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How to write code to use TSL237-LF sensor

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Joined: 3 years ago
Posts: 4
Topic starter  

Hello everyone!

I'm newish to coding and electronics in general, and I'm having some trouble using a light to frequency sensor.

The TSL237-LF.

I've scoured the internet for code examples and found a couple, but they do not seem to give me good readings. 

Does anyone have experience with this sensor, and could you please help.  I out of my depth on this one.


Thank you.


Joined: 5 years ago
Posts: 2045


So what is your circuit layout and what code are you using that does not seem to give you good readings?

I read that,
Power-supply lines must be decoupled by
a 0.01μF to 0.1μF capacitor with short leads placed close to the
TSL237 (Figure 17). A low-noise power supply is required to
minimize jitter on output pulse.

Have you met those requirements?

I also read that the Arduino is not all that great at reading frequencies. I am assuming you are using an Arduino?


Joined: 3 years ago
Posts: 4
Topic starter  


Hey, thanks for fielding my question.

I do have a 0.1μF capacitor in the circuit. the leads are about 6" though.

I am using an Arduino Uno, and it is powering the sensor.

Since I last posted; I used a different sensor, and have gotten much better results.  I may have damaged the first one when I soldered the leads onto it. 😬 I am new at this and expect to make mistakes.

the code I am using is:

int TSL237 = 2;
#define READ_TM 1000
int GreenLED = 8;

volatile unsigned long pulse_cnt = 0;

unsigned long cur_tm = millis();
unsigned long pre_tm = cur_tm;

unsigned int tm_diff = 0;

void setup() {

// attach interrupt to pin2, send output pin of TSL230R to arduino 2
// call handler on each rising pulse

attachInterrupt(0, add_pulse, RISING);

pinMode(TSL237, INPUT);
pinMode(GreenLED, OUTPUT);
digitalWrite(GreenLED, HIGH);

void add_pulse(){

unsigned long get_tsl_freq() {
// copy pulse counter and multiply.
// the multiplication is necessary for the current
// frequency scaling level. Please see the
// OUTPUT SCALING section below for more info

unsigned long freq = pulse_cnt;

// re-set pulse counter
pulse_cnt = 0;


void loop() {
pre_tm = cur_tm;
cur_tm = millis();

if( cur_tm > pre_tm ) {
tm_diff += cur_tm - pre_tm;
else if( cur_tm < pre_tm ) {
// handle overflow and rollover (Arduino 011)
tm_diff += ( cur_tm + ( 34359737 - pre_tm ));
if( tm_diff >= READ_TM ) {

// re-set the ms counter
tm_diff = 0;

unsigned long frequency = get_tsl_freq();




Here are a couple of pictures of the circuit. I am using a green LED with a 220kohm resistor for low light, as I don't want high frequencies, because I read that it overloads the Arduino.


What other controllers would you suggest? Or maybe another sensor would work better for what I am trying to do.  You can see my other post on measuring translucence to see what I'm trying to do.

Thanks again for the help.

Joined: 5 years ago
Posts: 2045

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