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Questions tagged [phototransistor]

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 at the cost of a slower response time.

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How to use Stepper Motor and GP1S094HCZ0F Photointerruptor to home

I am working on a robot project and am currently working on the neck joint. For this, the head will be turning, and I am using a stepper motor for this purpose as it has more than 180 degrees of ...
Collin's user avatar
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What component is missing?

I have an address sign that is supposed to light when it gets dark outside. The issue is the photodiode (assume that's what the part is) is broken and has broken off the board. I have tried connecting ...
Kasriel Lewis's user avatar
2 votes
1 answer
72 views

How to bright up LED when it's dark without wasting battery energy?

I am trying to design night light LED that brights up when it's dark. I know a solution using transistor that "drains" current so LED has not enough to light up. A current flow through ...
eSeverus's user avatar
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TCRT5000 combined with ESP8266 ADC voltage divider

I have a circuit with a TCRT5000 that lets me detect proximity since the reflected IR rays will make the photo sensitive transistor conductive and will pull down the voltage below the 10kΩ resistor, ...
Besi's user avatar
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Detecting OLED display refresh frequency using phototransistor

I am trying to detect the refresh frequency of an OLED display driven by an SSD1309 display controller. During the refresh cycle, each row of a frame is charged and driven for 65 DCLKS in a sequential ...
Joshua Dotson's user avatar
3 votes
2 answers
139 views

Is 3004M1C a photodiode or a phototransistor?

The datasheet describes the 3004M1C as a "high speed and high sensitive PIN photodiode". Distributors also label it as a photodiode. However, the datasheet mentions "Collector-Emitter ...
lukasl's user avatar
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1 answer
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Can TSOP1130 work also at 850mn?

In the sheet, they test it with a 940nm IR LED. There are no clear specifications for the wavelength (range) it works with. But I have 850nm LEDs (powerful ones). Will it work the same, or will it ...
IceCold's user avatar
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2 answers
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Can infrared light pass through solid materials?

I have an IR sensor at about few tens of mm (millimeter) from a heating source (incandescent bulb or heating element.) The phototransistor in my sensor is lead lined but I guess it is sensitive to a ...
Iskander's user avatar
3 votes
1 answer
222 views

Phototransistor sensitivity

Im a not an electronic engineer nor do I understand optical science so forgive my basic pleas for help. I want to detect a light on my heating boiler. I think the led is on a PCB and there is a tube ...
Mark E's user avatar
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1 answer
104 views

How do I split and isolate a digital signal?

I am working on a circuit that needs to observe when VAC is at zero cross. I have a photostransistor whose anode and cathode are connected to VAC line and neutral. I've connected 3.3VDC to the ...
Dan's user avatar
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2 votes
2 answers
170 views

Simple phototransistor circuit to turn on P-channel MOSFET

I'm trying to fully understand how phototransistors work and was wondering if this circuit would work to turn on a P-channel MOSFET when the phototransistor isn't detecting light. This is powered by a ...
tufelkinder's user avatar
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Replace photo diode and phototransistor with an IrDA chip

We have a circuit that communicate optically with a symmetrical circuit (exactly the same circuit at the other side). The circuit is based on a phototransistor SFH 320, a photodiode ZTHI55WA-3-SGM, ...
Renaud's user avatar
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1 vote
1 answer
71 views

TCST2300 Optical Sensor w/ Phototransistor Output - Rotary Encoder: Trying to Understand & Test

I'm trying to test a mechanical rotary encoder for a piece of industrial equipment. I'll attach pictures, but basically the encoder operates by monitoring a slowly rotating perforated wheel. The ...
AlphaBob's user avatar
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0 answers
49 views

circuit for phototransistor sound receiver

I'd like to build a phototransistor receiver. I've tried different sample circuits (I'm not any good in circuit design) and would like to ask for assistance. I am looking for a circuit that is capable ...
mate herd's user avatar
1 vote
3 answers
266 views

Amplifying and filtering a phototransistor circuit

simulate this circuit – Schematic created using CircuitLab I'm about at my wit's end here trying to figure this out and hope someone can help me with this. I'm trying to detect three frequencies ...
Barkley McCormick's user avatar
2 votes
2 answers
541 views

4N35 difference between two versions

Would like to know the difference between these two 4N35 optocouplers . They behave differently but cannot find what is related the "001Q" and "027Q" digit.
Ken90's user avatar
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2 votes
4 answers
166 views

Can a BJT be a voltage dependent resistance? What about a phototransistor?

I am trying to resolve what appears to be contradiction: When used in the active region, a BJT is modelled as a base-current-controlled current source. Given that it is acting as a current source, a ...
cgiustini's user avatar
16 votes
5 answers
2k views

Non-invasive bubble sensor

I'm trying to make a non-invasive bubble sensor. The liquid is going through a 3 mm plastic tube and the liquid is a clear saline solution. I believe the easiest solution is an optical method using a ...
Bommersooner21's user avatar
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31 views

Phototransistor receiver circuit output display 0 V

I am working on a sensor for my university project. The output displays 0 V, but when I put the light in, the value changes. When I put it in the box, it displays 0 V again. I am working with an ...
david mike's user avatar
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0 answers
54 views

Biasing phototransistor for homemade Reflectance sensor

I need a reflectance sensor like the TCRT5000 for a project I'm doing. The sensor should detect the transition from a dark surface to a white surface. I have infrared LEDs and phototransistors and ...
Virgil_Tibbs's user avatar
0 votes
1 answer
59 views

Light cutoff alarm circuit PNP output

The purpose was to check the voltage on the PNP tr collector side. So when we cut off the light, we expected about 12V. When we detected light, we expected it to be printed around 1.6V. I checked the ...
jji's user avatar
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1 vote
1 answer
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Phantom powered phototransistor

I'm working with phototransistors, using them to capture audio rate fluctuations in light levels. I'd like to move from my current setup which uses a 9V battery for nice clean power to one that uses ...
mo-seph's user avatar
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2 votes
3 answers
179 views

How does this old alarm system circuit work?

This is a pretty old alarm system based on an NPN phototransistor. Why are there two transistors here, T1 and T2? Can we say that T1 is an emitter follower that amplifies the phototransistor current ...
Jimmy Falcon's user avatar
2 votes
3 answers
138 views

Transimpedence amplifier with photo-transistor linearity

Given that the irradiance and collector current for a (random) photo-transistor is linearly correlated like below. Then I am wondering why the output voltage graph of the transimpedence amplifier ...
W30's user avatar
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5 votes
2 answers
253 views

Circuit works with one phototransistor but not with another

I created a circuit board with an SFH 309 FA phototransistor that works as an IR receiver for a serial data stream of a smart meter (this works without any problems). Now I've changed the circuit to ...
Bouni's user avatar
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1 vote
1 answer
297 views

Reading 100s photodetectors

I'm trying to measure light intensity at a lot of points in a project. I have about 250 photo detectors (BPX 65). When I had just 1, I tried connecting it to an Arduino board. But I'm not sure, what ...
user319750's user avatar
1 vote
1 answer
155 views

Infrared diode, phototransistor, and multimeter

I thought of creating a circuit for a light barrier. I got the required components: an IR LED diode, an IR phototransistor, an op-amp, a potentiometer, a blue LED, and resistors. After much testing ...
EndrManCZ's user avatar
-1 votes
1 answer
130 views

FPT100B alternative [closed]

I have a board that uses an FPT100B and a 271 chip as fibre optic receiver. The fibre optic receives red light, not IR. The FPT100B is not working. I am pretty clueless as to what I can use as an ...
user3604932's user avatar
2 votes
3 answers
979 views

How to extend useful life of IR LED and photodiode pair

I have an IR LED and photodiode separated by 3.5 cm. In practice, these devices get damaged very soon. (Some people that use this circuit report this problem). An engineer proposed to make them blink,...
Ando's user avatar
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3 votes
1 answer
761 views

What resistance should be used with a phototransistor to have fast rise/fall time?

I am trying to accurately capture the video latency and response time curve of an LCD display from a black image to a white image for the purpose of reviewing the accuracy of a couple of video latency ...
Allen Pestaluky's user avatar
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1 answer
445 views

How to choose a phototransistor or photodiode?

I've found a photoresistor (yes, resistor, probably 30 years old) in my scrap box, attached it to an ATtiny as ambient light sensor, with a 100kΩ resistor as voltage divider towards +5V. On power on, ...
stefan's user avatar
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3 answers
524 views

Ambient light sensor to a microcontroller

I am looking to make a small sensor board for something at home. I am familiar with embedded systems but my electronics knowledge may not be the best. For my situation, I would like to connect a ...
user1397215's user avatar
11 votes
3 answers
854 views

Triggering generic transistors with UV or green light?

Flashes of UV light can create electron-hole pairs in transistors. Or at least reports of the "UV flash bug" claim this happens in microprocessors. People observed raspberry pies reset when ...
ions me's user avatar
  • 341
2 votes
3 answers
422 views

What does the VCC pin do in this Optocoupler?

I have this optocoupler, and I am trying to figure out how it works. What is the VCC pin supposed to do? How does it supply current to the gate pin of the transistor? https://www.digikey.com/en/...
RGB Engineer's user avatar
2 votes
0 answers
62 views

Does a phototransistor have a minimum focal window? - Velocity Measurement of High Speed Object

My goal is to measure the velocity of a moving object that has several different changes in velocity throughout the actuation. I am planning on using a phototransistor to detect black and white lines ...
Nicholas Myers's user avatar
1 vote
2 answers
949 views

Optocoupler circuit to shift from 3.3V to 15V

I am trying to use the circuit below to shift a squared wave form (2kHz) with a peak of 3.3VDC to one with a peak at 15VDC. I am trying to do that with the circuit below, I am using the optocoupler ...
Charles Wagner's user avatar
0 votes
2 answers
322 views

Problem in sensor circuit using a Phototransistor for the Schmitt Trigger circuit

This is my Schmitt Trigger design, which trips at \$2.3V\$ and \$1.7V\$- Here, $$+V_{cc} = 9V$$ $$R1 = 51k \Omega$$ $$R2 = 22k \Omega$$ $$R3 = 330k \Omega$$ \$V_{in}\$ is a square-wave with 0-7V peak ...
electrovolt's user avatar
0 votes
2 answers
376 views

Help identifying 3-pin open-collector photo-transistor-like component

Can someone help identify the 3 pin photo device (not the entire module) on this "Icstation 5V Light Sensor Module"? (may be same as this one It seems to act as a photo-transistor, but yet ...
Daniel J. Greenhoe's user avatar
0 votes
2 answers
778 views

Amplifying a small signal from a phototransistor

I am building an amplifier for a phototransistor. It works well under normal lighting conditions. In my application, the light is very dim and barely produce any readable output. I tried to increase ...
Ahmad Al-Baghdadi's user avatar
0 votes
2 answers
203 views

Convert flame sensor ADC value to wavelength

I am working on a fire detector project using a flame sensor. This sensor can detect IR light wavelength from 760-1100 nm using a YG1006 phototransistor. I have read that if the wavelength is bigger ...
Mikhael 's user avatar
1 vote
1 answer
119 views

BC639 16 exploding on custom design

On a board I designed, a transistor, BC639 16, is exploding. A pinball machine has one board that has some design flaws. Its schematics are these: This PCB has 8 optos (QVE11233.0086) that are ...
Iñigo Perez de Isla's user avatar
2 votes
1 answer
649 views

Calculation for Resistor in Phototransistor Emitter

I decided to ask here for help, I am still new at electronics, I have been trying to figure out the definitions and graphs of this phototransistor, the PT1302 (datasheet here), my doubt is how can I ...
MtZandy's user avatar
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0 votes
2 answers
385 views

Understanding the phototransistor

I am trying to learn how a phototransistor works, and I have made a schematic to show how I understand the photo-diode and NPN transistor to be linked in a phototransistor. I think that when light ...
Orlando Alexander's user avatar
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0 answers
191 views

How to get the desired signal from a photodiode and phototransistor multisim?

The above is a visualization of an IR transmitter and receiver circuit I'm building. Sending a 2v and 1khz sine wave through a photodiode to a phototransistor. The figure above shows the outputs I ...
D'TEN BW DECIBEL TEN's user avatar
0 votes
1 answer
326 views

Understanding how a NPN transistor works

I have been trying to understand how an NPN transistor works, specifically in the case of a photo-transistor. As far as I can tell, it should be something like this: I don’t understand how current ...
Orlando Alexander's user avatar
2 votes
1 answer
818 views

When base is open, is the base-emitter junction reverse biased? How does leakage current from collector to emitter flow?

I've been studying photo transistors, but I'm rusty on leakage current in bjt. I don't get why CE leakage current is \$ 1+\beta \$ times CB leakage current. It seems like the bjt amplifies CB leakage ...
across's user avatar
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0 votes
2 answers
170 views

Why is there an additional resistor in this phototransistor circuit?

I'm currently working on a phototransistor that is part of a reflective optical sensor. Now I saw a circuit, which looks like this and I'm wondering why there is the (additional) resistor \$R_3\$ ? ...
JoS's user avatar
  • 5
0 votes
0 answers
229 views

Transimpedance amplifier design advice

I'm working on a transimpedance amplifier for a phototransistor in order to create a sensor that counts objects falling down a pipe. This is the sensor: https://www.digikey.it/short/0vq01q7h Datasheet:...
GothSean's user avatar
4 votes
2 answers
1k views

What is the "collector light current" of a phototransistor and how does it relate to the collector current?

I found the "collector light current" term in this datasheet (Vishay TEFT4300) but I can't find a definition for it on the internet nor figure out how it relates to the collector current. I ...
curioso's user avatar
  • 67
0 votes
2 answers
539 views

Optocoupler design - why does this circuit work?

I am busy with some calculations regarding the components around the optocoupler and I am now finding myself in a bit of a mental struggle. I have done quite a lot of reading (at least here, here, ...
wave.jaco's user avatar
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