Resistance-No Resistance wire welder

[awsum140]

No, the resistor goes between "+out" on the LM2577 board and the positive terminal of the capacitor. That resistor is there to limit surge current drawn by the capacitor as it charges and to isolate the LM2577 from the short circuit created by welding.

 

[LargeD]

I built the welder according to the instructables tutorial and, so far, it works perfectly. I want to thank everyone here. Without being able to read about the problems and advice of others, I am sure I would have had way more problems building it.

 

[barbas]

Could someone put links on all stuff needed from e- bay ? and maybe some pictures of the whole thing opened and assembled ? Total noob here but with good will to try

 

[LargeD]

Apparently I spoke too soon. I tried it out a couple of times right after I built it and it seemed to bond the wires together, but they break apart as soon as I try to work them into a coil. On top of that, I can only get a weld to happen about 1 out of 50 tries. I will try adding another capacitor, but I have very little confidence in this working at this point. I really hope I am wrong, but this has been a complete waste of time and money so far.

 

[awsum140]

LargeD, I've found that adding capacitance may not be the best solution. I assumed, and you know what that can do, that power in Joules is power in Joules so if you cut voltage you need to add capacitance to keep everything "equal". The problem is that the higher discharge current overheats the resistance wire between the zero resistance wire and the clip holding it. I started with 4000mfd at about 21-25 volts and had a lot of broken leads when I tried winding a coil.

I've cut the capacitance down to 2000mfd and increased voltage up to about 31 to 33 and am getting better welds that are far less prone to breaking due to over heating. I'd drop to 1000mfd but it's a pain to take my little CD welder apart. I am building a "new, improved" model that will allow me to select between 330, 470 and a couple of 1000mfd and provide up to about 60 volts. I'm still waiting for a couple of parts or it would have been built already.

Bottom line is that the arc is what actually produces the weld and if the capacitance is too high to produce that arc the wire gets overheated and too brittle to work with. Try less capacitance and a higher voltage first, I think you'll find it works much better.

(to be read at double speed)
Just my opinion, worth what you're paying for it. Your results and mileage may vary. No warranty or guarantee is expressed or implied. Proceed at your own risk. The end user agrees to hold the poster harmless and without liability. I am not a doctor, scientist, chemist or physicist and hold no academic degrees, nor do I play any of them on TV.

 

[LargeD]

LargeD, I've found that adding capacitance may not be the best solution. I assumed, and you know what that can do, that power in Joules is power in Joules so if you cut voltage you need to add capacitance to keep everything "equal". The problem is that the higher discharge current overheats the resistance wire between the zero resistance wire and the clip holding it. I started with 4000mfd at about 21-25 volts and had a lot of broken leads when I tried winding a coil.

I've cut the capacitance down to 2000mfd and increased voltage up to about 31 to 33 and am getting better welds that are far less prone to breaking due to over heating. I'd drop to 1000mfd but it's a pain to take my little CD welder apart. I am building a "new, improved" model that will allow me to select between 330, 470 and a couple of 1000mfd and provide up to about 60 volts. I'm still waiting for a couple of parts or it would have been built already.

Bottom line is that the arc is what actually produces the weld and if the capacitance is too high to produce that arc the wire gets overheated and too brittle to work with. Try less capacitance and a higher voltage first, I think you'll find it works much better.

(to be read at double speed)
Just my opinion, worth what you're paying for it. Your results and mileage may vary. No warranty or guarantee is expressed or implied. Proceed at your own risk. The end user agrees to hold the poster harmless and without liability. I am not a doctor, scientist, chemist or physicist and hold no academic degrees, nor do I play any of them on TV.

Right now I have 1000mfd at 32-33 volts. I don't think I'm having problems with brittle wires unless that causes the welds to break. My problem is that the welds are mostly unsuccessful and very weak if they do work. I got the LM2577 chip that was specified in the instructables tutorial, so I can't raise the voltage any higher without getting a different chip. If you don't think adding another 1000mfd cap will help, I won't bother.

Thanks.

 

[Scope666]

Right now I have 1000mfd at 32-33 volts. I don't think I'm having problems with brittle wires unless that causes the welds to break. My problem is that the welds are mostly unsuccessful and very weak if they do work. I got the LM2577 chip that was specified in the instructables tutorial, so I can't raise the voltage any higher without getting a different chip. If you don't think adding another 1000mfd cap will help, I won't bother.

Thanks.

I did the same as you, and I would say the 2nd 1000 helps a LOT. 1000 just didn't make strong enough welds for me. (so 2000 total now for me)

 

[awsum140]

With the voltage being limited, your only option is to increase capacitance. Give it a try at 2000mfd. I ordered a LM2587 boost board that goes up to 60 volts, actually about 57 volts under test, but significantly higher than a LM2577 board. That's why I am using relatively low capacitance in my "improved" model. The one I have now will go as high as 40 volts without a problem and it's nothing more than a bridge rectifier on a 26 volt transformer, but I can't easily change the capacitance without taking it completely apart and, basically, rebuilding the whole thing. Hopefully the missing parts, actually an ohm meter module, will get here tomorrow or Wednesday and I can get the new one built.

I am getting pretty good welds at 31 to 34 volts, depending on wire gauge, with 2000mfd at the moment though.

 

[LargeD]

Thanks guys. I'll try throwing in an extra cap and see what happens.

 

[awsum140]

Let us know how you make out!

 

[LargeD]

Thanks everyone. It works much better with 2000mfd at 33 volts. It still takes me a few (5 or6) tries to get a good weld, but I think that is to be expected.

Also, I normally do micro coils for my Protanks which I wrap on a drill bit and then squeeze with tweezers while torching. So far, I have found the following procedure to work best. Wrap the coil with an extra wrap (to make up for the loss of resistance wire), cut the legs very short, weld nr wire to the legs, squeeze and torch, and place in the coil head. Torching the wire before welding makes it more difficult to get a weld to stick. This may be obvious to most, but it wasn't for me .

Thanks again everyone.

 

[tarnishedhalo]

Move the 470 ohm resistor so it is between the capacitor and the power supply and the welding clips are directly attached to the capacitor. As it is connected it limits welding current surges, not charging surges. Connected between the power source and capacitor it will limit initial charge current and isolate the power supply from the welding clips, preventing it from seeing that short as the weld is done.

Awesum should there be two capacitors: one between the + battery and LM2577 +IN, and one between +OUT and the +cap? Or skip the +IN 220Ohm? Based on your recent experiment with 2000uF I'm going to try that with ~30V. I'm not sure what values to use tho for the two resistors at the +IN and +OUT. Any suggestions? Thanks!

 

[awsum140]

There's no need for a capacitor on the input side of an LMxxxx boost board if you are using a battery to power it. A capacitor installed there would be to limit "ripple" coming off of an AC supply, half wave or full wave rectifier supply. I also don't think a resistor is needed there at all, a fuse and diode for over current protection and reverse voltage protection might be a better idea though and an on/off switch with some kind of indicator lamp (LED) might prove handy.

For the "+OUT" resistor, I used 220 ohms at 1/2 watt. The idea being to limit surge current a little when the capacitors charge. While a 1/2 watt resistor may seem a little low in power dissipation, keep in mind that current flows to charge the capacitors, at most, for two seconds or so. It may start off quite high, over an amp, but drops off very quickly as the capacitors charge. I wish a had a decent DC scope to demonstrate the charge current curve.

 

[tarnishedhalo]

Thanks awsum I'll give that a go when my new board comes in this week. I'll be using a 220ohm 10W so maybe a little overkill . Good thing I got a handful of diodes on their way also. Just to be clear the black strip on the +IN diode (from + battery, fuse) would go TOWARDS the board correct?

 

[awsum140]

The black, or white, stripe or band indicates the cathode, negative, pole of a diode. It should be connected to the "+" terminal of the LMxxxx module to allow proper current flow. If it is connected incorrectly, the LMxxxx board will not work but would not be damaged.

 

[Firestorm]

Could someone put links on all stuff needed from e- bay ? and maybe some pictures of the whole thing opened and assembled ? Total noob here but with good will to try

You should read the OP - there's a link to an Instructables tutorial replete with pictures and it includes a list of the Digikey part numbers.

I understand that this is a long thread and people are not inclined to read every post, but people should at least check out post #1 in a thread as it often includes updated information and sets up the discussion. I don't mean to offend - hopefully someone new will read this and go to the first post for this good information.

 

[barbas]

I'm interested on last version with volt display and in my opinion display is very useful , OP tutorial is without one . And reason for links to items is simply because not all item are the same ( resistors etc ) and on that way ppl can order one that actually works. Threads like this usually led to improvement of original item.

 

[awsum140]

Check back about five or so pages, 50 or so posts. There's a post by yo han with a schematic diagram including a volt meter and an ohm meter.

 

[yo han]

I've made another update on that.
The Chinese eBay seller sent me a 4PDT switch instead of a 3PDT and I figured I could as well change my diagram so the switch also switches the power to the meters. I was planning on using a separate on/off switch but this way you don't need it anymore.

 

[tobarger]

Thanks yo han
We need guys like you