Project idea - Vibration sensor/logger for cars - Page 1
Forum section: electronics / projects

author: Skimask
author_rank: Super Contributor
timestamp: March 15, 2015, 05:04:03 am
content: Short story long...Got new tires about a month ago on one of my cars. Balanced, alignment, all the good stuff a guy should do when get new tires. Before I took it in, the car ran nice and smooth down the highway. No problems...just old/bald tires.Problem... The car had a vibration when I got it back from the shop and took it out on the highway. Took it back to the shop. They refused to do anything about it, told me I must've hit a curb and damaged something. No...wrong...didn't happen that way.End result...I got the manager involved, pointed out my history with that particular shop, etc. Got the tires rebalanced. Good to go, but they still charged me for the rebalance. Figured I'd cut my losses, let them re-balance the tires for a few $$$, and get the hell outta there.Idea...Thinking I could make a small PCB, something like an ADXL345 (or whatever is hot in the world of accelerometers these days), a microSD card, a coin cell, a couple buttons/LEDs, and a PIC to run it all. Back of the envelope thinking, maybe a few square inches of rectangular PCB. Something really non-intrusive so as to not interfere with driving.The premise...The shop basically straps/bolts this thing solidly onto the steering wheel, takes it out for a drive on a 'known' stretch of highway (eg. one that would be used every time for the same test).The circuit logs shakes/rattles/rolls on the SD card.You bring the SD card in, pull the data off the card, import into a charting program of some sort, run the data points thru some software filtering/DFTs/etc, and the output data would correlate to any shakes/rattles/rolls in the front end. Obviously wouldn't do much good for rear wheel shakes while mounted on the steering wheel, but could probably be bolted down somewhere in the rear to log data back there as well.After the software cooks on the data points, you get a visual representation of any shakes/rattles/rolls in the car BEFORE any work is done.When the work is done, you do the same thing.Assuming everything has been done right, any 'cooked' data would show a marked reduction in vehicle speed related accelerations.Last week, I did this same sort of thing using my smartphone (Galaxy S5) before/after I had the timing belt (and a whole bunch of other stuff) replaced on my Honda Odyssey. Laid the smartphone on the intake manifold cover, taped it down good and tight, started logging acceleration data, started the engine, put it in gear, etc. Let it log a bunch of data proving the engine was smooth.Sure as shit, got the van back from the shop, and the idle (in gear) was a bit rough with all the new parts. Put my Galaxy S5 on the intake like before, did some data-logging. Took the van back to the shop (obviously a different shop than the one for the tires), gave them my sad sad story, and of course, they called bullshit. Got the manager involved. Showed him my data-logging from my phone, got him in the van, proved my point about the rough idle. And again, sure as shit, they found a vacuum line buried under the intake cover that they only half connected. Not enough of a vacuum leak to trip a code, but enough to make the idle rough.Ain't technology a bitch?