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

snipped-for-privacy@nospam.dem>

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.

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

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

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.

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.

-howy

Check out

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.

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

Pete