BMW R1150 Turn Signal 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.
The original BMW module has four button functions: illuminate left signal, illuminate right signal, illuminate both signals (hazard mode) and cancel signals. The original module also has a power lockup that allows it to stay powered in hazard mode, even if the key has been turned off. Finally, on systems with electronic speedometers (like the Rockster), the module has circuitry to do distance-based turn signal cancellation.
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.
MOSFET PWM - Pulse Width Modulation combined with MOSFET transistors allow efficient dimming of the lamps. This can be used for attention-grabbing fade effects, or other features, such as running lights.
Lamp Test - Upon turning on the ignition key, the module fades the signal lamp brightness in and out. This gives the user an expected illumination of the console lights, so they can spot burnouts.
Burnout Detection - Built in current monitoring checks for signal lamp burnouts. If a burnout is detected a short blink occurs followed by the normal blink on the side with the bad lamp. This unique flash pattern is more indicative of a burnout than the faster blink used by BMW. The current detection is an adaptive algorithm, meaning the module will adapt different bulbs.
Voltage Indicator - After the lamp test, the module conducts a voltage assessment of the motorcycle's power system. The voltage is then blinked on both indicators. 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 13.0 volts in indicated:
Blink, PAUSE, Blink, Blink, Blink, PAUSE, Short-Blink, PAUSE, Long-Blink.
Turn Strobe - Pressing a turn signal button twice will cause rapid strobe sequences to occur then automatic turn signal cancellation. This is useful for lane changes and other times when you need to get the attention of nearby drivers. The strobe can be initiated any time the signal is on, by pressing the same button again.
Power Lockup - The turn signal module can lock in a power feed once it has been turned on. This allows key-off operation of hazard and courtesy modes. For power savings, after the power lock is automatically turned off by the module, less than 10 micro-amps are used by the module.
Courtesy Illumination - Pressing and holding the hazard button after turning off the key will enable the courtesy lights. The timer keeps the lamps on for 3 minutes. When only 30 seconds of light remain, the indicators rapidly blink several times as a warning that the timer is about to expire. You can restart the timer at any time the lamps are on by pressing the left turn signal button again for three seconds. The courtesy mode can be canceled by pressing the turn signal cancel button for three seconds, or turning on the key.
Hazard Lockup - If the module is put into hazard mode (while key is on), the hazard mode will continue to operate after the key is turned off.
Hazard Mode Select - The hazard mode has multiple profiles. Pressing the hazard button again while in hazard mode moves between these different modes. Hazards can be canceled by pressing the cancel button. The modes include:
- Standard: Both lamps blink on and off simultaneously.
- Escort: Both lamps strobe twice simultaneously, pause then repeat.
- Pull-over: Left lamp strobes twice, right strobes twice, then repeat.
- S.O.S.: Lamps simultaneously blink international distress code S.O.S.
Hazard Auto Drop - Pressing the right or left turn signal button cancels the hazard mode and operates in standard turn signal mode. Pressing the hazard button again causes the hazard to return to the last hazard mode used.
Hazard Battery Saver - If the hazard mode is enabled, but the motorcycle is turned off, the module continuously monitors the system voltage. If voltage drops below 11.0 volts, the module is turned off to prevent excessive drain on the battery.
Hour Meter - An hour meter measures up to 10,000 hours and can be accessed during startup. Pressing and holding the left turn button during the startup routine causes the hours to be blinked in the format xxxx.y, where x indicates the total hours since reset, and y indicates tenths of an hour. The numbers are indicated in the same fashion as the numbers for the volt meter. The hour meter can be reset by pressing all four control buttons (left turn, right turn, hazard, and cancel) during the startup routine.
Accelerometer - Through use of an on-board accelerometer, our module monitors gravity and lateral acceleration in real time. This information is then used to automatically cancel the turn signals after the rider exits from a turn.
Serial Port - The built in serial port allows connection and communication with future modules. For example, a communications controller can be added to allow signal button control of two-way radios and other devices (see Multilevel User Input). Or an LCD can be connected to display acceleration, menu systems, system voltage, operation time, and any other features of the module. You could even connect your iPod or other music player, and control the volume, play/pause, and skip features all from the convenience of your handlebars.*
Multilevel User Input (MUI) - It's rare that something is natural to use, and full of sophisticated features—the MUI is one of the rare exceptions. The MUI allows all four buttons to function normally (turn left, turn right, hazard, and cancel). However, the MUI allows multiple buttons presses for a total of 13 functions from the existing handlebar control buttons. Extra care was taken to make sure function presses do not interfere with each other. And a unique algorithm allows multiple buttons presses with minimal keystrokes.
Higher Visibility Mode (HVM) - Pressing all four buttons simultaneously will toggle the HVM. This causes all signal lamps to be fully illuminated. Turn signals still function in an inverted state. This mode was developed for use during heavy fog to increase drivers' awareness of the motorcycle.
Auto-Cancel Disable - Pressing and holding the Cancel button during the fade in/out startup sequence will disable the auto-cancel feature until the motorcycle is restarted.
This replacement module has been a success in our R&D. We learned a lot about how to deal with a noisy electronic system, as well as the need for accelerometers that can deal with a small signal to noise ratio. No determination has been made regarding making this a commercial product. However, we were able to significantly improve our vehicle indicator firmware libraries, and create very successful acceleration and button control handler algorithms for future products.
* Listening to any type of audio while riding may be dangerous. Digital Indigo does not advocate listening to audio while riding, and assumes no liability for the consequences of doing such. iPod is a registered trademark of Apple Computer, Inc.