Skip to main content

Questions tagged [optoelectronics]

Components, circuits, or systems that convert between electrical and optical (light) energy.

Filter by
Sorted by
Tagged with
2 votes
2 answers
57 views

4N25 Optocoupler design

Below is a simple 4N25 optocoupler circuit that I designed in LTspice. 10 mA is flowing through the input. It works in saturation. According to the datasheet in Figure 2 (CTR-sat), it says 0.7, so the ...
Mhan's user avatar
  • 373
0 votes
3 answers
128 views

Calculating current through a diode in a voltage divider circuit

I have a voltage divider circuit which I use to drive two LEDs with different luminous intensity. I understand that this is not the best way to do it but I wanted to control two LEDs with the same ...
Nikhilesh's user avatar
3 votes
2 answers
75 views

Sending arbitrary bitstream to SFP transceiver: minimum bitrate?

I'm trying to use a Small Form-factor Pluggable (SFP) as the laser source for a homebuilt laser gas analyzer, which means I don't actually care about transmitting data. The plan is to send an ...
ewineteer's user avatar
0 votes
0 answers
43 views

Finding poles of the transimpedance amplifier

I`ve been having problems with finding poles of one transimpedance amplifier. Acording to LTSpice the first pole should be somewhere around 1.6MHz, but I cant get that (I am getting about 200MHz). I ...
Огњен Пискулић's user avatar
0 votes
1 answer
77 views

What could the strange noise in the images be due to? They appear to be composed of 8x8 squares, and many of them contain different patterns [closed]

The question may seem silly, but I am curious about the structure of images from a certain biomedical image dataset. If you enlarge the following image fragments, you can see that they consist of 8x8 ...
forest-spells's user avatar
0 votes
3 answers
89 views

High-gain transimpedance amplifier with photodiode not functioning as expected

I am designing a trans-impedance amplifier using a TEMD7000X01 photodiode and an AD8551ARZ op-amp. RF is 100 kΩ, CF is 150 pF, and VCC is +3.3 V. The output of the op-amp is connected to an ADC pin of ...
Mohamed Hamouda's user avatar
0 votes
1 answer
110 views

Is there concept called dual ethernet? [closed]

I came across a word called dual ethernet while working on a project and it got me curious like is the word misspelled or is there any real concept on this?
Subzee's user avatar
  • 21
1 vote
0 answers
103 views

How to design a pulsed laser driver circuit?

I want to try a simple theoretical design of a pulsed aaser rriver circuit according to what specified in this guideline from LASER COMPONENTS. Since the guide is not exhaustive, I'd like to get some ...
Kinka-Byo's user avatar
  • 3,550
0 votes
2 answers
71 views

Design Suggestions for an Optocoupler Relay Module

I have designed this module to operate with input voltages of 5V and 3.3V (common in most MCUs). Additionally, I have equipped it with an optocoupler to isolate the MCU from the power section of the ...
Luis J. Mora's user avatar
1 vote
2 answers
223 views

Understanding optocoupler's operation through simulation

I am trying to understand how an optocoupler (4N25) works by looking at the datasheet and simulating a test circuit in LTSpice, but I am having some issues. To begin with, for the sake of trying to ...
gwn's user avatar
  • 31
2 votes
1 answer
181 views

SWD Connection to MCU and Appropriate Configuration for Reset Pin

I aim to establish a connection between SWD header and an STM32 MCU on PCB, having identified the relevant pins on MCU (SWO, SWCLK, and SWDIO). I have two inquiries: Is it appropriate to connect ...
Atrahasis's user avatar
  • 185
1 vote
4 answers
216 views

Does Optocoupler with Low Collector Current Work?

I am working on a schematic which was not started by myself. From the datasheet of LTV-816S-TA1-D, The CTR is from 300% to 600% and I set the forward current I_f to 5mA. However I notice that, given ...
andykkkk's user avatar
0 votes
1 answer
84 views

Current measurement from constant current source

I have a constant current circuit using an op amp circuit. I am implementing a current of 21 mA to drive a laser. Spec of laser: https://www.thorlabs.com/thorproduct.cfm?partnumber=L650P007 I would ...
Teena's user avatar
  • 101
0 votes
0 answers
101 views

Simulating an equivalent circuit model of a laser in LTspice, how does it solve this circuit?

I want to know how LTspice solves this circuit as there are node voltage (vj) dependent current sources (Ist and Isp) present in this circuit. Also, I had an unknown parameter, Ne, whose value I ...
L1234's user avatar
  • 47
0 votes
2 answers
250 views

Zero crossing detector - MCU interrupt is delayed

I'm trying to catch zero crossing (using below circuit) when it exactly happened. Rising and falling edge intervals are not equal and they need 0.3-0.7 ms to reach corresponding logic level. Let say ...
macola995's user avatar
  • 109
0 votes
1 answer
445 views

Connecting 6 push buttons with ESP32 with 1 common pin

Hey all I have 6 buttons that have the following voltage: I want to hook up a 4N25 to each one of these so I can use the ESP32 as a "virtual push" to each of these buttons. When the button ...
StealthRT's user avatar
  • 797
10 votes
4 answers
4k views

How does a 4 pin RGB connector work without ground?

The question is in title. Why there is no ground pin on the 12V RGB header? The 5V ARG header which uses only 3 pins has a ground. How does it work without a ground?
DEKKER's user avatar
  • 787
0 votes
2 answers
176 views

How to understand output of TSOP4838 IR receiver?

I am testing the output of the following basic IR transmitter/receiver circuits and not getting the result I thought I would. simulate this circuit – Schematic created using CircuitLab I have ...
RickyBoy's user avatar
  • 169
1 vote
1 answer
936 views

Is it possible to plot an equation in LTspice? I am supposed to plot an equation like this v(t)=d/dt(ln(pout(t)) + kPout(t)

In the equation mentioned above, Pout is the voltage at some output node in my schematic. Is it possible to plot the above equation? how to plot v versus time?
L1234's user avatar
  • 47
0 votes
0 answers
44 views

Quad IR pickup output inconsistencies

I've designed a quad IR pickup for a stringed instrument. The pickup works well, except that the output level of each string is different. Some strings (particularly the left two channels in the ...
violapwr's user avatar
0 votes
2 answers
281 views

Characterizing a PIN photodiode's 3 dB bandwidth

I'm currently attempting to characterize a PIN photodiode's 3 dB bandwidth. The photodiode input is a laser source that is being modulated by an ESA RF output that performs a frequency sweep from 0-1....
SamsUncle's user avatar
3 votes
1 answer
141 views

Safety regulations (USA) for high-power LED brightness (e.g. 1+ W)

For a "mostly" shielded sequence of 1 W where a user will see light bleed through small gaps in a device and (for argument's sake) might see a direct reflection of one of these 1 W LEDs (a ...
chroma's user avatar
  • 69
3 votes
1 answer
270 views

What is equilibrium carrier concentration in a semiconductor? Is it material specific? How to calculate it?

Is equilibrium carrier concentration dependent on doping density? If it is, then how to know how much the doping density should be for a particular semiconductor device?
L1234's user avatar
  • 47
0 votes
1 answer
128 views

I am simulating an equivalent model of a laser in LTspice shown below. I am supposed to plot the power at node Pout versus the input current

The issue is I am not able to plot the power without adding the load resistor which is not specified in the equivalent circuit. Is there any other way to plot the power? If not, then what value of ...
L1234's user avatar
  • 47
0 votes
0 answers
81 views

What makes an InGaAs detector more sensitive to infrared light?

What makes an InGaAs detector more sensitive to infrared light than visible light, considering that visible light has a higher photon energy?
Kicr's user avatar
  • 59
2 votes
2 answers
697 views

Implementing direct digital synthesis in STM32 microcontroller

I am working on a project that requires phase locking (digitally) of an output signal from a sensor to the reference signal which needs to be done on STM32 microcontroller. I am new to this area, and ...
Rima's user avatar
  • 133
2 votes
0 answers
109 views

Any theoretical reference for empirical equation for estimating oxygen saturation (% SpO2 = 110 - 25*R)? [closed]

The empirical equation used to estimate % SpO2 is based on the observation that the ratio of the red and infrared light absorbed by arterial blood (represented by R in the equation) varies linearly ...
Jahir hussain's user avatar
0 votes
0 answers
112 views

Difficulties with multiplexing PPG signal in pulse oximeter

I've designed pulse oximeter circuit. When one LED lights continuously, I got perfect PPG (Photoplethysmogram) signal. Then I measure PPG while blinking LEDS, like that: I got stuck. There is no ...
Dom.in's user avatar
  • 21
1 vote
2 answers
237 views

Detection of mechanical relay sticking

I'm exploring new methods to find if relay contacts have been stuck together without using auxiliary contacts of the relay. while searching I find out this block circuit: at this Toshiba page as far ...
David's user avatar
  • 41
0 votes
1 answer
81 views

Low pass filter (?) in Thorlabs PDs

What is the purpose of this circuit in all Thorlabs PDs? It looks like a second order low pass filter to me, but shouldn't it be two resistors in that case?
Helix Pasta's user avatar
0 votes
1 answer
115 views

How to drive this specific laser

I've done just a circuit to drive an old laser and it was like this one: I was wondering if it could be suitable for driving the laser whose datasheet is reported below. I have these requirements: ...
Kinka-Byo's user avatar
  • 3,550
0 votes
0 answers
88 views

Measuring low lux with ambient photodiode

For my application, I need to detect two light levels: pitch black (close to 0 lux) and a low ambient light level of about 0.1 lux (or higher). It seemed like the BH1680FVC ambient light sensor was a ...
donut's user avatar
  • 325
0 votes
1 answer
465 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
  • 103
2 votes
2 answers
139 views

BT136 TRIAC waveform

I am using a TRIAC to switch an AC signal (a typical example is shown in question Triac Switch Circuit using MOC3021 and BT136). When a BT136 TRIAC is used to switch a pure sinewave signal, I want to ...
kdm6389's user avatar
  • 107
7 votes
2 answers
1k views

How can we explain this strange phenomenon with an optocoupler switching?

Two optocouplers are connected according to the circuit below. The input voltage across the first optocoupler is a true square wave (3.3 V amplitude). The first optocoupler is an open collector output ...
Tommazo's user avatar
  • 71
0 votes
0 answers
117 views

DVD burner laser identification

I just disassembled the DVD writer from a laptop and scavenged some parts. Around where the laser and mirrors and opto stuff are packed together, I extracted these parts. Which one is the laser diode ...
Elementronics's user avatar
2 votes
3 answers
442 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
1 vote
3 answers
505 views

Using a LED as a debug serial port

I want to add a debug serial output port to a device that's sealed in epoxy. I plan to use one of three existing 3mm LEDs (red 617nm, green 568nm, or yellow 588nm), ±30° angle, that emerge from the ...
fgrieu's user avatar
  • 1,670
0 votes
0 answers
19 views

If composite transparent materials thermal and electrical conductivity can be adjusted t what would be benefit?

Will it be provided less thermal and electrical gradient to support less dissipative system development for opto-electronics and related technologies? For thermoelectric design how it cold be ...
Bablu Ghosh's user avatar
4 votes
7 answers
2k views

Is it possible to control the frequency of light?

I mean, controlling directly in the source, not filtering the light or arranging density of the medium. For example, brightness can be controlled by current or voltage directly. However, when I came ...
Ekrem_Abi's user avatar
4 votes
2 answers
1k views

Can anyone identify this chip which I think to be an optocoupler?

I'm trying to troubleshoot a Renishaw H-2000-5062-07-A optical receiver for a tool piece used in a milling machine. It has several of these 8-SOIC(?) parts and I very much suspect that they are ...
WNM's user avatar
  • 43
0 votes
1 answer
75 views

How to track, measure, manipulate and/or synchronize the phases of trapped ion qubits [closed]

I am working on a simulation of the Honeywell trapped ion quantum computer. The papers say that it tracks the phases of the qubits using "opto-electronics" but it doesn't give any detail.
Anna Naden's user avatar
0 votes
2 answers
85 views

Looking for 5mm discrete multi color LED [closed]

I want to make an electronic version of the Master Mind game as a hobby project. The challenge at the moment is to find right type of LEDs for the job. Below you ...
DEKKER's user avatar
  • 787
0 votes
1 answer
639 views

Why are low band gap semiconductors (like silicon) not ideal for most solar cells? Are their atoms ionized by higher-energy photons?

Most sources on the web say that 1.3 eV or 1.4 eV is 'ideal' for most solar cells... What happens to lower-gap, gapless or overlap materials (conductors)? Are they ionized, rather than sending their ...
Kurt Hikes's user avatar
-1 votes
1 answer
221 views

How to know which opto-coupler is suitable for high current application?

I would like a suitable opto-coupler to use as isolation from a 12V and around 30A current and another for 5V and around 30A. Are there any good opto-couplers for those ratings?
Pix's user avatar
  • 11
0 votes
1 answer
223 views

SSR for Attiny85 using Optocoupler and Triac

Looking for some advice, I am trying to create an onboard SSR to control the switching of a 120VAC load (heater/lighting), with an operating power of around 1500W max. I chose the following parts and ...
Tristen Michaud-Laughton's user avatar
3 votes
3 answers
5k views

How to know the minimum LED current of an optocoupler?

I am going to need to use an optocoupler to isolate two circuits in two situations. In both situations, a MCU GPIO will be driving the LED of the optocoupler to send a signal on the other end. I am ...
DrakeJest's user avatar
  • 917
0 votes
1 answer
53 views

What is wrong/missing from the process subsystem? [closed]

My teacher told me to reconsider the process subsystem but I'm not sure what is really missing from it. background story: when a guy is standing on the porch, the LED lights up
Unexperienced dude 69's user avatar
7 votes
4 answers
6k views

What is the purpose of using an analog optocoupler?

What's the purpose of using an analog optocoupler in this circuit? Why not a digital one? An industrial battery charger. Normal operating voltage to monitor ranges from 120 V (Battery low) to 180 V (...
albatross's user avatar
  • 143
0 votes
2 answers
793 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

1
2 3 4 5 6