Questions tagged [logic-level]

Logic level refers to the input and output voltage levels of digital logic, which is often 3.3 V or 5 V.

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Making a circuit switch using MOSFETs

I am trying to control the choice of 2 circuits using MOSFETs, at logic levels. Basically, I’d like to have one circuit feed bits to an IC in some conditions and another circuit do the same in ...
Fed's user avatar
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AVR32DA VIH threshold

I am looking into using an AVR32DA48 MCU for a design. The MCU will be powered at 5V and needs to interface with an IC at 3.3V. The IC is 5V tolerant and I am trying to figure out if a level ...
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Logic translator between different ground references

I need to translate a 1.8 V digital signal ("power good" from a DC-DC converter) from a "floating" voltage domain to a 3.3 V signal referenced to a fixed system ground. The source ...
mattmunee's user avatar
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4 answers
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Level shifting from 3.3V to 5V not working: voltage drops when attaching load

I am trying to trigger a laser using an Arduino. I used a power supply to determine that the laser needs a 3.5V (or higher) signal, at which point it draws around 2.2mA from the power supply. When ...
Timeverdrive's user avatar
2 votes
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Adding level shifter circuit conflicts with other microcontroller peripherals

I'm working on a synthesizer with multiple functionalities (OLED I2C screen, encoder, audio, midi input, several keys input) on a Xiao RP2040. I wanted to add a PS2 keyboard input. RP2040 GPIO are 3....
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I am using a logic level converter for my LED-Ring but it's not working

I am working on a small project where I am using a SparkFun Lumini LED Ring. The power supply for the ring is external, connected via its own cable and power adapter. I have connected the ring to the ...
xcido's user avatar
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Interfacing Delta PLC and Arduino (Logic Signals)

I am trying to connect a Delta PLC (DVP-10SX) to an Arduino UNO. What I'm trying to achieve here is to be able to exchange Logic signals between both the PLC which has a logic level of 0-24V and ...
ENG_MOH's user avatar
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Unable to read data through a MAX485 module

I used arduino code in order to grab RS 485 data from a sensor. The middleman is a MAX485 module. However, I was unable to read the data, even with code that works from previous examples. I hooked up ...
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Wired AND and OR question, logic levels?

In the "wired AND and OR" gates pictured can anyone explain what the voltage levels will be for each function? For AND, I see the output is A*B and for OR, A+B. Is this correct? Also, is ...
notaorb's user avatar
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Do I need a bidirectional logic shifter for UART

I need to interface my Raspberry Pi to my Uno hence I need to logic shift 5 V logic to 3.3 V. I will be sending data from the Uno to Pi and from the Pi to the Uno. My understanding is UART uses two ...
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Pushing a button press from a driver to three different transistors with three state logic

I am working on a project within my company that involves a relay board used to control three different motors when an external 24 V button is pressed. The existing setup works based on this principle....
Knowledge's user avatar
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What is the best practice to translate variable resistor 500k to infinity to logic levels?

I have a custom sensor that gives me resistance in the range of 500 kΩ to infinity, I want the 500 kΩ - 1.5 MΩ values to be perceive as a High input in my STM32 controller. Assuming Vin = 3 V and the ...
Chakra41's user avatar
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107 views

Solid state relay that can switch amplified audio signal using a control voltage

I want to evaluate whether I can switch an amplified audio signal (AC, load 8 Ohms, e.g. 20W) using a solid state relay. I already do this with mechanical relays. So I need an SSR with very linear ...
0__'s user avatar
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Drive an HX-53 IR Transmitter using an ESP32 and logic level converter

I have an ESP32 with which I need to drive an HX-53 IR transmitter. I'm facing some range problems particularly for three reasons: The HX-53 is supposed to be driven with 5 V. There is an LED in ...
user217354's user avatar
1 vote
5 answers
124 views

Why would an intermediate voltage level cause a metastability in a SR-latch

Transistors and logic gates are actually analog in nature they aren't digital they don't turn on or off at certain voltages. Image source: All About Circuits - Voltage Tolerance of CMOS Gate Inputs ...
John greg's user avatar
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Understanding TXB0104 logic level shifter from TI

I’ve been reading through the data sheet and have been having trouble finding an answer. I’m looking to use this to communicate SPI between a 5V mcu and a 3V3 device. Can the TXB shift the 5V to 3V3 ...
1W0n_29's user avatar
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What is meant by TTL in this context?

Regarding this driver manual, the analog input has range 0-5 V with 1 MΩ input impedance. But the manual also writes that the analog input is not TTL compatible: I thought the term "TTL ...
GNZ's user avatar
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4 votes
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LED Light Strip Control Circuit not working once assembled as a PCB

My project is to create a controller for some warm and cool LED light strips. The parts I used were an Arduino SAMD21, two FZ44N MOSFETs, and two 10 kΩ resistors. The Arduino sends a PWM signal to the ...
Kyle's user avatar
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6 answers
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Switching line between 5 V and ground using a 3.3 V signal

I am working with a PCB which looks like shown below. Switching the central line between 5 V and ground toggles the LEDs. I had this PCB connected to a 5 V Arduino dev board where the switch line was ...
Warren's user avatar
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Do I need to level shift the PWM signal from a Raspberry Pi Pico for regular RC servo?

I am trying to control regular SG90 servo with a Raspberry Pi Pico. My problem is that those servos produce maximum torque while powered by voltage between 4.8V to 6V (5V is optimal for me.) I powered ...
Papouc's user avatar
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1 answer
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High to Low logic level converter with MOSFET

I'm designing a sniffer circuit to tap input signals from various machines. The type of signal varies from input pulses and UART communication, the voltage varies from 5V to 12V. These are the ...
Max's user avatar
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Can I pull down with 5V logic a not-level shifted (which is at 2.8V logic pulled-up) input? How to pull it up to 2.8V again, with no level-shifters?

I have a Distance sensor which has an enable pin (XSHUT pin in the diagram) which is pulled high in its own PCB module at 2.8V, to enable it to work. My Attiny85 MCU, which controls the sensor, is at ...
Rodrigo's user avatar
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Choosing and understanding which MOSFET to use

I have what I think should be (and, no doubt, is) a very simple problem to solve. Using an ESP-01 with 3.3v logic, I want to be able to switch a 24v load (500mA max) on and off. The ESP-01 pin has a ...
NAB's user avatar
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Level shifter breaks down (repeatedly)

I created a Dometic Airco thermostat using esphome on an esp chip. The Dometic is expecting 5V on the serial control line, not the 3.3V coming from the esp. So I implemented a simple circuit using a ...
marcvl's user avatar
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2 answers
202 views

Fast unidirectional level switch from 5 V to 3.3 V

I came up with this circuit. Is it good or bad to use diodes? In my opinion, this is better than a divider or a FET, at least faster, as you can see from the waveforms. Will such a circuit create ...
GriDev's user avatar
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1 answer
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Level shifting/LED driving without lower voltage rail

What's the best way to drive 3 LEDs (2 mA each) with 1.8 V signals (500 µA max) when I have only the 5 V rail (1.8 V and 3.3 V rails might not yet be available). (For context: the LEDs are for showing ...
Sandro's user avatar
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Simple probe PCDU

I am currantly working on an aerospace engineering project at my university which will fly on a sounding-rocket and I really suck at electical engineering, so I basically need a complete explanation ...
Caeleste's user avatar
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Ensure that cable is not disconnected from my custom board

I designed a custom board, the board includes stm32 that turns on a control voltage that operates SSR and the SSR goes to the load: CTR comes from the GPIO of STM32. in my custom board, there is some ...
Knowledge's user avatar
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0 answers
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Connecting a ESP8266 GPIO Input to a 4.2V

I am following this great article on building a low power sensor using ESP8266. The author (Gadjet) connects the GPIO12 pin to a LIPO through a 10K resistor. I am not sure if this a great way to do, ...
Suresh Kumar's user avatar
2 votes
3 answers
963 views

Is P90NF03L 3.3V logic level MOSFET?

So I want to control my 12V (up to 10A) load through a 3.3V logic level MOSFET. I have purchased the P90NF03L MOSFET but I don't trust my datasheet reading skills so could someone please confirm that ...
DribbleNibble's user avatar
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168 views

How does a logic level converter with a N-channel MOSFET work?

I am trying to convert a 3.3 V digital signal to a 5 V digital signal. One way to do this is to use a logic level converter with a N-channel MOSFET and 2 resistors. I found the following schematic: ...
DGBMenno's user avatar
1 vote
1 answer
95 views

Could this logic level converter produce a short circuit?

I use this logic level converter for I2C. What would happen if the user programms the pin of the microcontroller on the low side accidentally as a "normal" output and the pin on the high ...
Felix Yah Batta Man's user avatar
4 votes
1 answer
241 views

Understanding the characteristics of a MOSFET as a switch

Edit 4: Thanks to the feedback in the comments I tested again and realized that the problem I describe below, with the output voltage being too low, happens regardless of whether the external device ...
Acmeist0815's user avatar
2 votes
1 answer
663 views

What is the voltage output from STM32 BluePill Digital I/O pins?

I am planning to use logic level MOSFET IRL540 as a replacement for my 5V 1 channel relay module to protect my Arduino pro micro from current requirements of the relay module. I would also like to use ...
DribbleNibble's user avatar
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1 answer
51 views

Interfacing LTC2492/6/8 via SPI: is voltage shift needed?

I'm a bit confused with datasheet for LTC2498. It says on page 27, section "Digital Signal Levels": The LTC2498’s digital interface is easy to use. Its digital inputs (SDI, fO, CS, and SCK ...
Gryphon's user avatar
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2 answers
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Is this a logic-level MOSFET?

I have the datasheet of a MOSFET but I can't tell if it's a logic-level MOSFET or not. I read that if an Rds(on) for Vgs = 5 V is specified, then it should be a logic-level MOSFET.
Qstudent's user avatar
3 votes
1 answer
275 views

Why does this MOSFET not switch 9 V?

I am designing a circuit so that I can mute/unmute a microphone using an Arduino/Raspberry Pi. I am using a CD4051 which is designed for controlling audio applications. The schematic is based off of ...
spuder's user avatar
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2 votes
1 answer
87 views

Two 3.3 V low signals to light bicolor LED

I have a GPS receiver board that has two output pins to indicate the unit's status. I'd like to use these pins to illuminate a bicolor LED so that Status 1 will illuminate green, 2 will be yellow, and ...
Travis W's user avatar
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2 answers
1k views

P-channel logic-level MOSFET that turns on properly when driven by an ESP32 (working from 3.0 V to 3.6 V) [closed]

I'm reading the specs of the ESP32 and I'm trying to find a P-channel MOSFET that I can drive with the GPIO pins. The specs say that ESP32 works from 3.0 to 3.6 V. Its logical zero is at most 0.1 VDD ...
verbessern's user avatar
2 votes
1 answer
333 views

What does this function table mean?

This table, part of the SN74LS138 datasheet, explains how inputs relate to outputs: However, I'm no electrical engineer and I don't understand the bit I've circled in red which says \$\small\mathrm{\...
noughtnaut's user avatar
2 votes
2 answers
875 views

Best way to detect high-impedance state

I want to build a logic probe. What is the best solution to detect a high-impedance state?
Elian Russel's user avatar
2 votes
1 answer
177 views

Using an open drain buffer as a logic level step down converter

I'm trying to convert a 3V3 UART to 1V8 UART with an open drain buffer, but the output of the buffer is always high. See the schematic below for the circuit. On the input to the buffer, there is a 0V -...
skipper_the_penguin's user avatar
0 votes
0 answers
51 views

Delayed start-up with no current consumption after

I have a delay circuit. My sole purpose is to disable the input from the orange line for some time after the power is on. After that this portion of the circuit should not consume any current. Here is ...
CaveScientist's user avatar
10 votes
3 answers
3k views

What does the voltage of an I/O pin mean?

I'm trying to figure out the Seeed Studio XIAO board (essentially a smaller version of the Arduino) and I noticed that there was a line in the specifications saying "All the I/O pins are 3.3V, ...
Rena W's user avatar
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2 votes
2 answers
217 views

Logic Buffer for SPI level Shifter 74LVC126

I am using 5V logic microcontroller and I want connect the Hardware SPI bus to SD CARD and Ethernet chip(W5500). Using below circuit I am not able to initialization SD card. Below is my schematic: ...
Shahreza's user avatar
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0 votes
1 answer
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Interfacing 2.85V logic modem with 3.3V microcontroller

I have Fibocom G510 modem. It has 2.85V logic level and datasheets says, that 3.3V is absolute maximum for logic pins. Maximum baud rate is 115200. Due to the limited space in the housing / on PCB I ...
Kamil's user avatar
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-1 votes
1 answer
188 views

5V Input and Output interfacing with 3.3V GPIO [closed]

I have a device (a motor drive) with 5V logic. My controller is 3.3V. I draw the two circuits. The right sides are fixed in the device. I have some exact questions about calculations. -...
Buruhazard's user avatar
0 votes
1 answer
1k views

Combining 5V and 3.3V SPI

On a current project I need to interface several SPI slaves to an ATSAMS70 MCU. The MCU, and some slaves, are operating at 3.3V logic levels. Other slaves need to operate at 5V, so I need a level ...
Michael Larsen's user avatar
0 votes
1 answer
44 views

How to connect dissimilar but close logic voltages between a chips logic out and a chips input enable pins

I have two chips and I would like the logic out of one chip to control the chip enable pins of another chip. I am just not sure how to do it. I have a chip with an output of 3.6v with logic on and -1....
axawire's user avatar
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0 votes
2 answers
767 views

ADS1115: Using 5V supply instead of 3V, do I need to increase the logic level signal from 3V to 5V?

I am using a microcontroller that has a 3.3V Logic level output. The microcontroller is connected to ADS1115 via I2C pins, and the ADS1115 can be powered with 3.3V or 5V depending on the range of ...
Sam Shurp 's user avatar

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