I have set up a breadboard to read the signals from a piezoelectric accelerometer. The piezo itself outputs 10mV per G of acceleration, so far i get a reading when I give it a thump, but the Arduino's in built ADC doesn't pick the signal when the piezo is shaken as exactly 1g, which I am using a shaker to do.
I have also tried an Adafruit 16 bit ADC, but that also does not pick anything up.
Attached a picture of my breadboard below, it consists of a 4.7ma constant current diode to power the accely, a 15v supply which is the minimum recommended for the sensor. a 10uF capacitor, charged by the accelerometer, and a 4.7k pull down resistor.
Does anyone have any ideas as to why it doesn't pick up low outputs?
The smallest signal an Arduino can measure is about 5mV. This will work on paper but in practice trying to measure down to a single bit doesn't work because of electronic noise (especially when you add a breadboard to the mix).
Similarly the 16-bit ADC.. The breadboard, wires, etc. is most likely drowning the signal.
You can try amplifying the signals with an op-amp but really it's much better to get an accelerometer with an SPI/I2C interface. These chips do all the measurements internally and you just read the results over the data bus.
joe642:
I will have a go with an op amp maybe, the accelerometer I am using is for industrial applications so they ebay one would be no good.
eBay is just an example, you can search for the chip at more expensive suppliers if you want to. I'm sure Adafruit will have one and Adafruit products are made in New York in the US of A.
It's really just an chip on a PCB though, there's not much they can do wrong even in China.
joe642:
Attached a picture of my breadboard below, it consists of a 4.7ma constant current diode to power the accely, a 15v supply which is the minimum recommended for the sensor. a 10uF capacitor, charged by the accelerometer, and a 4.7k pull down resistor.
Is that the recommended pull-down resistor value? Typically piezo elements produce
very small currents, so a large resistor value is normally needed to see a significant
voltage.
