Tigsich

TIGSICH – index-finger slide remote for IPOTools SuperTIG 200Di

A passive, torch-mounted current control that replaces the IPOTools FT-47K-CL8 foot pedal. A finger bar under the index finger does both jobs. Sliding it moves a slide pot, which sets the welding current. Pressing it clicks a push-on / push-off switch underneath, which starts or stops the arc at any current setting. The concept is the same as the 6061 Slide Lever.

Status: design rev 4, not yet prototyped. All board parts are in stock at Mouser (see section 7). The socket voltages on the machine have not been measured yet. See Open items.

---

1. Machine interface

The machine has a GX20 7-pin remote socket. The pinout is the same one used by AHP/PrimeWeld pedals (configuration.jpeg). It was confirmed by measuring the user's own FT-47K-CL8 pedal:

Decisions based on this:

• Pot value 50 kΩ linear. The pedal model name (47K) and the measurement (≈50 kΩ end to end) agree. The ±20 % pot tolerance doesn't matter, because the machine reads the wiper as a ratio of the reference voltage.
• No series trim resistors. The pedal's 0.5 kΩ minimum is simply the pot's residual resistance. The PTA datasheet specifies "500 Ω or 1 % max", which is exactly what the pedal shows.
• Pins 6–7 are bridged inside the GX20 plug, not on the PCB. This keeps the cable at 5 cores (thinner and more flexible on a torch).
• The switch itself must latch. IPOTools states the remote works only in 2T mode, so the machine's 4T latch can't be used with a momentary button.

Supply voltage (assumed, not measured)

There is no power pin on this plug. The only voltages present are the pot reference (across 3–5) and the trigger pull-up (across 1–2). Machines of this type typically put 5–15 V there, so the design assumes ≈12 V. Because the design is passive, the voltage only has to stay within the parts' ratings:

---

2. Architecture

How it's used:

1. Set the current: slide the finger bar. Rear = minimum, front = maximum. It stays where you leave it, because the pot's own 30–250 gf friction holds it.
2. Start the arc: press the bar down. The switch underneath clicks and latches (plunger and bar stay 1 mm lower), closing pins 1–2. This works at any slider position, because the bar slides over the plunger.
3. Change current while welding: slide the bar; the latched switch stays on.
4. Stop the arc: press the bar again.

The machine stays in 2T mode. The trade-off is that nothing stops the arc if you drop the torch: that takes a deliberate press. The same footprint takes the momentary TL2230OAF140 (hold to weld) if that's preferred.

---

3. Parts

Switches I compared (button heights above the PCB bottom, for a 1.6 mm PCB; subtract 0.6 mm for the 1.0 mm board):

Switch wiring: both poles are in parallel. The TL2230 datasheet shows rest = 1–2 and 4–5 closed, and pushed / latched = 2–3 and 5–6 closed. So 2 + 5 → TRIG_COM and 3 + 6 → TRIG_NO, and the rest contacts 1 and 4 are left unconnected. The two contacts in parallel give redundancy for a low-level signal.

Switch life is the weak point. The TL2230 is rated for 10,000 electrical cycles, about 5,000 welds (on + off). That's fine for hobby use, and it's a cheap THT part that's easy to replace.

Pot life: the PTA is rated at 15,000 slide cycles. With a set-and-leave slider (rather than a pedal that moves on every weld) that lasts a long time. A conductive-plastic slide pot of the same footprint is the upgrade path.

No filtering or ESD parts on the board. The original pedal is a bare pot and switch, and the machine's input circuitry was designed for that. If HF-start interference shows up, the first fix is a shielded cable with the shield grounded at the machine end.

---

4. Mechanics and heights (see docs/mechanism.svg)

The finger bar:

1. Hinge at A: its rear end is hinged on the cut pot lug with a pin (Ø ≈ 1 mm) through the lug, held by two clevis ears under the bar. Sliding the bar drags the pot slider.
2. Resting on the switch: its front part rests on the TL2230 plunger. The switch's own spring holds the bar up, so no extra return spring is needed.
3. Pressing: the bar tips about pin A. The distance from A to the switch is 12.5 mm at MAX and 32.5 mm at MIN, so the 1.8 mm switch travel is a 3.2–8.2° tilt. A rigid joint at A won't work; it has to be a hinge (or a printed flexure).
4. Finger pad: at the front end, 38 mm from A, just in front of the switch. Pressing close to the switch keeps the lifting force on the pot lug small. (Pressing far in front of the switch levers the lug up.)

Lid features around the switch:

• Square bore: a close-fitting bore round the plunger (3.0 × 2.0 mm head) takes the sideways friction as the bar slides across the plunger top, so the switch stem isn't bent. A smooth bar underside (polished aluminium, or PTFE tape) helps too.
• Side rails: two rails beside the bore keep the bar centred (it can't swing sideways around A). Their tops are the down-stop at ≈ 1.7 mm switch travel. That's past the 1.0 mm latch point and short of the 1.8 mm end stop.

All heights are measured from the PCB bottom, using nominal datasheet values, with a 1.0 mm PCB:

The height target (< 15 mm) is met. A 1.6 mm PCB would add 0.6 mm (≈ 15.3 mm). A 1.5 mm aluminium bar would add another 0.3 mm. Add the housing floor under the PCB (≈ 1–1.5 mm) to get the total thickness on the torch.

Other housing notes:

• Bar overhang: the bar is 38 mm from A to its front end, so it reaches ≈ 60.8 mm (MIN) to ≈ 80.8 mm (MAX) from the rear edge. At MAX it sticks out ≈ 18 mm past the housing front, toward the torch head.
• Lid slot: the slot for the pot lug is 20 mm of travel plus the lug width (check on the part, ≈ 5 mm), so about 25 mm long. The clevis ears and the bar cover it at every position; a thin skirt on the ears keeps dust out of the pot.
• Lid fixing: the lid screws into the pot's two M2 threaded holes (on top of the pot frame, 31 mm apart on the PTA2043). This clamps lid, pot and PCB into one stack. The PCB has no mounting holes, because there's no room at 17.4 mm wide. The PCB rests in grooves or on ribs in the housing floor, which also carry the press force.
• Mounting on the torch: two strap or zip-tie slots in the housing floor. The cable exits at the rear, alongside the torch hose.

---

5. PCB

• Board: 60.1 × 17.4 mm, 2 layers, 1.0 mm (chosen to keep the finger bar under 15 mm), rounded corners (R2), 0.4 mm tracks (signal-level currents). All copper is on the top layer, with no vias. There is no ground plane: the circuit has no ground.
• Width: the 17.4 mm is set by the 5-pad cable column: 14.4 mm of pads at 3.6 mm pitch, plus the 1.7 mm pad size and 0.65 mm edge clearance. The 2.0 mm strain-relief holes still take wires with insulation up to 1.5 mm OD, leaving 1.6 mm of board between neighbouring holes. The pot is 11 mm wide including its tabs, and the switch 7 mm. The two track lanes under the pot sit between the pot's mounting tabs and the board edge, with ≥ 0.45 mm clearance.
• Layout, rear to front (cable → torch head):
  1. Cable pads (J1): at the rear edge.
  2. Slide pot (RV1): its slider runs along the board centreline.
  3. Latching button (SW1): centred, 0.85 mm in front of the pot body.
• Routing: the pot and switch connections that pass alongside the pot run in lanes above and below the pot body.
• Pot direction: RV1 pin 1 (the rear end) connects to plug pin 3, so the rear slider position = wiper next to plug pin 3, i.e. P3–P4 ≈ 0.5 kΩ. If the machine gives maximum current at the rear, swap the wires on plug pins 3 and 5.
• J1 pad order (top to bottom) is chosen so nothing crosses. It's printed on the bottom silkscreen next to each pad:

• PTA2043 footprint: corrected copy of KiCad's. KiCad's Potentiometer_Bourns_PTA2043_Single_Slide puts pin 3 at 33.0 mm from pin 1, but the datasheet (dimension E) and Bourns' STEP model both give 33.5 mm. With Ø1.2 mm holes and 0.8 mm pins, the library version would not let the pot seat. The project copy (tigsich.pretty/Potentiometer_Bourns_PTA2043_Single_Slide_E33.5) keeps pins 1/2 where they were, moves pin 3 to 33.5 mm, and shifts the four mounting tabs and body outline by +0.25 mm, so everything is centred at 16.75 mm as on the part.
• TL2230 footprint: it's custom (tigsich.pretty/SW_E-Switch_TL2230), because KiCad's library doesn't have one. It was made from the datasheet PCB layout (component side): 2 rows of 3 × Ø0.8 mm holes, 2 mm pitch, rows 5 mm apart, pin 1 square. The pad numbers match the Switch:SW_Push_DPDT symbol: B = common 2/5, A = rest 1/4, C = pushed 3/6.
• 3D models:
  • SW1 uses E-Switch's own STEP model (tigsich.3dshapes/TL2230xxFxxx.stp, inch units). It is set in the footprint with a 90° rotation (the vendor model has its pin rows along Y) and a +0.75 mm Z offset (model origin is 0.75 mm above the seating plane). With these, the pins sit centred in the pads and the plunger top is 12.5 mm above the PCB, as in the datasheet.
  • RV1 uses Bourns' STEP model (tigsich.3dshapes/PTA2043-2015DPB103.stp, mm). Its "up" is −Z and pin 2 is at +Y, so the footprint flips it 180° about X and offsets it by (−0.85, +2.9, 0) mm. That centres the body on the tabs and puts all pins and tabs in their holes, with the body seated on the board.
  • Caution for the housing: Bourns only offered the model for the DP lever variant (…DPB103). We order CP (PTA2043-2015CPB503). The body, pins and slot are identical, but the lever shape differs (the DP lever in the model reaches ≈ 20.7 mm above the PCB top). Take the lever dimensions for the case from the datasheet's CP lever drawing, or measure the real part. The lever is cut down anyway.

Verification:

• ERC: 0 violations.
• DRC: 0 violations, 0 unconnected, 0 schematic-parity issues.
• Tool: KiCad 10.0.6.

---

6. Files

---

7. Bill of materials (Mouser)

Stock and prices were checked on 2026-09-23 through the pcbparts MCP (Mouser API, USD).

The Mouser order comes to ≈ $30, under Mouser's EU free-shipping threshold (≈ €50). Mouser ships to the EU with duty and VAT included, so there's no customs agent. Add other stock parts to reach the threshold.

Not at Mouser (buy elsewhere):

---

Open items / before first use

1. Measure the socket. With the machine on and the pedal unplugged, measure the DC voltage across 3–5, across 1–2, and from each pin to the case. It must be ≤ 30 V on 1–2 for the TL2230. Don't strike an arc (HF start) while probing.
2. Check the switch. Before soldering, check with a meter that the TL2230 closes 2–3 (and 5–6) only when latched. On the finished board, check that P1–P2 is open when the button is up and closed when it's latched.
3. Check the pot direction: the rear slider position should give minimum current. Swap plug pins 3/5 if needed.
4. Check part dimensions against real parts. The TL2230 plunger height sets the bar height, and the pot lug is cut and drilled to suit the hinge.
5. Design the housing and bar: lid with lug slot, plunger bore, side rails and down-stop, M2 screws into the pot, finger bar with clevis ears and hinge pin, PCB grooves, strap slots, cable gland.
6. Check the latch through the bar: make sure a press anywhere in the 20 mm travel latches and unlatches the switch reliably, and that sliding while latched doesn't unlatch it.
7. Test first on scrap: check minimum and maximum current, that the latch works with gloves on, and that HF start doesn't cause flicker. If it does, use a shielded cable.

Sources

• SSC C910-0725 info sheet (same 7-pin pinout)
• IPOTools FT-47K-CL8 foot pedal
• Bourns PTA series datasheet
• E-Switch TL2230 datasheet
• E-Switch TL2230 product page
• C&K PVA series datasheet (rev 2)
• Alps SPEF series (compared)
• 6061 Slide Lever (concept reference)