Automotive TPMS (Tire Pressure Monitoring) - Page 1
Forum section: electronics / projects

author: jackW
author_rank: Contributor
timestamp: December 06, 2020, 05:14:11 am
content: Hi everyone,Has anyone on here had much experience with tire pressure monitoring systems in car wheels?I am wanting to put some in my racecar and while the motorsport specific ones do work they are next level expensive.The main issue is we have 34 wheels that get swapped around the car through the event and it's a total pain to have to retrain every sensor each time.Would it be possible to make a short-range receiver that goes in each wheel arch that receives the data from the wheel that is right next to the sensor? I have done a bit of research on this but im not exactly an RF engineer so it's a little confusing.I have been looking for standard road car options but nothing really springs out as usable. (there is one Audi that has a receiver in one corner of the car and it can work out what tire is what by the gain on each sensor but it doesn't quite look ideal).Jack

author: poorchava
author_rank: Super Contributor
timestamp: December 06, 2020, 08:02:14 am
content: It could be done. You can determine which transceiver is closest to the receiver by comparing RSSI of incoming signals. For RF the difference is large at close distances.I'm not sure if that functionality is supported by any off-the-shelf TPMS system. They usually have a central rx unit and I think they assume u swap the sensors during wheel change. In truck industry which i have some experience with they are fixed to the wheel with a bracket that goes under wheel nuts.The sensors are usually throwaways which go to bin when the battery runs out. IIRC the TPMS my previous company made was comprised of 2 or 3 chips from Melexis (sensor + some random stuff, RF IC and third one which i don't remember what it did).

author: HighVoltage
author_rank: Super Contributor
timestamp: December 06, 2020, 11:12:57 am
content: Solution 1:Some TPMS do not need to be trained to the system and will be detected fully automatically.The only problem is that such system needs about 1 to 5 min driving before it is correctly recognized.Solution 2:Use sensors that can be programmed to your specific serial number.So all tires that you have prepared have already the correct serial number in them and they will be correctly recognized immediately.So, essentially you have only 4 serial numbers, always the same for each wheel position.A while back, I worked on such sensor development.

author: firewalker
author_rank: Super Contributor
timestamp: December 06, 2020, 01:49:11 pm
content: There is also a solution that doesn;t require sensors in the tire. If the car users one speed sensor per wheel for the abs (or TCS, ASR, ESC etc), you can check the speed of the wheel with each over. If the speed of a wheel is larger, then the diameter is smaller (that happens with air loss).Alexander.

author: elecman14
author_rank: Unknown
timestamp: December 06, 2020, 02:08:10 pm
content: Having 34 different serial number sensors may actually be beneficial. You could track trends at the single tire level. You could use something like rtl_433 to decode them and compare the output with a whitelist of the sensor serial numbers. Think some tpms sensors have a rotation sensor that only transmits during rotation so tracking what tires are installed may not be an issue.

author: ConKbot
author_rank: Super Contributor
timestamp: December 06, 2020, 04:54:11 pm
content: Quote from: firewalker on December 06, 2020, 01:49:11 pmOn street cars this works for detecting a low tire, but I suspect a race car is going to want actual tire pressure. Plus a car on the track is going to be experiencing significant tire slip angles in cornering (the reason you can shred a set in a day, even at the amateur level) so I suspect the ABS reading of different circumference will run afoul of that.

author: Marco
author_rank: Super Contributor
timestamp: December 06, 2020, 05:14:07 pm
content: How available are older systems with initiators in each wheel well? Those should be easier to adapt to fast recognition and fast update rates, but you'd still need to build your own receiver.PS. there are also Bluetooth TPMS from dodgy brands, both as internal valve stem systems and screw on, which would make it more of a software problem than a hardware one (still need to reverse engineer the way they communicate with the app).

author: coppice
author_rank: Super Contributor
timestamp: December 06, 2020, 06:56:03 pm
content: Quote from: firewalker on December 06, 2020, 01:49:11 pmThose systems are being used in lots of luxury cars now, even from people known for taking safety seriously, like Volvo. I guess the electronic units inside tyres are not long for this world.

author: jackW
author_rank: Contributor
timestamp: December 09, 2020, 08:10:42 pm
content: Hi All,Thanks for the replies.The in-wheel sensors are definitely the best option for us, I forgot to mention we are racing on gravel so external sensors will last about 4 mins. The tires are all replaced each event so the battery inside the wheel assembly isn't a huge issue.I'll do some reading about the versions with Initiators in each wheel. It would be really cool to have a receiver in each wheel arch which I would combine with a couple of analog voltage inputs for other sensors which then are put onto canbus to go back to the central display.To make matters more complex, we regularly stop on the side of the road and use the Jack in the car to swap the tires front - to rear etc.This is why it would be ideal if each corner could have its own receiver and only accept the strongest signal if that makes sense?Interested to hear if anyone has any further ideas