Note: The WBO2 project is defunct, and these pages are no longer being actively maintained.

DIY-WB Controller Construction Notes

DIY-WB O2 Rev5

Robert Rauscher
July 2001

The PCB is setup with separate power feeds for the heater circuit
versus the UEGO controller circuit. This allows the UEGO controller
circuit to be ground referenced to the measuring equipment.This prevents
ground loops from interfering with the UEGO circuit.

The two circuits are also isolated from each other. Hence they can
be connected to two separate power sources & reference grounds.

The UEGO controller draws 10's of milli-amps of current. If using
a data logger or similar power the UEGO circuit from that piece of
equipment. This allows the ground referenced Vout to be accurate
relative to the data loggers A/D ground.

If the same power source is used for both circuits run the power
to the heater circuit first. Then run some 22 awg from the heater
circuit over to the UEGO circuit. This is still a valid connection
scheme. It will work well when using an isolated measurment tool (DVM).

Refer to the schematic for more information on component specification.

Use crosshairs in PCB corners to locate & drill mounting holes.

Note on the PCB that the heater circuit U1 and R4 have very little room
around them for heat sinks. This was done on purpose. Move those devices
off board and onto a heat sink. The through holes have been made large
enough for 20 awg wire. Be sure to heat sink both U1 & R4.

Important: note the position of U1, the regulator faces OUT from the board.

For the sensor cable use 18 awg for the heater. Use 20 awg or 22 awg
for the sensor Vs, Ip & Gnd connections, and CalR if kept at the sensor.
The wires can then be wrapped with electrical tape. Convoluted tubing
can also be used in area where chafing may occur.

Vout is ground referenced, use J12 as gnd.

If the DIPs are socketed use the good machine pin units.

There are to 16-pin DIP and one 8-pin DIP areas that have no
traces on any pin. These are extra for user mods.

None of the external board connections use connectors. Connectors
are both expensive and unreliable. Use a through hole barrier strip
on the exterior of the project box. Then run wires from the pcb to
the barrier strip.

Radio Shack has some nice inexpensive boxes. The plastic ones with
the aluminum lids work well. The lid can be used as a heat sink. The
plastic box has rounded corners. It won't tear up the interior of the
vehicle or short out against anything. Radio Shack also sells an eight
position barrier strip.

Important: Make sure that whenever the engine is run with the UEGO sensor
mounted in the exhaust that the sensor heater is powered up. Running the
engine without the sensor at the proper temperature will ruin it.

The NTK sensor to be used is from a
Honda Civic VX, 1992-1995, #36531-P07-003

It is a five-wire sensor.

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