GRM version of steering and throttle data sensors?

Following the rest of the theme of my vintage Formula Ford racing for "reasonable" costs, i picked up a TraqMate data system for cheap cheap money.  With the cost of my last IPhone, zip tying that to the steering wheel and running HLT is less than optimal. And that wheel often ends up on the ground briefly upon exit of the car.   So the TraqMate is fully functional and I have the I/O module for it, so I can remote start my ReplayXDs, bring in an RPM channel, but it also has several analog and digital I/O.  I'd like to eventually pull in a throttle position and a steering position.  

But the cost of buying those new (as far I can see) are like 5X what I have in the system.

What's the GRM (ie, low buck) options for sensors?  String pots seem to the typical way to do this.  

Thanks!

Ps. And flipping through the latest issue of GRM tonight, there are a couple of articles about dealing with squiggly lines :-)

For steering angle, I'd either rig up a string potentiometer that wraps around the steering shaft, or a multi-turn potentiometer with a belt around the steering shaft.

How old is your car?  It should already have a TPS if it's got EFI.

Honsch said:

For steering angle, I'd either rig up a string potentiometer that wraps around the steering shaft, or a multi-turn potentiometer with a belt around the steering shaft.

How old is your car?  It should already have a TPS if it's got EFI.

It's an RF81 (an 81 Van Diemen), the closest thing it has to a computer chip is the AMB transponder mounted to the front bulkhead.  It does at least have one of the new fangled electronic tachs verses a cable driven one :-)

String pots are the normal way to do steering angle.  Was hoping to find a DIY method, but this may be an area where i just have to bite the bullet and buy the proper equipment.

Honsch may have been asking whether your car has the Ford Kent motor or the Honda Fit motor.

If it's a Kent motor, TPS sensor donors are common as dirt from virtually every EFI motor made in the last 30 years.

And using a bit ingenuity, you can fangle a TPS to act as a steering position sensor using some cord wrapped
around the steering shaft.

Most newer cars have steering angle sensors.  The one on the R53 seems to just slip over a standard 3/4DD steering shaft.  Most GMs also slip on the bottom of the column, but I have never bothered to investigate their mounting.

I was also going to suggest looking at GM sensors for steering. I would suspect older would be better as it is most likely more "analog" and not need so sort of interface to interpret the signal. In a perfect world it would just be some form of potentiometer. 

clshore said:

Honsch may have been asking whether your car has the Ford Kent motor or the Honda Fit motor.

If it's a Kent motor, TPS sensor donors are common as dirt from virtually every EFI motor made in the last 30 years.

And using a bit ingenuity, you can fangle a TPS to act as a steering position sensor using some cord wrapped
around the steering shaft.

Sorry, yeah, it's a Kent, not the Honda.  I wasn't thinking in terms of just re-using a stock sensor off a modern car, but that would definitely be cheap if I found a way to mount it.  The data system produces a 5V reference signal, and is looking for a 0 to 5 V (or some portion) return.  I can calibrate it for the range.  Some googling and it looks like modern TPS come in a wide variety, not just traditional potentiometer type.  

Thanks for the input so far!

I've seen a lot of potentiometer - and even Hall effect - TPSs adapted to carbs. Either one will give a 0-5 volt (or sometimes more like 0.5-4.5 volt) analog signal when supplied with a 5V reference signal.

I wonder if it's possible to adapt a TPS to a steering knuckle, although the linkage might get a bit weird. A string pot type sensor may be a bit easier, but I like the idea of adapting an OEM steering angle sensor.

You didn't ask for it but I'll post it anyway, this Bosch brake pressure sensor came stock on a lot of cars and would be easy to T into your braking system for that data as well.

https://www.finjector.com/documents/589822ac0fe60/0265005303.pdf

These are all the BMW's that use it so you should be able to find it in a yard and clip the wiring harness plug to go with it for a few bucks.

https://www.realoem.com/bmw/enUS/partxref?q=34+51+1+165+467

For really cheap and finicky, you could make a cam plate to put on your steering column and use a tps.  Set TDC of your wheel to 50% of the tps range and then you'll know whether you're steering right or left..

Got access to a 3d printer? I'd 3d print a gear for the steering shaft, a mount for a potentiometer, and another gear for the pot.  Calibrate the resistance to a steering angle. Good to go.

Depending on pedal arrangement. You may be able to do something similar. May involve a lever/cam on the pot and a small rod hooked up to the pedal.

After looking things over closer today, I don't see an easy way to connect a rotary pot, or a standard TPS to the throttle linkage at the carb, or at the throttle pedal.  The easiest solution would be a string pot mounted to the front bulkhead in front of the throttle pedal.  It would only need about 2" (or less depending upon where on the throttle pedal (bottom pivot) it is mounted.

A rotary pot on the 3/4" steering shaft seems like an easier install.

Look into front ride height sensors from BMW, Audi etc. that are used for headlight leveling. They look kind of like RC servos but act as position sensors. They're good for all kinds of things including throttle position sensors for carbed vehicles.

For a steering position sensor, OEM options are best if they can fit. If not, one option that may be worth looking into would be an optical distance sensor on the rack with a target where the tie rod connects to the rack. These are cheap and much more durable than any kind of potentiometer (especially stringpots which tend to get gunked up), the sensor will just need to be wiped off from time to time. They will need some calibration or post-processing to map the raw sensor data to useful steering position info though.

WonkoTheSane said:

For really cheap and finicky, you could make a cam plate to put on your steering column and use a tps.  Set TDC of your wheel to 50% of the tps range and then you'll know whether you're steering right or left..

How many turns are in the steering rack of a Formula Ford?  Throttles only go 90 degrees, street cars usually have at least 720, but I have no idea about a formula car of that type.

FWIW, I find that of the three "driver input" channels the throttle position is the most useful with brake pressure a close second.  Steering angle is pretty far back in third, I really don't use it very often.  So I'd prioritize adding the brake one first.  I actually have two brake pressure channels in my car, before and after the ABS, but I suspect that's not a concern in an FF. :-)

codrus (Forum Supporter) said:

WonkoTheSane said:

For really cheap and finicky, you could make a cam plate to put on your steering column and use a tps.  Set TDC of your wheel to 50% of the tps range and then you'll know whether you're steering right or left..

How many turns are in the steering rack of a Formula Ford?  Throttles only go 90 degrees, street cars usually have at least 720, but I have no idea about a formula car of that type.

FWIW, I find that of the three "driver input" channels the throttle position is the most useful with brake pressure a close second.  Steering angle is pretty far back in third, I really don't use it very often.  So I'd prioritize adding the brake one first.  I actually have two brake pressure channels in my car, before and after the ABS, but I suspect that's not a concern in an FF. :-)

 

ABS?  Yeah, that's some combination of my butt, and my ears, and neither is calibrated very well.  Threshold braking has always been my Achilles heal (not braking hard enough).  I checked steering tonight, a little less than 2 turns lock to lock, but if I'm over 90 degrees in either direction on the track something is seriously wrong :-)

Fuel sending units are low cost linear pots with convenient levers on them.  I've used them for temporary ride night sensors before.  They're kind of large but they're easy to mount.  For the steering input you might think about measuring rack movement rather than column rotation.

codrus (Forum Supporter) said:

WonkoTheSane said:

For really cheap and finicky, you could make a cam plate to put on your steering column and use a tps.  Set TDC of your wheel to 50% of the tps range and then you'll know whether you're steering right or left..

How many turns are in the steering rack of a Formula Ford?  Throttles only go 90 degrees, street cars usually have at least 720, but I have no idea about a formula car of that type.

FWIW, I find that of the three "driver input" channels the throttle position is the most useful with brake pressure a close second.  Steering angle is pretty far back in third, I really don't use it very often.  So I'd prioritize adding the brake one first.  I actually have two brake pressure channels in my car, before and after the ABS, but I suspect that's not a concern in an FF. :-)

Ah, yeah, with 2 turns that wouldn't work.  I was thinking of formula car steering racks which only had 300° of movement total...

Edit, whoops, replied to the wrong post. 

wake74 said:

ABS?  Yeah, that's some combination of my butt, and my ears, and neither is calibrated very well.  Threshold braking has always been my Achilles heal (not braking hard enough).  I checked steering tonight, a little less than 2 turns lock to lock, but if I'm over 90 degrees in either direction on the track something is seriously wrong :-)

Yeah, but you need a sensor that can mechanically go the entire range, even if you don't care about readings outside of the center 180 degrees.  String pots really are the right choice.  Have you tried looking at industrial/electronic sources for them, rather than motorsports-oriented ones?  Often the sensors that show up in racing catalogues for data are off-the-shelf parts marked up a lot...