Hi there, I got a DL1 & Dash2, do I need to bother with a wheel speed sensor?
What will I lose out on if I don't fit a speed sensor?
Thanks
Jim
Wheel Speed Required?
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tristancliffe
- Posts: 220
- Joined: Thu Mar 15, 2007 3:41 pm
- Location: Norwich, UK
- Contact:
Certainly most do not bother, but sometimes relying on the convenience of GPS lets us down.
The Honeywell GT101 is one of the most common sensors to use as a "rev counter" (GT = gear tooth). The R-T kit uses the very same. They are not overly pricey. Depending on your source, you may save a fair bit over the R-T offering, but it is unlikely. If you are pinching pennies and enjoy having a fiddle... but otherwise...
The greatest cost might be in mounting bracketry and chopper wheel, but the latter is typically unnessecary with road car hubs as regularly spaced bolt heads or other ferrous features normally suffice. If you have to pay someone to engineer all this the price rapidly climbs.
It is not much value other than having a redundant source of speed info if you don't sense both wheels on an axle. On a RWD fronts are interesting for wheel lifting in addition to Tristan's points, but most value can be gained by sensing the drive wheels to study differential behaviour.
Any form of LSD will significantly affect the handling balance of your steed. Of course, arranging and adjusting a tunable slippery is were the cost and effort stumps most amateurs.
The Honeywell GT101 is one of the most common sensors to use as a "rev counter" (GT = gear tooth). The R-T kit uses the very same. They are not overly pricey. Depending on your source, you may save a fair bit over the R-T offering, but it is unlikely. If you are pinching pennies and enjoy having a fiddle... but otherwise...
The greatest cost might be in mounting bracketry and chopper wheel, but the latter is typically unnessecary with road car hubs as regularly spaced bolt heads or other ferrous features normally suffice. If you have to pay someone to engineer all this the price rapidly climbs.
It is not much value other than having a redundant source of speed info if you don't sense both wheels on an axle. On a RWD fronts are interesting for wheel lifting in addition to Tristan's points, but most value can be gained by sensing the drive wheels to study differential behaviour.
Any form of LSD will significantly affect the handling balance of your steed. Of course, arranging and adjusting a tunable slippery is were the cost and effort stumps most amateurs.
fast set up!
So what is the fast way to set up on this Mk ! DL1 !
I have added a pair 21 tooth "triggers" to each drive shaft.
I have added a pair of gt hall effect sensors
I have added a 1k pull up resistor
Input to two of the four frequency inputs
added power from+5v output
So now how do I do the filters etc and set it up as kph???
I have had a brain fade!!!
Make it simple guys please
Thank you in anticipation
I have added a pair 21 tooth "triggers" to each drive shaft.
I have added a pair of gt hall effect sensors
I have added a 1k pull up resistor
Input to two of the four frequency inputs
added power from+5v output
So now how do I do the filters etc and set it up as kph???
I have had a brain fade!!!
Make it simple guys please
Thank you in anticipation
Are you able to log frequencies. Plotting those channels you should see what look like speed traces.
The DL1 model makes no difference.
If you can't see the channels listed in the drop down list, then you haven't turned them on in "Variable Manager". I'm talking about "Analysis" software now.
If they are there, but empty, then you haven't configured the logger properly.
This is done from the "Configuration" software.
What version of software are you using?
The DL1 model makes no difference.
If you can't see the channels listed in the drop down list, then you haven't turned them on in "Variable Manager". I'm talking about "Analysis" software now.
If they are there, but empty, then you haven't configured the logger properly.
This is done from the "Configuration" software.
What version of software are you using?
the latest download version of software is loaded.
I have a graph that shows a trace,but when the wheels are not turning the trace on the grid moves (drops down from zero) why?
It is displayed as rpm ...how do i convert to speed?
So under the configure area do you set it to read "pulses'?
Can you walk this silly person through it please!!!
I have a graph that shows a trace,but when the wheels are not turning the trace on the grid moves (drops down from zero) why?
It is displayed as rpm ...how do i convert to speed?
So under the configure area do you set it to read "pulses'?
Can you walk this silly person through it please!!!
The negative reading makes no sense, but let's not worry yet.
Are you looking at a graph of logged data against time, or have you set up monitor to view the action live?
If you haven't used the config tool yet, I'd better say that it talks to the logger via the CF card. Your instructions are saved to the card in the SETUP.BIN file. This is now obvious from the software or help if you've progressed that far.
Each time the sensor sees a "tooth" in the chopper disc, it is read as a pulse by the logger's electronics, but you don't want it to count pulses. How you set the config doesn't change how the graph is labelled.
Speed is mathematically like a frequency, something per unit of time.
Just tick Freq measurement and save...
The variable manager names the raw frequency into what ever you want to call the value, and changes the value using whatever maths you apply to it.
The interface in the Monitor software is very similar to that in Analysis.
Look for External Inputs.
With them opened up, down the list you'll find what should say (default names) frequency 1, etc.
Open up the pair of the first four frequency _ that correspond to the channels your sensors are connected to. With the sensors on the same end of the car, assuming the same chopper wheel on both sides and no stagger (chosen difference in tyre diameter), you will put the same settings into both dialogues.
Check that the Advanced Options are all "none set". You might revisit this once you're up and running.
Under "sensor type/.. ", choose "Custom".
You will have to type a formula in the rectangular field underneath.
The numbers depend on your tooth count, tyre size and what units you want to use for speed.
You have stated 21 teeth and kph. As an approximation for the tyre size factor, we will use diameter. We might as well use the software's built in calculator. It's more to type, but you'd have to write it down or key it in to some other calculator anyway.
We'll do the tyre bit first. Your measurement will be 0.6 m or thereabout. We want the circumference which will tell us how far you travel per wheel revolution, so..
Type 0.6*3.14
you want km so continue
0.6*3.14/1000/21
we've divided by the tooth count because .... you know
If you left it there, the scaling in your conversion of a frequency to speed would be sufficient to output km per seconds, so you keep typing
0.6*3.14/1000/21*60*60 ... making sense?
That's the complete formula. Fill out the "units to display" and click OK.
Now you're in the main variable manager again. The next section, Variable Name, gives you the opportunity to call it a Wheelspeed. The name will appear in the drop down lists, etc., but only if you ...
Place a tick in the box at the left and click apply down the bottom right of the variable manager.
The Minimum, Max etc should be "None set" first off.
The speed that this calculates will be greater than the GPS speed if your diameter measurement was accurate. The tyres' effective diameter is always less than the static measurement, even at top speed. Modern tyres (radials) grow very little. The more load on the tyre the more it gets squished up. You will have to reduce the diameter figure (or just type an additional *0.9 in the formula) by about 90% to get the wheelspeed to match GPS speed.
It doesn't even take brake application to have the rear wheelspeed fall below GPS speed when you take your foot off the throttle at high revs, or conversely when accelerating.
If you're fussy, you would disengage the clutch and whack the car in neutral at about 150 kmh to get the best callibration.
Before you get that far, but after you have observed an apparenly sensible graph, go back to variable manager and enter 0 for the Minimum and 250 (300 if necessary) for the Max. There is bound to be the occasional big spike in the data that could give an instantaneous reading many times over the real maximum, that will cause any automatic graph scaling to reduce the height of your actual speeds to a barely readable magnitude.
The trace will not be smooth like the GPS speed. If you have to "Smoothed over" more than 0.2 to get rid of obviously false small spikes, then it's time to use an Advanced option.
I've used Maximum rate of change for my wheelspeeds. The value required certainly depends on the number of teeth and how accurately they are shaped. I've no idea if it depends on the type of sensor or anything else.
You will probably not see much logic in the number that tunes the appearance best. I use it for noisy RPM and I'll be buggered if it makes much sense.
At the risk of stuffing you up, I'll say that with a 23 tooth wheel, 250 gets rid of most of the crud. You will see that if you try to make a nice clean trace, you will start loosing information. Professional teams with high quality everything at their disposal still have noisy traces.
Be warned, it's called "Advanced" for good reason.
I hope I've listed all the steps that it's easy to overlook.
Good luck.
Are you looking at a graph of logged data against time, or have you set up monitor to view the action live?
If you haven't used the config tool yet, I'd better say that it talks to the logger via the CF card. Your instructions are saved to the card in the SETUP.BIN file. This is now obvious from the software or help if you've progressed that far.
Each time the sensor sees a "tooth" in the chopper disc, it is read as a pulse by the logger's electronics, but you don't want it to count pulses. How you set the config doesn't change how the graph is labelled.
Speed is mathematically like a frequency, something per unit of time.
Just tick Freq measurement and save...
The variable manager names the raw frequency into what ever you want to call the value, and changes the value using whatever maths you apply to it.
The interface in the Monitor software is very similar to that in Analysis.
Look for External Inputs.
With them opened up, down the list you'll find what should say (default names) frequency 1, etc.
Open up the pair of the first four frequency _ that correspond to the channels your sensors are connected to. With the sensors on the same end of the car, assuming the same chopper wheel on both sides and no stagger (chosen difference in tyre diameter), you will put the same settings into both dialogues.
Check that the Advanced Options are all "none set". You might revisit this once you're up and running.
Under "sensor type/.. ", choose "Custom".
You will have to type a formula in the rectangular field underneath.
The numbers depend on your tooth count, tyre size and what units you want to use for speed.
You have stated 21 teeth and kph. As an approximation for the tyre size factor, we will use diameter. We might as well use the software's built in calculator. It's more to type, but you'd have to write it down or key it in to some other calculator anyway.
We'll do the tyre bit first. Your measurement will be 0.6 m or thereabout. We want the circumference which will tell us how far you travel per wheel revolution, so..
Type 0.6*3.14
you want km so continue
0.6*3.14/1000/21
we've divided by the tooth count because .... you know
If you left it there, the scaling in your conversion of a frequency to speed would be sufficient to output km per seconds, so you keep typing
0.6*3.14/1000/21*60*60 ... making sense?
That's the complete formula. Fill out the "units to display" and click OK.
Now you're in the main variable manager again. The next section, Variable Name, gives you the opportunity to call it a Wheelspeed. The name will appear in the drop down lists, etc., but only if you ...
Place a tick in the box at the left and click apply down the bottom right of the variable manager.
The Minimum, Max etc should be "None set" first off.
The speed that this calculates will be greater than the GPS speed if your diameter measurement was accurate. The tyres' effective diameter is always less than the static measurement, even at top speed. Modern tyres (radials) grow very little. The more load on the tyre the more it gets squished up. You will have to reduce the diameter figure (or just type an additional *0.9 in the formula) by about 90% to get the wheelspeed to match GPS speed.
It doesn't even take brake application to have the rear wheelspeed fall below GPS speed when you take your foot off the throttle at high revs, or conversely when accelerating.
If you're fussy, you would disengage the clutch and whack the car in neutral at about 150 kmh to get the best callibration.
Before you get that far, but after you have observed an apparenly sensible graph, go back to variable manager and enter 0 for the Minimum and 250 (300 if necessary) for the Max. There is bound to be the occasional big spike in the data that could give an instantaneous reading many times over the real maximum, that will cause any automatic graph scaling to reduce the height of your actual speeds to a barely readable magnitude.
The trace will not be smooth like the GPS speed. If you have to "Smoothed over" more than 0.2 to get rid of obviously false small spikes, then it's time to use an Advanced option.
I've used Maximum rate of change for my wheelspeeds. The value required certainly depends on the number of teeth and how accurately they are shaped. I've no idea if it depends on the type of sensor or anything else.
You will probably not see much logic in the number that tunes the appearance best. I use it for noisy RPM and I'll be buggered if it makes much sense.
At the risk of stuffing you up, I'll say that with a 23 tooth wheel, 250 gets rid of most of the crud. You will see that if you try to make a nice clean trace, you will start loosing information. Professional teams with high quality everything at their disposal still have noisy traces.
Be warned, it's called "Advanced" for good reason.
I hope I've listed all the steps that it's easy to overlook.
Good luck.
I would love some input on my data!!!
I would love a few ideas on people's views of my logged data from the recent hillclimb at Collingrove in South Australia.
I can email the file to anyone that would like to look and tell me where they believe I can go faster or improve!
I can email the file to anyone that would like to look and tell me where they believe I can go faster or improve!
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stephen hooker
- Posts: 33
- Joined: Thu Oct 26, 2006 9:18 pm
- Location: Sydney, Australia
- Contact:
I would be interested in that
Send through to me at "mtce at ozemail dot com dot au". Let me know what car etc. I run the hills here in NSW. I will see if I can help you. Cheers.
Last edited by stephen hooker on Wed Apr 09, 2008 9:37 am, edited 1 time in total.
Stephen Hooker
Sydney, Australia
Sydney, Australia
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