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Upgrading the Scalextric APB C7042

Just a few points of clarification regarding the above APB upgrade posts:

1/ The optical isolator block. 

This is an alternative rather than addition to the widely used ‘Riko’ cable i.e. the opto block contains both optical isolation I describe PLUS the chip which converts from USB to RS485 - the latter being the format required for communications into the APB. Optical isolation is modern practice when using the RS485 protocol in industrial environments. Hence the existence of this off-the-shelf ‘block’. The purpose of optical isolation is to remove ground loops and to better protect the system from noise spikes and electrostatic damage. Optical isolation achieves these objectives very effectively in industrial settings. That said, whether the approach helps protect the APB from it’s known sensitivities to electrostatic damage is unproven at this point - time will tell :)

2/ The high speed sensors.

These upgraded sensor boards enable the APB to be located in places on the race track where speeds may reach 10m/s and still achieve 100% accurate lap detection. The standard powerbase is good to approx 6-7m/s which is slightly less than the max speed of standard out-of-the-box Scalextric F1 cars. So this upgrade is all about moving the APB into a niche ‘enthusiast’ zone where higher performance cars (e.g. NSR in my case) are being raced on the SSD platform.

3/ The pit sensor board.

This is based on the RCS64 (and Kare) software architecture and firmware. It provides an alternative solution to the ‘Pit-Pro’ approach for RCS64 and it adds in start finish lighting control as a bonus. This is all thanks to the RCS team and Kare’s very nice firmware. It’s a compact solution.

All three of the above have been tested extensively on a routed track and plastic track over many months - many thanks to Dave L for those many months of endurance testing and racing support.

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Another area of interest to me, which maybe is of interest to others too, is the subject of increasing current drive from the powerbase.

There is an established method which involves opening up the powerbase, cutting connections and tracks and then adding some rewiring. It has been in use for many years but does impose certain limitations which I wanted to avoid.

Instead, I am exploring an approach which is analogous to systems in the audio HiFi domain where separate modular components are wired together with the final stage being a high power amplifier.

This approach uses what I term a high power module (HPM) which connects between the powerbase and the track. The powerbase provides its track packet signal via (yes you guessed it) an opto-isolator. The powerbase itself is unloaded. All the track power (current) is provided directly into the HPM from a variable voltage power supply. In my case this is a Fusion 600W Power supply.

The advantage of this approach is that the HPM can be used to upgrade the APB and ASrC PRO. I have built a batch of mark1 prototypes what are currently under test at track level. This version uses 34 Amp rated MOSFETs and includes current overload sense circuits too. It has already been shown to function correctly with SSD decoders on routed and plastic raceways. The mark2 prototype will include D132 compatibility.

The whole point is to provide a route to six car operation where high current motors are in play e.g. NSR evo king etc. And, also the approach provides a route to meet the higher current requirements when more than six cars are in play, for example when extending track power for a 10 car race, or perhaps 14 cars or more :)

As the usage cases for the HPM described here extend beyond just the APB, I shall start a new thread on the subject. It is none-the-less a useful upgrade in the making for the APB and other powerbase based systems.

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Here is one of the mark1 prototype HPMs. Power flows along the red/black wires from the power supply to the HPM. The SSD squarewave AC signal then flows along the thicker yellow/green wires from the HPM to the track. The thinner yellow/green wires are used to sample the track packet signal from  the main powerbase (via an opto-isolator).

The photo dates back to May 2023 when trials commenced. In the trial shown in the photo a 10Amp bench-top powerbase was used rather than the Fusion 600W I mentioned earlier.

The prototype includes both an electronic current sense fuse (resettable) and an automotive blade type fuse as a final level of protection.

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(14th-Nov-23, 05:37 PM)Dr_C Wrote:  Thanks Andy,

And just to add, the ‘riko cable’ is a well established and well liked solution. For most, a mean time to failure of 5 years sounds pretty good. The opto-isolator approach is simply another option for consideration. As mentioned the module is available online from computer stores. 

‘DSD TECH SH-U11F Isolated USB to RS485 RS422 Converter Built-in FTDI chip for Industrial Application’

If anyone is interested, it does require a three wire connection into the APB i.e. A,B and 0V. And of course, these three wires are fully electrically isolated from the incoming USB wiring - which is the whole point :)


That's a very neat combination of isolater and RJ12 adapter. Do you have a link to where I could find the RJ12 board? Thanks

Hi SlotracerM,

There are three options:

First simply to use the screw terminals which are fitted as standard and connect a 3-wire cable which has an RJ12 plug at one end (I will share a wiring diagram).

Second is to use the RJ12 printed circuit board which can be fitted onto the screw terminals of the opto module using 90 degree header pins. This reduces the risk of cable strain.

Third is to use the RJ12 printed circuit board as replacement for the standard screw terminal block. This is my preferred approach as per photos earlier in this thread and again it minimises the risk of cable strain.

I have plenty of the small printed circuit boards (PCBs) so please send me a private message using this forum if you would like me to pop one in the post for you.

While I remember - I will follow on with some wiring photos/diagrams. There are only three wires so it’s absolutely straight forward.


Follow the link above to see further details on how to install the DSD TECH opto-isolator block to interface between the APB C7042 powerbase and the USB port on your RMS computer.


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