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MagnusThome
MagnusThome New Reader
6/21/19 12:47 a.m.

collinskl1
collinskl1 GRM+ Memberand Reader
6/21/19 7:39 a.m.
wvumtnbkr said:

I really want this on my new build...

 

I just need it in a kit form with clear instructions.  

 

How much for all 4 wheels and everything to use this with Harry's laptimes?

 

Want!  But not good at the integration.

Same - would definitely be onboard for buying a complete kit.

MagnusThome
MagnusThome New Reader
6/22/19 8:41 a.m.

I had some fun (slightly overinspired ;-) track driving on thursday with a friend on the Gelleråsen track :-)

The Gopro mount snapped so I ended up with a sub optimal temporary solution where the camera is mounted way too low, so the view out of the car is really crappy in the video :-(

No the phone is not in the way of my view at all (since I'm almost 2m tall) but it is really obstructing the view in the video.

Interesting to see how temps change in different track sections!

https://www.youtube.com/watch?v=0ZWt0y0hJ2g

 

MagnusThome
MagnusThome New Reader
7/1/19 4:04 a.m.

Finally a good video with camera in the right position and so on. Again, interesting to see how fast the tires heat up, how the inside of the inside wheel heats too and so on:

 

https://www.youtube.com/watch?v=JjM8beZJZ2o

TS
TS None
8/5/19 8:08 a.m.

Hi there,

first of all I would like to thank you for your efforts in making this happen. RejsaRubberTrac is exactly what I was looking for in order to actually understand better how the tires behave rather than wild guessing.

This being said, I plan to build four units for myself and, probably, some more for a friend. They are to be fitted in two Lotus. Apart from the more exotic bodywork-related questions concerning the cars and limited space in the wheelhouses, my other questions are quite general, I would assume.

 

Functionality:

  • I must admit that I have not completely understood what the optional distance sensor is intended for: is it somehow used to aid internal temperature calculations of the moving wheel, or is it rather an actual separate measure for damper movement (e.g. for detecting roll)? If the latter, it would only make sense if the sensor is mounted completely pointing straight top-down onto the top of the tire, right?
  • Re the sandwich mount: is it supposed to house the two sensors and be connected to the Mainboard using waterproof automotive-grade cable connectors?
  • What is the practical limit of # BT devices in such environments? GPS, Camera, 4x RRT, TPMS. That is quite a lot. Is this an issue?
  • How are the sensors  calibrated? How do I tell e.g. HLT where the wheel ends? How is the damper travel for the distance sensor normalized to 0-100%?

 

Possible improvements:

  • Did you ever consider an additional separate temperature sensor to measure tarmac temps for the corresponding section of the track?
  • Would it work using only one mainboard per axle and connecting two sensors to it? This would reduce both active BT devices and components necessary. Or are limitations in computing power an issue here?

 

Components:

  • IR transparent film for the lens: can I test IR transparency with a TV remote control? I have some old used motorcycle visor “Pinlock” screens that have some scratches somewhere but enough “good” areas to cut something out as lens protection. They are visually excellent and I would hope that IR would pass through...
  • Still need to make more precise measures, but I would assume we need 120 degree “-BAA” FOV sensors. Did you ever come across some of these _with_ daughter board? I did not find them on AliExpress at all, as these are all “-BAB” sensors. On the other hand: without daughter board, how would I fit them in the sandwich mount?
  • Have you ever considered this unit? It is about a fifth of the price of the Bluefruit and has similar specs, yet an exotic CPU: LOLIN D32 V1.0.0 - wifi & bluetooth board based ESP-32 esp32 ESP-WROOM-32 4MB FLASH Arduino MicroPython Compatible: https://s.click.aliexpress.com/e/bxFE5Mc0 and https://wiki.wemos.cc/products:d32:d32

 

Fitting:

  • Are there any known issues with fitting the unit on the inside of the wheelhouses (given enough space for the wheel to move of course)? At your M2 you have fitted them above/outside the wheelhouses pointing through a hole. I do not think this is feasible here...
  • What is your experience with the front axle steering movements of the wheels? Is it actually sufficient to have the sensor mounted statically?
  • Is it an option to mount the distance sensor directly on the damper?

Thanks a lot,

TS

P.S.: Registration failed on your forum multiple times for me at rejsa.nu...

MagnusThome
MagnusThome New Reader
8/5/19 3:25 p.m.

Yay, nice to hear more people building these :-)

My replies mixed with your questions here below:

 

  • I must admit that I have not completely understood what the optional distance sensor is intended for: is it somehow used to aid internal temperature calculations of the moving wheel, or is it rather an actual separate measure for damper movement (e.g. for detecting roll)? If the latter, it would only make sense if the sensor is mounted completely pointing straight top-down onto the top of the tire, right?

Yes, totally separate just to get movement. You can simply skip it. And yes, straight top down hitting the very top of the wheel is best but aiming at an angle will still get you data, just slightly scaled. Also take note that turning the wheel might change the distance depending on caster, camber gain and so on depending on what spot on the tire you measure on.

 

  • Re the sandwich mount: is it supposed to house the two sensors and be connected to the Mainboard using waterproof automotive-grade cable connectors?

If you use the mainboard I designed they are soldered together directly with no cables at all. There are a series of pictures showing how all the parts are mounted together here https://github.com/MagnusThome/RejsaRubberTrac/tree/master/pcb

 

  • What is the practical limit of # BT devices in such environments? GPS, Camera, 4x RRT, TPMS. That is quite a lot. Is this an issue?

Antti at Racechrono has done performance testing and with much slower older hardware in your phone you might get reduced data update rates in a worst case scenario. I noticed that running OBD2 + GPS + 2 RRT + Video worked flawlessly on my quite old OnePlus One. BUT if I at the same time played music or took a phone call over bluetooth that sound would cut out a bit.

 

  • How are the sensors  calibrated? How do I tell e.g. HLT where the wheel ends? How is the damper travel for the distance sensor normalized to 0-100%?

You need to aim the sensor correctly. I have a resistor that I run some current through from a USB powerbank, then I move the hot resistor in the sensors field of view on the tire to aim the sensor correctly. If you place the sensor so it overshoots a bit, catching temperatures outside the sides of the tire you'll easily see when driving on track where the tire edges are due to the huge temperature drop in the display. But I have mine aimed correctly, the outer color bars in the display exactly matching the outer edges of the tires. 

The distance sensor shows the distance to the tire in millimeters. There is an option to add an offset in the software code if you want it to show 0mm when the car is stationary on flat level ground and then show the movement with positive and negative distance values instead.  But you really will never get a 100% perfect zero when stationary since this will change slightly with amount of fuel, driver, tire wear, unleveled ground and just tolerances in the chassis.

 

  • Did you ever consider an additional separate temperature sensor to measure tarmac temps for the corresponding section of the track?

No :-) That could be a one single point measurement though. Or simply aim the sensor so the outer color bars aim at, and show, the tarmac temp!

 

  • Would it work using only one mainboard per axle and connecting two sensors to it? This would reduce both active BT devices and components necessary. Or are limitations in computing power an issue here?

The load on the phone is rather on the total amount of data transferred and that would be the same. I do think it would lower the load slightly but not enough to warrant the design change. And personally I wanted to stay away from any external cables.

 

  • IR transparent film for the lens: can I test IR transparency with a TV remote control? I have some old used motorcycle visor “Pinlock” screens that have some scratches somewhere but enough “good” areas to cut something out as lens protection. They are visually excellent and I would hope that IR would pass through...

Sorry, I don't know. Try it!

 

  • Still need to make more precise measures, but I would assume we need 120 degree “-BAA” FOV sensors. Did you ever come across some of these _with_ daughter board? I did not find them on AliExpress at all, as these are all “-BAB” sensors. On the other hand: without daughter board, how would I fit them in the sandwich mount?

No, I have never seen 120 degrees FOV on a small board :-( But it's easy to solder the sensor sans daughter board directly onto the mainboard that I designed just using the sensors own long legs to mount it a bit above the board when soldering it onto it.

 

Yes, it was the cpu I aimed for initially! But the bluetooth BLE was very unstable with all the libraries I tried and after a lot of hours I put it aside. Old school bluetooth (non BLE) works great on it but that didn't help me. I haven't given up on it totally, I might give it another shot someday but that is in the future.

 

  • Are there any known issues with fitting the unit on the inside of the wheelhouses (given enough space for the wheel to move of course)? At your M2 you have fitted them above/outside the wheelhouses pointing through a hole. I do not think this is feasible here...

It's just the distance to the tire with the FOV you have which is important really. There is normally good space to mount and ample distance to the tire up in the shock tower but I didn't find any 100% nice way to mount it there with a snap-in/out holder. Tried strong magnets but it didn't work out well on my particular car. 

 

  • What is your experience with the front axle steering movements of the wheels? Is it actually sufficient to have the sensor mounted statically?

Yes absolutely, if you mount it aiming at the top of the tire from straight above it is not a problem. Well... not for a drifter car with huuuuge steering angles. But for a racing or trackday car, yes. Of course each car's specific steering / front axle geometry can affect this theoretically but with normal steering angles and normal suspension movements it works well.

 

  • Is it an option to mount the distance sensor directly on the damper?

The distance sensor can be connected with external wires of course and mounted anywhere, separate from the thermal camera sensor. Just an issue of cables and housings that needs to be done..

 

  • P.S.: Registration failed on your forum multiple times for me at rejsa.nu...

Mail me at magnust@gmail.com and I'll set it up for you. I know it's far from optimal with all the Swedish language when trying to register, sorry! I'll copy this post and add it there so we can continue there if you want :-)

clutchsmoke
clutchsmoke SuperDork
8/28/19 9:19 p.m.
wvumtnbkr said:

I really want this on my new build...

 

I just need it in a kit form with clear instructions.  

 

How much for all 4 wheels and everything to use this with Harry's laptimes?

 

Want!  But not good at the integration.

I can do the soldering if need be. That's a part of my day job.

MagnusThome
MagnusThome New Reader
10/1/19 11:59 a.m.

I have two built and ready sensors extra that I've used during testing that I'm selling.

They are 60 degrees field of view so check how you can mount them on your car with correct distance between tire and sensors.

https://rejsa.nu/forum/viewtopic.php?t=116644

(Use google translate? The page is in Swedish)

Reach me at magnust@gmail.com

 

 

djhedges
djhedges New Reader
6/30/20 1:07 a.m.

First I wanna say well done.  Especially the documentation you've put together. 

I spent many hours pouring over technical spec sheets about infrared sensors back in 2016 trying to create my own tire temp sensors.  The array sensors I found at the time didn't have a broad enough temperature range.  That and I really have no idea what I'm doing when it comes to circuit boards and soldering sensors.

When I find the time, maybe this winter I'll have to give this a go.

michurebmann
michurebmann New Reader
3/29/21 2:37 p.m.

Hey guys

Im Michael Rebmann from Switzerland, I NORMALY go 2-3 times per year to the Nordschleife to cure my Petrolhead-syndrome. Because of the syndrome i try to collect as much data as possible while Driving on the Nordschleife and make some Videos out of it, so i can watch them when i miss the Nos too much

Im a little late, an i will hope i get some response, because its a long time since last reply in this thread....

So i Got my self a M5-Stick and a M5 Native IR-Sensor, the sensor is a MLX90640 with a resolution of 32x24. Its basically a newer version of the MLX90621 used in your project, and maybe a bit of a overkill for this. The M5-Stick has a built in LCD, built in Bluetooth, built in battery and built in connectors for external power supply (5v and 3,3 i believe). The chip is a standard ESP 32 chip used with Arduino IDE. Both together cost around 130 bucks

So my idea is to do the same with my equipment..... I can code in different languages (c#, Java, python) but im not familiar with the C coding but i think this will not be a problem. I already tested the example projects for the MLX90640 and archived to communicate with my phone via Com-port (serial communication)

My Big problem is:  I struggle a lot to find out in which format i have to send the data to my phone and how to bring Harrys Lap Timer to show/store the data. 

-Should the M5 answer request from harrys laptimer or just push the data to the phone always an in a specifiv interval?

-How can i map the data in harrys laptimer to save the data in the CSV file?

-How can i map the temperature to show life in harrys laptimer? i found no infos how you map your project to harrys laptimer.....

 

Im so happy if someone can explain me the part between my programm and harrys laptimer,  how they communicate together

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