Just a reminder, the above board made by APCircuits has worked out well. They are a 7/7 mil service however the board was designed for 6/6 mil process of OSHpark. The problem was the turn around. APCircuits had the order on a Wednesday night and it was delivered Monday afternoon. Total cost is $88 dollars shipped with Fedex Priority which was $30 for 4 boards. OSHpark is 17 shipped for 6 boards.
APCircuits are very good, they reminded me that there were “errors” in the board, but as previously mentioned I told them to go ahead. I haven’t found a single problem with the boards and I’ve tested all the small traces. I have tested the RTD sensor lines but they are larger to decrease resistance so I’m not concerned.
Above is the board connected to the debugger, battery and a single full bridge setup which is connected to my 4 setup test arm used in thermal testing from here. This means it’s pretty much equivalent to the Stages One powermeter. Single sided, but that’s just for testing out, coding and debugging.
Below are a few more pictures.
I expect that I’m going to have to re-adjust timelines. I’m away beginning of next month for a wedding and waiting until I’m back to order the strain gauges needed. I’m going to look into re-adjusting my proposed schedule and see what I can do. The “to do” list is still extensive but nothing impossible. The hardest thing really was the reflow. While still not perfect it’s fine. Again, the solution was to ditch the BGA package. That’s advice for any hobbyist with a DIY reflow oven. BGA is too much of a headache, QFN is hard but not impossible. Still haven’t received any import bill for mouser yet.
- Finish coding that couldn’t proceed until the boards were completed and working
- I only coded initially for one side
- I’m cheating and only outputting raw reads to the power, this is mainly for debugging
- Sort out UART connection to help “debug”
- Look at implementing TE/PS measurements – This is low priority as no head units can read it
- I won’t code thermal until later and I get a sample RTD from omega
- Enclosure design – I decided to hold back a bit on this due to adjustments that might need to be made for the board design.
- Instrument another crank (or V3 to conserve cranks, have to rework it by removing old gauges and installing the new ones in the right locations (slight movement and different gauges)) and connect up powermeter.
- Mount battery, measure current consumption.
My rate of work on this has to slow down anyway from both a financial position and a time position. The board was the main hurdle at this point, right now getting it together. However I am seriously looking at Kickstarter when it comes to Canada in order to offer the Board (~$40), Dev units ($500 – 600), and final units on Hollow Forged Cranks ($700 FCC Approved). At least that’s the goal. I’ll know more when I get circuit board manufacturing quotes and find out minimum order quantities in a few weeks.