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Custom built digital power base misbehaves

1553 Views 9 Replies 6 Participants Last post by  anttu
I've managed to build an scalextric digital power base using the schema and code from Electric Images.
Everything seemed to work fine with one car running on a simple oval track for at least 5 min. After that I added a straight lane changer and that's when confusing things started to happen.

When the car goes over the "eye" of the lane changer, the car stops immediately and leaves buzzing on the track (a little like putting an analog car on a digital track). The lane changer also sounds strange (tr-tr-tr-tr), like it tries to flip the lane, but can't. If I lift the car away from the track and wait a few seconds and then put it back, everything is fine until I run over the lane changer again...

The thing is that I can get it working by adding a small resistor in series with the 12V power feed to the track. I actually noticed this by accident, because I removed the fuse for the track power and put an amp meter in its place (because it was the easiest place to break the circuit on) to make some measurements, but then everything worked fine
I then put back the fuse, and the problem was there again
Also tried a short cable, same thing....I almost went nuts! What could be the difference between using the amp meter and a fuse/cable?? Hmm...the shunt resistor! I then tried replacing the fuse with a ca 1ohm 5W resistor, and everything worked fine again!

Can someone explain to me what's going on here!? I'm confused. Why isn't this taken into account in the schema on the Electric Images site?

Btw, I notice that the schema for the original 4 car power base from Scalextric, found here, does include some resistors in series with the track circuit (R15, R16, R18), but I understood from some other forum thread that these are used for current monitoring by the controller. Or can they be there for some other reason too?
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Ok. Thanks for the tip. I have actually thought about sending Ian an email, but have been too busy coding my win application that communicates with the processor the last weeks

The idea of the project is to not buy the rather expensive advanced power base but instead build it myself, as all the hard work is already done by the guys at Electric Image, with the addition of an USB interface to communicate with the device.

I can tell that at the moment I can read all handset data, track current (not verified if accurate), track power enabled flag and show this data in a WinForms application. I can also take control over the power base and let data flow through the application, read from the handsets, before sent to the cars, and thus be able to control separate channels (cars) from the application as I like. This gives me the possibility to have pace cars running around the track at static speed. In future I might implement some recording/playback to run ghost cars (just for the sake of learning).
I have also built a translation module that converts my PIC communication protocol to the SNC protocol so that my application can forward and receive data to/from e.g. PC Lap Counter or SSDC over a virtual COM port which should give me all the joy these applications can provide with fuel consumption etc...

The next big thing to get to work is car detection using IR sensors, which also can be found on Electric Image's pages. My goal is to incorporate this code into the same PIC and get that data over the USB line too.

If someone is interested I could post some pictures/screenshots with the current hardware/software status.
I'm might perhaps release the code of the application as open source licensed sometime, but I think I'll wait 'till it's more stable
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I've actually started a blog about my home projects (mostly scalextric stuff at the moment). Please take a look at

I got the ID sensors to work and now it's only a matter of software hacking to get it into PC Lap Counter or SSDC!
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QUOTE (chris99 @ 1 Jan 2013, 17:40) <{POST_SNAPBACK}>Hi Anttu,

Did you ever get any further with this project?


QUOTE (GregK @ 1 Jan 2013, 17:53) <{POST_SNAPBACK}>I think that this might be the result.

Hah, funny you

I've actually found a fix to the "crashing-at-lane-changer" problem by adding a electrolytic cap with a few houndred uF near the PIC.

I've also finally got the circuit board built into a box with connectors, so anyone (at least I think) can set it up and drive.
Regarding the ID sensor, it's also implemented and connects to the box, however I'm having some problems with it not "seeing" all cars all the time (at least last time I tested with a faster car).

Below is a picture with the whole setup

What's working so far is of course standard driving but using my own software I can also
- make throttle calibration
- setup brake settings
- override any hand controller and that way create pace cars
- lap timings (best lap for each car)
- convert my usb data to the standard SSD protocol and using a virtual COM port fool any SSD compatible software to belive it's communicating to a real device and make use of their fuel management, pace cars, lap timings etc etc

However, I still have a few problems that must be fixed
- for some unknown reason the USB communication is dropped randomly, causing the virtual COM port commuinication to be dropped and the cars to stop working.
- the ID sensor (as mentioned above) drops too many laps to be usable at all, however, other time I tested it, it almost worked 100%.

One thing I can admit, in case someone else tries to build something similar, you will certainly not save money on it!

I thought the original SSD PB was overpriced, but have changed my mind now that I know how much the parts costs and how much work it actually takes to build your own. However, I have the luxury to be able to implement whatever I want in my PB
And it has also been interesting and I've learned a lot!
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