I suppose im asking Nene and John Bennett and mayve Dave S??
anyway i need to get a hold of a load of strain guages and i also need to make up a wheatstone bridge type circuit for them, and i need something to link them up to a laptop.
The idea being that i will be measuring the strain of something and logging it through the laptop.
ideas, solutions etc welcome
Kev I had to do something similar a few years back.
I think I used data logging hardware from here.
http://www.windmill.co.uk/strain.html
not 100% where we got the gauges themselves from , but a quick google shows here would be a good start.
http://www.hbm.com/products/listprod...y=3&mm=3,33,-1
dont foget some good superglue to bond them.
hope this helps.
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That's pretty whizzo there (£775 quid might be out of Kevs budget I'd guess, mind you).
Is this a uni project? If you've got the time, I can give you software to get a pic to read in analogue values between 0-5V and send them to a PC (via usb or serial), then display it, but you'd have to make/buy the strain gauge amplifier stuff.
any idea with what sort of forces you'd be looking at kev (ballpark)?
i'm guessing it's for something along the lines of chassis flex / torsion?
i can get you some diagrams for 12vDC strain gauge circuits, and possibly even the strain gauges themselves if my old man's got a free hour as he deals with a lot of companies in that field (most new ships have strain gauges dotted around the hull).
they're pretty straight forward really from what i remember, depending on which setup you choose, if you use half or quarter bridge you'll need some resistors in the circuit normally.
I'll get some stuff sent through from my old man for you.
if you let me know what sort of strain range you're after i can ask him if he can acquire some
the computer stuff i have no idea about, bennett's department
all good answers guys cheers
Yeah i was thinking more like £100 max.
and yeah was not very good at hiding that eh, yeah its to measure chassis flex, planning on using maybe 50 or so strain guages.
basic idea is to drift a set course and measure (and chart through the pc)the flex, then fit differant parts of a roll cage and re-measure it
hope you like soldering
i've sent my old man an email mate, i'll let you know what he comes back with
For that number of strain gauges I think I would be looking towards I2C based analogue samplers.
Iv'e been out of electronics for about 5 years now, and was never THAT interested when i was an engineer tbhso iv'e never heard of those chips nene.
Stu, the soldering dont bother me mate, only thing that concerns me is the 12v guages, well id imagine a pc wont take more than a 5v line......
50 strain gauges!!!!!! get the 2000grit out then, you'll have to prep the surface you want to attach them to to a high polish. did some fitting of these when we were measuring A-pillar flex in ofset frontal impacts but I'm pretty sure we piggybacked them into our 108 channel aquisition kit though. I'll see if I can contact a friend/ex colleague and get some info
not doing frontal impacts Danny, well hope not anyway, but i do have a reputation for that
so hopefully should just need a wipe with ipa and a dab of superglue to hold em.
gonna be about 5 on each side of the chassis, on the sills, bout the same along the front and back of the drivers compartment
and same again crossing over the compartment (think St.Andrews cross).
and then some along the boot floor and the front cross member.
And a couple on each strut tower.
hmmm...... guess i should really do the A pillar's and B pillars too and then i suppose the roof as well......
need to draw the line somewhere.......
Any help would be greatly appreciated.
(i mean materials finding help btw)
Well, I2C is actually I²C (I squared C) or IIC. It stands for Inter-Integrated Circuit and is a lowish speed communications protocol. You can use it to attach lots of funky little devices, such as ADCs, DACs, digital I/O, or just to send commands to misc other devices. The bit you're interested in, though, is ADCs with an I²C interface. That way, if you're really considering 50 strain gauges, you can run a single I²C cable out to little boxes around the car with a multi-way ADCs in them instead of having to run 50 cables back to a single datalogger.Originally Posted by Kev
Iv'e been out of electronics for about 5 years now, and was never THAT interested when i was an engineer tbh
It's very common nowadays, for example PCs use it for communication to the on board voltage and temperature monitoring stuff, you know how your computer magically knows what resolution your monitor can do? That's I²C as well built into the monitor cable. Oh, and sometimes a TV or something can control a VCR through the SCART cable? I²C again
The PC itself won't be doing the sampling, no matter what you do, so it doesn't really matter
coolio, thanks for that
just to confirm a little, im not planning on sampling 50 odd guages individually.
ill daisy chain them, so the sills, althoughh there will be 5 guages, only 1 line
So should have about 12-20 samples
Hoping to be able to view this as a 10 sec real time graph, well 12 individual graphs on the one screen type of thing
Ah, so not quite so crazy then
Have a look at this - http://www.i2cchip.com/
You should be able to just use a USB adapter and then write a little program to sample each channel as you need to.
just a random idea type thingy.......
how about mounting a laser source (one of those pointer pens, not goldfingers death beamin one corner of the car, projecting into the middle of a target on the other side of the car. then measuring how far the beam swings.
sounds more fun than strain guages
You could use a webcam to measure it I guess.
That doesn't tell you how much the car is twisting though.
depends where you postion the lasers and the sensors
intregueing grim, but vibration would fcuk about with it.
anyway turns ouy the uni should have enough strain gauges for me and also a datalogger.
bonus!!
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