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0
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2answers
70 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 ...
1
vote
2answers
126 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 ...
0
votes
0answers
40 views

XBEE's w/ Photo-resistor isn't making LED change brightness?

Below is a circuit draw up of my configuration. My problem i'm having is my LED is not changing in brightness as fast as I wanted. It seems there is a huge delay and I want to know why this is. Below ...
2
votes
1answer
63 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
votes
1answer
75 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 ...
-4
votes
1answer
166 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, ...
0
votes
2answers
116 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: ...
4
votes
2answers
2k 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 ...
1
vote
2answers
303 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
votes
3answers
471 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 ...
11
votes
2answers
825 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 ...
1
vote
3answers
571 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 ...
1
vote
2answers
246 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 ...
-1
votes
3answers
2k 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
votes
2answers
846 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
votes
2answers
289 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 ...