VanSpoof - Prototype 2 - Shrunken PCBs

In my last post, about Low Tech Prototyping , I worked out the VanSpoof PCB had to be no bigger than 31.5 mm by 21.5 mm to fit in the space left over from removing the motor.

I wanted to reuse the existing wiring in the cable and e-shifter body, so I had to find sockets to match. I roughly measured the connectors on VanMoof's e-shifter at about a 1 mm pitch. I therefore guessed that they were likely to be JST-SH connectors , SHR-04V-S-B, going in to JST-SR headers, BM04B-SRSS-TB .

A VanMoof e-shifter, showing PCB & connectors. The PCB removed for a clearer view of the socket.

To make sure I didn't make a very costly mistake, ordering fresh PCBs with incorrect footprints, I thought I'd better pick up a couple of sockets to double-check.

A close up of the VanMoof PCB and a JST socket next to it. They are not the same size.

That beige component is my brand new JST socket. The original white sockets are definitely not the same size or pitch!

The old adage is if it's not JST then it's probably Molex! The closest pitch that Molex do is 1.25 mm , well within the tolerance of me eyeballing-it-with-some-digital-callipers.

A close up of the VanMoof PCB and a Molex socket next to it. They are exactly the same size. A Molex socket on the end of a VanMoof e-shifter cable.

That's much better! The Molex sockets look like a much better fit, right down to the shape of the pins and cut-outs on their back wall.

For those playing along at home, the correct 4-wire socket for VanMoof e-shifters is a Molex PicoBlade series, 53398-0471 .

Unfortunately, Molex's SMD footprint is quite a bit wider than JST's, so the board needed a fair bit of layout work to make everything fit.

A dimensioned PCB layout with a JST SMD footprint. A PCB render with a Molex connector in the same place.

With the socket and its footprint confirmed and the board laid out I could now happily, and safely, order my new PCBs.

A stack of bare VanSpoof PCBs. One has been removed from its frame and placed on top. The name AISLER can be seen on the frame.

Checking the new board for fit against the Low-Tech MDF prototype proves my measurements accurate. The PCB nestles snugly into the space left by the old motor.

An MDF prototype placed in the void. A bare VanSpoof PCB placed in the void.

Placing one of the demo Molex sockets from earlier on to the board gives an idea of how it will look, fully assembled.

A close up of a bare VanSpoof PCB placed in the e-shifter housing. A Molex socket has been placed on top of the SMD footprint.

It also triple-check confirms I picked the correct footprint for the layout. Phew!

2025-04-08