[DStage]

Hi there!
I wanted to practice EasyEDA today so I thought I can put that time into some more use Here's what I've come up with.

WBOOS Mini is a Wide Band Oxygen Sensor module based on the SLC Free, no surprise there Unlike my "regular" WBOOS project the target for this one is to be a part of a larger project such as an ECU. Its compact sizes of little over 15x15mm should make it relatively easy to fit in many designs.
The only thing it's missing to be a standalone controller is a 5V regulator as it takes its supply from the host board.

Obviously it doesn't have the LCD connector like in WBOOS or original SLC Free. However, since I've recently added a support for 7 segment LED display (based on TM1637) to WBOOS it can also be utilized in WBOOS Mini. Signals for LED display are available on the main pins.
There are a few extra pads added on the backside of the board for extra features and experiments.

Unlike in bigger WBOOS here I had to revert to a simple PWM filter for output sgnal as I counld not possible fit an active filter on a board this size with a single side component population. But many projects seem to be just fine with this approach and anyone with a OCD for filtering like me can always add more on the host board
I did manage to keep a better than original SLC solution for reference voltage. I figured that having the 5V coming from outsides gives some uncertainty over the stability etc. So I really did not want the simple voltage divider here. Add actually the TL431+resistor takes same area on the PCB as 2 resistor + a cap.

In many ways the concept is the same as with DIY-EFI TinyWb. WBOOS Mini is slightly smaller, not that size matters The TinyWb adds a serial (UART) output, I may think about it and add that to the SW as well. And obviously WBOOS Mini is a DIY module that anyone will be able to manufacture so has a potential to be cheaper, if that's important to your project.

As for the costs and manufacturing, I target JLCPCB here as always. The MCU is not kept in stock by them so it has to be specially ordered. This may be a slight complication for small orders. Thus, the project may be more suitable for a but bigger quantities like 25 pcs and redistribution to whoever needs one (perhaps together with the whole ECU).
If my estimations are correct the cost without shipment but including VAT should be under 5$/Euro.

What remains to be seen is how the tiny MOSFET deals with the heater, but that requires a real life experiments.

OK, what do you guys think? Is there a place for such a module in DIY ECU community?

[PedroV9]

Very cool! I also have a smaller version (not too small) that I use to mount the conditioner directly onto the connector.

The housing is 3D-printed, and the inside is filled with epoxy resin.

It’s an interesting approach because it reduces the number of components in the vehicle’s wiring, making it just a slightly larger connector instead of adding extra modules.

[DStage]

Oh, nice. It reminds me of the good old LC-1

I've just made mine slightly larger 15,5x15,7. This 0,55mm really hurts my feelings but this way the connectors footprint is nicely fitting 12,7mm/500mils and we all love those round sizes... or is it just me?

[DStage]

Ok, 15,5x15,5mm and that's my final word!

Of course those goldpins can be mounted on the bottom, whatever user prefers.

[DStage]

In a few days I'll be ordering WBOOS Mini+ where "+" means it can be a full standalone 12V powered controller. I basically added the voltage regulator in that variant but in a way that allows it to be cut off. By default the board is 23.9mm x 15,5mm and cutting off the regulator part makes it a 5V module identical to regular WBOOS Mini so 15,5mm x 15,5mm.

JLCPCB already has purchased the CPU for me and it's waiting for the assembly.

Main thing to check is how the transistor for the heater will handle its task. We'll see.