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Darkover

Darkover

Archangel
Jul 29, 2021
5,649
i used a astable multivibrator for a ir emitter and a Monostable Multivibrator combind with a ir receiver and sr latch basically creating a invisible line that when crossed would sound a buzzer the sr latch was used to remember it had been triggered basically a continuous source of ir was emitted and the ir receiver would rest the Monostable Multivibrator

Astable multivibrator: generated a continuous pulse signal to drive the infrared emitter — this keeps it emitting modulated IR light, which helps with noise immunity.

IR receiver + monostable multivibrator: The receiver resets the monostable pulse, meaning as long as infrared receiver is seen, the monostable doesn't time out — clever debounce/integrity handling.

When the IR beam is broken: The monostable isn't reset anymore, so it times out and its output changes.

SR latch: Captures that the line was crossed, holding the triggered state until manually reset.

Buzzer: Alerts that the beam was broken — created not just a trigger, but a memory of the event.
Images
Monostable diagram
Zk3PI
 
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lamy's sacred sleep

lamy's sacred sleep

what's a way to just be competent
Nov 22, 2024
1,522
electronics on the sui forum, awesome
 
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GlassMoon

GlassMoon

😶‍🌫️
Nov 18, 2024
389
Nice, it's been a while since I embarked in these kinds of projects. The top one is the IR emitter, I guess? With the values of the capacitors and resistors as they are, it appears to me it would slowly blink rather than send a high frequency noise immune pulse?

If you have old remote controlled devices which you can get parts from, those IR receivers usually work in the 30-45kHz range with a bit of noise filtering built in. They may even be TTL compatible, such that an Arduino could be used to check for and record interruptions.
 
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Darkover

Darkover

Archangel
Jul 29, 2021
5,649
Nice, it's been a while since I embarked in these kinds of projects. The top one is the IR emitter, I guess? With the values of the capacitors and resistors as they are, it appears to me it would slowly blink rather than send a high frequency noise immune pulse?
i built it back when i was 16 in 2002 from salvage parts of old electrical equipment likes TVS and remote controls, the top one is the IR emitter but the circuit diagram is just a circuit of a astable multivibrator taken from the internet for illustration purposes only.
If you have old remote controlled devices which you can get parts from, those IR receivers usually work in the 30-45kHz range with a bit of noise filtering built in. They may even be TTL compatible, such that an Arduino could be used to check for and record interruptions.
i haven't done any work with electronics for about 20 years now Arduino wasn't even a thing back then
 
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