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June 30, 2022 13:32
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/* | |
simple example for optical distance sensor with IR LED and BPW40 | |
LED has 470R series resistor and is connected to pin given as IRLED (Pin 8 / PB0) | |
BPW40 is wired with collector to +5V, emitor to 1k8 to ground. | |
Emitor of BPW40 is capacitively coupled with 100 nF to pin given as BPW40 (pin A1, PC1) | |
That pin also has a 100k resistor to ground | |
(D8) + 5V | |
| | | |
470R | | |
| c | |
V (bpw40) 100n | |
- e---------||---0-----> input pin (A1) | |
| | | | |
| 1k8 100k | |
| | | | |
GND GND GND | |
LED and BPW40 are pointed in the same direction. Reflection is used to measure distance. More reflection assumes closer object. | |
Object could also be 'more reflective' instead of closer, so to measure distance use a uniformly reflective object e.g. brown/grey cardboard. | |
AC coupling eliminates DC noise (daylight) | |
Resistors values are 'what was on hand'. Other values might work even better. (Higher LED current). Tune to taste. | |
cc-by-sa 2022 Lucas, www.eluke.nl | |
*/ | |
const char IRLED = 8; // pin for IR led for distance sensor (Pin 8 is PB0) | |
const char BPW40 = A1; // pin for fotodiode of distance sensor (A1 is PC1) | |
const int tickmillis = 25; // how fast/slow the loop ticks, in miliseconds | |
// Make this NOT match a harmonic of your local mains frequency so synchonous detection eliminates mains hum. | |
// 25 should be ok. | |
void setup() { | |
pinMode(IRLED, OUTPUT); | |
Serial.begin(19200); | |
} | |
void loop() { | |
// put your main code here, to run repeatedly: | |
static unsigned int prevmillis=0, nowmillis=0, sample; | |
nowmillis=millis(); | |
if((nowmillis-prevmillis)>tickmillis){ | |
prevmillis=nowmillis; | |
// pulse IR led and synchonously read reflecion from capacitvely coupled fotodiode | |
// (Synchronous detection / rectification) | |
digitalWrite(IRLED,HIGH); | |
distance = analogRead(BPW40); | |
digitalWrite(IRLED,LOW); | |
Serial.println(sample); // plot with Arduino Serial Plotter | |
} | |
// TODO: optionally average out samples further, or directly use as 'distance' measurement (dist = (dist + sample) << 1 ) | |
} |
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