This was the worst soldering job I’ve ever done. I’m building this robot arm project kit, and there are a couple of limit switches that need to be soldered. It didn’t go very well.
I grabbed some wire, of the same small gauge as the stepper motor wire cut-offs that the instruction manual says to use, and it was just terrible.
I would normally use crimp-on terminals, but there’s no space where this is to be installed. There are a lot of “I wouldn’t design it like this!” issues with the build, but I’m also learning a lot of good practices unrelated to the wiring.
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This is part of a kit put together by one person, and it’s really good so far, all things considered. I’ll talk more about it another time.
Anyway, I was also using 63/37 solder, which typically behaves better than 60/40.
I’m not sure what went wrong. It’s not a fresh spool of solder, but it’s also just a few years old. Maybe added flux would have helped. I think it was a heat issue.
I used my usual narrow chisel tip. The limit switch terminals took some time to heat up, and they also heated up the plastic housing in the process. I expected them to cool down quickly, but they didn’t.
The solder took longer than expected – for 63/37 solder and even 60/40 under well-controlled conditions – to cool and solidify.
I couldn’t position everything 100% securely and motionless, and so it took some finagling. That means more heat. More heat meant it took longer to let go of the heat.
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After the first terminal was done, I did a better job of tinning everything for the second and third joints. Or so I thought. No, that didn’t help – by the time the solder flowed to create the secure electrical connection between the wire and terminal, there was too much heat, again.
Next time maybe I’ll grab a heatsink or large alligator clip to dissipate more of the heat.
I have plenty of heat shrink. But apparently the size I keep in my electrical workbench doesn’t have a high enough shrink ratio. I’ll have to check my supply cabinet next time – I’ve got other styles and brands.
It turned out this is okay, because of how the limit switch was to be installed. The gap allowed me to slice the heat shrink and route the wires.
This is an inelegant design, with respect to form and function.
Yes, right angle terminals might have worked here, but I don’t have any. Even if I did, I definitely wouldn’t have this size. I declined to keep a selection on hand, as I deemed right angle connectors too pricey to justify for extremely rare occasions. And they still might not have worked here.
I checked continuity after soldering and again after heat shrinking to ensure I didn’t break the limit switch.
Someone asked me on message how I did this. Honestly? The wrong way that requires 3 hands. The right way involving grabbing some test leads with alligator clip attachments.
I’m building this kit because I want to learn the mechanical components in a way that you can only get from hands-on time. But it’s providing for a lot of wiring experiences as well.
Maybe I should have used a larger wire, but I don’t think it would have made much improvement. I’ll have to figure out a good way to solder the next few limit switches.
This is how the wiring started off. I really hope all goes well because otherwise this is going to be a troubleshooting nightmare.
Daisy chaining wiring connections like this is a bad idea. Why? Let’s say that the last joint isn’t receiving power. Where could the joint be? There are multiple potential points of failure, and it will complicate the process of tracing an issue to the cause.
But, I figured I’ll build the kit according to spec, and then see how it goes, otherwise it’d sit unbuilt for the next 5 years. This setup has worked for a lot of people, and so I’m just tugging on every connection as I go along to ensure nothing is loose.
Here’s where I’m currently at.
I ran into a defective hardware component, and everything is on hold until the replacement comes in.
Here’s the defective drive spindle. There’s a mounting ring that needs to align here, but the keyway slot is off-center and so it cannot bolt together.
The kit creator quickly sent a replacement and said that this happened to another customer recently. It’s still on the way.
I recently started pushing myself to make good on a lot of self-promises.
With some projects or hobbies, the process or path can be a lot of fun. But there are others where the middle part just has to be worked through to get to the good parts.
This robot kit, and everything it entails, is a way for me to learn through action, rather than reading. It’s a stepping stone to what I really want to work on – a shortcut to learn some things.
I have a project I’ve been meaning to start on, and I haven’t made much progress with the first stages. The kit I’m working on has greatly accelerated my progress.
Messing up the solder joint a bit – that’s just an unfortunate bump in the road. I normally work with smaller switches. I have more limit switches to install – next time I’ll be more prepared. Or not. Sometimes it takes a few tries to develop a skill or technique, and other times very many tries.
You can learn without failing, but you can’t fail without trying.
I rarely have to solder small wires to large terminal pads. I didn’t do well here, but I tried, and made progress. It feels good.
All that said, got any good tips?
Brandon
Seems like a design issue, as you speculated. Tabs intended for quick connect fittings are great at conducting heat back to where they shouldn’t (i.e. the devices plastic housing), as they weren’t designed for soldering. Combine that with the large thermal mass of that tab relative to a wire, and you end up with problems – it’s tough to beat physics.
That being said, you mentioned using an alligator clip as a heat sink – I’d definitely recommend one going forward. I have quite a collection of alligator clips in my kit, and I use them often to pull some heat away past the solder joint.
I had a professor help me solder some surface mount chips for a project I was working on way back in college, and he turned me onto felt tipped markers that were filled with flux. They can be hard to find, but I keep those on hand for these situations, as well, and they do help a lot. They are also excellent when trying to solder a part intended for automated surface mount soldering to a development board with solder pads; you can just ‘write’ over all the pads, line up your part, ‘tack’ down a corner or two while holding the part, and then run your tinned chisel point along the side of the device whether that’s 4 terminals or 40.
fred
Sounds like a bad design for soldering. A small alligator clip might not have helped much – since the mass (heat capacity) and heat conductivity of the tabs might have been higher than the clip. Heat sink clips are often made of aluminum because of the decent heat conductivity – but in your case something like a sterling silver thin tie bar might have better.
Matt_T
If those tabs have a hole in them sticking the wire through it helps with positioning. If not you could drill them if it’s really fighting you.
Flux won’t hurt. The pens Brandon mentioned should be carried by wherever you order electronic bits.
Beyond that you probably need a bigger iron.
MM
I’ve been soldering since I was a child. My father was into HAM radio and I learned very young.
In my experience the number #1 thing you can do to make your soldering easier–if you haven’t already–is to get a good modern iron, the kind with a heater and sensor located in the tip of the tool. These keep a much more even heat than the old style with the heater in the barrel of the tool. This heats joints up faster and there is also less overshoot.
It might also have been the case that your iron had insufficient wattage or perhaps too small a tip. There’s two ways you can solder big terminals or big wire: you either wait for the whole thing to slowly heat up, at which point the solder flows and then you have to wait ages for the whole thing to cool back down again. The other way is to have a good strong iron that is powerful enough to heat just the area where you’re soldering locally, BEFORE the heat has time to flow into the rest of the part. This is the ideal situation because the terminal itself acts as a heat sink and sets the joint the moment you remove the iron. You’re putting less heat into the parts overall so you can work faster with less risk of melting insulation, damaging components, etc.
You can easily make 90 degree terminals out of normal ones by bending them. Of course if you are working with fully insulated terminals then you would have to cut the insulation off first.
In my experience, most of the time soldering gizmos like “third hands”, heat sinks, and similar are band-aids for the real problem: wrong iron for the job, or poor technique like not tinning parts before joining.
Another thought, I’m not familiar with that brand of limit switch, but I have found off-brand parts sometimes have a strange plating on their terminals that doesn’t seem to ‘wet’ very well. If you found it was hard to tin the terminal before you soldered it then you might try some more aggressive flux.
ermine9
This is one of my most favorite comments of all time! I hope this will motivate me to try soldering again.
I had a school project for which I needed to solder a bit. I thought I was going to learn how to solder, instead I just gained PTSD.
Al-another-Al
I recently got a USB-powered iron with interchangeable but cartridges. Hooked up to a DeWalt 20V battery with a 100W USB-C adapter.
It heated up to the temp in a few seconds. I was still talking about it and waving it around in the air when it started smoking, and beeped.
Now, I’m looking for more things to solder. Going to tackle a Synology storage appliance with a finicky power button.
Jared
That looks weird to me. I think extra flux would have helped considerably. It looks like you had to overheat it to get it to flow.
Hepdog
I solder 18awg-ish wire to the backs of potentiometers and to the metal chassis (of guitar amplifiers) with an ancient, giant, 100W soldering iron. The kind with a wooden handle and a fabric braided 2-conductor power cable.
The reason this iron is 10X more effective at soldering to heavier objects than my Hakko soldering station or my Weller 80/100W soldering gun is the mass of copper at the tip. It quickly and effectively dumps heat into large objects.
Clean the item your are soldering to first, scuff it with 220-grit sandpaper, apply a bit of flux, and tin the item. Tin the wire as well. They should go together easily once both are tinned.
I would test the contacts on your limit switch – there is a possibility that excessive heating has damaged the internal components.
example iron on ebay: 335384928196
Thanks,
Hep
Stuart
About testing for switch function and continuity – I did that after soldering and again when heat shrink was set. I was so sure it was literally cooker, but it worked fine, so far.
Rya
Looks like you didn’t have the soldering iron hot enough. Need more heat for very short time. To little heat, you have to hold longer melting plastic before flowing solder. There are also limit switches with solder tabs instead of connector tabs
I personally would never have the wires against the metal. You could solder wires in another direction or bend the tabs. I would most likely drilled or tapped the tab and used ring terminals with bolts. With ring terminal you rotate wires to where they fit best
I also would never daisy chain those phoenix connectors. I have problems with wires staying in them. I would not want wires to fall out in the middle and several things stop working instead of one thing
Stuart
Could be – I have a bigger tip somewhere for exactly this type of application, and I’ll try that one next time.
Ooh – I like the idea of ring terminals – thank you!
I partly purchased this set with review intent, and so I need to build it as the manual/guide shows. And also it means I can just *do* rather than *think* which is the other part of the reason I bought it.
Matt_T
Double bootlace ferrules are good for daisy chaining. The single ones are better for those phoenix connectors too. Especially with fine stranded wire.
The crimp tools that work well with doubles can be spendy though. Maybe Stuart could get a review sample from Knipex or Weidmuller Lol.
Stuart
I did consider that for a moment. I own the Knipex crumpet, but don’t keep any double ferrules on hand. If I rework the wiring, it’ll be single point connections to DIN rail terminal blocks.
I’m also not thrilled with how close together the motor controllers are.
Mark W. Ingalls
When soldering small-to-big stuff like you have here. I like to place the big object on a temperature-controlled hot plate I cobbled up years ago. Set the hot plate to a safe temperature for the component (like 125° C for instance) so that you don’t have to push so much heat with the tip.
Also, I never, ever trust the flux inside a hollow core spool, because it gets “rancid” fast. Since you’re soldering wires to spades, and not to a PWB, you can even use plumbing flux if you have to. Amazon has lots of varieties of flux in tubes and tins…
Kurt
I keep a needle bottle of Kester flux next to my solder station, and use it for every job. My solder game has been improved since I’ve done this.
Jsb
Might be a nickel plating which needs a flux. Flux, higher wattage, higher mass iron, pre- tinning always seem to work for me in this type of soldering. Almost like a small copper pipe plumbing jog. IeWould use a Metcal with a large tip at work before i retired. Two irons also seems work.
Re-Engineer
20 years ago when I switched careers, I bought a Metcal for myself as a going away present. It’s what I used as a professional technician, and I knew I would be doing some consulting work for a while. I still have it and use it a few times a month. It can lay a bead of solder all the way across a sheet of copperclad board with the right tip size.
Plain+grainy
I’m wondering on certain applications, spot welding the connections might be the preferred method.
ColeTrain
What you need is a switch like that with through hole terminals. Bend the wire through the hole and clamp it to the terminal with some forceps and you got about the easiest solder job you could have. Even a half ass decent solder job is going to be a more reliable connection than pretty much anything else.
Plain+grainy
As long as you don’t alter the terminal by drilling holes yourself.. Drilling holes yourself can be detrimental in many ways. And possibly dangerous.
Plain+grainy
I’m certainly no expert on it. Just what I read!
Stuart
The metal hardware is drilled and tapped for these switches. The contact arm is sized for other hardware.
Matt_T
They look like Omron knock-offs. Sourcing replacements with solder holes in the tabs shouldn’t be a problem if you don’t want to drill them.
Stuart
I’m building this as designed, as review consideration was part of the purchase intent. There will be time for modification later.
Jeff McCray
I would recommend always using flux, once I started using flux it was like a lightbulb lit up for me.
I now use flux with every solder job.
WB
Always use flux. What kind of flux, depends on how difficult it will be to clean the item/solder joint after it’s made. Easy to clean/good access – rosin paste, or liquid rosin. Hard to clean/moderate access – water soluble flux. Impossible to clean/no access – no clean flux.
63/37 solder melts at 183 C/362F. If you’ve got to run an excessive amount of heat (more than 350C) to your iron, you need a bigger tip. Always use the biggest tip possible for the application. More thermal mass, better heat transfer, heats up the solder pad before heat soaking the component.
Keep the tip tinned and wet…
And don’t forget to hold your tongue right!
MM
You make a very good point, keeping the tip tinned and wet is huge. And I think that’s a problem that people experience with many of the lower-end irons. A lot of the ones that plug straight into a wall socket with no transformer or ‘power station’ seem to have chrome or nickel plated tips. These are terrible because the solder won’t stick easily, it tends to bead off like water on a waxed car. If the tip isn’t tinned the iron is useless. You need to be able to keep a little wet bit of solder on the tip, when you bring the tip to the work this little bit of solder acts like oil on a frying pan, it conforms to the shape of the parts and provides area for the heat to flow. Keeping the right amount of “wet” on the tip of the iron is a skill you learn with practice. Too little and it takes a long time to heat the joint, too much and you make a mess and risk bridging terminals.
I have a 30-some-odd-year old block of Sal Ammoniac (ammonium chloride) in my electronics toolbox, this is for cleaning and tinning tips of irons. It’s rarely necessary on high quality electronics tips, but it is useful for old-school cartridge heater irons, resistance type soldering guns, etc.