[Dr_C]

A small windscreen mounted two digit LED display to show car ID (race number).

Inspired by the ideas of a user by the name of Flag Slot Racer, I decided to design a two digit 7 seven segment LED display for windscreen mounting on 1/32 scale slot cars such as GT3 and GT4. The design uses 0.2 inch displays i.e. the vertical height of the numbers is approx 5mm.

The design is based on the ATtiny3226 microcontroller and can be ID programmed in a number of ways including UART, UPDI or directly from the decoder’s main microcontroller using an industry standard SPI bus.

In the first variant I plan to read the IR LED signal directly from the SSD decoder. This signal includes car ID (and whether or not the lane change button is pressed).

This approach perfectly matches the six ID method used by Scalextric Sport Digital.

As some will know, I’ve extended the SSD ID method out to ID36, so these small displays will also perfectly match this extended approach. 

The benefits of using the IR LED signal to control the display are that the interface between decoder and screen display is kept very simple, and also any change in decoder ID is immediately auto updated onto the display. (BTW the decimal point within the display can be used to signal a lane change request - i.e. a useful system diagnostic.)

Here is the prototype PCB showing the location of the ATtiny3226 and the LED biasing resistors. The LED display modules are to be attached on the other side of the PCB. The board measures 14.5mm x 12.5mm.

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[BAracer]

Now what would be clever would be if it showed the car position in the race...P1, P2 etc.

(not that what you are proposing isn't clever already!)

[Dr_C]

Hi BAracer, yes, following on from Flag slot racer’s original ‘new idea’ post for the windscreen displays there was a discussion around displaying the order of the race pack. Apologies, I am remiss in that I don’t remember who proposed this extra feature. 

Anyway, I believe it will be hard to retrofit this feature in an SSD setting but it is certainly part of my plan for the 36 ID wireless system. Here the RMS can send additional data to the in-car wireless decoder such as the running sequence.

The implementation I have in mind will display the running order as observed at the last pass of the S/F line i.e. not quite real time… but, none-the-less, it should still be quite nice.

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[Dr_C]

I am hoping this little project will move forward quite quickly - at least for the ID read-out (and lane change signal) variant.

And this is for the following reasons:

1/ the PCB has been fabricated ready for component assembly.
2/ the firmware should be a ‘simplified down’ variant of the S/F lap detection firmware which has already been tested extensively across all 36 IDs which are in scope.
3/ I need these windscreen displays as part of my ongoing track-level trials of the new 36 car wireless system. They will be especially important in helping to keep track of ID numbers as the ID pairing algorithms are tested :)

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[Dr_C]

As already mentioned the primary objective here is to create a windscreen mounted display which shows car ID in the range 1-6 for Scalextric digital and 1-36 for the new 36 car wireless system.

The two digit display panel is connected directly to the decoder via either a three wire or four wire interface.

The three wire interface uses the decoder’s IR LED signal to provide ID information.
The four wire interface uses either uart, I2C or or SPI for communications between the decoder and the display module.

While the display is intended for windscreen mounting a nice secondary application will be implemented too. In this second usage case the display can be mounted into a track piece and integrated directly with an IR phototransistor based ID sensor… the result will be a track piece which displays car ID as the car traverses the sensor. This should be a very nice piece of diagnostic hardware - and it’s a zero effort by-product of the windscreen display project.

Results for the windscreen display AND the ID displaying track piece will be shown in due course via this thread :)

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[Drifter2]

Being able to quickly and easily read the ID of any car would be a handy feature.

[Dr_C]

Thanks Drifter2.

For the track piece, I’m thinking of a Scalextric single lane track piece with a window cut at the edge of the running surface for the small two digit display module. This will be connected to a small satellite sensor board for IR ID detection. There will also be a small rectifier/regulator circuit. The idea will be to run the device with SSD power or simple DC (the latter could be from a bench power supply or for portability a small battery).

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[Dr_C]

   

The project is starting to take shape :)

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[MrFlippant]

Very cool to see a functioning prototype as opposed to an image taken from an Amazon product page.

Keep on innovating! :)

[Dr_C]

   

A car displaying its ID.

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