Silicone lead for soldering iron -- recommendations? - Page 1
Forum section: electronics / projects

author: ebastler
author_rank: Super Contributor
timestamp: September 03, 2020, 06:39:54 am
content: I would like to modify the output lead of an old notebook power supply, to use it with a TS100 soldering iron. Looking for a temperature-proof and flexible 2-wire cable to carry approx. 3 A (at 19 V).The selection of silicone leads available online is limited, and having to order remotely, the specs do not give me a good idea how the stiffness/weight will feel in practical use. Does anybody have a recommendation, either for a specific brand & type of cable, or for a specific vendor on ebay or such? Reasonable shipping costs to Germany preferred...Thank you!

author: Whales
author_rank: Super Contributor
timestamp: September 03, 2020, 06:47:43 am
content: All of the silicone leads I have ever used are very soft (especially compared to PVC). So soft in fact that the copper inside takes most of the strain and breaks more easily. Do stiff silicone leads exist?N.B. possible alternative to silicone leads: clothes iron cord. It might be too thick for what you want.

author: 2N3055
author_rank: Super Contributor
timestamp: September 03, 2020, 06:48:06 am
content: I bought some "KSGER Silicone Wire Cable" from Ebay and it was OK.. Heat resistant, silicone and nice and pliable..Copper quadrature was small (0,4-0,5 mm2) but that is enough for few amps, and soldering iron is not drawing that much current all the time.. You can get 4 wire one and used them in pairs for more capacity.

author: vk6zgo
author_rank: Super Contributor
timestamp: September 03, 2020, 07:56:25 am
content: Quote from: Whales on September 03, 2020, 06:47:43 amThat is pretty much what the old "firestick" mains operated irons used!

author: evac
author_rank: Contributor
timestamp: September 03, 2020, 09:06:33 am
content: I bought a TS100 recently and just did exactly this the other day.I got single silicone wires in red/black color and twisted them together. They're pretty cheap (€2 for 2 meters shipped) and you can find almost any wire guage you want.The silicone has enough grip that the wires stick to each other and stay twisted together.In my case I bought 22AWG 60-strand wire, 1.8mm in outer diameter, very light and flexible, not even noticeable during soldering.The wire guage was okay for this use, the tips on my TS100 draw a maximum 3.1A at 24V, and I measured 1 meter of wire at ~58mOhm, so for both cables an expected voltage drop of ~360mV, which I confirmed by measuring the voltage at the iron under load.That's a 1.1W loss which over 2 meters of cable shouldn't cause any trouble, especially considering the typical duty cycle of the TS100 at this voltage is quite low.I also had some trouble to find nice and compact barrel plugs, so I ended up buying a cheap one and 3D-printing a shorter housing for it, already with the right diameter for the silicone wire. Can post pictures of the result if anyone would be interested.

author: Gyro
author_rank: Super Contributor
timestamp: September 03, 2020, 09:14:20 am
content: This is the one I use (actually I use it on one of my supplies, they used to do a slightly thicker 6A rated version, which I use on the other)....https://www.ebay.co.uk/itm/2-Core-EWK-Silicone-Rubber-DC-Wiring-Cable-4-amp-2x0-25mm-Flexible-LED-Solar/163699838807It is extremely flexible and doesn't drag on the back of the TS100. I think the same seller is on Amazon too.The cores are alittlethin (you would use thicker for the same rating in PVC insulation) so it's best to work out and use just the length that you need to minimise voltage drop.Also make sure that you use a decent connector to connect to the TS100 - you want one with a fork shaped inner contact (they have yellow insulation), as you would see on a laptop... not a simple centre tube type, which aren't rated for more than a few hundred mA.

author: werediver
author_rank: Contributor
timestamp: September 03, 2020, 06:18:59 pm
content: My solution to the TS-100 cablewith groundingproblem is this:- two 0.5 mm² wires (silicone jacket) for power- one 0.25 mm² wire (PVC jacket) for ground- silicon-coated fiberglass sleeve (⌀ 4 mm,this) for extra protection and bondingIt's the softest cable with grounding I could get or make. Not saying it's perfect, but it's pretty good for me

author: ebastler
author_rank: Super Contributor
timestamp: September 03, 2020, 09:20:02 pm
content: Thank you all, great input!@Gyro -- thanks also for pointing out the plug differences. I had noticed the yellow insulation sleeve on some notebook plugs, but had not been aware that it correlates with the better inner contacts.@werediver -- nice idea with the ground lead routed through the outer tubing. I need to check whether the notebook supply I have earmarked has a grounded output, and come up with a solution one way or the other.

author: evac
author_rank: Contributor
timestamp: September 03, 2020, 09:52:43 pm
content: Thought I would also share some pictures.Have to say I'm really happy with how it turned out, the cable is light as a feather.Quote from: Gyro on September 03, 2020, 09:14:20 amGood point, I didn't consider this. I used a cheap plug with the "tube" type inner connection and even though I didn't notice any voltage drops, I will consider to change to a "fork" type plug for a more reliable contact.

author: Gyro
author_rank: Super Contributor
timestamp: September 03, 2020, 09:55:04 pm
content: Quote from: ebastler on September 03, 2020, 09:20:02 pmAh, I'd completely forgotten, I resolved the tip grounding issue on my TS100 by bridging C26 on the PCB (schematic attached). This connects the Tip to the outer barrel of the supply connector. It will of course introduce some noise on the tip from the voltage drop along the -ve lead but I haven't found it to be a problem. As I mentioned, it is best to keep the flexible silicone lead to the shortest convenient length, the heavy adaptor output lead has a much lower resistance on its outer braid conductor.werediver's method will definitely give less noise at the tip - nice solution!P.S. While vaguely on the subject of ergonomics, adding a PTFE washer to the 'nose' makes all the difference...https://www.eevblog.com/forum/reviews/ts100-soldering-iron-test/msg1343465/#msg1343465P.P.S. My TS100 / Lidl 20V drill battery portable setup - using the Silicone 2 core cable that I linked previously...https://www.eevblog.com/forum/reviews/teardown-lidl-20v-2ah-lithium-battery-pack-and-charger/msg2469087/#msg2469087

author: werediver
author_rank: Contributor
timestamp: September 04, 2020, 07:44:36 am
content: Quote from: Gyro on September 03, 2020, 09:55:04 pmI'd strongly recommend against doing so. This may be suitable for the power supply you are normally using with your TS100 (if you ground the negative DC output), but that renders your TS100 harmfully incompatible with other power supplies, like the cheap 19 VDC bricks often used to power TS100 (I use such more often than not).The cheap 19 VDC bricks may not use the ground lead internally at all (that was the case with my unit). Due to some capacitive coupling the DC outputs may have half the mains AC on them (capable of supplying only small current via a capacitive divider).Now, if the circuit you're working with is grounded (intentionally or not), which is a good way to protect it from ESD, you're "powering" it with that high AC voltage via the soldering iron tip, which can easily damage active components.TS100 tip is normally isolated from the supply lines and should only be directly connected to ground.

author: werediver
author_rank: Contributor
timestamp: September 04, 2020, 08:26:51 am
content: Quote from: ebastler on September 03, 2020, 09:20:02 pmI usually use a cheap 19 VDC brick power supply that came in a bundle together with my TS100. That brick does not use the ground lead internally at all. I had to open it and just use the ground lead to arrange a ground outlet on it (without grounding any of the output DC lines).TS100 tip is normally isolated from the supply lines and I'd recommend to only connect it directly to ground (well, some people would want a few megaohms of resistance to the ground, but that's not the industry standard).

author: Gyro
author_rank: Super Contributor
timestamp: September 04, 2020, 09:49:25 am
content: Quote from: werediver on September 04, 2020, 07:44:36 amYes, I am well aware of Y cap current leakage - I would (and did) only use a grounded negative, decent quality PSU, an old IBM/Lenovo in my case. Second-hand high quality brand laptop bricks on ebay are almost always preferable to the cheap no-name stuff with dubious safety clearances that is sold these days. I avoid them unless I can internally inspect them for quality and layout. With a grounded output PSU, bridging C26 is a convenient way of being able to quickly plug and unplug without having to undo the grounding screw - useful in my case where I seem to quite often switch between mains brick and battery pack. As I said previously, your implementation will result in a lower noise tip ground, even with a grounded output PSU.You're right, I should have made that clear for less experienced readers, however ebastler is aware of the potential Y cap leakage issue. Some have actually reported stability issues then running the TS100 with particularly leaky / noisy floating output PSUs and a separately grounded tip...https://www.eevblog.com/forum/reviews/ts100-doesn_t-function-properly-when-earthed/

author: werediver
author_rank: Contributor
timestamp: September 04, 2020, 11:52:23 am
content: Quote from: Gyro on September 04, 2020, 09:49:25 amThat's curious, thank you for mentioning. Luckily, I have no such issues with my setup either because of a better grounding, or because of a less noisy / leaky supply. Still, good to be aware of a potential fault mode of the tool I use.

author: NiHaoMike
author_rank: Super Contributor
timestamp: September 04, 2020, 01:23:54 pm
content: Instead of jumpering across the capacitor, add a 100k-1M resistor in parallel.

author: Gyro
author_rank: Super Contributor
timestamp: September 04, 2020, 03:09:35 pm
content: Quote from: NiHaoMike on September 04, 2020, 01:23:54 pmThat's an interesting one. I've often thought that it would be sensible to have some series resistance on an iron tip, in the same way as an ESD strap - if only to stop you taking chunks out of the tip when accidentally attempting to solder something you've forgotten to power off! Also to reduce any low impedance ground loop current spikes.I know this has been discussed before in relation to soldering irons in general, but I don't remember what consensus was reached (I remember one argument was that you want to know as soon as possible if you're soldering something that's still powered!), however, afaik,allof the (ESD safe) iron manufacturers tie the tip directly to mains ground.I agree that a parallel RC network including C26 could be a useful solution, the question is sizing. You need to be able to eliminate switching (PWM) noise being coupled from the element to the tip, the 100nF of C26 is hopefully enough to swamp this, however if the R is too high, then there is the possibility of causing insulation breakdown between tip and element, and also of C26, if you accidentally touch a high voltage node (maybe this is a reason that they are normally grounded?), too low a value would smoke the R. Some experimentation of R and C values might yield a good compromise though. I'm just not sure why nobody does it (in general).

author: werediver
author_rank: Contributor
timestamp: September 04, 2020, 03:20:40 pm
content: My understanding of the reasoning behind grounding soldering iron tips directly (as you, Gyro, have briefly mentioned) is safety: let the circuitry fail quick and safe (by blowing fuses) rather than late and painfully (by electrocuting the operator).That doesn't help working on powered devices, right, but when safety is concerned, doing so is a no go (perhaps, there are special cases, but then, I'm sure, special protocols and measures are involved).