People have been reporting problems with Superslot DPR modules. Cars will suddenly go out of control, either going to max speed or stopping. Cars will then not go until the car has been removed from the track and replaced to re-boot the car.
OK, I've been head down on this for a while trying to bottom the issue.
Here are my findings, and a solution.....
To start with lets dispell a few myths:
Axle proximity has nothing to do with this. I've tried with the chip on the roof and it still happens. Equally proximity to the track has no effect.
Missing ferrite man is not the cause. My best "faulting" car has both in place at guide and motor.
Powerbase is not the cause, I've had this with 4PB, stock V1.5 6PB, and PB-Pro-SHA
So a few thousands of laps later what have I found?
With no LC in the circuit you have no problem. So we do have an electrical noise problem. Trials with the chip isolated shows it is not an inductive effect from axle, passing LC coils etc, it has to be noise that is conducted up the wires, i.e. picked up from the rails.
First thoughts were that a corrupt data packet causes the runaway or stopping. As the occurance of the fault always happened immediately after crossing an LC I thought it was possibly the break in the current at some critical point in the read sequence. Or the other thought was that the processor was getting a reboot and then defaulting to zero or full throttle.
Wrong.
I lashed up a DPR with a 470uF capacitor across the 5V supply to the chip.
That made a bit of difference to the time to the fault, but it would still happen. And reset would take a 5 second lift off the track. So we can be sure that the processor still had juice and didn't brown out.
A discussion with Superslot pointed towards the XLC exit being part of the issue. Sure enough the braids on my Porsche 997 were quite spread. I pulled them in close to the guide. Magic! problem disappeared completely.
Now as I had a PB-Pro SH I had no worries about shorts so I splayed the braids out wider and ensured a good short on every passing. Enough to dim the display. I could now get very consistent faulting behaviour from my car. With the extra capacitor mounted it allowed the car to run for 20 laps rather than 6, but it still only postponed the inevitable.
So where is the problem? On the exit of the LC is a place where the joining lane rail gets very close (about a mm). Solution? Insulate the last 5mm of the rail by painting with a black enamel paint at the positions I have marked in red on the photo. Or keep your braids very very tidy.
Riko
Editado 2 de Marzo del 2009 por RikoRocket
