Search for LDR in Topics

LDR Calibration ?

I am planning to build a lumenmeter but I am not getting how to calibirate the LDR and do not have any lumen meter so if could tell the estimate lumens out of a 5w CFL or any other device might help

Question by Bot1398    |  last reply

Someone on LDR!!!

I'm new to this site, I'm interested in someone in a long distance. We both live 1900 miles apart I live in New Jersey and She lives in Central America. I first known her who's actually beknownst to my Step-Siblings of mine while she still is and was an employer at a Teen Clothing Store about two years ago which a Step-Sibling of mine owns the place. Just a month ago just hours before My parents and I we're to go back home as our Spring Break Came to a conclusion, We exchanged phone numbers so we can reach contact after I asked her's. Then weeks later I called her home and she's only answered once. I called once again many times the problem is that she doesn't still answer the reason for this is cause she barely uses her phone due to the High Violence there. I know the phone number to her job but the problem is that I don't want to get her in trouble since her boss isn't there all the time. Some think that She's rejecting me and she's not because she did gave me her number. If she wasn't interested in me She wouldn't give me her number. She doesn't even know how to use the internet or chat. Another thing is that She doesn't have a Home Phone Either. I plan on sending her maybe a letter but I want to see if u can tell me if I could also give her a Friend card or anything at all so she can cheer up. I plan to see her once again when we come back there this August and i'll tell her the truth if not I might go on. She only lives with her brother and Sister. She and Her sister work together there. Sometimes I feel confused that I really want to get to know her. Some think she has a boyfriend but she told me she's not cause they said that she does but I really can't buy what othes might say so It's good to feel with me to drop some comments. I'll just enjoy life as always doing what I do during my normal routines. I haven't thinked of her much then before I will keep that as a promise. We'll thanxs anyway!!!

Topic by Pcons16  

LDR Grid + Smartphone = ?

Hi, I've got an idea but I don't know what it can be used for, yet. Maybe you'll have some ideas for useful applications based on this concept. The idea is to make a grid of LDRs which fits the size of a smartphone/tablet screen, write some code which draws a similar grid on the screen (or just switch images of that grid) so that each LDR will be affected by the light (and color) provided by each cell from the screen.

Topic by nivini    |  last reply

how to make ldr do high power work(12v motor) without becoming hot?

My ldr works fine in controlling 1.5 & 5v motor but connecting in series but when i switch to 9v and 12v motor it becomes hot  maybe i can decrease its heat by adding resistor parallel to ldr so motor will get required current and ldr wont have to suffer all current or maybe i have also changed power source in second case to a 12v and 3amp  i thought i am not ta\ing 3 amp current according to I=V/R but P=VI so if current decrese my power source's voltage .

Question by Atul009    |  last reply

Hi, I need some help to understand how is this working. Answered

This is the source of my question. My question is : why is the LED lighting up as it gets dark ? I taught that a LDR (light dependent resistor) is supposed to let current pass only when light is shining on it (source), so why here is it letting current pass only when it's dark. And what is the role of the transistor in this circuit ? Any clarification is much appreciated, Thank you.

Question by Eunix    |  last reply

Suitable transistor or IC to run 1 Watt LED in low voltage? Answered

I want to run 4 x 1Watt LEDs from a 3.7V source (10000mAh). LED DC Forward Current: 350mA The purpose is to sue it with a motion sensor. Please suggest a transistor or IC with maximum efficiency. Update: I found that the "IRF 540" Mosfet is a good solution.

Question by shijilt    |  last reply

LDR or optical reflective sensor?

I am planing to make a line following robot without micro controllers. So I am using a light sensor connected to an AND GATE (the other input being the current to the motor). So since I am using" an and "gate I want the input current to be an absolute zero or some value ,ie the current should not be varrying with the light intensity. Besides I think I might drop the "and gate" thing and use an OPAMP instead as it would give me a varrying output current which is all I need

Question by chrissunny94    |  last reply

How to use LDR to be run with 12v DC motor?

I want make a project that will run in light but as light turns off, circuit should be break   Im using : 1. 12V / 2Amp motor 2. LDR 3. 12 v supply 4. Laser light Whenever light appends on LDR circuit should pass 12v for the motor and whenever light is brocken circuit should have total resistance so what Kind of components should i use or suggest me LDR based for above circuit

Question by Drg3    |  last reply

How do you inverse the function of a LDR (Light Dependent Resistor) ....? Answered

I know the schematic diagram ... But I don't know how it works ... please can someone explain me the inverse function of a LDR I've posted the schematic diagram also! Thanks

Question by harshesh    |  last reply

What is this black thing next to the capacitor??? is it an LDR?

Http:// ha the shape of half a cilider, and two terminals comming out of it... what is it?it was in an IR controlled mini car...

Question by amando96    |  last reply

how to construct a simple circuit using LDR and transistor? Answered

Materials: LED, LDR, BC337 transistor, 10k trimmer, 500ohms resistor.. 

Question by animeguild53    |  last reply

How to convert LDR reading to lux readings?

I want to make a digital lux meter using a arduino but I am quiet confused on how do I convert LDR reading into lux reading.Please help me for the conversions. 

Question by Bot1398    |  last reply

how to make Automatic light dimmer using LDR?

I tried to make this light dimmer circuit but it's not worked because of my  LDR exploded  why is that..  any similar circuit diagram ? thanks.... This is the circuit i used..

Question by ishan udyoga    |  last reply

how to use LDR as a relay for RC car to increase voltage to motor

Hi there,  I would like to know more about how LDR's work, its quite difficult to source 3 volt relays in South Africa, so I had an Epiphany, why not use 2x  LDR 1x for Forward and 1x for Reverse on an RC car, I don't know much about how responsive the solution is, how many seconds or milliseconds delay  there is? Does it work like a switch?  would it be a viable option on an RC car? I'm sure this could apply to little 3 volt RC cars upwards, I know brushless is the way to go, however this would indeed be a great learning experience.  kindest Regards, Lee Reddy. 

Topic by Leereddy1818    |  last reply

Multiple Photocell Problem (Arduino)?

Hello, I have a problem with using more than 1 photocell. I am using the AnalogReadSerial example to test each one and they are giving me junk. I have tried just one wired to the board and it works fine, but when i wire 4 into a breadboard it gets messy.                                                                                                                                                                                  Here are some pictures                                                                                                                    

Question by D5quar3    |  last reply

arduino and 4051 IC?

I have followed your instructions in and I successfully. I now make the same project but with 11 light sensors use arduino uno rev 3 and 4051 IC. Please help me to modify the original code to work with arduino uno rev 3 and 4051 ICs. Thank you very much link about arduino and 4051 1. 2. 3.

Question by ylinggarjati    |  last reply

Fitlight trainer using arduino

I want to make a fitlight trainer with arduino. I want to make it with leds and LDR ligtht sensors. A random light pops up and when you hover over the sensor it sets it to LOW and then another random light pops up and over and over. Can anyone help me with this idea? I have the code for one light: int LDR = 0;     //analog pin to which LDR is connected, here we set it to 0 so it means A0 int LDRValue = 0;      //that’s a variable to store LDR values int light_sensitivity = 20;    //This is the approx value of light surrounding your LDR void setup()   {     Serial.begin(9600);              pinMode(13, OUTPUT);      } void loop()   {     LDRValue = analogRead(LDR);      //reads the ldr’s value through LDR     Serial.println(LDRValue);       //prints the LDR values to serial monitor     delay(50);        //This is the speed by which LDR sends value to arduino     if (LDRValue > light_sensitivity)       {         digitalWrite(13, HIGH);       }     else       {         digitalWrite(13, LOW);       }   }

Topic by JordyK4    |  last reply

Transistor help.... very basic, LDR/LED

I'm trying to make a very simple circuit to light an LED based on light from an LDR. I have all the components, it's a white LED, I'm using two AA batteries, and the LED glows brightly when I attach it to the batteries, but when I attach it to the LDR, it is either dim or dimmer due to the resistance... I'm sure I need to use a resistor for this... I have some assorted PNPs and NPN2222As... I've looked at a couple tutorials, but none of them seem to work... does anyone know how to do this without any (or as few as possible) other components? Thanks

Topic by perkinsb1024    |  last reply

Arduino LDR tachometer (RPM counter)- not sensitive enough ?!?

Ladies & Gentlemans  ... I would like to ask you, what I'm doing wrong, in this RPM counter ??? As mentioned in my previous questions, I 've got an ARDUINO and I started with my first part - of my project. To count RPM / or speed. I'm using a LDR (light dependant resistor) and green laser as light source. The scheme is like this: + 5V ------- LDR -------------Analog pin 1                                     \                                       \--------resistor (220kOhm) --------- GND The code for this project looks like this : int LDR=1; // LDR is on analog port 1 int val=0; // this is the value, I get from the LRD void sextup(){  Serial.begin(9600); } void loop() {  val = analogRead(LDR); // read the value getting from LDR Serial.println(val); if (val<1018) {delay(4000);} } To explain the value 1018 in the IF condition ... when pointed the laser on the LDR,I get value from 1019-1020. So my idea was, when the value decrease just by one or more ... let me know, that the laser beam has been interrupt. But I realised, that I can cross the laser beam very quickly, and the LDR/Arduino will not notice it. I really don't know, where I'm going wrong. My few suggestions are : 1. wrong method - to use LDR ... should I use something else ??? 2. wrong RESISTOR value ??? ... should I change to different value to make it more sensitive ??? (I tried 2 different values = 220kOhm, 46kOhm ... that's what my voltmeter said :) ... but with both of them I have the same result ) 3. should I use different code ??? Any ideas ??? Thank you in advance for your answers. Zholy

Question by zholy    |  last reply

Does anyone do Automated Car Wash System by using Arduino with LDR?

I wish to know how am i able to write a program which i could control the water spraying, brushing and drying by using arduino.  My project is to use a laser pointer which will send the signal to the LDR and it will trigger the water to spray, brush and dry the toy car on the conveyor belt. Can anyone help me?? I'm a diploma student, and my supervisor is a mad man which who asked me to do such project which he doesn't know either.  The first image is how i think my circuit looks like The second image shows what i had done

Topic by ahchuan.ycc    |  last reply

Laser trip switch? Answered

Hi I want to use a laser and a ldr to switch on a relay using arduino once the laser is tripped the relay turns on and once it trips again its off  could some one help me with the code and schematics i want to use pin 9 as in1 on the relay  thanks a ton in advance

Question by TheGreatResistor    |  last reply

Run a few 1 watt LEDs using transistor from 3.7v ?

Hi , I want to control 5 X 1W leds using a LDR. It will be running on a 3.7v 4500mAh battery . I have the LDR circuit. The problem I face is , normal transistor are not capable of running 5W leds (1W X 5) , it just heats up. i tried some high power transistors , they seem to provide less voltage to the leds. I need a transistor , which can be used as a switch , it should work well in 3 v , should be able to handle max 5W. Any one have any idea ?

Question by shijilt    |  last reply

LDR and/or PWM for energy efficient 'smart' dimmer?

Is there any way to combine a Light Dependent Resistor or other light sensor with a Pulse width modulator to (energy efficiently) dim indoor lighting in the presence of sufficient natural light?  Thanks!

Question by bbawco2    |  last reply

What to do with old robot? / Cybot

I found an old robot that was part of one of those 'build it yourself' magazine series. I was gonna eBay it but found there was actually quite alot of cool stuff in there so I've compiled a list and I'm gonna make an instructable using some of the parts, But I need ideas / help.Here are (the best) parts.2x sets of ultrasonic emitters / receivers2x LDRs large2x smaller photoresistors (used for line following)2x set of inrfa red emitter& reciever leds2x bright white leds + various others2x 9v motors & gear housingsLCD display 5cm squreeepromspeed controllers selector switches etcand a load of pre programmed processors that can't be reused.some more technical details here

Topic by madmanmoe64    |  last reply


Hey!!i started working on a project based on ldr and i realised dc motor and ldrs don't work together so before i buy ac motors i wanted to ask that will it work??thanks in advance.

Topic by robo10302    |  last reply

Arduino alarm with LDR and RFID disable feature?

Hello. I understand that this sounds like an unbelievably simple idea, and so I thought it would be. I have successfully written this first code, that detects an RFID tag and sounds a beep, but I am struggling with getting the second to work. Any ideas? First Code -- this one WORKS! Code: /*------------------------------------------------------------------ This is a sample code for RDM630 RFID reader by Spekel( This work is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 Unported License. -------------------------------------------------------------------*/ #include #define rxPin 2 #define txPin 3 #define SPKR 7 char code[20]; int val = 0; int bytesread = 0; //------------------------------------ //create a Serial object RFID SoftwareSerial RFID= SoftwareSerial(rxPin, txPin); void setup() {   Serial.begin(9600);   Serial.println("Serial Port Activated");   RFID.begin(9600);   Serial.println("RFID Reader Activated");   Serial.println("Scanning...");   pinMode(rxPin, INPUT);   pinMode(txPin, OUTPUT);   pinMode(SPKR, OUTPUT); } void loop() {   val = 0;   bytesread = 0;   while(bytesread < 12)   {     // read 12 digit code     val =;     if(val == 3)     { // if header or stop bytes before the 10 digit reading       break; // stop reading     }     if(val != 2)     {       code[bytesread] = val; // add the digit       bytesread++; // ready to read next digit       code[bytesread] = '\0'; // add the NULL     }   }   if(bytesread >= 12)   { // if 12 digit read is complete     Serial.print("RFID Detected - Tag: [");     for(int i=0; code[i]!='\0' ; i++)     {       Serial.print(code[i]);     }     Serial.println("]"); //print the whole 13 bytes     for (int i=0; i<200; i++) {  // generate a 1KHz tone for 1/2 second   digitalWrite(SPKR, HIGH);   delayMicroseconds(300);   digitalWrite(SPKR, LOW);   delayMicroseconds(300);   }     Serial.println("Scanning...");   } } --- You didn't even need that but I assume you understand the setup now --- The second code is exactly the same, apart from it contains and LDR that decides whether or not the value it receives has changed enough to sound the alarm and does so, allowing the alarm to be deactivated by an RFID. This does NOT check to see if the RFID tag is the correct one, that is to be written in later. At the moment I get a constant beeping whether or not the RFID tag is used to dissarm, or there is no beep at all. Any ideas?? ^^ Please actually read this before answering my Question!! Code: #include #define SPKR 7 #define rxPin 2 #define txPin 3 char code[20]; int val = 0; int bytesread = 0; int lightPin = 1; int variable = 0; int secondVariable = 0; int differenceVariable = 0; int ledPin = 13; SoftwareSerial RFID= SoftwareSerial(rxPin, txPin); // --- Initiation Complete --- void setup() {   Serial.begin(9600);   RFID.begin(9600);   pinMode(rxPin, INPUT);   pinMode(txPin, OUTPUT);   pinMode(SPKR, OUTPUT);   variable = analogRead(lightPin); } // --- Setup Complete --- void loop() {   variable = analogRead(lightPin);   Serial.println(variable);   delay(50);   secondVariable = analogRead(lightPin);   differenceVariable = variable - secondVariable;   if ((differenceVariable^2) > 200) {           val = 0;       bytesread = 0;       while(bytesread < 12) { // read 12 digit code           val =;           if(val == 3) { // if header or stop bytes before the 10 digit reading               break; // stop reading           }           if(val != 2) {               code[bytesread] = val; // add the digit               bytesread++; // ready to read next digit               code[bytesread] = '\0'; // add the NULL           }           for (int i=0; i<200; i++) {  // generate a 1KHz tone for 1/2 second               digitalWrite(SPKR, HIGH);               delayMicroseconds(300);               digitalWrite(SPKR, LOW);               delayMicroseconds(300);           }         }       if(bytesread >= 12) { // if 12 digit read is complete           Serial.print("RFID Detected - Tag: [");           for(int i=0; code[i]!='\0' ; i++) {               Serial.print(code[i]);           }           Serial.println("]"); //print the whole 13 bytes           for (int i=0; i<200; i++) {  // generate a 1KHz tone for 1/2 second               digitalWrite(SPKR, HIGH);               delayMicroseconds(300);               digitalWrite(SPKR, LOW);               delayMicroseconds(300);           }           Serial.println("Scanning...");       }    } } Thank you very much for any help that you can give, AMouse197 (I accidentally posted this in the wrong forum so have moved it)

Question by anonymouse197    |  last reply

How to get the right voltages to make a circuit with laser pointer, LDR and motor?

In short, it is for a uni project, and what I would like to do is shine a light (laser or white light) onto a prism that would have a LDR to detect the light and trigger a motor - the motor is attached to the prism to make it spin and refract the light to the next prism for a chain reaction mechanism to happen (I'd have 3 of them operating in a circle, maybe..) What I really need to know is what types of components to buy as there seems to be different kinds of every one, different voltages. (for example, how strong a laser do I need to be detected by the LDR, etc etc...) Don't want to fry anything! Thank you very much for you help! :)

Question by matisha23    |  last reply

Arduino DFPlayer MP3 player with Light sensor (LDR Module) as trigger

Hi everyone :) Yet another question... So I got my self a DFPlayer mini (mp3 player module) for Arduino, and a nice tutorial on how make it work, but I want to use s Light sensor (LDR Module) instead of a button (I just need play and pause or stop for my gift box) So at the moment if I connect the LDR instead of the button and give it some light, it turns the music on and off constantly/repeatedly because the LDR is constantly sending a HIGH signal, not just once like the button. Here is the question part: How to modify the code, so it only turns on the music when it gets HIGH signal and off if it gets LOW ??? Here is the modified code (I took out the auto play and the next and previous commands: ///              MP3 PLAYER PROJECT /// #include "SoftwareSerial.h" SoftwareSerial mySerial(10, 11); # define Start_Byte 0x7E # define Version_Byte 0xFF # define Command_Length 0x06 # define End_Byte 0xEF # define Acknowledge 0x00 //Returns info with command 0x41 [0x01: info, 0x00: no info] # define ACTIVATED LOW int buttonPlay = 3; boolean isPlaying = false; void setup () {   pinMode(buttonPlay, INPUT);   digitalWrite(buttonPlay, HIGH);   mySerial.begin (9600);   delay(1000);   playFirst();   isPlaying = true; } void loop () {   if (digitalRead(buttonPlay) == ACTIVATED)   {     if (isPlaying)     {       pause();       isPlaying = false;     } else     {       isPlaying = true;       play();     }   } } void playFirst() {   setVolume(20); } void pause() {   execute_CMD(0x0E, 0, 0);   delay(500); } void play() {   execute_CMD(0x0D, 0, 1);   delay(500); } void setVolume(int volume) {   execute_CMD(0x06, 0, volume); // Set the volume (0x00~0x30)   delay(2000); } void execute_CMD(byte CMD, byte Par1, byte Par2) // Excecute the command and parameters {   // Calculate the checksum (2 bytes)   word checksum = -(Version_Byte + Command_Length + CMD + Acknowledge + Par1 + Par2);   // Build the command line   byte Command_line[10] = { Start_Byte, Version_Byte, Command_Length, CMD, Acknowledge,                             Par1, Par2, highByte(checksum), lowByte(checksum), End_Byte                           };   //Send the command line to the module   for (byte k = 0; k < 10; k++)   {     mySerial.write( Command_line[k]);   } } Thank you ever so much!!!

Question by GellertK    |  last reply

How to increase the light sensitivity of a DARK SENSOR CIRCUIT?

I recently managed to replicate a dark sensor circuit using a LDR, a 220K & 330 ohms resistor, a BC547 transistor and a LED. But the problem is that it is very little sensitive to light. During daytime there is no problem but at night, under the CFL light it doesn't sense the light and turns on. To turn off the light, I have to illuminate the LDR with a external light source and that too very close. What I want is that the LED should light up only when there is complete darkness. How should I modify the circuit to increase the sensitivity?  The circuit diagram is as given below.

Question by Arijit Chatterjee    |  last reply

Changing the sensor

Hello guys, I want to make this circuit I just don't want any light to be visible. So, I was wondering if I could just change this LDR sensor to a IR sensor and still get the desired results.  Thanks,

Topic by HavocRC    |  last reply

Can any one help me with a LDR linked on off light project?

I need a simple circuit please help me. Moreover I am totally ignorant about Electronics but can try to make if guided with correct description. Am a layman in Electronics. 

Question by bannutechniclor    |  last reply

Help with simple transistor circuit.? Answered

I want the LED to turn on when it's dark. But  it remains on and taking out the LDR doesn't affect it. I couldn't post a picture but i made a replica in Fritzing EDIT: The transistor is 3904 NPN.

Question by Hafiz Mohammad Shayan Tariq    |  last reply

Can an LDR be used to activate a circuit after everything has been built?

I working on the gender announcement for our next baby and having some slight issues with the activation action.  I have built a circuit based on an ATtiny85 that causes two separate LEDs blink back and forth at a quickening pace underneath a Batman logo or Wonder Woman logo until the LED stays light under the Superhero representing the sex of the's a BOY!   I have had some custom cardboard boxes made and created form inserts and completed the circuits but I am at a dead stop with the activation.  I have thought about contacts around the side of the inside of the box with a non conductive material that would come down from the lid to prevent activation.  My issue would be the reset and 100% success rate.   My guiness thought would be to make the circuit Light reactive but I have NO experience with this and since the circuits are done minus power and/or switch can I still add in a Light Reactive switch using an LDR?   Any help would be greatly appreciated, my wife is driving me crazy about getting these done since i"ve been procrastinating

Question by njeast13    |  last reply

How to build Auotmatic Street Lights Control Using LDR and Arduino for 3 LEDs using 3 LDRs

so , what should I do ? What will be circuit diagram ? What changes should be done in Program ? Thank You ! Please Specify Circuit and Programming . Can I use 3 different Arduino or Use Single Arduino .

Question by npawar    |  last reply


HI GUYS. I HAVE A LDR light sensor I would like to use to turn on a light bulb through a attin85. when I upload the sketch to the Arduino it works fine. but when I upload to the attiny, I can't get it to work. am I'm wiring it wrong? when I put my signal from my ldr sensor to AO and 2 to the led it works on Arduino, but when I do that with the Attiny85 it doesn't do anything. The sketch did upload correctly though so it has to be me wiring it wrong or I need to change the code maybe to cater to the attiny85?my sketch is int LDR = 0; int LDRValue = 0; void setup() { pinMode(2, OUTPUT); void loop() { LDRValue = analogRead(LDR); delay(50); if (LDRValue < light_sensitivity) { digitalWrite(2, HIGH); } else { digitalWrite(2, LOW); } }

Question by jman2018    |  last reply

LDRS (Large Dangerous Rocket Ships) Rocket Competition hosted by Kari Byron

I just finished watching Kari Bryon hosting a Rocket competition on the Science Channel in Lucerne Valley California I Missed the initial showing on July 5th.   But they seem to be replaying it now and then (I saw it on July 10th, at 10 PM EST

Topic by Goodhart    |  last reply

Plz suggest a place in india to buy all the parts like audrino, LDR etc

Hello i live in kolkata, west bengal, india..and cannot find many a things to successfully make a project. Can u suggest me a place to buy the required parts in kolkata? i cannot buy from ebay as i dont have credit/debit card.. which type of shop do i generally get all the parts..? AUDRINO IS A TOP PRIORITY,,other things are...LDR, TRANSISTORS, variable and fixed resistors, breadboards, capacitors , batteries, RGB LEDs and LASER Modules...

Question by hbiswas    |  last reply

automatic switching of street lights by using ldr and relay

 hey me and my friends were ton a project of automatic switching of a street light depending on the brightness in the surroundings. so we decided to use an ldr(light dependent resistor). here in this circuit ldr has low resistance in brightness(only few ohms) and very high resistance in complete  darkness(nearly 1M ohm).so the transistor Q1 becomes on in day times and Q2 becomes off and hence the relay remains in NC(normally closed) state and the lamp will not glow. at night the transistor Q1 becomes OFF and Q2 becomes ON and hence the relay goes to NO(normally open) state and the lamp glows.and the sensitivity of the device can be varied by adjusting the potentiometer  now i just want to know are there any defects in this circuit so can u please help me in knowing the drawbacks and correcting them and i want to know whether i can connect a relay in place of a fuse as shown at bottom

Question by spartans    |  last reply

Attiny 85 not working

HI GUYS. I HAVE A LDR light sensor I would like to use to turn on a light bulb through a attin85. when I upload the sketch to the Arduino it works fine. but when I upload to the attiny, I can't get it to work. am I'm wiring it wrong? when I put my signal from my ldr sensor to AO and 2 to the led it works on Arduino, but when I do that with the Attiny85 it doesn't do anything. The sketch did upload correctly though so it has to be me wiring it wrong or I need to change the code maybe to cater to the attiny85?my sketch is int LDR = 0; int LDRValue = 0; void setup() {pinMode(2, OUTPUT); void loop() { LDRValue = analogRead(LDR); delay(50); if (LDRValue < light_sensitivity) { digitalWrite(2, HIGH); } else { digitalWrite(2, LOW); } }

Question by jman2018    |  last reply

How can I make the LED in this 555 schematic be off when the sound is on?

I am building this laser ray sound circuit using an LDR where the 220 ohm resistor is for a DJ, but thats beside the point. He wants the LED to be off when the sound is playing but on when its not playing how would I modify this circuit to do that?

Question by powerman666    |  last reply

how can I do a bicolor led on/off candle whit a ldr and a 555?

I need do this for my school but i don't have any information

Question by mariaflorencia    |  last reply


HELP!!!!!!!!!!!!!!!!!!!!!!!!!!!!   I am still "green" in the arduino feild and dont understand the code completly and I am trying to make an arduino theremin using a speaker and a ldr (light-dependent resistor)   PLEASE HELP!

Question by Laserman595    |  last reply

Would this require Programming?

Hi! I'm building a laptop bag alarm for a project I'm working on, and I'm pretty new to electronics. Would anyone know how I could make a system where a switch would be flipped to turn 'the alarm' on or off, and when that switch is flipped, the system would do nothing when the security system is triggered. The security system being 3-8 LDR sensors inside the bag, that will trigger some sort of logical part, that would be able to make the decision whether or not to sound the alarm, based on the status of the switch (flipped or normal)  I'm a programmer, so the system looks like this to me:  IF ALARM_SWITCH_ON && LDR_TRIGGERED { TRIGGER LIGHT && SOUND }  IF ALARM_SWITCH_OFF && LDR_TRIGGERED { DO NOTHING }  ELSE { DO NOTHING } Anyone know how this could be made with circuitry? or whether it would require programming? If it required all circuitry, is there anywhere I could get help with drawing up a circuit diagram?  Cheers & Thanks!  Karan

Topic by KodeKaran    |  last reply

how to code on NEO PIXEL 60 LED CLOCK Answered

Please help me to make neo pixel clock. compenent  I am useing    1)    Arduino Nano,  DS 3231, LDR and ws 2812b  ring 60 led Please help me in coading

Question by binods7    |  last reply

PICAXE Ciruit Help needed! I'm trying to figure out why my circiut is not working. Can anyone help? Answered

Note: I have attached a copy of my programming and the schematic of the circuit. As part of my school systems engineering course, I have decided to build an automated chook shed door. For the electronic side of this project i'm using a PICAXE microprocessor (PICAXE 08M - to be exact) to control the up and down operation of the door - which is done using a 12 volt linear actuator, all powered by a 12 volt battery (eventually to be rechagred by a solar panel). My theory is to basically read in the light level using an LDR and then based on this level to open the door, or close it. The is designed to work through the use of 3 relays (all with built in diode protection). The first relay is connected to the 12 volt power which supllies power to the other set of relays, and in effect the actuator, when ouput 0 is turned to high (I'm using transistors to do this as seen on the in the shematic). When I want to reverse the the motor I again turn ouput 0 to high, but also ouput 1 to high which switches the the other coupled relays (again using a tranistor) and in effect the polarities of the actuator.I'm also using two microswitchs on the bottom of the vertical sliding door as a safety mechanism, so that when the door is closing and an obstuction occurs (i.e a hand or piece of wood), its programmed to lift the door for about a second before trying to close again.  As mentioned before it acts a safety mechanism so that no little fingers can be chopped off, and the actuator it self doesn't overload and blow up (although I'm pretty sure it has inbuilt protection for this anyway). Ok anyway to the problem, I have wired everything up as to the schematic I have provided, and loaded the program onto the chip (which it does successfully do) - however its not performing as desired. I have placed the same program onto another identical PICAXE system (except it is not obviously connected to all of the stuff mine is) and it works fine. I have also tried reducing the complexity of the program and taking out the LDR readings in the code, and when I do this,  it does successfully turn on the relays as desired. For some reason it appears that the LDR is reading a full light level even when I place my finger over it, and because the IF statment in the program relies on a low LDR to operate, the code which turns on the relays never gets to execute.  At first it seems that there may have been a problem with the LDR, so I changed it  with a new one, but again it continues to read the highest value of 255 (or 1 byte) and therefore the program never executes as desired. I'm not sure why the LDR keeps reading the highest value. CAN ANYONE HELP!

Question by Mattdog123    |  last reply

555 timer photovore (light seeking robot) is unbalanced? Answered

I have prototyped a 555 timer photovore   (light seeking robot). I have built it and i am getting good responses from the LDRs. but when the sensor inputs are equal (heading straight toward light) one motor goes faster than the other. it is the same motor that is faster every time. I have noticed that the robot kinda uses one LDR as a control sensor(to compare to other sensor), the other sensor is the one that makes more of a response to the motor. That might not be true but that is what it seems like. I got the idea from this video: In the video, it mentions that he also used a "trim pot to fine tune his robot" If that is what i need, please explain to me with a picture and words how I would incorporate that in the circuit. I have also attached a schematic that i used to make the circuit., and some pictures of my breadboard setup. Please tell me if there is anything wrong with the setup, or any thing that I could change. I'm very desperate to get this working, as I have already spent $45 in this robot. Please help me. Thanks for reading!

Question by Chowmix12    |  last reply

How to show change in current?

I am making a trainer kit for my students. The kit will show the operation of resistors in series and in parallel. In series circuit I connected an LDR with a piezo buzzer which shows the change in voltage. But the same thing does not work in the parallel thing. The change in current does not affect the buzzer. Any Idea what can be done to solve the problem is appreciated?

Question by artworker    |  last reply

laser beam alarm using NE555 ?? circuit question

Hi all my project idea : using laser beam and LDR to make a security alarm circuit , when the beam is cut , it will trigger the NE55 circuit for certain time (5 seconds only ) there is a lot of 555 dark-activated circuits on the WWW,  i know , but all of them are like on/off switch what i need is one with adjustable delayed time can you help me ??  thanks in advance

Question by lu2a    |  last reply

How to calculate base resistor value of a transistor

Hello all. I'm trying to make autologht OFF and ON . Compnent: 1. Relay : 12 DC volt 2.tramsistor: BC547 3. LDR (I don't know specificatiom) 4. Source supply volt: 12 DC volt. 5. Resistor (need to know value) So how do I calculate of resistor? I have attache my circuit design n type of relay I'm using Thank you

Question by SangpoSangpo    |  last reply