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signal conditioning circuit for LDR

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Osawa_Odessa

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Good evening, everybody!
I am having a school project in which I need to measure ambient light and coontrol a light. When it is dark, the light is turned on.
I have just finished it but my teacher ask me have to use a signal conditioning circuit. I have searched about it but it seems hard to me. There is one circuit here:https://www.thcalasanz.com/thcal/buffer_ldr.html
However, I am not sure if it is a good idea. Could you suggest some circuits that I need to consider?
Bellow is the circuit and my project.
Your help is greatly appreciated!
P.S My project is work well but it doesn't have signal conditioning circuit. I think more about it but I really can come up with a good one.:???:
 

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Last edited:

Although a pic or microcontroller is an easy way to do the task...

I believe the aim of this lesson is to use the simplest devices which will do the job.

An op amp is a convenient way to detect the sensor's resistance in strong or dim light.
The signal conditioning circuit is really more like a wheatstone bridge.
It detects the voltage differential on the sensor, then amplifies it, then turns the led on or off.

In other words, the op amp decides by analog calculation. The pic makes the decision by digital / programming calculation.
 
BradtheRad said:
Although a pic or microcontroller is an easy way to do the task...

I believe the aim of this lesson is to use the simplest devices which will do the job.

An op amp is a convenient way to detect the sensor's resistance in strong or dim light.
The signal conditioning circuit is really more like a wheatstone bridge.
It detects the voltage differential on the sensor, then amplifies it, then turns the led on or off.

In other words, the op amp decides by analog calculation. The pic makes the decision by digital / programming calculation.
Click to expand...
Thanks a lot BradtheRad!
Do you mean that I don't need microcontroller at all?
How about Light Level Sensing Circuit here: https://www.electronics-tutorials.ws/io/io_4.html
Is it considered a signal conditioning circuit?
Is there a circuit that create the signal from LDR to two level 0V and 5V then I will use pic to control a lightbulb? This is a part of my project and the project use pic16f8777a therefore I think I need to use pic with it.
 

Yes, you should be able to adapt one or more of the examples at the electronics-tutorials webpage. A single transistor may be sufficient, if you can adjust the resistor values correctly.

To condition the signal may mean you amplify it...
or it may mean you shift its volt range up or down, or you remove noise, or you turn it into square-ish pulses, etc. (Or a combination of effects.)

The pic should be able to detect 0 and 5V. Be careful how much gain you give your original signal. The pic may be harmed if the incoming signal voltage is above 5 or below 0V.
 
simple method with darlington transistor

ldrlght.gif

ref: http://www.technologystudent.com/elec1/ldr1.htm

LDR with op-amp:

light sensor.jpg

View attachment light-Sensor.bmp

LDR-Light-Detector-circuit.jpg

Ref:
http://www.electronicecircuits.com/electronic-circuits/ldr-light-detector
**broken link removed**
http://www.gammon.com.au/forum/?id=11011

u can try with 555 too cheap and the best method. works pakka... :)

electronic-mailbox-front-door-with-ic-555.jpg

LDR-photo-alarm.jpg

Ref:
**broken link removed**
http://www.electroniq.net/555-timer-circuits/555-timer-photo-alarm-circuit.html

for ur knowlege gaining u can try all three method.
 
Last edited:
Thanks a lot jpsganesh and BradtheRad!
I arranged some of these circuits and it works well:-D
 

all the best Osawa_Odessa :smile:
 

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