A photoresistor or light-dependent resistor (LDR) or photocell is a light-controlled variable resistor.

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65 views

What is RadioShack 276-0326?

It says it is an ambient light sensor, but is it a phototransistor? Something else? It has Vcc and Vout pins. Bonus points if you include a data sheet.
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1answer
42 views

How to delay the transistor turning on using a photoresistor?

I am a beginner in electronics, my project is the following: I am trying to build a simple circuit to switch on and off my garden lights according to the brightness level. More to the point, I'd like ...
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1answer
46 views

Photocell and Relay switch not working properly

I am trying to build a simple circuit to switch on and off my garden lights according to the brightness level. More to the point, I'd like the lights to turn on when it's dark and off in the morning. ...
1
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1answer
75 views

Sodium metasilicate pentahydrate and Photoresist Universal Developer Crystals same chemical?

I'm thinking about using the photo method for etching PCBs so I need a developer for the positive photo resist. There is this sodium metasilicate based universal developer that people online seem to ...
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2answers
67 views

dimming led with photoresistor

I want to dim a led in a circuit if there's less light. However, the Photoresistor I'm working with reduces the resistance when there's more light. How can I achieve the opposite effect on resistance ...
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3answers
99 views

How to avoid Relay buzzing noise? (LDR dependent)

I have the following circuit where I'm switching a relay based on whether it's day or night. I made a voltage divider using a pot and an LDR, which leads to the NPN transistor. So when it's dark the ...
0
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0answers
59 views

Combine LED with accelerometer in small size for violin bow frog

The question was extended from the post: Violin bow position tracking with SMD LEDs and photoresistors. It is easier to understand the problem and the purpose here with the link, but I will elaborate ...
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3answers
225 views

Violin bow position tracking with SMD LEDs and photoresistors

Objective: Marking labels indicating the positions of the violin bow on an acoustic signal, for example, a single musical note played by a full-length bow. The following video shows the example I am ...
3
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2answers
135 views

Component to detect the state of an external LED

I need to detect the state of an LED in a machine that I cannot connect to in any electrical way. So I would like to measure the light emitted from this LED. The conditions: The ambient lighting is ...
0
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1answer
90 views

light dependent 5V switch

I wired up this light dependent switch which works fine. when in daylight and covered. how can i make it work when the light source is dimmer? ie is it a case of changing 1 of the resistors?
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1answer
201 views

How to control a motor with a photoresistor

I have a little 2 to 5 volt hobby motor that I would like to control with a photoresistor aka photocell. What is the simplest way to control the circuit? Is there a photo resistor with enough range ...
0
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2answers
153 views

Night activated LEDs

I want to use a photo resistor to make a circuit like this But instead of light causing the led to turn on, I want darkness to cause the led to turn on.
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3answers
253 views

Separating Digital GND from Analog GND

I'm connecting CdS photoresitor and ADC (MCP3204) to the RPi. And MCP has DGND and AGND. I am about to connect both GNDs to the GND on RPi's GPIO, naively. Is that problematic if I want to read the ...
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1answer
1k views

Use a photoresistor to read an IR LED from an Itron energy meter

I want to read my meter at home with an Arduino board. My meter, an Itron C1S, has an IR emitter that pulses once (10ms width) every Wh. I want to know if it is theoretically possible to use a ...
2
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1answer
379 views

How can I detect when an LED changes color from red to green and quickly send a message to a PC to capture an image from a camera?

I am working with a 3rd party IR curtain system, and the only way to tell in real-time that something has pierced the curtain is an LED at the top of the sensor pole that changes from green to red ...
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1answer
63 views

Knowing the type of output signal

I have a digital photocell, where after dissembling, I see that it uses a ATMEGA88 chip(datasheet of the chip), but I do not have the schematic of the photocell. The whole photocell has only a pair ...
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2answers
1k views

What do Capacitors do in a System with a Speaker?

I made a circuit based on a diagram from my physics teacher. The circuit has a 555 chip connected to seven wires that make up a circuit. The circuit includes a photocell resistor that acts as a ...
4
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2answers
384 views

Are photoresistors reliable for light sensing applications?

I've used photoresistors for hobby projects before, such as this one: http://www.foxytronics.com/learn/electronics/kit-guides/starter-electronics-kit-guide/making-an-led-light-sensor However, now ...
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2answers
144 views

How to light a LED using photo transistors output?

I built a circuit using RPR220 photo sensor to detect the surface displacement caused on a material when external force is applied. I could see the output on a CRO even when there are minute changes ...
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2answers
214 views

Simple circuit reacts to touching a node

I am trying to repeat a circuit from this post. For some reason it does not work properly, and trying to fix it I figure out strange behavior. LED turns on if I touch R3 with my finger or with ...
2
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1answer
111 views

circuit analysis of DC-source, inductance and modulated resistance

Here's an interesting problem. Consider a DC voltage source (for bias), an inductor (supply wires, for instance) and a resistor, which changes its resistance as a function of time: \$ R(t) = ...
2
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1answer
490 views

Reversing a Photoresistor

I'm a total newbie at this, but I have a photoresistor set up so that it controls the shorting on an audio circuit. When light is on, it shorts and cuts the sound. When it is dark, it closes and ...
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1answer
912 views

How do I build a light-activated motor? [closed]

I'm trying to build a motor that is activated when light shines on a photoresistor/transistor (can anyone explain the difference?), but I'm totally lost right now. I can only utilize wires, batteries, ...
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2answers
270 views

Sensing Light Differences in Photo-Resistors

I'm planning to make a little device that detects when a path of laser light is broken. The device will have 3 photo-resistors and three corresponding lasers. Like so: ...
5
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2answers
8k views

Basic circuit to keep LED either on or off depending on night/day

How can I have a LED either on or off (not in between) depending on night or day with basic electronics? I have created the circuit below, but it only shines and in darkness it dims. The ...
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2answers
501 views

detect a change in state of voltage divider without using ADC

I am using a photoresistor for a laser trip wire setup to detect motion. I am a little short of adc channels here so would like to use a simple GPIO to read the state of the photoresistor ckt. I am ...
2
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3answers
767 views

Whats up with my photoresistors! (Wonky readings, non-stable, I'm missing something)

I'm working on a photoresistor array with my arduino, and I'm having a little trouble getting stable readings. I'm driving 7 rows one at a time with arduino's digitalWrite(pin,HIGH) command and ...
12
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2answers
940 views

Not sure how to name what this resistor is doing?

I have a basic circuit that uses a photoresistor powered by a five volt source. I had made this project to show my son about various sensors and had used a circuit I had found online. It looks ...
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3answers
942 views

Reading From a Large Array of Photoresistors

I'm an undergrad just starting to study Electrical Engineering. For the first hobby project I'm starting, I want to use a microcontroller to read analog voltage values from a very large array of ...
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2answers
339 views

Do LEDs Need UVLOs (Undervoltage-Lockouts)?

I'm currently working on a project involving (I think 3mm, 1.5VDC) Infrared LEDs. However, due to my photoresistor, I think the current, voltage, or whatever (forgot) will vary greatly to minuscule ...
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3answers
3k views

Zener Diode for Minimum Voltage Regulator

I forgot the name of it, but I remember one post where it said that you can use a zener diode as a "minimum voltage regulator". I don't think I used the right term for it, but here's what I'm doing. ...
2
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2answers
1k views

I want to build an interactive LED Table. What are my options for a controller?

I have seen a couple of videos and instructables where people have created a matrix of LEDs controlled by photodiodes/photoresistors inside coffee tables, so that when you put your hand over the table ...
3
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2answers
386 views

Light detector linearity with varying wavelength

Given the same intensity of light, in varying wavelengths, which is typically more linear with their output: Cds (photo resistor) or a Photo transistor? I would assume that the junctions in the ...