For any add-on boards such as VR conditioners, optos and OEM interface boards
#39166
Did this a long time ago, took the open source WB controller offered by 14point7, stripped and shrunk it down to a tiny, connector sized controller.

I haven’t tested how accurate it is, however it does appear to work. Feeding spent gasses from a propane torch.
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#39172
@chipboy,

Yes, I did design the board in KiCad. However, (most of) the circuit design and more importantly the code that's loaded on the Cypress micro ( system on chip ) are all taken from the 14point7 open source controller.

All i did was choose a pin compatible surface mount version of the chip, and simply did not include the LCD.
I had to buy a Cypress programmer, think it was like $30-$40 and used that to load the code.

The Cypress controller was really inexpensive, IIRC it was ~$2.00 direct from Cypress, a hand full of resistors and caps at pennies each, a 5v regulator and a mosfet for the heater. Its been long enough ago now that I don't remember the exact cost, but i remember i was hoping to keep the cost per unit under $10 (including the price of the PCB) and I think I was able to do that. I used OSHPark for the PCB, because at the time they offered 2oz copper on a 0.8mm board for basically the same price as a 1oz 1.6mm board. That being said, I could probably get the boards much cheaper now through JLBPCB or similar vendor. I went with 2oz copper because I wanted ample current capability in the heater traces, and i wanted to minimize the effect the heater current ground had on the rest of the analog circuitry.

The idea was to encapsulate the board in a ( 3Dprinted ?) connector and seal it all up, and use 4 or 5 wires to use the WBO2, +12v, ground, liner V-out and signal ground, with the option of a NB signal on the 5th wire if needed.

The board could also be used on a PCB as a daughter card as well, that's the reason for the separate sensor connector adapter board.

Image

Edit, just pulled up my OSHpark order, it was $6.40 for 3 boards, so ~$2.14usd per board, guessing someone could get them much, much cheaper through JLB PCB or the like.
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#39251
I could post them here I suppose, if there is interest.
However the schematic is available from 14point7.
I substituted comparable SMD components but the schem is the same.

I may build a few more of these, but honestly I think it would be better and simpler for most to just buy the $35 OEM version from 14point7. Having to buy a programmer to load the code would be a sticking point for most people I think.

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