Author Topic: LED Replacement Board for Gear Indicator in OEM Cluster  (Read 1314 times)

Offline rbm

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LED Replacement Board for Gear Indicator in OEM Cluster
« on: March 09, 2018, 07:14:42 PM »
I'm finishing up working on a new electronic board and posting my progress here.

The age of our bikes means that certain electronic components, like the LCD displays in the instrument cluster, are reaching their end of life.  The gear indicator is one of those components that slowly dies by having the liquid crystal fluid leak between the glass.  The LCD used by BMW is special and not available from any electronic parts supplier in the world.  But this is where my board comes in.  The board I've designed is a drop-in replacement for the LCD gear display.  It will fit on the GPI board inside the cluster and will replace a failed LCD display.

Below are pictures of my working prototype.



The board is held in with 2-56 screws in the original holes.  The board shows as being a little oversize but I'll correct that in the next batch of printed circuit cards.  The displays I chose are Red in colour but I can choose other colours as well.   It is necessary to make one small modification to the GPI board to get this to work.  The modification consists of cutting through one of the PCB traces on the board and soldering a small jumper wire across two pins on an IC.  The modifications are not difficult.  You can see the modification in the photo above, right at the top of the GPI card.



Others have added a LED display to the OEM GPI board but needed to heavily modify the board in the process.  Not here.  There are small pins that contact the original pads on the GPI board, as you can see in the photo above.

I have one last task in this project and that is to design and 3D print a part to accept the two mounting screws.  Once I have that complete, I'll start to offer this for sale.

6th Gear Modification
Slightly related to this, it is possible to modify the BMW GPI board to indicate 6th gear.  I helped a guy with this modification as he was installing a K100 cluster on a three-wheeled vehicle.

The modification is to add a small jumper as illustrated in the photo below.  Once done, the GPI board will indicate gears 1 through 6 and neutral.

  • Regards, Robert
Toronto, Ontario

1987 K75 - Build Blog @http://k75retro.blogspot.ca/

Online Martin

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Re: LED Replacement Board for Gear Indicator in OEM Cluster
« Reply #1 on: March 10, 2018, 12:50:02 AM »
 :clap: :clap: As always an excellent piece of engineering.  :2thumbup: :2thumbup:
Regards Martin.
  • North Lakes Queensland Australia
  • 1992 K75s Hybrid, Lefaux, Vespa V twin.

Offline billday

  • ^ SuperNatural Motobricker
  • Posts: 996
Re: LED Replacement Board for Gear Indicator in OEM Cluster
« Reply #2 on: March 11, 2018, 10:02:52 AM »
  Once done, the GPI board will indicate gears 1 through 6 and neutral.


That's so awesome. My K only has five gears, looking forward to having 6 after I install this mod.

Seriously, thank you for your service!
  • New York State, USA 10977
  • 1985 K100

Offline KRider

  • Motobrick Curious
  • Posts: 25
Re: LED Replacement Board for Gear Indicator in OEM Cluster
« Reply #3 on: March 18, 2018, 11:19:35 AM »

Looks real nice! I know some use that board to get off the gear neutral indicator with a universal digital speedo, tacho instead to use relays. But should it be possible to use that board to to get a gear indicator to work in a universal speedo with built in gear indicator?


Offline rbm

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Re: LED Replacement Board for Gear Indicator in OEM Cluster
« Reply #4 on: March 18, 2018, 11:39:46 AM »
Hi,

No, it's not possible to get this board to drive the typical integrated gear indicator in an aftermarket gauge. The only functions you can "export" from this board is neutral detect and start enable.

The aftermarket gauges that I have seen offered on Ebay and through custom shops provides 6 individual wires to drive the internal display, each wire dedicated to a gear number.  The gauge expects the wire to be grounded to indicate the selected gear.

This OEM board has a BCD to 7-segment decoder chip (a CD4543) that will drive each outputs on the chip in combinations that represents a decimal digit between 0 and 7 on the LCD display.  See my OEM schematics page for the details. There is no function on that chip that is compatible with the gauge.
  • Regards, Robert
Toronto, Ontario

1987 K75 - Build Blog @http://k75retro.blogspot.ca/

Offline KRider

  • Motobrick Curious
  • Posts: 25
Re: LED Replacement Board for Gear Indicator in OEM Cluster
« Reply #5 on: March 19, 2018, 06:58:25 AM »
 Ah, i see should be to good to be true:) Thanks for your answer.
 I have send you a PM about the TPGI board you have have designed.

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