Month: July 2020

#0003: Basic techniques for connecting wires

Otto

#0003: Basic techniques for connecting wires

picture comparing: pig-tail, straight solder, and western union splices

Connections discussed:

  1. Straight solder splice
  2. Pig-tail splice
  3. Western Union splice
  4. T-junction splice

STRAIGHT SOLDER SPLICE

picture showing two wires with their exposed copper ends coated in solder
picture showing a basic straight solder connection between two wires

The straight solder connection is made by aligning two opposite facing wires in adjacent-parallel, tinning them individually, then soldering them together. This joint is most suited for smaller gauge wires. Especially in low-voltage or low-current applications.

I find I use this joint frequently when prototyping and stringing various PCB modules together, such as power-supplies and buck-boost converters. This is because it allows me to make a more than strong enough bond very quickly; and without damaging the wires, by avoiding subjecting them to repeated mechanical strain. For example: by twisting them together and soldering, then de-soldering and unravelling them whenever I want to disconnect a module; as is the case with the other types of joints. With this connection however, it is simple: align and solder to connect; then apply flux, heat, and pull apart to disconnect.

The straight solder connection is actually rather strong in my opinion. When applied properly, it creates a bond that can not be pulled apart easily. I tested this joint by wrapping the wires around my hands then trying to pull the joint apart. It might eventually give, but only after considerable force is applied.

Despite it’s initial success with my basic stress test; I still wouldn’t recommend using this type of joint for any permanent applications. This is because, in my opinion, I don’t believe that it will stand up well in most real-world settings. Settings that involve: temperature swings, vibration, or constant stress on the wire and joint. These things can exacerbate any small imperfections in the weld to the point that they can create fissures that can either cause problems like intermittent connections or outright brake the bond. Since the solder is the only thing keeping the connection, any stress applied to it isn’t mitigated by anything. This strain coupled with environmental heat would make this type of connection unreliable in the field. An example of this would be wiring around an engine.

Still though, as long as the wire is not subjected to any real or ongoing strain in its application, it is not a bad option to utilise this type of connection. Especially for temporary or semi-permanent add-ons to an already established system. For example adding a voltmeter module to an electric bicycle to keep track of the battery levels. That way the module can quickly be de-soldered off or be further modded later with a switch as an example. This type of bond also has the smallest footprint. Allowing smaller sized heat-shrink to be easily applied as insulation.

PIG-TAIL SPLICE

picture showing a pig tail splice between two wires
picture showing a pig tail splice between two wires, the connecting twist stands at a right angle between the two connected wires, revealing some broken copper strands within the connection.
picture showing a pig tail splice between two wires, the connecting twist has been folded down onto one of the wires

The pig-tail or rat-tail splice is probably the most common type of connection that I have encountered in the wild. It is made by holding two wires in adjacent-parallel (facing the same direction), then twisting the exposed ends together. Its a quick and dirty solution to make a good mechanical connection. Usually this type of connection is insulated with either sticky tape or even heat-shrink for a semi-permanent solution. It is not soldered in many cases, as the twists and tape tend to make a ‘good enough’ connection for the use-case.

The alignment of the connecting wires is something to take into consideration when deciding whether or not to use this splice. In cases where the wires are to remain adjacent-parallel and facing the same direction; the pig-tail splice is a good candidate. It will allow the user to join two wires next to each other, whilst minimising any change of location, necessary in order for the wires to accommodate the new connection. Example use-case: connecting 2 or more adjacent wires within a ribbon cable. Additionally, with this setup: the connection can be easily soldered and insulated with heat-shrink by sliding it over the open end.

However in cases where the user is joining two opposite facing wires, they are usually left with a connection made up of a twisted pair that veers off at a right angle. This is then folded onto one of the wires in order to apply insulation. This is mechanically weak, as it concentrates any stress on the wire/connection or more accurately “pulling force”; at the bend. The first twist where the two wires meet.

This configuration of the pig-tail splice rarely takes solder well without ending up with an overly large footprint or bulge that the user has to then slide heat-shrink over. It is also too easy to melt the wires whilst soldering because of how close the insulation on the wires are to each other.

To conclude, this connection is good in solder-less temporary or semi-permanent applications. But if you want a more permanent bond (especially for opposite facing wires), the western union splice is a far better solution.

WESTERN UNION SPLICE

picture showing two wires being lined up for a connection
picture showing the exposed copper ends of two wires crossed over each other
picture showing an unsoldered western union splice between two wires
picture showing a western union splice between two wires

The western union splice is named after the Western Union Telegraph Company. This connection involves crossing the exposed ends of two opposite facing wires together, at a mid-point between the wire’s exposed tip and the start of it’s insulation: in an “X” shape. Then twisting them around each other’s exposed base sections. Continue twisting until the insulation of the opposite wire is reached. Then trim off any excess exposed wire tips. This makes a linear and very strong mechanical connection between the two wires; by maximising the contact area the wires have with each other within the connection. It also functions as a knot of sorts, and once properly soldered, it becomes essentially stronger than either wire itself. In addition it has a relatively small footprint and consequently takes to sliding heat-shrink over it rather well.

This is probably my most favoured splice for permanent connections. However for those same reasons, it is also largely inappropriate for temporary applications. This is because it becomes a hassle to de-solder and untangle the wires. This process will also almost definitely damage the wires involved; by fraying and breaking some copper strands from the stress of unravelling.

THE T-JUNCTION SPLICE

picture showing a T junction connection between three wires
picture showing a T junction connection between three wires

The “T” junction splice is any connection where you add a third wire to an existing connection. The most basic version involves removing the insulation from the mid section of a wire; then wrapping another wire around the exposed section before soldering it in place. Then insulating it. This method can also apply to any of the above connections – and the strength of the additional connection usually depends on the strength of the underlying connection.

You could opt to pig-tail together three wires into a T-junction (or four into an “X”, etc…), or straight solder three wires, or even create a western union splice, then tightly hitch the third wire over that connection for maximum strength.

At its most basic a ‘T’ junction splice is exactly that. Three wires connected together in a rough ‘T’ shape. Everything else is up to the user, and largely depends on the use-case and it’s needs.

SOURCES / REFERENCES / FURTHER READING:

https://en.wikipedia.org/wiki/Western_Union_splice

https://en.wikipedia.org/wiki/T-splice

https://en.wikipedia.org/wiki/Rat-tail_splice

https://en.wikipedia.org/wiki/Point-to-point_construction

https://en.wikipedia.org/wiki/Printed_circuit_board

https://en.wikipedia.org/wiki/Solder

https://en.wikipedia.org/wiki/Flux_(metallurgy)https://en.wikipedia.org/wiki/Soldering

#0002: Cleaning up after an alkaline battery leak

Otto

#0002: Cleaning up after an alkaline battery leak

picture depicting a stack of rusted and leaking double A batteries

This will be a rather basic guide on how to clean out a device after an alkaline battery leak.

Whenever I come across an old device, that for some initially unknown reason refuses to power on. Chances are, that someone left disposable alkaline batteries inside it, and that they have leaked. There are a number of reasons as to why people leave batteries inside devices. Predominantly: laziness, ignorance, or forgetfulness. There are also a number of reasons as to why these same forgotten batteries leak. Batteries with mixed charges, reverse charging each other, or a constant low current draw causing leaking; are but two examples.

Unfortunately, a more in depth look into what causes disposable batteries to leak is outside of the scope of this article. However it is something that I am interested in exploring at a later date. Check the further reading section of this article for the hotlink to that, when I eventually get round to penning it.

I cannot count the number of times I have opened the battery compartment of a device, that has been left in storage for a while; only to be greeted with a vented battery, rust, and the the blue-white fuzzy carpet of alkaline crystals growing out of it. Meshing into, fusing with, and corroding the negative terminal’s spring contacts. This infection then proceeded down the circuit and further into the device and onto more complicated/valuable components. In this regard, an unstemmed battery leak has the potential to brick a device.

picture depicting heavy alkaline battery leak on battery spring terminal

So, how do you deal with it? Well, if caught early and the leak hasn’t progressed far beyond the battery itself, and a bit of surface level corrosion on the spring contacts; then it is really not much of an issue. A quick wipe down with a damp cloth after disposing of the batteries, should suffice. I recommend using isopropyl alcohol to dampen the cleaning cloth, mainly because it becomes non-conductive very quickly by evaporating readily. It also doesn’t leave any contaminants like water might. However water is fine to use in a pinch; just make sure it is fully evaporated and that there is no substance residue left after cleaning; before you power up the device.

picture depicting very light alkaline battery leak on battery spring terminal

If the leak has had the time necessary to progress further into the circuit and deeper into the metals. That’s when you have to take more invasive steps in order to remove it. There are two main ways to deal with an advanced battery leak. Which one to use, largely depends on circumstance. The most important factor being whether or not the affect parts can be removed from the device.

Method #1: Acid Bath

The first method of remedy, requires the removal of the affected parts and the use of an acid bath. Removing the affected parts, will likely require de-soldering. Next, create a bath, of vinegar and water at a ratio of approximately 1:3. So 25% vinegar and 75% water, or thereabouts. This leaves you with a mildly acidic solution for you to submerge any affected parts within. Mix the solution well, then drop the parts in. Leave it for some time. How long for based on your own judgment. I recommend 30 minutes to a couple of hours depending on the invasiveness of the alkaline crystals into the metals.

picture depicting an acid bath (blue tub with vinegar-water inside it), and a pair of forceps

Remove the parts from the solution when you think that they have been in there long enough. At this point, they will require brushing down, to remove any stuck on materials. Use a strong bristly brush for this, something like a firm toothbrush will do. For those wondering, a wire brush would probably be overkill for this application, especially since the subjected parts would likely be rather small, and wire brushes are traditionally made for uses with larger items. Wire brushes will also likely remove the finish on the metal parts, that is if the acid bath hasn’t done so already.

picture depicting heavy alkaline battery leak on battery spring terminal

The main reasons why I recommend using a mildly acidic solution to counteract the alkaline crystals is: one, in order to minimise the severity of the reaction between acid and alkaline; and thus minimise the chances of additional corrosion or damage done to the metals in the process; and two, to minimise the chances of the acid removing or damaging the metal’s finish by reacting with it. It should be noted that plenty of parts in modern mass produced devices are made up of mixed metals, then given a chrome finish for uniformity.

picture depicting battery terminals with chrome finish removed by the acid bath

I should note that when I say ‘part’, I am referring to simple primarily metal constructs within devices; such as spring terminals or basic switches. I am not referring to more complicated components such as resistors, capacitors, transistors, or anything more sophisticated than those examples. This is because the acidic solution is very likely to compromise the internal structure or chemistry of any components submerged within it, if the leak’s corrosion hasn’t done so already. Bricking the component in the process. More on what to do with leak affected components mentioned later.

picture depicting two leak corroded battery terminals with chrome finish removed by the acid bath

After brushing all foreign materials off of the parts, dry them off, then wipe them down with a cloth laced with isopropyl alcohol. Continue until you are confident that you have removed all contaminants including traces of alkaline crystals and the acidic solution. Once this is done leave the parts to dry fully, before then placing them back into the device and likely soldering them back into the circuit they come from. That’s it, done.

Method #2: Acid Wrap

The second method of removing alkaline crystals is used when the affected part cannot be removed either from the device or it’s circuit for whatever reason. A good example of this is when a part is either welded, crimped, or glued into place; making it’s removal potentially too destructive to consider lightly.

picture depicting two spring contacts, one clean and the other covered in alkaline crystals
picture depicting two spring contacts, one clean and the other covered in alkaline crystals (front view)
picture depicting two spring contacts, one clean and the other covered in alkaline crystals (back view)

This method requires either tissue paper or cloth. Id est, something that can soak up liquid and cling to a particular structure without external pressure/force. I use tissue paper for this example. Soak the tissue paper in a diluted acidic solution; enough so that it has plenty of solution available but not enough that it drips excess. Then wrap it around the affected parts and wait for time, before removing it and brushing off any loose materials. Rinse and repeat until it looks done. Then clean and wipe down the part with an isopropyl laced cloth. Done.

You can adjust the ratio of vinegar to water to your liking. I still recommend a mildly acidic solution to minimise the severity of the reaction (and any damage caused from it), but the more acidic the solution is, the quicker it’ll dissolve the alkaline crystals off of the affected parts. From my experience a ratio of 1:1 seems to work out well.

Another tip for this method is to properly isolate the rest of the device from the part you are currently working on. This is done to avoid any accidental drips from the tissue paper or off-spray caused by brushing. Vinegar-water and electronic components are best left separated. With that in mind, I recommend using a plastic bag and tape. The plastic bag functions as a waterproof membrane and the tape holds it in place. Simple.

picture depicting two spring contacts, one clean and the other covered in light rust (viewed with chassis)
picture depicting two spring contacts, one clean and the other covered in light rust (front view)
picture depicting two spring contacts, one clean and the other covered in light rust (back view)

Dealing with components

Now that the basic method of cleaning metal parts has been explored, you may be wondering as what to do when the leak has reached more complex components. Well, the answer is simple. Try to remove whatever battery residue you can mechanically; i.e. just using a brush or a small chisel of some sort. Then de-solder/remove the component from the circuit. Test it appropriately. I recommend having both a multimeter as well as a multi-function tester on hand for this. If it is still within specification, solder it back into circuit; if not, replace it. There is not much one can do for any affected components beyond this. Once a capacitor or resistor is broken, it needs to be replaced.

Conclusion

As a final note, I should also mention that in a lot of situations: replacement of the affected metal parts is probably the more appropriate recourse to severe leak damage then repair might be. This means replacing spring terminals, and creating jumper wires as replacements for corroded PCB traces. This is because the repair can weaken the metal, leaving one with brittle spring terminals or a trace with more resistance in it than initially intentioned. However having said that, if you either can not remove the part, or don’t have the prerequisite replacements: then an ugly repair is better than no repair at all.

Sources/References/Further reading:

https://en.wikipedia.org/wiki/Alkaline_battery#Leaks

https://upload.wikimedia.org/wikipedia/commons/7/76/Alkaline_Battery_Leakage_Inside_a_Product.png

https://en.wikipedia.org/wiki/Isopropyl_alcohol