do I will share it. I think its in the first link somewhere... I have a set of boards in my hands. I just need to get the parts and some time to put it together.
Think this link works for the parts. https://secure.reichelt.de/index.html?&ACTION=20&AWKID=1203408&PROVID=2084
Riba I only posted this because of your struggles. I wish you well my friend.
vehiculeselectriques
100 mW
- Joined
- Oct 8, 2008
- Messages
- 35
Please it's the JP spot welder thread don't mix it with other welder DIY, open new thread !
and please be patient
Sat Apr 16, 2016 11:43 pm
Sun Apr 17, 2016 11:55 am
riba2233 is fighting severe disease so let him decide when time is right to make it happen;
take care of you riba2233, whishing you better health !
and please be patient
Sat Apr 16, 2016 11:43 pm
markz said:
Sun Apr 17, 2016 11:55 am
riba2233 said:There will be new thread with all info, neatly organized and detailed
riba2233 is fighting severe disease so let him decide when time is right to make it happen;
take care of you riba2233, whishing you better health !
Thank you all for your good wishes guys, I really appreciate it!
My main motive about all this was to provide easy and affordable way to make 18650 packs, so of course you can mention other solutions, and I encourage that. But it would be preferable if you could only link to other threads, simply because of keeping things on topic and better organization 8)
My main motive about all this was to provide easy and affordable way to make 18650 packs, so of course you can mention other solutions, and I encourage that. But it would be preferable if you could only link to other threads, simply because of keeping things on topic and better organization 8)
ohzee
100 kW
riba2233 said:Thank you all for your good wishes guys, I really appreciate it!
My main motive about all this was to provide easy and affordable way to make 18650 packs, so of course you can mention other solutions, and I encourage that. But it would be preferable if you could only link to other threads, simply because of keeping things on topic and better organization 8)
You did a most excellent job at assisting current and even future pack builders.
Keep fighting the good fight. Positive thoughts from me to you.
Keep us updated bud.
riba2233 #1 fan
jimwebo
1 W
Get well soon mate.
Jim
Jim
shr00m
10 W
- Joined
- May 18, 2016
- Messages
- 75
So in this thread there is a link to buy 3 boards for 48 bucks but i only need one... I figured since the kits / built units arent being sold anymore i could snag one of the boards cheap... but riba wants 40 for 1 board and a pic. I have a pic programmer so the pic isnt the issue. I totally and fully respect what riba has done and put together and im not trying to negate that... it just seems its pretty much open source and i thought the purpose of this was to offer a "cheap" spot welder... at 40 bucks for just the board and 50 + 15 shipping for the probes (how much does it cost to ship probes in the mail?!?!??! wont they fit in an envelope? priority mail flat rate is like 6 or 7 bucks....) then add the price of the components also and at these prices it starts to get close to the price of a chinese spot welder with handheld probes and i realize this is a better welder but its beside the point... im looking for someone to go in on 3 boards for 48 bucks i just need 1... i would hate to pay 40 bucks for a pcb i guess if i have to i will just order the 3 and sell them later... get well soon i mean no disrespect at all riba its just the spirit of me and i thought this site was mostly DIY and DIY for cheap... thats the goal im after so anyone wanna go in on boards please PM me... ive already ordered all the other parts and ive decided i will make my own probes because 65 bucks is kind of crazy for premade probes from battery cables.... again no disrepect im just trying to do this on a budget it is a hobby and my hobby budget is smaller than id like...
tomjasz
1 GW
shr00m said:
""No disrespect" then you roll in here half cocked expecting someone to give their work away at prices you deem fair? Check out rates for shipping overseas and find us those budget rates. You can't just stuff hardware in an envelope. YOU DO REALIZE THAT THE POST FROM CROATIA ISN'T $6?
Please before whining about your budget, stop and use some common sense. JP has done more for those of us building than you can even imagine. Why is it DIY n00bs think their work is somehow worth more than anyone else.
Buy the boards and sell them, but no that's up to someone else. Your whining about the costs is disrespectful and without merit. You've a lot to learn about forum behavior.
