[Dr_C]

I wanted a simple Infra-Red (IR) Light Emitting Diode (LED) which can be programmed to strobe using any Scalextric Sport Digital (SSD) car ID signal.

The result is a small circuit board which measures 9mm x 10.5mm and which connects directly onto a standard 3mm LED and which is controlled via a 4 wire input. The device is known as a Smart IR LED.

   

The inputs come straight from the car’s digital decoder and consist of the following four signals:

+3.3V
Decoder +LED signal
Decoder -LED signal
0V

To use this new system component, instead of wiring an external IR LED to the decoder in the usual way, in this case the two LED signal wires are connected to the Smart IR LED together with two additional connections for power i.e. +3.3V and 0V. Power is taken direct from the decoder.

The Smart IR LED can take as input the standard lane change signals from various digital decoder manufacturers (e.g. Slot.it/oXigen, SCX-A or Scorpius) and it converts these signals to a mark-space-ratio strobe (with Lane change signal inversion) that follows the Scalextric protocol and therefore which functions with SSD lane changers.

Key points:

1/ The Smart IR LED can be programmed to any ID in the range 1-36. This means up to 36 cars can race together.

2/ The Lane Change function can be activated either by an incoming SSD signal with any mark-space-ratio (therefore oXigen and Scorpius decoders could be used) or with a simple high/low input signal as available from SCX-A decoders.

3/ This approach is compatible with standard SSD lane changers for IDs 1-14. It is further compatible with all IDs 1-36 when used with the ATtiny processor upgrade for SSD lane changers which I have shown elsewhere on this Forum.

4/ This approach, hopefully, will enable oXigen, SCX-A and Scorpius wireless systems to run alongside each other. And, as above, each will trigger SSD lane changers (either standard versions for 14 cars or ATtiny upgraded versions for up to 36 cars).

5/ The approach avoids any requirement to reverse engineer the products from Slot.it/oXigen, SCX or Scorpius - this is simply a ‘piggy-back’ approach.

6/ The Smart IR LED is used for car identification and lane change signalling. It is not a solution for vehicle control - this relies of track packets and/or 2.4GHz packets.

7/ I should add, this is an experimental approach and not a commercial product at this stage.

The experimentation and fun continue…

c

[Dr_C]

   

Four of the Smart IR LEDs in the foreground which are awaiting fitment of their 3mm LEDs. Eight unpopulated pcb boards in the background.

A second version of the board is designed for direct assembly onto a Slot.it/oXigen O201b2 decoder. This makes for a nice simple installation.

When this approach is used to combine SSD decoders with Slot.it/oXigen decoders. The total number of cars on track could potentially be as high as 6+20 i.e. 26 cars.

Fortunately this is within the limits of PC Lapcounter (currently 32 cars maximum). So there is already a suitable RMS in place.

c

[Dr_C]

   

Smart IR LEDs designed into a header board  which uses solder points to connect onto a Slot.it/oXigen O201b2 decoder.

When in SSD compatibility mode these decoders can normally strobe on SSD IDs 1-6. With the Smart IR LED fitted, the assembly can be programmed to strobe on any ID in the range 1-36.

The O201b2 decoder is assembled in AC mode to ensure it can run on a SSD track alongside cars with standard Hornby decoders.

The Smart IR LEDs I showed earlier have been fitted into various Scalextric cars using the O201c1 decoder with a 4pin JST plug on a flying lead. They are functioning perfectly correctly on all IDs.

I now have a grid of eight NSR Mercedes AMG GT3s which are awaiting the combined Smart IR LED and O201b2 decoders. I plan to run these on IDs 21 through to 28.

c

[Dr_C]

   

Photo 1: NSR Mercedes AMG GT3 with 6-way header socket fitted and awaiting plug-in fitment of Smart IR LED board for lap counting and O201b2 decoder for throttle/brake control.

   

Photo 2: The same NSR Mecedes AMG GT3 with the Smart IR LED electronics and O201b2 board fitted.

For lap detection and lane changing the Smart IR LED can be programmed to strobe on any of 36 unique IDs.The first six are SSD IDs 1-6. For 7 and above the SSD mark-space pattern (with inversion for lane-change) has been extended.

This particular car is currently running on ID 21.

c

[Dr_C]

   

[Dr_C]

So to re-cap:

1/ The above car uses an O201b2 decoder and is controlled using an SCP3 or ARC throttle flashed as O2. All the buttons and switches on the SCP3 function as standard for O2(Slot.it oXigen) including brake adjustment.

2/ No O2 dongle, magnets or Hall sensors are required as a completely different method of lap counting is employed.

3/ In addition to the O201b2 decoder, the car includes the electronics for the Smart IR LED function. This is programmed to strobe on any ID in the range 1-36. The strobe includes signal inversion for lane change as per the SSD method although extended out to all 36 IDs.

4/ The ID strobe merhod is compatible with standard SSD lane changers for IDs 1-14. If higher IDs are required, i.e. more than 14 cars then a simple microcontroller swap-out is required (this requires removal and replacement of a SOIC-14 surface mount conponent so some intermediate level soldering skills are required).

5/ Using the Smart IR LED aproach to lap detection, a range of under-track sensors have been designed which provide ‘signal-conditioned’ inputs to a purpose designed ‘sensor hub’ device which then transfers the detected IDs via USB to a laptop that is running PC Lapcounter RMS. The present version of the ‘sensor hub’ has eight sensor channels. Four sensor channels are for lap detection (i.e. a four lane start/finish line) and there are two pairs of sensor channels for pit entry and pit exit (i.e. two independent pit lanes).

One application option here is to run six standard SSD cars (strobing on IDs 1-6) and then to add in up to twenty additional cars running O201 decoders with Smart IR LEDs. So that’s a SSD/O2 combined system limit of twenty six cars.

Yes, that’s probably more cars than most of the world’s digital 1/32 scale tracks can handle and certainly the power levels required for this number of cars on track presents a challenge. This track power challenge is being addressed using an in-line High Power Module (HPM) as discussed in another thread.

Many thanks for your interest.

c

[Dr_C]

System testing of the Smart LEDs continues on a number of digital racetracks in a number of countries.

The photo below shows Smart LEDs which can be interfaced with standard oXigen decoders in order to generate a range of ‘SSD-style’ IDs in the range 1 to 36.

   

Each Smart LED is pre-flashed to a specific ID. Hence in the photo each Smart LED has a blue label showing the ID in use.

The Smart LED includes a standard 3mm IR LED and has a four pin JST connector.

The four JST connections are:

Red:     +3.3V from decoder
Yellow: Expernal LED+ (A) round LED pad on decoder
White:  External LED - (K) square LED pad on decoder
Black:   0V from decoder

The Smart LED reads the staystraight/lanechange signal from the decoder (on any ID) and translates the output strobe signal to the pre-flashed ID. As mentioned this can be any value in the range ID1 to ID36. As per the Scalextric protocol, inversion of the mark-to-space ratio is used to indicate a lane change request.

For anyone involved in trials of the Smart LEDs I will share a simple wiring diagram showing how to connect the Smart LEDs to commercial in-market decoders.

The Smart LEDs can be used with any decoder brand which generates a SSD conpatible IR LED strobe signal. The Smart LEDs shown are designed for use with 3.3V decoders, though earlier versions were tested with 5V decoders.

In the future, and once fully proven, the 36 car ID method may be integrated directly into the main microcontroller within the decoder.

c

[Drifter2]

Hypothetically, this concept could be applied to say a slot car with a commercial micro RC receiver and brushless ESC + motor.

[dvd3500]

words, words, words, words, words, 
I kind of feel like "The Cat" from Red Dwarf: What is it?
Is this just a way to Scorpio/Oxygen hardware on Sports SSD or something?
I don't see the use case...
Or does it make toast ? (another red Dwarf reference...)

[Dr_C]

@dvd3500, Ha ha, thanks for the nice reminder :) 

yes probably the best way to think of Smart LEDs is as a building block for developers of digital slot car systems. It extends the SSD method for car identification (and lane change requests) from the standard Scalextric limit of 6 cars up to a new limit of 36 cars.

But like all building blocks it’s useless on its own. Here it needs compatible track sensors and an interface to a race management software package. These now exist too.

So how can it be used?

Well here are some examples:

1/ A Scalextric ARC PRO or APB C7042 powered system with six SSD chipped cars plus additional O2 or SCX chipped cars with the latter two types using Smart LEDs for lap counting cross-compatibility. In our trials to date we have focused on 10 cars.

2/An O2 based system where under-track ID sensors are used in place of O2 magnets and in-car Hall sensors. Here the objective is to add options into the O2 digital eco-system.

3/ As mentioned, it’s a building block for developers. In my case the ID detection method is being tested in readiness for integration directly into some new wireless in-car decoder designs.

Yes - more words - but does that add some clarity of purpose? apologies if not!

@drifter2 - great idea :) the onboard microcontroller could read a standard servo PWM (pulse width modulation) signal instead of a generic ‘SSD-style‘ mark-to-space signal. Perhaps it could auto switch between the two formats? Below 500Hz the input is treaded as a servo PWM signal and above 500Hz it is treaded as mark-to-space signal. Do-able.

c