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Can't get Microbit with laser trip wire alarm to work

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Hi!

I'm trying to get this to work, but can't
https://littlebirdelectronics.com.au/guides/73/laser-head-sensor-with-micro-bit

I've noticed that the light dependent resistor is differently laid out from the one in the tutorial, and have accounted for that accordingly. (i.e. VCC is on the right in the right unit - picture below - as opposed to on the left as per the tutorial)
Is this picture below ACTUALLY the light dependent resistor?  With the black bulb at the top the actual light dependent resistor?
ldr.jpg 106 KB

There are other bits and pieces that are a bit weird.
Step 5 refers to the "buzzer module", but I'm *pretty* sure it's meant to be the light dependent resistor.

Steps 13 & 14 are referring to the sensor value being above 600, but I only ever see it in the ~500 range. BUT, that's possibly because I've set it up wrong?

What I'm trying to find out is... Are the steps in there still accurate for the latest model of things?
Also, I can't figure out how the laser trip wire changes the resistance of the setup. The analog pin read is off of the light dependent resistor, but the laser is connected - as far as I can tell - with a single *write* pin. The only thing that I can think of, is that the laser is meant to be pointed at the light dependent resistor. However, the setup in the diagram does not allow for that at all since the laser won't be pointing at the resistor at all.

So yes, very confused, can't figure out how to get this working. >.<

Any help please? :D 

Cheers

asked December, 25, 2021
Jonathan Tan

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