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Microcontroller Based Smoke Detector

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eddietang

New Member
Can anybody help me, im doing a project , my title is build a simple microcontroller based smoke detector, it just a simple circuit with output led and buzzer and input ldr but im dont what component i need to use and how to build the whole circuit and so the programming work. Can anybody help me plz?
 

BioniC187

Member
From what you have listed, i am assuming you are planning on using the ldr to detect when the light source dims(based on the intro of smoke) and then activate the led and buzzer?
 

KeepItSimpleStupid

Well-Known Member
Most Helpful Member
I would think something like this could work: **broken link removed**

I would think that the distance needs to be rather far apart because more smoke means more attenuation.

So, at power up, you could do a calibration. In operation, you would want to check for aging. Either the detector gets some dust on it over time or the combo ages. In the box itself have a recalibrate button for when someone cleans the detector with a burst of air or have it happen when the lid is removed/replaced.

The basic design is a current to voltage converter and a constant current source.

You need a low battery alarm with a possible blinking LED.

You need a test button.

You can buy smoke in a can to test detectors.

For extra credit:
You could make it mains powered with battery backup
You could make it addressable.
Allow multiple detectors.
Use and EOL terminator.
Have them talk to a min panel.
 

eddietang

New Member
i just need a simple smoke detector wif pic16f84a by using ldr to detect when the light source dims and then activate the led and buzzer.
 

KeepItSimpleStupid

Well-Known Member
Most Helpful Member
You still need to signal condition the sensor and the battery voltage varies over time. So, the LED needs a current source or a voltage source and a resistor. The output could be just a resistor and a phototransistor to ground, BUT you would have to make the circuit ratio-metric meaning the output is relative to the supply voltage.
 

BioniC187

Member
He could have voltage regulator and an indicator when voltage is low and operation is compromised. 9V source, 5V regulator
 
Last edited:

colin55

Well-Known Member
The PIC16F84A does not have an ADC. You are advised to go to a PIC16F628A.
You will also need an amplifier on the output of a Darlington Photo Transistor to detect the small change in output.
 
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