Accelerometers, microcontrollers, displays...

Is there a reason you want a piezo accelerator? These have their uses,
of course, but the cheapest and most compact accelerometers tend to be
MEMS-based units, which use micro-cantilevers. They also can register
constant gravity, which piezo units cannot. Parallax, among others, sell
a 3-axis model for under $40. It connects to a BASIC Stamp or most any
microcontroller. Most of the digital output units these days have all
the signal conditioning built in. The older accelerometers, or those
made for high-end instrumentation, have analog outputs that you'd want
to condition.

The interfacing to an LED would be through the microcontroller, and any
can power a set of 7-segment displays. Digikey, among others, sell the
3-4" LED. You could also get a graphics LCD, but then you'd need a
graphics library for your microcontroller, if you don't want to write it
yourself. The 7-segment displays are much easier.

-- Gordon


pete@nospam.demon.co.uk wrote:

You can also get wonderful LCD displays that have a 4-bit
microcontroller interface. With a few lines of code, you can send it
commands to display any ASCII character at anty position. They run at
about 20 Euros / 25 US$.

Also, you need to decide if you want 3 or six accelerometers. If you go
with 3, you can measure acceleration in all directions but nor rotation.
You can get them in a single part on an easy to use carrier from
Parallax.

If you want to use 6 accelerometers, you can also measure rotation, but
you have to use 3 dual axis units and mount them at a distance. Again
Parallax has those ready to mount. It you go with the bare chip, you'll
have to use reflow soldering and know a bit about the external
electronics required to drive the chip.

           mm@matthiasm.com "Matthias Melcher" writes:

Thanks for the reply, Matthias.


No, I'm not interested in rotation (yet!) -- I just wasn't sure
whether or not I'd need one or two accelerometers in order to
measure +/- accelerations on each axis.


The less I need to know about external electronics the better.  
If there were a "Connecting accelerometers to microcontrollers
for dummies" book I'd buy it!

Thanks,
Pete
--
   "We have not inherited the earth from our ancestors,
    we have borrowed it from our descendants."

           NOSPAMgort@NOrobotoidSPAM.com "Gordon McComb" writes:

Hi Gordon,
Thanks for the reply.


None at all -- I'm basically a software person and just thought
that piezo accelerometers would be cheaper/easier to interface/
easier to install.  Obviously not -- thanks for the info!


I'll check out those -- my only experience in this area is with
the 68HC11 many years ago and, apart from their rarity these days
I'm sure they would cost a whole lot more than the simple sort of
microcontroller I'd need to make this device (which will be used
as a datalogger for a car).  So long as it will do the job, the
cheaper the better.  As for the accelerometers, I wasn't sure
whether this would require 3 or 6 sensors for full 3-axis
measurement -- it appears from what you say that the Parallax
device will do that.


Good to know; in my hardware ignorance I had assumed that the
devices would output a voltage and that I'd need a microcontroller
that had enough A/D pins.


"Easier" gets my vote :-)  Time now to go looking on the 'net.

Thanks for the pointers,

Pete
--
   "We have not inherited the earth from our ancestors,
    we have borrowed it from our descendants."

Check out http://www.sparkfun.com/

There are triple-axis accelerometers and dual-axis gyroscopes.


A/D pins are common. A PIC can have a lot; the 18F2620 has at least
12 A/D's. I prefer to use SPI.
--
D. Jay Newman           ! Author of:
jay@sprucegrove.com     ! _Linux Robotics: Programming Smarter Robots_
http://enerd.ws/robots/  ! "Heros aren't born, they're cornered."

Thanks everyone for the replies; I'll be doing some research on
the Net this weekend, and maybe some shopping...

Pete
--
   "We have not inherited the earth from our ancestors,
    we have borrowed it from our descendants."

I have used 7260Q Triple Axis accelermeter from freescale its great and
easy to use. You can also select the G-range 1.5, 2, 4, 6 g.

http://www.sparkfun.com/commerce/product_info.php?products_id%2

I would just plug this into the ADC ports on an AVR combined with a
serial lcd and you will have something up and running in no time at
all.

Hope this helps.
Michael

We designed in an Analog Devices ADXL210jqc but didn't needed it after
all.
I think they cost us about $20 each for 20 pieces.

The output is a PWM signal that can be read by a microcontroller
without the need for sensitve Analog to Digital conversion circuitry.

http://www.analog.com/UploadedFiles/Data_Sheets/ADXL210E.pdf
http://www.analog.com/en/prod/0,2877,ADXL210,00.html

-howy