SDL Speed output

[Martin]

Hi,

Is it possible to add a simple speed output out of an SDL to drive an Odometer? (trip meter in a rally car)

At the moment im getting speed and distance from a GPS and coverting that to groundspeed. From groundspeed I generate Lapdistance by having a condition trigger the beacon. I set a Condition to trigger an output at every change of ten meters lap distance. This helps a lot since you done have to fit odo probes that get hit by rocks.

Could Motec make this a bit easier to do in future releases please? Running it from the SDL`s Odometer is not suffiecient since its base resulution is 100m. At least 10m resolution is needed.


Thanks
M

[DarrenR]

Hi Martin,

Currently the SDL doesn't have frequency or duty outputs (obviously) and i doubt it will be added in the near future.

Your method of generating a speed output is pretty good, however using the beacon to reset the lap distance at 10m you can only go up to ~35kmh before the 1s (minimum) beacon hold off stops it working.

The best way to do this kind of thing is to do the integration using a 3D table.
Setup a 3D table, output channel 'GP1 (0dp)', X axis 'GP1 (0dp)' with points 0, 9999, 10000, 19999. Y axis = 'Ground Speed' with points 0 and 200kmh.

Fill out the table,

Code: Select all

        0       9999    10000   19999
0       0       9999    0       9999
200     555     10554   555     10554


The GP 0 (0dp) channel is actually mm travelled in 1/50th of a second. Because the result of the table is also one of the axis, each time the table is calculated (50 times a second) it adds on the distance in mm travelled in that time, up to 10000mm where it resets to 0mm. 555mm is the distance travelled in 1/50th of a sec at 200kmh.

This seems to work up to ~300kmh, counting up and resetting at > 10000mm, pulsing the AUX output. The pulsing looses resolution at higher speeds meaning the pulses become inconsistent but gives the right number of pulses for the distance travelled!

Hope this is a solution for your problem.

Cheers,

[Martin]

Your method of generating a speed output is pretty good, however using the beacon to reset the lap distance at 10m you can only go up to ~35kmh before the 1s (minimum) beacon hold off stops it working.

The lapdistance reset at 1000m. What is the max lapdistance an SDL will handle?
Aux4 pulses for a change of 10m in lapdistance.


Could you please put it in a blank SDL config?

Thanks
Martin

[DarrenR]

Oh i see, i misunderstood. I hadn't thought of using 'changed by' in the output condition, that works a bit better!

Max lap distance is 32767m. Still the problem with using the beacon is it puts a lap in your logging every 1000m (or whatever you set it to reset), so can't use any of the lap timing functions.

The output is only calculated at 25Hz meaning the max frequency is 12.5Hz and the max speed is 450Kmh. Fine for one pulse every 10m, but not much finer.

I made a mistake in the table in my last post too, the speed on the axis should have been 100kmh not 200kmh.

[Martin]

Hi Darren,

I used they way i discribed in a rally this weekend and it worked perfectly!

Im using lap distance and I reset (not another beacon) each 1000m so there are no beacons in the logged data. Should I send you the config ?


Next step is to use GPS speed and not the ABS pump speeds so that re cal of the ODO is not needed when you switch to wetweather tyres.


Thanks for sending me your config
Regards
M