I want to measure my vehicle shock absorber movement. The shock's travel range is about 12" to 3". I like to get at least 100 measurements per second. 500 SPS would be great.
Any suggestions on what sensor to use?
Thanks, Gerry
Linear Position Sensors are what are commonly used for this application, but they are quite expensive (US $80+ea.)
I recently installed a suspension kit that used Rotary Position Sensor's that seems to work well. it needed a fairly long lever (4.5 inches) to accommodate the necessary travel which made mounting a little trickier, but not too bad. I have found them for as little as US $10 ea. just be sure to get ones that are designed for 90 degree's travel and not the multi-turn style.
You will have to do the math to determine lever length so that you get the proper range of movement without overextending the sensor which will damaged it.
The Arduino read rate is adequate for your app but, just of of curiosity what will you do with the readings? If you want to data log them, whats your plan for that?
A 90 deg Rotary Position Sensor sounds good. What about the mechanical linkage? Are there any drawings how that's implemented? Where can you purchase the linkage? Didn't find anything on ebay.
Yendis- I have a LowLatencyLogger from sdfat that stores data into SD memory. The data goes into Excel to be analyzed. I've used it with the accelerometer ADXL345 to measure vehicle suspension.
Measuring shock movement will be interesting. It's something to do to keep my mind active while in retirement.
There has been at least one previous similar discussion, so you might use the search box in the upper right of this page to find it.
I'm afraid you will need to make your own linkage.
What that kit used was 2 - 1/4" heim joints with a 1/4" threaded rod connecting them for the vertical arm.
Then a piece of 1/2" wide 16 gauge steel bar stock for the horizontal lever.
To find the lever length needed, you just need to calculate the side of a Isosceles Triangle
The formula needed is: L=1/2H√2 where L = length of lever, and H = length of travel
So for the 9" of travel mentioned in your first post : 1/2(9) = 4.5 and √2 = 1.414 so 4.5 * 1.414 = 6.36 inches
Bump it up to 6.75" or so to give a little bit of a safety margin, you don't want to be hitting the stops since it will damage the sensor.
I think I got the picture. The rotary position sensor connects to the bottom section of the shock. One end of a 1/2" flat iron stock, ~6.75" long (which is the lever) connects to the sensor shaft. The other end of the lever connects to a vertical bar (which can also be flat iron). The other end of the vertical bar connects to the top of the shock.
There are 2 pivot points: top of shock, and the vertical-to-lever connection. These connections can be made with a bolt, washer and nut.
Sounds simple.
Do you have a P/N or suggestion for the rotary position sensor?
Thanks
Close But you will likely have to mount the sensor to the frame of the car and the vertical end to the bottom shock mount. At least that's how it was for that kit.
this is because the horizontal lever put's the sensor 6.75" away from the vertical center-line of the shock .
I won't be home for a few days so I can't suggest one at the moment.
I don't know if it would be accurate enough for your application, but I was looking into using a GM TPS (Throttle Position Sensor) for measuring suspension movement. They are available for under $10.
Charles
Gerry48:
Yendis- I have a LowLatencyLogger from sdfat that stores data into SD memory. The data goes into Excel to be analyzed. I've used it with the accelerometer ADXL345 to measure vehicle suspension.
Gerry I am looking at a similar project to measure vibration and have also been looking at using the ADXL345. Are you able share any information on your project to get me headed in the right direction?
Dear colleagues
I want to measure a suspension deflection at vehicle with leaf spring suspension.
I don't like the idea of linear/rotary encoders because in rugged conditions it may be finished.
Can we do it with magnet field sensors? With installation like this
thanks!