Phototransistors are in effect a bipolar transistor with a transparent enclosure so light can reach the junction of the base and collector. Compared to a photodiode they offer increased gain, but that comes at the cost of a slower response time.

learn more… | top users | synonyms

0
votes
3answers
31 views

Surface-Mount Prototyping (AXL 335 & SFH 7050)

I'm working on a senior project and I'm having some trouble prototyping with surface mount components. I know you can find SMT adapters out there for most SMT chips and components, but I've been ...
0
votes
0answers
50 views

Phototransistor saturation

Consider a circuit involving a phototransistor shown in Figure 1, the Vout should be linearly related to the light intensity. In my prototype, the phototransistor can become saturated easily even when ...
1
vote
2answers
44 views

A protecting circuit using GPIO of the BeagleBone (Black or Green)

I'm really trying to develop a cape since I need to use 7-8 GPIO-Pins of my BBB Green and Black as Output. I'm too afraid to destroy the board somehow, so I was thinking to implement a solution which ...
0
votes
1answer
46 views

Light Detector/Identifier circuit using photodiodes

I'm currently completing my final year project and am currently stuck going round in circles as how to complete it. To summarise: I need to design a circuit which is capable of IDENTIFYING a light ...
0
votes
1answer
42 views

normally open or normally closed OptoMos

In the following OptoMos datasheet the OptoMos is defined as Normally closed, when there is no input the output is closed. But in other OptoMos like the SFH618A-2 i can't find if the OptoMos is NO or ...
1
vote
1answer
76 views

Designing photogate for Raspberry Pi 2

Please help: I am building a photogate. I was looking for help in building a circuit for the Raspberry Pi 2. A little background: I am still a highschool grade 12 student! and I have a basic ...
1
vote
1answer
67 views

Will this phototransistor circuit work?

I'm building an 8 stage coil gun for a physics project, and I want to verify this circuit as I've never used a phototransistor before and I'm still pretty new to mosfets. Here is a schematic: The ...
1
vote
2answers
100 views

Why won't my phototransistor interrupt my microcontroller?

I bought a couple of phototransistors. They all have one lead shorter than the other. I assume that, like normal diodes, this means that the longer lead goes to V+ and the short end goes to GND. I ...
1
vote
1answer
59 views

How to use same 'input' for two circuits

First of all, please excuse my complete lack of knowledge in electronics :) Let's start with a little bit of context. I am trying to modify a machine that already uses a photo-interrupter to measure ...
1
vote
2answers
58 views

Designs for a 3-lead phototransistor?

I'm working on a primarily optical project, but I need to get a simple circuit working. I'm working with an npn 3-lead phototransistor (datasheet). I was trying to get the current from the ...
2
votes
2answers
62 views

Photogate IR LED or laser

Hi I am trying to build simple photo gate to measure speed of incoming ball. I decided I will use one photo gate with high frequency. Because ball is much smaller then the box, which is comming in, ...
1
vote
1answer
87 views

Can anybody identify this part - I think it is a phototransistor of some kind?

I suspect this is some kind of phototransistor, except it has three leads instead of two. It has no part number anywhere on it. Is anyone familiar with it?
0
votes
1answer
36 views

Phototransistor Values

So currently I am using a phototranssitor to detect light from several IR LEDS; however, I am having some trouble. I am currently using the right side of the circuit in the picture half way down the ...
5
votes
2answers
138 views

Opto-isolator output from collector vs. emitter

I have an Isocom ISQ2X quad opto-isolator (datasheet) that I will use to drive a logic input. The opto-isolator's simplified model given by the datasheet is pictured below. The transistor base pin is ...
0
votes
1answer
71 views

How to Compute bias Resistor for phototransistor Value?

I want to use this phototransistor in an Arduino project: https://www.kingbrightusa.com/images/catalog/spec/WP3DP3BT.pdf I calculated the value of the phototransistor bias Resistor (R1) by the ...
-2
votes
1answer
295 views

Use an LED as an input to a phototransistor in LT-SPICE [closed]

As a part of a project I am producing a light gate incorporating a photo-transistor and an LED. The design features feedback between the the LED and photo-transistor, so it would be useful to be able ...
3
votes
1answer
129 views

What are the differences between optoisolator output styles?

Digikey lists optoisolators with several output types: Darlington Darlington with base Photo FET Photovoltaic Photovoltaic, linearized Transistor Transistor, with base What are the differences ...
-1
votes
2answers
260 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.
0
votes
2answers
407 views

Understanding the CNY70 Reflective Optical Sensor

As far as I know, TM4C123 LaunchPad safely accepts voltages values up to 3.3V . I got a CNY70 reflective optical sensor and want to connect it to one of the analog input ports safely as in the ...
2
votes
2answers
480 views

how to get the RGB value of a color using phototransistor or photodiode?

I'm making a color analyzer which can measure Red, Green, and Blue portions of a color (ex: 128,255,0).I'm not supposed to use pre-made color sensors and need 1% ACCURACY. I used three LEDs - R,B ...
2
votes
1answer
166 views

how to measure RBG values of a color using phototransistor

I am developing a circuit which can measure RGB values of a given color. I have used LED to transmit light and reflected light is filtered by 3 R, G, B filter papers. Earlier I used LDR and found that ...
0
votes
2answers
173 views

is it a photodiode or a phototransistor?

I have been working on a circuit which involves a photosensitive element soldered on a PCB. I am confused whether it is a photodiode or a phototransistor. Is there any means by which I can figure out ...
1
vote
2answers
159 views

Simple Phototransistor Motion Detector

I am trying to make a simple motion detector for objects within a few feet in a very small footprint with minimal parts. I don't need to know much info about the motion just simply if there was motion ...
1
vote
2answers
468 views

MIDI to Arduino with a 4N38 Optocoupler

I ordered a set of optocouplers the other day and was excited when they finally came in. Unfortunately, I've having a bit of trouble getting them to work. Simple on/off tasks work fine but when I ...
1
vote
2answers
172 views

Opto-coupler base connection speed influence

I am using a 4N25 opto-coupler for 5kHz to 10kHz application. In some datasheets the turn on and turn off times are mentioned to be 3us. I am wondering if this opto-coupler is suitable for my ...
0
votes
0answers
52 views

how to connect light transistor to serial out

I want to be able to communicate between two computers through a laser. On the laser's side, I have a raspberry pi turning it on and off. On the receiving side, I want to somehow connect a ...
1
vote
1answer
167 views

Are IR phototransistors always dark, are IR LEDs always clear?

I've been working through the "Electronic Circuits for the Evil Genius" guide and someone bought me a components kit for the guide specifically. I already have some phototransistors where the plastic ...
1
vote
2answers
274 views

isolated input circuit to check regular switch or photo-transistor

I am trying to develop a circuit that is compatible with a regular switch (push, reed, other) and also a phototransistor. The application is pinball, where there are any number of switches and IR ...
1
vote
2answers
61 views

Photocoupler interface

I found a CNA1011K photocoupler laying around and I wish to try it out. Could someone explain what the parameters from the datasheet mean and how to use them for particular circuit parameters? LED ...
0
votes
2answers
366 views

Calculate pull-up resistor for phototransistors

I have made a sensor which uses six IR phototransistors, three per sensor block, opposite it is a matched IR diode(940nm). This is in turn connected to a MCU. The function of the circuit is an ...
1
vote
1answer
94 views

photo-transistor Biasing

How to bias a photo-transistor (the resistance in the collector) given that: Vcc = 5v Vce(sat) = 0.4v Ic(on): min: 0.2 - 1.6 max: 0.6 - 2.4 I'm using ...
0
votes
1answer
107 views

Simple and Cheap method to detect object proximity in the dark

I am interested in detecting if an object (e.g. small box made of non-conductive material like plastic/acrylic/wood) is placed on top of a surface (e.g., a table), I don't need to identify the object, ...
1
vote
1answer
142 views

Phototransistor resistor value help

I have a rowing machine that I'm trying to replace the computer on. It uses a phototransistor switch to detect flywheel rotation speed. The phototransistor is an Optek OPB365T55. Here is the ...
1
vote
2answers
116 views

Optoisolator not turning off

I'm using an optoisolator for high side switching a Nixie tube. For some reason, the optoisolator is not fully turning off, allowing the a very minimal amount of current to flow through the Nixie ...
0
votes
1answer
311 views

Load resistor value for phototransistor switch

According to this application note from Fairchild (btw, I find Fairchild's application notes to be of immense value - thanks to all who have taken the time to write one), the load resistor value for a ...
3
votes
2answers
196 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 ...
1
vote
1answer
152 views

Phototransistor bandwidth issue

I'm trying to sense IR wave with a phototransistor circuit. The circuit operates well under DC operations (I mean 3V or 0V through inputs). However, if a square wave is supplied from UART input, ...
0
votes
2answers
218 views

IR Led & Phototransistor pair bandwidth issue

I'm trying to sense IR wave with a phototransistor circuit. The circuit operates well under DC operations (I mean 3.3V through inputs). However, if a square wave is supplied from UART input, after ...
1
vote
1answer
116 views

Photointerrupter issue

I have circuit with photointerrupter GP1S092HCPIF. The documentation is rather weak and D-shape pin strange but I need a small SMD type. I hopefully identified pins correctly and when soldered on ...
0
votes
1answer
154 views

Ambient Light Sensor + Comparator

So I've been looking at options to create a way of controlling whether a flash will fire based on the amount of light in the surrounding environment. Early note: Everything has to be surface mount ...
0
votes
1answer
101 views

Strategy for up to 40 ADC inputs using alert feature

I'm working on a project where I want to monitor 40 phototransistors (IR breaker beams), but without having to constantly poll the ADCs. Ideally I'd want a digital pin pulled when one of the beams is ...
2
votes
1answer
3k views

How to amplify the signal of a TCRT5000 phototransistor

I'm trying to read the IR signal from my Itron C1S Power meter. It has an emitter that lights up for 10 ms every Wh of consumption. This question is based on my prior question: Use a photoresistor ...
2
votes
3answers
602 views

How to design a power switching circuit using a photo-interrupter

Okay. I'm completely at a loss here. I was trying to design a switching circuit for a 3A load (Solenoid) using a photo-interrupter. I got to about here: But I have no idea what to look for in my ...
0
votes
2answers
625 views

Photo-Interrupter Usage

One of the projects I am working on requires a number of photo-interrupters to be used. I was wondering if someone could explain how to use them correctly? I was thinking something like this: ...
0
votes
1answer
2k views

How ICBO gets amplified to ICEO in BJT when base is open

I have been doing some reading about ICEO and ICBO, but couldn't really understand how ICBO is getting amplified (1+ beta) times to reach ICEO, in the open base condition. This is my understanding ...
0
votes
1answer
4k views

ICEO, ICBO physical interpretation in BJT

I am stuck with the equation: ICEO = (1+β) ICBO My questions are: What is the physical interpretation of this equation? Will both the currents exist simultaneously? Are any of the reverse currents ...
0
votes
3answers
3k views

How to connect IR sensor ( Infrared detector/receiver )?

Would you give me a hand ? I have an IR sensor with 3 pins. It looks like the one in the picture, and I did not find any datasheet for it on the internet. actually, I have 3 questions : 1- I want ...
1
vote
1answer
221 views

Is a DVD sensor a photodiode or an array of them?

Is a DVD sensor just a photodiode or an array of them? I need to know if it is a CMOS with an array of them or just a single sensor.
0
votes
1answer
773 views

How do I use a phototransistor for a line follow robot?

I'm building a line follow robot for a competition in 2 months and I'm using Arduino but I have no idea how to find the line (what sensors needed). I did some research and discovered that if I can use ...
0
votes
2answers
261 views

Pixel resolution phototransistor array

I would like to ask if anybody knows some technology which is like array of phototransistor with accuracy in mm . Like some display on which I put someting and get by wire data of pixel which are ...