Kitbashed Resistance Soldering- Ideal for N scale

[peteski]

I just bought a used American Beauty 250w system on Ebay for $280.  I coulda bought an M1a and built this! 

Good move John!

Ron, have you ever looked at the max. recommended current rating for a phono jack? 

[reinhardtjh]

Ron, have you ever looked at the max. recommended current rating for a phono jack? 

I saw that and kinda wondered...  But maybe if you don't pull the jack while the current is flowing it won't matter.. too much?

[LV LOU]

 Ron,have you considered regular pencil lead for the electrode? I bet you could just carefully sand two sides off.. Also,to make it variable,there are multi step resistors you can get,I've used them on slotcar throttles.You attach the main wire to one end,and use an alligator clip on the tabs on the side to change the ohm rating..I think I may build this,but I have a heavy duty rotary resistor I may try out.

[mmagliaro]

I saw that and kinda wondered...  But maybe if you don't pull the jack while the current is flowing it won't matter.. too much?

Pulling the jack doesn't really matter, except that even if you had a jack that could take the rated current, and you pulled it,
the arc might make so much heat that it melts the darn thing. 
But in the meanwhile, if that jack isn't rated for, say, 15 amps at 5v, it's only a matter of time before that thing burns
up.

[Lemosteam]

Certainly not to criticize, but I was wondering why a jack was used instead of a simple two prong plug rated properly.  Worried about cord wrap?  It might be a good idea to use some really flexble rubber sheathed wire between the unit and the pencil.  You can buy that by the foot at HD.  I relpace all of my power tool cords with that when the insulation fails.  Nicely flexible.

[u18b]

Good move John!

Ron, have you ever looked at the max. recommended current rating for a phono jack? 

Good question.  Don't know.

But that is why I chose the big plug and not the little 1/4" plug in for ear buds.

The plates on this plug are huge.

After a couple of comments on the plug, I did a little "stress test".  I put in a new carbon electrode and and heated a piece of brass and solder non-stop until the electrode got too thin.

So this answered two questions. 

1.  How long does an electrode last?  Answer.  About 45 seconds.  IN a way, that sounds like not very much, but remember, this unit is designed to be used for about 5 seconds at a time.

2.  How did the plug hold up?  After 45 continuous seconds of running, when I stopped the electrode (took my foot off the pedal, or the thin electrode broke) I IMMEDIATELY pulled the plug out.

Assumption:  If the amperage were taxing an object, the object gets warm/hot.

Result- the plug was BARELY even warm.  Almost not noticeable.

So it sounds secure in my mind.

[u18b]

Ron,have you considered regular pencil lead for the electrode? I bet you could just carefully sand two sides off.. Also,to make it variable,there are multi step resistors you can get,I've used them on slotcar throttles.You attach the main wire to one end,and use an alligator clip on the tabs on the side to change the ohm rating..I think I may build this,but I have a heavy duty rotary resistor I may try out.

Sure, it might work.  But ...... 

1.  You would have to cut off the eraser end and find a way to get electricity to the connection end.

2.  The carbon will burn off, so you will have to continually sharpen the pencil?

3.  Won't the pencil housing overheat (wood = fire,  composite = melt)?

[up1950s]

It would be a dead short if power was on and the phono plug was pulled . I did this on a power cord into a tube type amplifier in 1969 that was designed for me by a Navy buddy the year earlier . What a bonehead move on my part to incorporate that so I could remove all the external wiring . While plugged in on both ends I removed the jack from the amp , lights dimmed in the house , sparks , arcs , smoke , welding noises , then the house circuit breaker had enough . My parents yelled upstairs " what happened , you ok " . Reply " nothing , just testing my new amp " . Figured I would embarrassingly share this for the humor and as a warning to others .

[u18b]

As for the danger of pulling the plug while it is working.....

1.  Why would I want to do that?  haha.

OK, let's assume someone's foot gets caught in the cord while I'm working.  Or whatever.  Cord gets yanked.

2.  How would this be any different from the safety test I did when I touched the brass iron tip directly to ground on purpose?  There is a small spark and then the unit shuts down.  And stays down until you reset it.

3.  That's why I made the hot wire (red, 5 volts) the very tip, and the barrel the ground.  The way the socket works, I think what you are describing is impossible.  When the plug begins to pull out, the tip dis-enghages pretty quickly-  all that is left is ground.

Look at this photo I found googling.
http://tctechcrunch2011.files.wordpress.com/2009/02/jack-plug-socket-switch.jpg?w=528&h=329

I have no idea why person has "problem here" labelled on the photo, but that helps us since that tip is the hot wire.  When pulling the plug while juice is flowing through this socket, a short could only happen if the tip was still touching that long flexible part WHILE at the same time getting down to where the ground is.

But that is why these are designed the way they are.  The black plastic insulator is the dividing line.  When that line gets to the area of ground, the tip has ALREADY disengaged.

So it is a good question, but I don't think it is a problem.

[C855B]

Richie's situation may have been that his amp was built with a shorting-type jack. Both shorting and non-shorting 1/4" phone plugs/jacks were commonly used in electronic music audio. Shorting types solve problems where devices need to be connected in series, also, shorting-type plugs are a make-before-break design so the loaded circuit is not left in an open state, which in old designs could fry things.

Since Richie's amp sounds like it was a home-brew, it was probably a simple choice of whatever was lying around in the junk box rather than paying close attention to the type of jack/plug. That's one of many reasons we don't use 1/4" phone plugs as power connectors. Ron's use here is a shoulder-shrug, although I personally would use something more robust (Anderson Power-Pole) since phone plugs are not generally power-rated.

[u18b]

These are good questions.  And I really care about safety.

So I took the lid off and took three photos to illustrate what we are talking about.

Here is the plug in its socket, and it could be fully in use.  Red is the hot side, blue is the ground.



Now, micro seconds here...... A foot has caught the cord and the plug is "yanking".  The tip is just touching, so electricity is still flowing.



But a little bit further pull in the yanking process and.....  the tip is no longer charged because there is now a gap between it and the hot contact.
And note, you can still see the black insulation band.... so it would have to come out even MORE before the tip is touching ground.

Thus the ONLY way that a short can happen is if there is an arc from the hot brace to the tip while it is retracted to the point that it is grounded in the tunnel.  And by then, that gap would be almost twice as big.


Possible, but I don't think it is a problem, honestly.

[LV LOU]

Sure, it might work.  But ...... 

1.  You would have to cut off the eraser end and find a way to get electricity to the connection end.

2.  The carbon will burn off, so you will have to continually sharpen the pencil?

3.  Won't the pencil housing overheat (wood = fire,  composite = melt)?

When I said to sand the sides of the pencil,I meant sand it to the lead,and pull the wood off.Better yet,use a big honking carpenter's pencil..

[LV LOU]

These are good questions.  And I really care about safety.

So I took the lid off and took three photos to illustrate what we are talking about.

Here is the plug in its socket, and it could be fully in use.  Red is the hot side, blue is the ground.



Now, micro seconds here...... A foot has caught the cord and the plug is "yanking".  The tip is just touching, so electricity is still flowing.



But a little bit further pull in the yanking process and.....  the tip is no longer charged because there is now a gap between it and the hot contact.
And note, you can still see the black insulation band.... so it would have to come out even MORE before the tip is touching ground.

Thus the ONLY way that a short can happen is if there is an arc from the hot brace to the tip while it is retracted to the point that it is grounded in the tunnel.  And by then, that gap would be almost twice as big.


Possible, but I don't think it is a problem, honestly.

There would only be a short if you had a wire on the third[as of now,unused..] terminal.

[u18b]

Well, this has been a learning experience.  Haha.

I hope everyone knows:

1.  I'm not claiming to be any kind of expert.

2.  In fact, I've never done any resistance soldering.  The units are pretty expensive. (good ones about $500).

So I admit I've been speaking from both ignorance (of actual experience) and using the little information I've gleaned here and there.

3.  It is also obvious from a few comments, that some of you are just like me-  wanting to get into resistance soldering, hesitant about cost, and have read some of the same kitbashing stuff I have read.... and you've been thinking about the same thing.

So a couple of very helpful (and patient) forumers who DO know something about resistance soldering have been trying to help my understanding.

Be patient while I walk through this.

As I say in my paper, traditional soldering irons work by resistance.  They are really like a toaster.  Electricity flows through a wire that heats up (like a toaster).  That wire is wrapped around a metal core and the core heats up (slowly) and cools off (slowly). 

What I have created (only refining some non-original ideas by others, sometimes poorly written) is really a very controlled soldering iron.  In some ways, what I have built is not too terribly different from a light bulb.  Electricity flows through a small filament and the heat is intense (and gives off light).

So what mine does (as opposed to a traditional soldering iron) is place a TREMENDOUS amount of heat in a pretty SMALL area.  Further, it is on almost instantly.  It also stops almost instantly. 

So in many ways, what I have made is a VERY fine pointed soldering gun.
http://www.aaroncake.net/electronics/300w_soldering_gun.jpg

These guns produce an intense amount of heat.  Heat up quickly, and cool down fairly quickly.  But they are unsuitable for most of our work in that they produce too much heat in too big an area.

A pencil lead focuses the heat to a VERY tiny spot (one millimeter!).

True resistance soldering uses metal electrodes.  You place them close together.  When turned on, you are essentially creating something of a controlled short.  The electricity is flowing from one tip, through the brass,  to the other tip VERY close by.  And since it is a kind of short, the metal BETWEEN the points gets very hot quickly.  And everything heats up evenly (not surface to inside) but almost inside out.

So here is a resistance soldering tip from Micro-Mark.  This is just the electrode.
http://www.micromark.com/needlepoint-electrodes-set-of-2,7892.html

In my conversation with a forumer, I pointed out....  I thought that what I built is like the cheaper Micro-Mark soldering station.  Here.
http://www.micromark.com/microlux-resistance-soldering-unit-with-single-electrode-handpiece,10952.html

Notice in the photo that the ground wire is pretty far away.

The person humorously responded in essence-- the photographer who took that photo had no clue what he or she was doing.  The ground should be RIGHT next to the place you are soldering.  Haha.  That person would be heating up almost ALL the handrails in that photo.

So this has been a learning experience.

All I know is.... I had a brass Kumata Trainmaster that had loose handrails, broken antennas, and a crooked cab.  Trying to use a traditional soldering iron just did not work.

This thing I have created (whatever you want to call it) worked.

[u18b]

It has also been pointed out that there is a danger of fumes with this.

Aside from whatever burning polymers do....

A little reading shows that burning the carbon will produce some carbon monoxide.
http://en.wikipedia.org/wiki/Carbon_monoxide_poisoning


I just happen to have a CO detector in my house.... and it just coincidentally sits about 7 feet away on an adjacent wall.

No alarms yet.

Maybe this would be a problem if I was using this to built a lot of custom built turnouts.

I have not really been using it that much.

So for that reason, I'm pulling the document down from my website.  I'll add a warning and repost at a later date.  After I do some re-writing.

And probably it would be best to use this in the garage/outdoors.

Any other information which should be included in the next revision is welcome.