BMW K bikes (Bricks)

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robmack

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I reverse engineered the LCD Gear Indicator board as part of my project to build a drop-in replacement for the LCD. I then proceeded to reverse engineer some other boards and draw their schematics, as well as collected schematics from other sources and re-interpreted those drawings. The flasher unit schematic is not my work; it is available online. I'll add more as I convert the BMW OEM circuits into schematic drawings.

GPI This is the board that is located in the OEM cluster underneath of the Tachometer on the right side, containing the LCD that shows the currently selected gear:




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Basic Circuit Description
Power is supplied through pin 15 (+12V) and 31 (Ground). A diode, V7, ensures that reversing the polarity of the power will not destroy the components on the board. VIN is fed to the Start Enable circuitry and to the regulator V9. Regulated VDD supplies the chips with power as well as other parts of the circuit.

The TGPI switch connects to A, B and C inputs. Diodes, V3, V4 and V5, form a neutral detect feature that operates the Start Enable circuitry. The three transistors, V8, V9 and V10, creates a +12V signal on the output, LEERL, that drives neutral and the starter relay. Diodes, V1 and V2, detect when the selected gear is higher than 5th and will send a signal to IC1 to blank the LCD display. IC1 decodes the inputs and displays a digit on the LCD via PAD-A through PAD-G.

IC2 is an oscillator that creates a high power signal that powers the LCD. This signal is output on PAD-COM and consists of a 67Hz 100V 50% duty-cycle squarewave.

Speedometer and Odometer
This board is located in the OEM gauge cluster and converts the output from the speed sensor in the final drive into a signal that drives the speedometer servo motor.





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Tachometer
This board is located in the OEM gauge cluster and converts the output from coil #1 into an RPM reading on the tachometer gauge.




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Early Fuel Level Sensor (4L/7L lights)
This board is located in the OEM gauge cluster for the early K-bikes prior to 1985. The fuel sensor was a pair of thermistors. These devices illuminated a lamp in the OEM gauge cluster that showed when the fuel remaining in the tank was 7 litres and 4 litres. This is an interpretation of a schematic posted by Bert Vogel on K100-forum.




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Flasher Unit
This schematic was posted online at the K100-forum and I am including it in this collection.




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Clock
This schematic is of the clock in the OEM dash. To test that all segments of the display are working, press both switches together at the same time.
All segments will light up. When the switches are released, the clock will reset to 1:00. One complaint of the clock is that it only shows 24 hour time. To get the clock to display 12 hour time, use an Xacto knife to cut the trace at pin 22 (labelled "S5" in the schematic) and then take a 30GA solid wire and join S5 to VIN. This will change the clock to display hours between 1-12.




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Last edited by robmack on Sun Jun 03, 2018 11:48 am; edited 10 times in total


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Robert
1987 K75 @k75retro.blogspot.ca
2011 Moto Guzzi V7 Racer
http://k75retro.blogspot.ca/
    

Dai

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You learn something new every day. I had no idea that you needed an oscillator to drive the LCD. I'd assumed that they were a bit like LEDs; add power and away you go.


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'83 K100 upgraded to K100RS spec
Others...
'78 Moto Guzzi 850-T3, '79 Moto Guzzi 850-T3 California,'93 Moto Guzzi 1100ie California,
'03 Suzuki Blandit GSF600SK3 (NFS any more because wifey has claimed it)
    

Ringfad

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Thanks for sharing. This is great work.

Have you ever done one for the speedo amplifier ?


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;BMW;K100RS Style Black 1987 105K Km ;BMW; K1 Black 1993 51KKm ;BMW;K1100RSRed 1993 70k miles ;BMW; K100 16V Black (ex ElectricMonk)
    

robmack

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@Ringfad wrote:Thanks for sharing. This is great work.

Have you ever done one for the speedo amplifier ?
This is on my TODO list.


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Robert
1987 K75 @k75retro.blogspot.ca
2011 Moto Guzzi V7 Racer
http://k75retro.blogspot.ca/
    

charlie99

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fantastic work yet again rob

and thanks for sharing


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cheezy grin whilst riding, kinda bloke ....oh the joy !!!! ...... ( brick aviator )

'86 K100 RT..#0090401 ..."Gerty" ( Gertrude Von Clickandshift ) --------O%O
    

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