about LDR component

tunatopraktan · Joined: 19 Mar 2021 Posts: 13

Hello friends,
I have a circuit to print pcb. The circuit has a LDR. I know all components model number except LDR. How can i understand the model of LDR ? I will send the circuit with BOM list to China to make pcb and i don't want to be used different character LDR.

temtronic · Posted: Sat Apr 10, 2021 4:35 am

LDR ( Light Dependent Resistor) have high resistance when in the dark, very low resistance when in bright light.. They are 'nonlinear' devices and the datasheet will have both a chart of 'typical' values as well as a graph to aid you in using them.
The BOM should give the part number and mfr of the LDR. Normally you use the LDR in a voltage divider with a fixed resistor. That value depends upon how it's to be used(on/off vs linear). You'll probably need an opamp buffer between it and the PIC, depending on which PIC you're using and the 'quality' of the signal.
Some 'damping' may be needed for , a simple capacitor as an R-C filter works well. I suggest some serious 'bench time' to decide the proper values of components, testing under real light conditions, since a PIC is involved,coding as well as hardware can 'fine tune' the performance of the device.

Jay

Ttelmah · Joined: 11 Mar 2010 Posts: 19538

Yes, Light Dependent Resistor, is the commonest meaning of 'LDR'.
Unfortunately, it can also be used for a low dropout regulator, and probably
a few other things as well... Sad

If it is a Light Dependent Resistor, then if you have one you can test, the
obvious thing is to measure the resistance 'dark', and again at a known light
level (probably use a light meter app on a mobile phone to give a measure
of this). You can then calculate the basic slope and resistance for the particular
unit.

temtronic · Posted: Sat Apr 10, 2021 9:56 am

yeesh.. never thought of Low voltage dropout regulator... Confused

Those weren't invented when I starter 'electronics' :lol:Hmm, I wonder if '0A2' would be the great,great,great grandfather of the LDR? Wink

I'm betting not many KNOW let alone USED them......

That's the problem with 3 letter 'words'.. different meanings based upon age and occupation....
Jay

tunatopraktan · Joined: 19 Mar 2021 Posts: 13

Thank you very much friends.