TS100 Grounding System


It’s a grounding solution for the TS100 soldering iron, with a bonus USB-PD trigger case. The ZY12PDN case slips over the version with screw terminals, and snap-fits in place with modeled detents. The ground lug slips over the existing USB-PD supply prongs, and tapes in place. Nickel mesh shielding tape goes over the plastic prong to make the ground connection. On the other side, a tab of conductive tape brushes/jams against the USB-C shield, which is connected to the negative side of the 20V system. This alone takes care of the high voltage mains pickup I outline below. An additional 1M resistor between the barrel jack and the grounding screw on the TS100 provides lower impedance to the tip for ESD safety.


The TS100 is my go-to soldering iron, since it’s compact, self-contained, and has great thermal performance and tips I like. I even have a second one for travel – since its input is 20V DC, supply options abound, including battery.

However, being DC powered, the grounding scheme is at the mercy of whatever you plug it into. It has a little grounding screw connected to the tip for you to add a grounding strap if you so choose, but that’s hardly convenient.

My go-to power scheme is to use a 60W USB-PD supply with a ZY12PDN trigger to send 20V over thin silicone wires that make the iron very maneuverable on my bench. However, as a result of the floating-tip-on-floating-supply grounding scheme, the tip actually picks up mains 60HZ noise at nearly full amplitude, showing 146Vp-p to earth ground on my scope – check out the measurement in the bottom right of the scope below.

Oscilloscope probing the floating TS100 soldering iron tip while plugged in, showing a messy 60Hz waveform at 146 volts peak to peak.

The tip-earth impedance in this configuration is extremely high, >3.5Mohm, so this isn’t a threat to personal safety. However, the high impedance could be an ESD concern, and I swear I’ve run into problems caused by that high voltage before. I can’t be totally sure, but I think my iron was responsible for corrupting a Raspberry Pi CM4’s EMMC while I was reworking a carrier board. In any case, I’d rather have no voltage waveform on the tip, and a responsible ESD-safe impedance to ground of like 1MOhm or something.


Ground-coupled low-voltage DC supplies are surprisingly hard to come by. Virtually all USB-C and cellphone supplies are two-pin, non-polarized, fully isolated designs, since that’s safest for the user. In fact, I know of exactly ONE USB-PD supply with a ground-coupled USB-C shield: the Apple PD supplies you get with a MacBook, and only if you use the 3-prong grounded cord wall attachment.

My MBP supply is bulkier than necessary, I only have one, and I don’t want the huge cord on my bench, so I decided to add a ground tie to my current supply.

I 3D-printed an add-a-prong ground to tape onto the supply, and shorted it to the USB-C shield on the other side with a strip of conductive tape I have on hand for RF shielding. A small tab folded double to stick to itself sticks out about halfway over the open USB-C female port, which makes decent press-fit contact with the plug shell. This tape is nickel rather than copper, so it shouldn’t corrode or oxidize or otherwise get too crusty over time. The ground prong is pretty fragile, but my workbench power strip is very gentle on it. A metal stud with a thin flange glued to the supply would be better, but such a thing wasn’t practical for me to build without a lathe and still would have been weaker than a purpose-built plug. I looked for compact pass-through devices but nothing struck my fancy.

This takes care of all the mains pickup, but the iron tip is still floating = ESD danger. In my testing, the tip impedance is actually only a couple megaohms, but it still feels like it should be ==1Mohm. To take care of this, I just screwed a 1Meg resistor onto the ground screw on the iron, and jammed the other side against the shell of the barrel jack.

1Mohm resistor between TS100's ground screw and barrel jack input

No more weird memory issues on my prototypes!


  1. River B
    August 22, 2022

    – I use the Pine64 Pinecil Iron, but it also has a ground screw in the back.
    – the current Pine64 Pinepower Desktop comes with 3-pin socket in the back and a 3-prong grounded cord. has PD65W-20V-3a. $37.99
    – also saw a Basues one on Amazon 65w $59.99 ( I have not tested this one). called “Baseus PowerCombo 65W, USB C Charger, All-in-One GaN3 USB C Charging Station with 2 Outlets Extender” it has 3-prong cord.
    I prefer USB-C chargers with 3-prong cord, but yes harder to find for good price. I’m disappointed that the new EPR chargers like apple 140W-28V are only 2-blade.

  2. River B.
    August 22, 2022

    And I just remembered, the TS100 is different, you can only do DC power, so you are more limited on Grounding choices. on Pinecil, can do DC power in which your solution also helps for grounding, or can do USB-C PD chargers for power. in which there are only a few on the market that are USB-C PD and also have 3rd ground Prong.

  3. August 22, 2022

    @river do you happen to know whether either of those USB power hubs actually earth-grounds the negative or even the shell of the USB outputs? It’s entirely plausible they don’t anyway.

  4. River B.
    August 23, 2022

    I will be ordering the newest PinePower desktop Mid-Sept when the V2 irons are also in stock to get in same shipping and will let you know.
    I will also see if someone else in Pine64 discord chat can check theirs since the 3 – prong version has been out for a few months and someone else should have it.

    What I can tell you is that I modified my 2021 version Pinepower – swapped figure 8 for 3-prong socket (mickey mouse/clover leaf). and jumped to all usb shields and did a couple other things internally, (mod of power supply not advised lol). Any rate. on this one, I modified, I have continuity between 3rd prong of cord and the front usb shields for all 5 ports.
    Feedback I got from someone close to their development says that modification of Pinepower may have lead them changing it to 3-Prong grounded. at time In Pine64 community chat, I posted photos and how I did it, and got advice from EE people in the channel to be sure, we backwards engineered it. the hole in back for figure 8 was able to fit a PCB style Clover leaf socket from the market without any modifications, and the PCB seemed to be designed for it already, it had hole spot for PCB style 3-prong socket.

    I’ll let you know when I ask community to check theirs if someone has a multimeter and a newer Pinepower.

  5. River B
    September 8, 2022

    just got the 100W Baseus 3-prong grounded charger , some good and bad news:
    – 3rd ground prong on cord has continuity to the 2 AC plugs on the side
    – all the USB port metal shields have continuity to each other.
    – bad news is that non of the 4 USB shields have continuity to the ground prong of the cord. why didn’t they tie the usb port shields to the ground?

    This is disappointing, I’ll probably return this. I will let you know when I get the other ones.

  6. River B
    September 8, 2022

    I guess ama zon link was taken out but the one I tested was the
    “Baseus PowerCombo 100W, USB C Charger, All-in-One USB C Charging Station” the USB- shields on the port are not connected to the ground prong of the cord.

  7. River B
    September 9, 2022

    I have now tested also the Baseus PowerCombo 65W, USB C Charger, All-in-One (also comes with 3-Prong cord). Same problem as the 100W version. Good news, all the 4 USB port shields have continuity to eachh other.

    Bad news, they did not tie a single usb metal shield to the ground prong of the ground cable. if they had done this small easy thing, their two 3-prong chargers would be better than all the rest on the market. But they missed the opportinuty. I wish someone could tell Baseus, they could prevent current leakage issues on devices if they took advanatage of the 3 prong cord that comes with those 2 chargers.

  8. River B
    September 22, 2022

    Good news. got the 2022 Pine64 PinePower Desktop 120W charger today 9/22/2022.
    * All the front USB metal shields have continuity to eachother
    * Also, all USB shields have continuity (are connected ) to the 3rd Ground Prong on the cord which means all the shields go to earth mains.
    * this is Fantastic for me. I highly recommend Pinepower over all the other 3-prong chargers on the market. of the ones I could buy & test, like the Baseus PowerCombo ones, Only the Pinepower has the usb metal shields with a connected patch to real earth ground by way of the cord ground prong.
    * and PinePower is only ~$38 on pine64.com I order it when I’m ordering other Pine things, like the V2 Pinecil soldering Iron (since it’s $12 shipping, I try to add more to the order). even at 38+ 12 = $50 it’s still cheaper than any of the Baseus ones that are not properly grounded on USB.

    Hope that helps.

  9. September 23, 2022

    That’s great news, thanks for the update!

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