A light dependent resistor (LDR) is a resistor where the resistance decreases with increasing light intensity.
2
votes
2answers
135 views
Making an obstruction avoiding device without microcontroller
I want to make a toy device which spins to the left whenever there is an obstruction in front of it, without any microcontroller. Can anybody please check whether my approach in building the device is ...
5
votes
4answers
449 views
Why use a pull-down resistor with a LDR and microcontroller?
I am looking at this:
http://learn.adafruit.com/photocells/using-a-photocell
It's connecting VCC <-> LDR <-> resistor <-> GND. And the analog ...
0
votes
0answers
44 views
Using ldr to power a circuit on night
I've been trying all night to use a 10k ldr to power on a circuit at night without sucess.
It's a simple circuit that uses a MAX1555 to charge a lipo battery and at night it should turn on a led ...
1
vote
2answers
66 views
Peak voltage rating means voltage drop?
This LDR is said to have Peak voltage rating of 400V in the description. Does this equal the voltage drop, meaning that I need to supply at least 400V or is it the maximum voltage value?
3
votes
1answer
70 views
Making an adjustable resistance
In my latest circuit, I needed an adjustable resistance to adjust the ratio of a nearby ldr. It looks roughly like this: (btw, I'm not so sure that this schematic is correct. Feel free to fix it :)
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0
votes
1answer
115 views
virtual light communication
I have to design a project that uses an LED to transmit data and a LDR to receive the data or signal from the LED. But the problem is I have to use two Arduino UNO boards, one for LED transmit and ...
4
votes
1answer
462 views
How to inteface LDR with microcontroller?
I need to interface LDR with micro controller,
While searching some circuit ideas on the internet I came across two different ideas.
One was using a voltage divider circuit with another resistor and ...
8
votes
1answer
1k views
Plugging a LDR into GPIO pins of a Raspberry Pi
I want to connect a LDR into the GPIO pins of my Raspberry Pi, I know that Raspberry Pi doesn't have an analog-to-digital converter so what I want to do is to signal a HIGH signal (3.3v) on the GPIO ...
3
votes
3answers
249 views
Making a burglar alarm
I am using a passive infrared sensor TMP006 to make a burglar alarm. However I notice that the data returned is not accurate enough. Are there any other ways by which I can improve my accuracy. Or ...
2
votes
1answer
2k views
Light sensor switch using LDR
What is the reason for using the transistor (2N3904) is this circuit? What good is this transistor doing in this circuit.What happens if we remove the transistor from this circuit? And what will ...
4
votes
1answer
639 views
How to find Emitter and Collector of an LDR
How can we find the emitter and collector of an LDR. I am using it in the following circuit but I don't know how to identify which terminal of the LDR is emitter or collector.
Here it is mentioned ...
2
votes
1answer
358 views
Strange data from arduino LDR sensor
I'm getting strange data from my LDR sensor.
Without any significant changes in light is constantly goes from 0 to its max value 1023 and back.
What could be the problem? Is it possible my LDR ...
1
vote
1answer
198 views
LDR circuit does not change sound frequency
I am a complete beginner in the field of electrical engineering. In the Arduino cookbook, there is this circuit:
I have been trying to reproduce it, and I do hear a sound after uploading the ...
1
vote
2answers
255 views
LDR Component Obsolescence
The Light Dependent Resistor (LDR) that I use in MintyTime, Excelitas Tech VT93N2, has been discontinued by the manufacturer. I'm having trouble finding a comparably priced (e.g. < $0.50 @ 100+) ...
0
votes
2answers
404 views
Will this circuit work? AND Gate behaving strange?
I've just built a circuit using Yenka, and it's meant to be a system that basically senses light, and whether a switch is on or not, and when both of these are true, the buzzer will, buzz.
I'm quite ...
4
votes
4answers
906 views
Relay? No clue how to breadboard?
I've got a circuit diagram I'm working from, this one:
And I'm currently trying to breadboard it, as seen here:
I've been trying to search google on how to wire a Relay, and am not yielding any ...
3
votes
1answer
346 views
Help breadboarding a circuit?
I've been building a light based alarm system, using an LDR, Op Amp, AND gate, some resistors, and an output of buzzers..
Here's my circuit so far... It beeps when it senses light as well as being ...
2
votes
3answers
258 views
Logic problem with alarm system?
In short, I have a bag that I'm making, the top of the bag is lined with LDR's (3-6), and there's a hidden switch to toggle the alarm on/off. I'm horrible at circuits, but I program, so it looks like ...
6
votes
5answers
975 views
Will there be any effects on a signal in a long wire?
I am going to need a large length of wire from my microcontroller analogue input to a LDR or similar sensor. The length of wire is likely to be about 100m so will it have any affects on the reading ...
1
vote
1answer
636 views
Response curve of an LDR?
Can someone tell me (or link me) the response curve of an LDR. I don't mean the frequency response, just the intensity response; is it linear, or logarithmic?
