Hello everyone
i have some questions about the Analogue to Digital Converter inside the Arduino ATmega168.
I've got a speed sensor have two wire, which is generating around 10Vmax in Alternating Current.
I know that the Arduino could only take 5V max input. So here's the question, can i just reduce the voltage of AC to 5V that allow the arduino to do the conversion ? i mean 5V AC to the arduino and then calculate the gear speed through the ADC and timer.
Yes you can use a simple voltage divider (a couple of resistors in series) to measure a 10 DC voltage. You have another problem in that an AC voltage has a negative voltage value half the time and negative voltages are not allowed to be wired to an Arduino I/O pin. So you really need a diode and filter cap wired to rectify and filter the AC voltage and then wire it to a voltage divider.
Lefty
which is generating around 10Vmax in Alternating Current.
Is that 10V peak-to-peak? RMS? Is it a sine wave? A square wave? Is it the voltage that's varying? Or the frequency?
You can't really decide how to measure until it's clear what you're measuring.
Is that 10V peak-to-peak? RMS? Is it a sine wave? A square wave? Is it the voltage that's varying? Or the frequency?
You can't really decide how to measure until it's clear what you're measuring.
yes, it is peak to peak
and it is sine wave. The max frequency is around 3KHz which is showing through the oscilloscope.
If i drop the voltage to 5V and convert it to DC, could i use the arduino to help me for converting the Analogue to Digital (sine wave to square wave) and then calculate the wheel speed.
i have see the example in learning of arduino, there is a calibration which is using light sensor, is it? it is translating the analogue to digital that can activate the LED.
is the calibration using the ADC (Analogue to Digital Converter)?
You want to measure frequency, not voltage. Best to use a diode to drop the negative swings, a voltage divider to get to 3.5-4Vm and go into a digital pin. You might even figure out how to use the timers as counters to determine frequency.
http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1231326297
THX !
That's the thing that i am searching
counter ! 
ah, i still have a question
If i am doing the conversion, ADC, i just drop the voltage and change it to DC first, right?
then writing the script like using
int sensorPin = 0;
int sensorMin = 1023;
int sensorMax = 0;
void setup() {
Serial.println("Frequency Counter");
void loop() {
// read the value from the sensor:
sensorValue = analogRead(sensorPin);
i am still trying to write, :-[