Ever needed an application where the resistance of a resistor needed to vary proportionately in response to a PWM or a varying analog voltage? Yes, this is where an LED-LDR opto-coupler becomes so useful. The following image shows the symbol for a LED LDR opto-coupler. Any other regular opto-coupler, such as an LED/transistor, LED/FET, or […]
LDR
Simple LDR Motion Detector Alarm Circuit
Here I have explained how to build a simple LDR based motion detector sensor circuit using ordinary parts such as LDRs and opamps, reasonably accurately. What are Motion Detectors Motion detector or sensor alarm is a device which detects the presence of a motion or movement within a certain fixed range and raises an alarm […]
Blinking LED Circuit using LDR and Resistors
This is perhaps the most simplest looking LED flasher that does not depend on any semiconductor. This LED blinker circuit utilizes ordinary passive components like a few resistors, a capacitor and an LDR. Meaning, this LED flasher does not depend on transistors or ICs to create the blinking effect. Circuit Description The LED-LDR combination is […]
9 Useful LDR Circuits Explained
In this post I have explained 9 LDR circuit projects that uses LDR light sensor to trigger a load ON/OFF through a relay. These circuits are mostly triggered by the absence or the presence of light on the LDR. The circuits are built using transistors, op amps and LDR along with a switching relay. Let’s […]
Solving LDR Controlled LED Emergency Lamp Problem
The following post discusses the troubleshooting of an automatic LDR controlled emergency lamp circuit which was requested to me via email by one of the keen followers of this blog. I have explained about the issue and its solution. Technical Specifications Dear Sir, I am following you on your website and I thank you for your valuable […]