WBo₂ 2D0 OEM Wideband Unit

2D0 was designed to be a low cost unit that is integrated into other devices. This often means using special connectors with point to point wiring. The 2D0 module can be supplied with or without connectors. (refer to the order page). The additional connectors Tech Edge can supply include the three 5.08 mm (0.2") pitch headers (x3, x4 & x8) with their mating plug-in and screw-to connectors, RJ45, green power and red status LED, & circular 8 pin panel-mount cable connector. These are shown at left in front of the basic 2D0 unit. Click on the image for bigger pop-up. Note that the 0.2" (green) connectors shown will normally be supplied not soldered in as it's possible to insert them so the header leads face inwards (minimises the unit's footprint), or outwards (easy maintenance).

The circular male 8 pin connector is the same as that found on other version 2.0 WBo2 units and is, solder bucket style & panel mount with the nut and washer behind the panel. This connector mates to a female 8 pin that is on the WBo2 end of the sensor cable. These cables are available in a few standard lengths (2.6 m & 4.0 m are the most popular).

An additional RS232 cable (with RJ45 and DB9 connector) for PC communications is available separately.

Jumper shunts J1 & J2 are located at the centre of the board, J3 is located between pins 3 and 4 of the 0.2" headers. Click to enlarge the image.

J1 - (FLASH) should normally be OFF except when using the rescue re-flash function to update on-board firmware, and only then if there is a corruption of main program memory. Refer to WButil.exe for details and HXF files.

J2 - (CAL) should normally be ON at all times, and is used for factory calibration and testing Note that free-air sensor calibration is quite different and is done using the WButil.exe utility.

J3 - (SIG GND) provides a link between the SIG- output and GND and is used when a single ended output (this is WB_lin+ on the SIG+ pin) is required. Remove J3 when differential output is required, but in this case ensure WB_lin- on the SIG- pin is connected to the destination input's GND_d point. For differential output there should not be more than a Volt of so difference GND_d and the 2D0's GND point. This topic is discussed further here.

The WB_lin output on 2D0 has default values a little different to other WBo2 units. Remember that the WBo2 configuration program WButil.exe lets you change these defaults.

Dual Slope Linear Output

Rather than the default linear AFR = 9.0 to 19.0 span of WBo2's standard 0 to 5 Volt output (see it here), 2D0 has a Lambda=0.65 to 3.0 span (*) over the 0.25 to 5.0 Volt range in two linear segments centered about Lambda = 1.2 at 3.25 Volts. This is shown in the graph at right. (* equivalent AFR range is 9.56 to 44.1). The effect of this is to reduce the resolution of the rich tuning range (AFR=9.6 to 17.6 covers 3.0 Volts) at the expense of better resolution in the lean range.

The actual formula for the dual slope follows the general straight line formula y=mx+c. In the formula below, L is Lambda, and V is voltage:

• Rich (L = 0.65 -> 1.2) :   L = (0.55/3.0)*V + 0.60467    (ie. L = 0.18333*V + 0.60467)
• Lean (L = 1.2 -> 3.0) :   L = (1.8/2.0)*V - 1.5                (ie. L = 0.9*V - 1.5)

Note very carefully, the rich graph starts at Lambda = 0.65 and a voltage of 0.25 Volts. The lean graph ends at a Lambda of 3.0 and Voltage of 5.0. Outside that range you should consult the next paragraph on Bounded Output. Lastly, note that stoich (ie. Lambda = 1.0) has a voltage of 2.159 Volts. To convert the above formula to AFR, remember that:

• AFR = AFR_stoich * Lambda.

Another 2D0 feature is the setting of valid Lambda limits by clamping WB_lin to a fixed voltage when Lambda is higher or lower than the bounding limits. This scheme allows a recording device to determine if the WB output is valid (must be greater than 100 mV). The default Lambda bound limits are 0.65 and 3.0 and a bounding Voltage of 100 mV. If Lambda is richer or leaner than these values then WB_lin will be fixed at 100 mV. In the image at right this is shown as the grey area to either side of the light green (rich) and the pink (lean) range. The actual clamped value is shown down the bottom in the light blue region.

It's possible to change the clamp values for 2D0 by modifying configuration parameters. The WButil.exe program is run, and in the Comms tab the following commands are manually entered in the Command box. The same program can re-program the output table(s) from the AFR Tables tab. This sequence defeats the clamping action by setting the rich Ipx threshold limit to 0 and the lean limit to 0x3000.

• s6300   set low threshold (low) at 63 to 00 (hex value = rich Ipx threshold)
• s6400   set low threshold (high) at 64 to 00
• s6700   set high threshold (low) at 67 to 00
• s6830   set high threshold (high) at 68 to 30 (lean Ipx threshold)
• w         write to update the EEPROM (takes a seconds or so)

Remember that if you re-flash the WBo2 unit with newer firmware, the setting entered above will be lost.

The SV_out signal is intended for analogue displays like the LD01 but can be used as an alternate, lower resolution, single ended output.

To generate SV_out, the processor uses a 65 word lookup table with linear interpolation. It converts the normalised pump current (Ipx) into a 10 bit value representing SVout. A hardware PWM (Pulse Width Modulation) pin on the processor generates the actual SVout voltage.

SVout is compatible with the Vout signal from the original oz-diy-wb unit (and the 1.5 unit's Vwb). It can be used to drive the analogue LD01 display (or the older 5301 if you change its connector).

The default SVout, shown at right, varies between about 1.0 Volt for a very rich mixture (Lambda=0.6 or AFR=9), to 2.50 Volts for a stoic mixture, and to 3.1 Volts for a lean mixture (AFR=25). In free-air the SVout should be exactly 4.00 Volts when the unit has been free-air calibrated correctly.

The default AFR vs. SVout relationship is shown in the Vout table/graph page. The analogue Vout is a continuously available signal that may be logged with a high speed logger. We recommend at least a 10 bit converter for best accuracy, but as the measuring range is small (less than 3 Volts), measuring resolution is reduced compared to using a smaller AFR range over a larger voltage range.

Note that as well as the three RS232 signals on Y1, for convenience, the RJ45 connector (Y8) also carries those same signals. click on the image to see the way the RJ45 is numbered. The 2D0 unit transmits logged data (Lambda/AFR and the analogue and pulse inputs) on its Tx line [pin 3] and receives commands (from PC or display) and code updates from a PC on its Rx line [pin 2].

The diagram at left shows the wires within the cable and also the connections at each end. Note the pin names change from left to right - the 2D0 unit's Tx pin transmits to the PC's Rx pin (and vice versa). [pin 1] is the shield for the Rx and Tx data lines as well as being the return data path.

WBo2 to PC cable

Here's an image of the actual RS232 cable for connection between a PC and 2D0's RJ45 connector. The cable is used for either logging to a PC, or for re-flashing its code (under control of a PC). If you need to extend the cable then a standard straight through male-female DB9 extension cable should be used (ie. not a cross-over or null modem cable).

Serial Data logging - Lambda, Analogue & Pulse

As noted above, as well as the Lambda/AFR input the unit produces, there are two extra inputs ..

• one analogue input P1 (0 to 5 Volts input - output is logged in user 1 field), and
• one pulse input P3 (can be used as an RPM input, output is logged in the RPM count field),
• (and P3 is their common GND),

.. that can be logged, although no buffering is provided for these inputs. The actual output is logged in a data frame that is fully described in the logging information section (default frame type is 1). The pins of the PCB for the inputs are shown in the diagram at right or can be found in the top right hand corner of this popup overlay and labelled unbuffered inputs.

We suggest you update to firmware 0658 or higher, so this section if for reference purposes and applies only to the 0652 firmware.

Operation with firmware 0652: Press the Auto-Cal button for at least 4 seconds, or until the red LED begins a fast flashing to indicate it's performing an Auto-Cal. If the sensor is in stable free-air then after 15 seconds the LED will do a slower flash indicating completion of the operation. At this point the free-air calibration has been calculated but not saved. There are two options

• to complete and update the calibration, push and hold the button for two seconds (and less than 4 seconds). A new free-air calibration value is written and the red LED displays normal status again. The amber heater LED will do a fast flash for about 1.5 seconds to indicate that the calibration parameter is being updated.
• to stop the new value being saved, give the button just a short press.

After either operation, the red LED will return to showing status (normally this will mean being on solid). Note that if you don't see the amber heater LED doing a short quick flash, then the new calibration value has not been saved. If the new value is not saved, to retrieve the old calibration value, simply cycle the power to the 2D0 unit, and it will reload the previously saved value.

The image shows the 150k ohm resistor that should be added to the underside of the 2D0 board to add support for the LSU 4.9 sensor. This resistor supplies the necessary bias current. and runs between Vs and +5 Volts - it must be removed if you revert to an LSU 4.0/4.2. Remember that you also need different firmware for the LSU 4.9 sensor that operates the heater at a different impedance and has other specific modifications. The firmware is available from the HXF files section.

WARNING : Operating the LSU 4.9 with LSU 4.2 firmware will result in the heater being over driven and short sensor life or even sensor destruction. Using the LSU 4.2 with 4.9 firmware will also result in inaccurate results but, importantly, too-low heater temperature which may also shorten its life as it cannot burn off impurities.

The image also shows another shot of the parts for the 2D0 Auto-Cal modification.