BMW R1150 Fuel Indicator Module
Developing systems for motor vehicles presents the engineer with one of the toughest environments for electronics. Consideration for wide voltage ranges, high voltage spikes, reverse polarity situations, significant temperature extremes, and shock and vibration are just a few issues to be considered. To test our designs in these environments, we choose to develop a module for the BMW R1150 series of motorcycles.

Background Information
The original BMW module is called the "Needle Dampening" module. It is located in the fuse box, and has four pins. Battery Negative, Battery Positive, Sensor, and Lamp. The module monitors the low fuel sensor, and if the sensor stays in a particular state for approximately 19 seconds, that state is indicated on low fuel lamp on the console. If the sensor line is low (negative) for 19 seconds or more, the low fuel indicator is illuminated. If the sensor line floats (no polarity) for 19 seconds or more, the low fuel indicator is turned off.

Our Design
Our goal was to take the original BMW module, and improve upon it. We did that through the following:

Identical Form Factor - Our module had to be the same size as the original. This allows the standard BMW cover to be used, as well as creates a module that plugs in without any modification to the motorcycle.

Lamp Test - Upon turning onthe ignition key, the module fades the fuel lamp brightness in and out four times. This tests the lamp, and compliments our intelligent brake controller, another RADDAS R&D project.

Voltage Indicator - After the lamp test, the module conducts a voltage assessment of the motorcycle's power system. The voltage is then blinked on the low fuel lamp. The system uses 300 millisecond blinks for numbers one through nine. Zero is blinked using a 900 millisecond blink. And a period is indicated through a 100 millisecond blink. Each character is separated by a one second pause. For example, the voltage 13.20 volts in indicated:
Blink PAUSE Blink-Blink-Blink PAUSE Short-Blink PAUSE Blink Blink PAUSE Long-Blink.

Low Fuel Timer - When low on fuel, the standard BMW module illuminates the low fuel lamp. Our design does that, however once a minute it blinks the amount of minutes you have been in a low fuel state. For example, after nine minutes, the lamp blinks nine times then returns to steady illumination. This provides an escalating warning blink as time passes.

Critical Low Fuel Indicator - After 15 minutes of low fuel the module goes into critical low fuel mode. This replaces the steady illumination with a continuous fade in and out. For example, after 16 minutes, the lamp with blink 16 times, then fade in and out continuously until 17 minutes, where it will blink 17 times, then continuously fade in and out.

Status Memory - Low fuel timing isn't as useful if it's reset after the motorcycle is turned off and then on again. Our module uses NVRAM to store its current state. This memory doesn't require any power, and is retained regardless of ignition or battery power. For example, assume you have been low on fuel for eight minutes, and turn the motorcycle off without refueling. Upon turning the motorcycle on again, the module will go through its lamp test and voltage display, then the low fuel light will blink eight times then illuminate steady. Upon refueling the motorcycle, the low fuel light will be turned off, and the memory reset to zero minutes.

Project Outcome
This replacement module has been a success in our R&D. We have determined that there isn't enough market interest to make this a commercial product. However, the vehicle indicator firmware libraries, and parts of this circuit design will be referenced for future commercial RADDAS designs.

Needle Dampening Module
Pictured above is our R1150 Needle Dampening Module with the protective cover removed. The module plugs directly into the BMW without any need for modifications.