Uploaded February 2025 | Updated September 2026, 2 weeks ago
In this video I'm going to give you a quick introduction to light dependent resistors, LDRs or photoresistors - call them what you want.
These light dependent resistors are very useful because they can be used as cheap light sensors for many electronic gadgets.
They're made from a form of semiconductor material, but they are still classed as resistors because they don't act like diodes or transistors.
There are two circuit symbols used for LDRs: the one with the rectangular resistor is probably more common, although the zig-zag line version is still seen quite often.
In terms of their construction, they're made from a semiconductor material, cadmium sulphide is very common, but indium antimonide and other materials are increasingly used.
LDRs have contacts on the top and to maximise the light capture they often have a zig-zag or interdigital pattern as we see here.
The LDRs have a high resistance in the dark, possibly several megohms and in the light the resistance can fall to as low as a few hundred ohms. The main disadvantage of these photoresistors is that they are slow to respond.
Find out more about light dependent resistors / photo resistors: electronics-notes.com/articles/electronic_components/resistors/light-dependent-resistor-ldr.php
Website homepage: electronics-notes.com
Please don't forget to subscribe to our YouTube channel: youtube.com/electronicsnotes?sub_confirmation=1
In this video I'm going to give you a quick introduction to light dependent resistors, LDRs or photoresistors - call them what you want.
These light dependent resistors are very useful because they can be used as cheap light sensors for many electronic gadgets.
They're made from a form of semiconductor material, but they are still classed as resistors because they don't act like diodes or transistors.
There are two circuit symbols used for LDRs: the one with the rectangular resistor is probably more common, although the zig-zag line version is still seen quite often.
In terms of their construction, they're made from a semiconductor material, cadmium sulphide is very common, but indium antimonide and other materials are increasingly used.
LDRs have contacts on the top and to maximise the light capture they often have a zig-zag or interdigital pattern as we see here.
The LDRs have a high resistance in the dark, possibly several megohms and in the light the resistance can fall to as low as a few hundred ohms. The main disadvantage of these photoresistors is that they are slow to respond.
Find out more about light dependent resistors / photo resistors: electronics-notes.com/articles/electronic_components/resistors/light-dependent-resistor-ldr.php
Website homepage: electronics-notes.com
Please don't forget to subscribe to our YouTube channel: youtube.com/electronicsnotes?sub_confirmation=1
