E-textile Hard/soft Connection

If you work with electronics and textiles, it is often difficult to connect the soft e-textile to the hard electronics. While there are many solutions for this already, I found that a very simple and robust solution was missing: just clamping the textile to the electronics board.

In this instructable I will show you how I made such a connector for a recent project where we needed 12 e-textile connections, arranged in a grid of 6 x 2.

Step 1: Components

For this connector, you will need:

1. A piece of textile with the e-textile part of your circuit and the correct landing pads (we'll get to the design of the landing pads later on). Size: about 20 x 7 cm.

2. A pcb (electronics board) with the hard (inflexible) part of your circuit and the correct landing pads (again, we'll get to that later). Size: about 20 x 7 cm.

3. A piece of felt (about 2 mm thickness; not needed if the fabric you use is already thick). Size: about 20 x 7 cm.

4. A piece of hard material as backing (I used another pcb for that, but you can also use some acrylic glass or wood). Size: about 20 x 7 cm.

5. 3 nuts and bolts, size M3

In my case, the circuit was already on some thick felt, so I did not use an extra piece of felt. (The extra felt is only needed as padding between the textile and the backing material and to make sure the forces are evenly distributed.)

Step 2: Design the E-textile Landing Pads

The landing pads on the e-textile side are strips of 10 mm wide and at least 10 mm long before they become more narrow.

The landing pads are arranged in 2 blocks, each consisting of 3 rows and 2 columns. Note that in this design, the connector is on the edge of the textile and the landing pads on the right side fold over and connect to the circuit on the backside of the textile (it's a two layer circuit).

If your design allows so, you can of course move the connector a little more to the center so you have more room to fan out the connector and keep the complete e-textile circuit on one side.

The spacing between the 2 blocks is 2 cm. We will make a small hole in the center later on so the contacts will be pressed against each other evenly.

Step 3: Design the Landing Pads on the Pcb

For this project I did not design a pcb. Instead I just stuck some copper tape to some FR4 board. Unfortunately, I forgot to take a picture of the back side of the pcb and I only have a picture of the front side. However, the back side looks very similar to the front side except that it does not have any solder spots (so the surface is as flat as possible).

The design itself is just some 1 cm wide copper strips that are pasted on the pcb and folded over to the other side. The spacing between the strips is again 1 cm and the spacing between row 3 and 4 is 2 cm (to have room for a hole).

On the top side I soldered some wires to a standard 12 pin boxed header so I could attach a ribbon cable. (For my project, the pcb was a converter PCB to go from a 12 pin boxed header to the e-textile circuit. In a later design, the landing pads will be integrated on the pcb itself so there will be no more ribbon cables.)

I also added a hole on top and bottom. In the photo above the holes are filled with M3 screws.

Step 4: Putting Things Together

When you've made both the e-textile part and the pcb part, it's time to put things together.

Carefully align the pcb, the textile and the backside material (in my case: a 2nd pcb) and drill 3 holes to fit the screws.

Attatch the screws and check the connections for any shorts or open circuits to make sure everything is working as expected.

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