Month: September 2018

Firstly, I only ordered one push-button instead of two. Annoying, but not a big deal.

Secondly, the perfboard had logos printed all over it. No chemical would get them off. Sanding didn’t get them off. When I used a dremel, I discovered the pigment went deep into the substrate. I figured that maybe this was just the particular supplier that DigiKey was using, so I ordered some straight from the public BOM on Mouser. It is exactly the same. So I am down $34 on perfboard I can’t use.

I have ordered yet another perfboard for $23 from DigiKey from a different manufacturer. Hopefully this one won’t be covered in logos. So $57 on perfboard alone. So far!

Thirdly, I missed that the boards on OSH Park need an additional diode near the battery switch. Fortunately I had a suitable Schottky diode lying around.

Fourthly, when I was adjusting the HV it mysteriously stopped working, and the PIC started to get hot. I guess I shorted the HV to the PIC, though I don’t recall doing so. So I am down the HV and the PIC. The HV part is $14. The shipping is $10. So I am now down an extra $60 with little to show for it. Plus I had to unsolder the HV. Fun times!

Since there is little else I can do at this point, I built a prototype case with the styrene sheet. This is so I can test the positioning of the openings on the case before I get some metal ones fabbed.

Anyway, here are the boards, with a gaping hole where the power supply should be 🙁

Its time to actually start building this divergence meter:

I ordered the parts from Digikey, which have arrived. I chose to program the PIC16F628A myself, by which I mean upload the hex file from Tom Titor. Partly this is because I figure I might modify the program at some point. So I bought a cheap pickit 3 copy off ebay.

I’ve also been re-familiarizing myself with SolidEdge 2D as I would like to get the case pieces fabricated, so I will need an accurate CAD model, and I have used SolidEdge in previous projects.

In addition I have been mulling over how to actually build the case. Ideally I would like to make my own posts with a square cross-section and tap them for screws – I really don’t like the idea of gluing things together – however that is way beyond me at the moment. I also toyed with the idea of using styrene sheets  that are used in modelling. So in the end I bought samples of various materials and practiced gluing things together:

The top sheet is aluminum. The bottom sheet is steel. The left hand blob of glue is JB Kwik, the right hand blob is JB Putty. I glued some aluminum rod to the sheets with an overhang so I could try and pull them off. I roughed up everything with a dremel tool before hand and cleaned it all up with Isopropyl alcohol. In the end I was surprised how strong the bond made by the JB Kwik was, so I am reasonably confident that I can glue standoffs to cut sheets to make the case.

I also glued square rod to the styrene sheets. The bond here was actually pretty good, but they peeled off if I flexed the sheet. When I examined the styrene, it had been softened by the cement. I will probably use the styrene sheets to make some prototypes from my drawings to check that I got all the measurements right.

Now I need to start some soldering.