Saturday, 9 January 2016

Laser cutter + surface mount MPU programming

I designed a PCB that has to fit in a space that is very constrained. The PCB uses SMD micro controller, and there is no space for a dedicated programming connector on the board.

To solve this I simply placed PCB pads connected to the MPU programming pins. I ordered some spring test probes from BangGood. If you are willing to wait a couple of weeks this is the cheapest place for these.

The PCB design software I use, DesignSpark allows me to export a mechanical .dxf file for the PCB.
I imported this into my laser cutter software to allow me to cut a 3mm MDF sheet with holes where the MPU programming pads are:

It's a bit over the top using a laser cutter for this, but: 1) It cuts quicker and more accurately than I can. 2) The probes have an odd diameter, 1.3mm which is a drill size I don't have, but the laser can do any size hole.

I cut two of these, and used them in parallel to align the spring probes:

I ran the hot melt glue gun between the two plates to fix them.

And epoxied the wires to the molex connector that plugs into the PicKit3 programmer and the jig itself:

This jig enables me to simply press it onto the PCB. The spring contacts guarantee a good connection. And programming takes a few seconds. It's quicker than plugging a MPU into a programmer, and then transferring it to the target board.

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