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38 Threads found on edaboard.com: Led And Ldr
Here is an experiment of an ldr used as an amplifier. It uses a neon tube, but a common led can be used, improving efficiency possibly. I have done this using a led and it amplifies. The drawback is the slow response of the ldr, so it is suitable only for low end audio ranges. However, very big voltage (...)
As your light indicator worked well on a breadboard, something has happened by soldering. Check the transistor and ldr, other components see to be OK. Test also the led, some are sensitive to soldering temperature. To calculate resistor values, use the DVM to measure its resistance at max light and dark. From this (...)
are you sure you want to detect darkness or loss of power or both? The key aspects require the light sensor to be blocked from light from the leds and battery backup.
A small ldr is approx 10K when illuminated and 1M when dark. This varies at least +/-1 decade depending on size and ambient light. YOu can invert in many ways. Use a pullup R with ldr on input to ground or visa versa. You can drive the led ANode high or drive the Cathode low with Anode to V+ (eg 5V) (...)
You could even use the PV sensor to drive an NPN to disable a self biased Type N FET to switch the led from the low side.
The opamp is missing a positive power supply voltage. The opamp has WAY TOO MUCH positive feedback. EDIT: Nothing limits the current in the leds.
The lousy old (46 years old design) 741 opamp output voltage cannot go low enough in your original circuit to turn off the transistor. The circuit will work if you use an opamp from an LM358 dual or LM324 quad. The circuit posted by Deep might be showing a positive and a negative supply. It is missing an important resistor in series with the led t
1)i have connected 3v dc supply ldr ant led in series 2)i have connected 3v dc supply with potential divider circuit by resistor and ldr and connected it to led the second works good.does first one works
I have an aquarium where I've made a Nightlight, with a number of blue led diodes. View picture. My desire is that it turns on automatically when it starts and gets dark in the evening, how can I fix it? Are there components I can use on my plus wire which has this feature? 100260
How to make a simple switch to turn off a led during daylight using only one transistor, jfet or mosfet, and a light dependent resistor ? No other components, besides the white led and a 3.5V cell ? Is there a way to turn on at dusk, off at dawn with that minimum of components ? Or, does a reverse coheficient (...)
As I've posted elsewhere, it will work if you use the darlington BD679 device without changing the ldr or it's series resistor, BUT the value of R1 must be dropped. The calculation for it's maximum value is: R = (Battery Voltage - led forward voltage - VCEsat of the BD679) / led current. So if we assume led Vf is 2.5V (...)
Off the top of my head - without being tested and without knowing your compiler or target processor - Maybe something like... #define led = PORTA.0 void main(void); int adc_val; init_adc(1); while(1){ read_adc(1); if(adc_val > 500){ led = 0; } if(adc_val < 480){
Most white leds work above 3.3V. There may be a voltage doubler inside. Check voltage on led. This converter then, is controlled by ldr.
Hello! I want a high when a certain voltaghe level is reached, like having the led on if the sensor measures at 2.5V and led of if the sensor senses 1.5V Your explanation is not accurate. Since you gave your explanation after Barry, I think you don't want an hysteresis, so please can you describe your suystem fully? What about 2.
How about trying a different colored filter in front of the ldr? Maybe red, since the led output has very little red in it. ---------- Post added at 18:36 ---------- Previous post was at 18:31 ---------- second choice. Turn-on level - 400 like in your program. Turn-off level: Store what the light lev
Hi friends, i have purchased a heart beat sensor with ldr and led built in.. In their website they have not mentioned how to measure heart beat also... i have attached the link so please suggest me how to start the program in c. i am interfacing with 8051 and using Keil u vision 3... Thanks in
Hi all, I want to know if there is a standart component (optocoupler) which has light bulp at input side (instead of led) and at output side a ldr (light dependent resistor) I don't want led input because I want the ldr voltage to change with the voltage change at input side. Thanks (...)
The best solution is to use Red led and a ldr. Both of these can be mounted in a closed housing but make sure no external light enters the housing. Similar circuits diagram for you need can also be found at Explore Circuits - Your Gateway to Electronic World
I need Pulse counter schematic, which count data from led / ldr pulse.If you have please help.
i had used lm35 for temp, humidity sensor for land humidity sendor and ldr for light.. and used a robot that moved on a line ( liike line following robot) and would transmit the parameters after stopping for a while and transmitting the data... the data is received on the othe end using a (...)
An ldr is a variable resistor. If you connect one end to 0V and the other end to +5V through a resistor you will get a variable voltage. An ADC can be used to digitized that voltage and turn the leds on at certain thresholds. You don't actually need a controller. One comparator for each led would do the (...)
If you are after somthing simple, maybe you'll be interested in a voltage controlled dimmer based on an led and an ldr .. see attached picture .. Full desription is available at: Rgds, IanP :D
Hello, I was wondering how can I achieve a soft keying envelope in CW mode? My approach is to vary the output power using a light dependent resistor and a attack release generator to controll a led pointing to this ldr. Is there any other way to achieve a soft envelope generator for CW? Any links/schematics would be appreciated
That is the well-known HeMon project. What problem do you have with it? The project (look for it in Google) has photos of the ldr/led part. Oh. Nigeria? Black skin? Does an led shine through black skin?
The problem nw is, when there's no light on the ldr, the led will turn ON but once i put a light on ldr, the led is OFF. Simply reverse the positions of the ldr and R1. Then the led will light when there is light and it will turn off when there is no (...)
Hi friends im doing a heart beat sensor project, the circuit contain high intensity RED led and ldr for detecting heart beat. by putting finger in between led and ldr we will get heart beat. For getting better out put can i use low power lazer diode instead of high intensity (...)
Yes. It is possible to detect smoke with Mega32. But for compactness 8pin device like Tiny13 or 15 may also be used. If the smoke detection is only the requiremnet, actually there is no need for microcontroller, instead it can be done simple with a led and ldr arrangement. Cheers.
The ldr has a value of 1KOhm with direct light from a Laser pointer and, can have a value up to 1MOhm without the light. I measured these values myself when experimenting my Laser Burglar alarm. Just one concern, as I can see from the schematic, you are using an "InfraRed led". I don't think that the photoresistor (ldr) (...)
If anybody can tell me how to measure the speed or rpm of a DC MOTOR. if i m giveing the digital PID controller output to PWM and then driving DC MOTOR TO CONTROL SPEED.now i am stuck at giving back the feedback to the controller. i have few ideas: :idea:1. use ldr and led circuit to measure pulses generated at diffent (...)
Hello Do you know: 1. What is the maximum sensitivity wavelenght or color for a CdS ldr. Can this be paired with a red led? 2. ldrs have a good electrical linearity - a linear resistor, not adding distortion? (the light - resistance characteristic linearity isn't imporatant for me) I need to do a clasic simple and (...)
DEAR FRIENDS, Sence the signal with a ldr and an led and use proper amplifier and filter circuit to produce the niddle pulse. each time the heart beat. after proper wave shaping the microcontroller can count those pulses with a formula for the count in 1 min. and display it on 7-seg or (...)
Hi guys i just wanna seek some help from you, I'm building a ldr base sensor im using a super bright led red,blue and green also the output of the ldr is being feed to a ADC0804 to be used with my PIC16F84A. Is there anybody that can give me a circuit for this sensor, that would help a lot.
hi, can I make myself a colour sensor? I want to sense Red or Green colour. If I use a Red and Green led as transmitter and two light sensor as receiver, could this idea be implemented? The distance to sense will be not a matter. thanks.
Hi buts101, Attach a led with ldr and cover the led and ldr so tht only reflected light falls on ldr. For more about path following robot, see my book MY EXPERIENCE IN AUTONOMOUS ROBOTICS It is a free book. You can get it from yahoo group-booksbybibin (...)
You can do it by using an led and ldr arrangement, but it won't be that much accurate. Use one ADC at the output of ldr to identify the colors. Source code and tutorials for interfacing ADC with parallel port is available on the book MY EXPERIENCE IN PRALLEL PORT INTERFACING you can get it from yahoo (...)
This combination, led+ldr, may be difficult to find, so here is the recipe for building one by yourself: Regards, IanP
The ldr's are light dependant resistors In the Data Sheets how do i find out the Taper,range,sweep,contrast from light to dark or dark to light how the resistance changes? The taper from 0 resistance to 100K whats the taper of a ldr's? and how would i find this out in the data sheets? Doesn't the Lamp/led/Light (...)
Why do u use infrared?? You can make with bright leds. All u have to do is replacing a lens infront of the led.. Receiver circuit is so simple...You can make it with 741 opamp IC and ldr...