automatic street light controller dbt

[Rinu]

This is my first proj in microcontrollers and i’m really confused on how to interface the ldr to 8051.

do i need to make use of an adc or a comparator , or is it possible that the output of ldr circuit can directly be fed to the microcontroller pin????Please do help me with a circuit diagram

 

In addtn to this i also have a pir sensor interface to 8051 for variation of light intensity at night on human detection…

Thanks in advance !!!

[Ashutosh Bhatt]

using  LDR with an ADC or comparator depends upon what you want to do

if you simply want to ON / OFF LED light as light fall / not fall on LDR then use comparator

if you want to vary intensity of LED as light intensity changes then use ADC

 

yes also you can fed direct output of LDR to micro controller. in that case try to detect logic 1 on pin when light does not fall on LDR

[Rinu]

My project is automatic street light controller with light intensity variation at night based on human detection.The lights will be on with 50% power when there is no human detection by the pir sensor and light intensity will be maximized when person is detected.

 

 I’m sorry bt i didnt clearly understand the last option on feeding the output of the ldr circuit (which is analog) to mcu directly, is that possible by suitable coding or something or is it done using some circuit ?

[Ashutosh Bhatt]

forget about giving direct output of LDR to micro controller

because you need to vary intensity so you have to use ADC.

as light intensity falling on LDR changes LDR op voltage chages.

this voltage is given as input to ADC so its digital output will also changes. change in this output will change intesity of LED.

to change LED intensity use built in PWM of AVR controller.

 

[Author]

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