[SWoRd]

QUOTE (randybrown @ 18 Dec 2004, 05:02)Has anyone come up with a viable alternative power pak for the Scalextric Sport Digital track? Those of us planning to run multiple cars (more than two) will need a second power pak, so I'm curious if anyone knows of an alternative to the primary source.I think a 10A variable laboratory supply, would be a safe bet.

QUOTE Also, I'll mention this: I was running in motors on new digital cars tonight. I took one off the track, put it back together and run some test laps while the other was still running, stationary and at a slow RPM.

When I was reving the motor along straights, I noticed the stationary motor's RPM drop noticable. This leads me to believe that, even when running only two cars, performance on the SSD would be improved with a second power pak.Only a very stiff supply will help on this situation. A regulated supply would be the best for an existing solution.

An even better solution would be to build in current mode regulation into the car controller. The microcontroller could sense the slot voltage drop, and compensate the PWM signal accordingly. This will even compensate for voltage drop across the slot.

It will ofcause not be possible to put more than full power to the motor, but if we design a 20 or 24 volt solution, there will be plenty of headroom for top speed regulation. A 24V supply with a 16V maximum motor output, has 8V regulation allowing a third of the supply voltage to drop before performance is influenced. A solution like this, will allow the use of a fairly weak (read cheap

) unregulated power supply, without the performance being influenced by voltage drops.

At the same time this will reduce the slot current, and allow more cars on the track. They will not be influenced by each other. It will also allow you to feed the track at one point only, relieving you of the tiresome task of running multiple power connection points, because the voltage drop is not important anymore.

It just so happens, that my current clot car controller design supports current mode regulation.

Søren

 

[SWoRd]

QUOTE (justmarty @ 18 Dec 2004, 13:07)so how do we get it soren??Well, it's a bit too early yet. I have a lot of software development ahead of me for the different controllers (base station, car, lane change, light). I won't have something up and running this year, so patience is required.

I've posted all the diagrams, so please feel free to work in parallel if you're in a hurry

When I've got all the bugs ironed out, I'll be willing to supply some boards, providing I'll get the expences covered. I'm not sure about the final prices, because the production cost depends on the quantities involved. So the prices could vary a bit depending on how big an interrest there will be for a system like this.

Søren

 

[SWoRd]

QUOTE (Xlot @ 18 Dec 2004, 13:10)I just wonder if a 24 V-ish supply wouldn't be a bit risque' for totally exposed rails (not mine, of course!)24V is still defined as low voltage, so you wouldn't need regulatory safety testing on anything but the external power supply.

QUOTE And - again from the exasperated club racing slant - how accurate would be the 16 V max. output - more importantly, could it be overridden by cheaters?Well it could in theory, but you'd need to modify the embedded control code in the base station and car controller.

I can think of a couple of things we could do to make it more difficult for potential cheaters.
1) We could avoid making the embedded controllers source code public. We could distribute it in a coded format, that would make it difficult (but not impossible) to modify).
2) We could implement a code CRC validation feature, that would allow the base station and PC software to verify that the embedded code of the various system components have not been tampered with.

You can never completely protect a system from hacking, but a few simple security tools should be enough ... after all, this is just a hobby?.
I know that people tend to get very competitive with slot racing, but I still think that a fair amount of faith in your fellow slotracers sportsmanship is in place.

How would you protect yourself from a guy that carefully conceals a tuned motor as something more inferior? (for example by swapping motor sticker or what have you?). I think it's a lost cause to try and make a completely bullit proof system. If we build in the above mentioned safety features, I don't think we'll have serious problems.

QUOTE Finally,

"It just so happens, that my current slot car controller design supports current mode regulation"

Could you elaborate a bit more - but please as down to earth as possible - does this perchance match my suggestion of setting a current threshold that overrides the speed (voltage) command to the PWM - so car classes are simply defined by max. amps ?I just wanted to point out, that my current car controller can measure the current drawn by the motor realtime, and regulate the PWM signal accordingly.

That could form the basis for a motor controller that is not sensitive to slot voltage variations.

Søren