Hello

I have an error somewhere obviously in my elementary setup here.

Picked up one of these today

Just a small photo resistor light sensor

https://osepp.com/electronic-modules/sensor-modules/69-light-sensor-module

Came across a schematic on the Ostepp website for it. Looks like this.

https://osepp.com/downloads/pdf/LIGHTSENSOR.pdf

Simple Voltage divider circuit.

I found the part of the photo resistor and it is a

http://szhaiwang.en.alibaba.com/product/518889404-212333514/5mm_photoresistor_MJ5516_5_10k_OHM.html

Just for the hell of it, i built a circuit simulation in multi sim

The photo Resistor has a range of 5 ohms to 10k ohms

So i wrote a little matlab script to plot the output voyage based on a 5 volt input

Got the plot and confirmed the results with my MultiSim model

Notice at 5V reference with the Photo resistor set to 5k i get about 700mv

With the plot being about 5000 ohms on the photo resistor i also see about 700 mv on my matlab plot

Looks right. and it also confirms with the voltage range I'm seeing on the multisim model

So i take the doodad out of the box and throw 5 volts on it to give it a try.

The output range according to my multimeter

is from about .600 volts to 2.8 give or take a little and depending on what kinda light you have in the room on or off

Can anyone see why multi sim and my math is so far wrong from what the circuit is actually doing?

Cant find any documentations from the manufacture about what it should be outputting

The resolution from the device via the math and multi sim shows very little resolution making it hard to read on a micro controller so i did in fact question it when i saw the results

Can anyone see what i did wrong? Only think i can think of is that schematic is not correct for the part because i hope i can do some voltage divider math at this stage in the game

I have an error somewhere obviously in my elementary setup here.

Picked up one of these today

Just a small photo resistor light sensor

https://osepp.com/electronic-modules/sensor-modules/69-light-sensor-module

Came across a schematic on the Ostepp website for it. Looks like this.

https://osepp.com/downloads/pdf/LIGHTSENSOR.pdf

Simple Voltage divider circuit.

I found the part of the photo resistor and it is a

http://szhaiwang.en.alibaba.com/product/518889404-212333514/5mm_photoresistor_MJ5516_5_10k_OHM.html

Just for the hell of it, i built a circuit simulation in multi sim

The photo Resistor has a range of 5 ohms to 10k ohms

So i wrote a little matlab script to plot the output voyage based on a 5 volt input

V_source = 5;V_source = 5;

**R1 = 5000;**

R2 = 1000;

R3 = linspace(5,10000,500);

R2Combined = zeros(1,500);

Vout = zeros(1,500);

for k = 1:500

R2Combined(k) = (R3(k)*R2)/(R3(k)+R2)

Vout(k) = R2Combined(k)/(R2Combined(k) + R1)*V_source

end

plot(R3,Vout)

R2 = 1000;

R3 = linspace(5,10000,500);

R2Combined = zeros(1,500);

Vout = zeros(1,500);

for k = 1:500

R2Combined(k) = (R3(k)*R2)/(R3(k)+R2)

Vout(k) = R2Combined(k)/(R2Combined(k) + R1)*V_source

end

plot(R3,Vout)

Got the plot and confirmed the results with my MultiSim model

Notice at 5V reference with the Photo resistor set to 5k i get about 700mv

With the plot being about 5000 ohms on the photo resistor i also see about 700 mv on my matlab plot

Looks right. and it also confirms with the voltage range I'm seeing on the multisim model

So i take the doodad out of the box and throw 5 volts on it to give it a try.

The output range according to my multimeter

is from about .600 volts to 2.8 give or take a little and depending on what kinda light you have in the room on or off

Can anyone see why multi sim and my math is so far wrong from what the circuit is actually doing?

Cant find any documentations from the manufacture about what it should be outputting

The resolution from the device via the math and multi sim shows very little resolution making it hard to read on a micro controller so i did in fact question it when i saw the results

Can anyone see what i did wrong? Only think i can think of is that schematic is not correct for the part because i hope i can do some voltage divider math at this stage in the game

Last edited: