Questions tagged [logic-level]

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

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123 views

TMC2209 why are separate motor and logic voltages needed?

Why do motor drivers require separate motor voltage and logic voltage? I am looking to use a TM2209 stepper motor driver. Below is a schematic of how I intend to power it. I'll also be using a MCU, ...
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101 views

What are the usual logic voltage levels in MCUs and other modules?

It's a 100% beginner's question. Assuming that I have a device with VCC = 5 V, is it true that HIGH level will be always something around this 5 V and LOW level will always be something around 0 V? Or ...
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22 views

For the DVR8825 IC chip (not the carrier/module), nSleep and nReset need to be HIGH, why does connecting them to the IC's 3.3V out not work?

A breadboard prototype was made using the DVR8825 carrier/module: A microcontroller's HIGH was connected to nReset and nSleep. Now a prototype was made using the IC/chip. It's 3.3V output was ...
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23 views

MCP23017 Expansion HAT logic voltage

Does anyone know the voltage range for the MCP23017 HAT - 32 channel I/O Expansion HAT's logic pins to register a HIGH signal? I know the supply voltage range is from 1.8V-5.5V, but I'm assuming it's ...
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209 views

Gate resistor with "logic level" MOSFETs

I need to drive 2 logic level MOSFETs from digital outputs of a microcontroller (3.3V). These will be used to drive a low-power push-pull converter at 500 kHz. I have identified these "double&...
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1answer
56 views

Level shifter for Neopixel connection guidance

I want to use a Neopixel LED strip, with 20 LEDs. I am using an ESP32 chip. Hence I need a level shifter. I have decided to use the 74HCT04ADG because it is cheap and most importantly still in stock ...
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2answers
79 views

Using a diode to clamp a 24V logic output to 5V

I have a controller board (the Teknic ClearCore) in which output signals are pulled up to 24VDC. I am trying to interface with a TLC5947 LED driver IC rated at 5V maximum control input voltage. The ...
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3answers
143 views

Bi-directional level shifter for serial communications

I want to know if I need to use a bi-directional level converter to send data from an ESP32 to a 5V display, using serial communications (TX and RX). I understand the serial communication is uni-...
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31 views

2.8V UART to 3.3V and 5V MCU automatically

I'm designing a PCB of SIM800C Module. Just to improve myself and it is my first project so I'm a noob sorry.. I want GSM module to communicate(from RX,TX pins) with STM32, Raspberry, Arduino. But the ...
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75 views

Why are *actual* RS232 transceivers RX thresholds so narrow?

I'm having horrible communication issues with an RS232 line. It's near a fat load (not good) and it's a printer (so the comm errors are literally visible). After investigation I actually detected the ...
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561 views

Logic level converter from 29V to 5V schematic

Does it looks a good schematic to do a proper 29 V to 5 V logic level conversion, any improvements or suggestions?
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1answer
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I2C voltage levels and inter-operability with Sparkfun Boards

I'm trying to design around Sparkfun's I2C products to work with Adafruit sensors, specifically Sparkfun's I2C Multiplexer, Differential Endpoint, and Differential Midpoint. From what it looks like, ...
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3answers
249 views

Logic Level Shifter 24/12 V to 3.3 V

I have a ESP32 and Industrial Sensor with voltage output 0-12 V and 0-24 V. How can I interface 2 logic levels with my 3.3 V ESP32? Can I use a BSS138 or do I need another module?
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75 views

Voltage output of a sensor with 3.3V & 5V supply

I want to connect Sharp GP2Y1014AU0F Dust Sensor with an ESP32. According to the datasheet, the VCC can be from 0 to +7V (5V recommended). With Vcc = 5V, the sensor output voltage varies between 0.6 ...
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Differential Signaling and RS485 difference?

I am trying to wrap my head around the difference between differential signaling (mainly LVDS and LvPECL) and RS-485. All seem like differential signaling for serial communications. From the TI Page, ...
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67 views

What can I do to see only the logical values in the MOSFET input?

(Animated GIF of the simulation is here) This is a simple circuit that makes the MOSFET turn off, as the temperature of the NTC thermistor rises. As you increase the temperature in the diagram, the ...
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57 views

Pulse duration detection evaluation (opto) LT-22222 from dragino

My question seems simple but i can't find the answer on documentation. (or I don’t have enough skillz) I have this energy meter with pulse output: https://cdn.store-factory.com/www.compteur-energie....
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Will this interface work? HCSL Clock interface

I have an HCSL interface and I want to make sure it will work correctly. The oscillator is a AX3HAF1-125MHZ part and the receiver is the NXP LS1046 device. The specs for the oscillator are: Output ...
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2answers
73 views

What is the purpose of these logic level enhancement mosfets in this schematic? [duplicate]

Below I've included a schematic that belongs to a adafruit light sensor, the VEML7700. The output of the light sensor is fed into the source of a mosfet which seems to always be ON since the gate is ...
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1answer
46 views

Non-monotonic signal crossing VIL and VIH

I'm using a logic buffer SN74LVC2G125 (SN74LVC2G125 datasheet) which is powered by 1.8V and has VIH and VIL of 1.17V and 0.63V, respectively. If I have an input signal like below, could the buffer's ...
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105 views

Why does the 74LS32N behave like an AND gate?

First of all I am a beginner. I am practicing with the 74LS32N (OR Gate) IC , I noticed that it behaves like an AND gate instead of an OR Gate. Only when both the inputs are 1 , the output is 1 , (Led ...
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65 views

8-channel/octal equivalent of 74HC125

I have a 12v powered 16-channel relay board, that required 5v logic level signals to control the relays. However, I am using a Raspberry Pi to control this, which has 3.3v logic level outputs. I have ...
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1answer
109 views

74HC08N doesn't latch [closed]

I am using the 74HC08N chip. Why doesn't the first AND gate latch itself? I have connected the output of the first AND gate to its own input. I have used two resistors, the one on top is a pull-up and ...
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61 views

Level Shifting - Signal Scaling - Scale Analog Signal Voltage

I have a variable voltage called Vreg (Voltage regulated) which is output of switching regulator (buck converter) and is less than 12v. Also there is ANALOG Signal ...
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2answers
93 views

IRLZ44N MOSFET switch - voltage drop across brushless fan

simulate this circuit – Schematic created using CircuitLab I have an IRLZ44N with the gate connected to a 3.3v logic output pin as shown in the diagram below. The brushless fan is rated at 5v ...
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1answer
181 views

I2C Level translator 5 V to 1.8 V using MOSFET, output look weird

I am designing an I2C level translator using MOSFET. I am using BSS138 DATA SHEET. My clock can go up to 1 MHz. The output is not coming properly for fast mode plus (CLK = 1 MHz, RISE TIME = FALL TIME ...
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1answer
134 views

I2C: Do I still need pull-up resistors if I use a logic level converter? I

Electronics newbie here. I have the following setup - three Arduino Nanos, a BME280 sensor, an MPU6050 gyroscope, a GPS GT-U7 (Goovvv Tech) module and an 128x64 (1.3in) OLED display. All except the ...
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273 views

Microcontroller maximum and minimum source and sink current

I'm using the S32K142 64-pin microcontroller. I have a question about this table: What parameter does the maximum sink current and source current depend upon? The marked line in the table says that ...
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1answer
219 views

What is the output logic levels of this STM32?

I am struggling getting my head around the input and output logic levels, mostly the output levels of this STM32 (STM32F446xC/E). This table shows the output logic levels as dependent on if it is a ...
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29 views

Bi-Directional Logic Level converter 1.8V-5V using MOSFET

I need to connect an Event Detection pin (pin of the NXP NTAG 5 component) to a GPIO of the NXP i.XM6 processor. The problem is that the NTAG 5 pin has a logic level of 5V and the GPIO has a logic ...
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35 views

5v Signal to 24v Input for CNC Machine Probe

Background Info I have a CNC probe which acts just like a NC switch and opens when triggered, I am trying to modify a circuit for use with my CNC machine controller inputs which use a 24v signal to ...
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4answers
121 views

Degenerated signal at a logic level converter

I'm trying to pair a motor controller, and a bi-directional logic level converter to feed a microcontroller with a motor speed signal. Some signals have already been successfully converted, but a ...
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0answers
43 views

Question regarding isolation and level shifting

What are the requirements that make one choose between physical isolation and simple logic level shifter circuits when you have two devices communicating with each other. For example, a circuit ...
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2answers
115 views

Understanding how this bi-directional logic level shift works

I'm having a bit of trouble understanding how this logic level shift circuit works exactly. The design is from Sparkfun. Hhere is the schematic: For my application, the LV and HV are the 3.3V and 5V ...
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116 views

High current bus bars on PCB controlled with mosfet and Raspberry Pi

I need to be able to switch up to 100 amp @ 48v DC with a Raspberry Pi. I came across this video which is what I am trying to emulate: https://www.youtube.com/watch?v=dhIbZa6yg5k at 1:15 in the video ...
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33 views

load sharing circuit power supply and battery with turn off mechanism

I have my power supply VDD with 5 V. If my power supply is connected to the circuit, the MOSFET M1 should block my battery voltage. If the power supply is disconnected (VDD = 0), the transistor M1 ...
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41 views

Connecting Geiger Counters in Coincidence

So for this Geiger Counter kit from mightohm (https://mightyohm.com/blog/products/geiger-counter/), does any one have any suggestions for what circuits to build to connect two detectors in coincidence?...
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Is it safe to drive a 5V servo using a logic level shift board?

I would like to turn off and on a servo while it is not used. The LV would be 3.3V and the HV would be connected directly to s lithium battery. Could it work if I replace R4 with a servo? What problem ...
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1answer
183 views

Logic Converter driving logic level Mosfet Gate

I am wondering if anyone can comment on the feasibility of this circuit. My ultimate goal is to switch a 12V solenoid on and off using a 3.3V microcontroller, but I have had trouble so far. I want to ...
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42 views

MicroUSB to MCU interface with logical level conversion

I'm trying to interface a micro USB port to a microcontroller but I'm not sure about something. The micro USB port will be connected to a computer with a simple USB cable and that will give me a 5V ...
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75 views

Logic level mosfet wont drive solenoid

I am trying to find out why my current mosfet is not working by looking over the datasheet. Ultimately I am just trying to buy a mosfet that I know will work, but I want to understand the datasheets ...
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1answer
86 views

Problem into shifting from 3v3 to 5v using a BJT

I've encountered a problem when I've made a small circuit to shift logic level of my 3v3 MCU to a 5v signal. Probably I've misunderstood usage of BJTs. Here's schematic: As said, my purpose is to ...
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137 views

Replacing optocoupler with a more reliable and durable device

I am working on a project where I need to have some sort isolation from a machine sending out highs and lows in terms of 24vdc to 0vdc respectively. And I'm using a microcontroller like ESP32 that ...
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1answer
62 views

Convert High voltage output ( 15V ) to 5 V

I want to use : DSD 70 Dual Channel Hall Effect Speed Sensor and integrate it with an MCU ( arduino ) atmega , so I have to convert the output of the sensor to 5V to be able to read it by the MCU. Any ...
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1answer
80 views

Data Logic Levels Sent From Sensor Are Not Going All The Way Low

I'm having issues receiving data from a 3.3 volt logic level R503 Fingerprint Module that is sent via it's Tx pin using UART. The logic levels are converted to 5 volts using a bi-directional converter....
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1answer
90 views

In a NOR gate not connected to any power supply, how can the output be '1' if both of the inputs are '0'? [duplicate]

I was reading about SR Latches and this very weird (and silly) question popped up in my head. Here, when A and B is 0, then Q is 1. Suppose that this NOR gate is lying in air, not connected to any ...
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138 views

Is it possible to use a MAX232 to convert 0 to 5V PWM to 0 to 12V PWM to input to a motor driver requiring 0 to 12V PWM logic?

I'd like to drive a 16kHz PWM signal at 0.5mA into the input of a motor driver expecting logic levels of 0V for LOW and 12V for HIGH, and expecting a PWM signal around this frequency. The PWM signal ...
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0answers
49 views

voltage level handled using optocoupler [duplicate]

I want to program at89c2051 chip. I am referring circuit diagram where the optocoupler is used to handle the 2 voltage levels (+12V and +5V). i didn't understand how Pin A0 and A1 will control the ...
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1answer
90 views

Multi-level NAND circuit simple conversion

I am working on understanding the NAND conversion. I have just got the basics of two-level NAND conversion, and when I went to the book example for a multi-level NAND conversion it used solved an ...
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48 views

How to read a 5.5V IC push-pull output using a 3.3V microcontroller?

I have two devices that I need connect, one fed with 5V, the other fed with 3.3V, and I also have a level-shifter, TXS0108E, that allows communication between two circuits, one working in 3.3V and ...

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