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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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3answers
182 views

Monitoring signals on a bus with LEDs

I'm looking for a way to visually monitor logic signals on a bus with use of LEDs of different colours. The conditions are: I want to be able to visually distinguish the following states: a) Logical ...
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2answers
2k views

Fast bidirectional 3.3 to 5V level shifter

For a hobby project of mine, I'm thinking about connecting some old 5V SRAM chips like this one to a 3.3V - capable FPGA. The target frequency is 50MHz. After some simulator experiments I found out ...
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2answers
521 views

How to read a high voltage logic signal with pic microcontroller

On my circuit I have a voltage detected (TC54) to detect when the level of the battery gets low. The output of this ic is high when there is enough battery, but it will be at battery voltage (12 or 15 ...
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1answer
528 views

What is quad 8:1 MUX?

In my assignment i'm asked to show a block diagram for quad 8:1 Multiplexer. But i have no idea what the word quad means in this question. Can someone help me?
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2answers
2k views

5V to 3.3V logic level converter

I am trying to connect an ESP8266 module to an Arduino. Giving the fact that ESP8266 runs at 3.3V and the Arduino at 5V i need a logic level converter from 5V to 3V3. Is there a way i can build one ...
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1answer
335 views

How can I raise a CMOS 1.8V output to 5V LVTTL input with a MOSFET?

simulate this circuit – Schematic created using CircuitLab I'm trying to drive a 5V LVTTL UART input on a ATMega32u4 with a 1.8V CMOS ouput on a Telit UL865. I'm using the NTE2987 enhancement ...
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1answer
118 views

Is it safe to leave floating the low voltage supply of a logic level shifter?

I need to interface two devices, one runs at 5V and the other at 3.3V. In order to safely interface them, I'm using a simple logic level shifter (LLS) of this kind: It's a pretty straightforward ...
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1answer
207 views

STM32F4 Nucleo - how to set pins low while uploading firmware?

I am busy trying to write some firmware for a system with a whole lot of digitally controlled hydraulic components, and it's a complex system so there is a lot of tweaking of the algorithm and ...
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2answers
72 views

PIC24 Build-In Voltage Regulator

In the datasheet of the PIC24FJ256GB206, I have read that there is an onboard voltage regulator which will drop the core voltage to 1.8V. My question is: Will the logic levels of output pins also drop ...
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5answers
277 views

How to “shift” a logic LOW of 2,5 V to GND?

I'm trying to control a 24 V LED strip with a device that has its own control mechanism and PWM output. (The output PWM frequency is 1 kHz.) The device itself requires 5 V, and since it does not draw ...
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3answers
281 views

Reverse signal protection for two devices with different voltage levels

I want to design a circuit that is capable of blocking reverse voltage signals but allowing forward voltage signals to pass through. The original problem and solution: I was designing an Arduino to ...
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3answers
1k views

Why are so many pins of 8086 active-low?

Why are so many pins of 8086 active-low? Does it have to do something with the fact that more circuits are able to sink current than to source current, or is there another reason for it?
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2answers
104 views

Waveform to (5V) rectangle

I've found some interesting electronic projects which I wanna build, but I'll need a frequency meter for at least 1MHz. Sadly, I don't own one, but I found on the web that an Arduino UNO could do it. ...
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2answers
676 views

Three Way Light Switch using Two Binary Switches

Somebody presented me with an interesting problem that I can't seem to figure out. Is it possible to build a three-way switch circuit for a light bulb (akin to common household light fixtures) using ...
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1answer
632 views

turn level-based input to edge-triggered input [duplicate]

I'm trying to figure out with the most minimal part count how to convert an input of a digital IC to an edge-triggered input. I am using the 82C55 IC and the input on it I want to make negative edge-...
3
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1answer
365 views

MCU HIB pin only pulls Buck/Boost EN pin every-other Hibernation

MCU: TM4C1294NCPDT Buck/Boost Converter: TPS63051 Hib dedicated LDO: MIC5504-3.3YM5-TR I have a LiPo battery coming into the board, feeding both the TPS63051 and the MIC5504. Tiva's HIB pin is ...
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1answer
75 views

Which Low Input Current Buffer Chip?

I would like to get a PC to flash seven LEDs in response to program events. I plan to use the parallel port which is provided on the motherboard I am using by a Fintek F81866A "super i/o" LPC chip ...
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1answer
165 views

Zener diode level conversion of tristate output

I have an MCP73831 li-ion charger connected to an ATMega1284p. The charger has a tri-state status pin which can be High(5V), Hi-Z or Low. The ATMega runs at 3V3. I want to be able to read the value ...
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3answers
116 views

Resistors to make an 74hcxx IC behave like a 74hctxx IC

I made a circuit that is supposed to detect when all 8 output lines are logic high. I connected the inputs of a 74HC30 (8-input NAND) to the data lines of an AT28C256 (ROM). After a while, I checked ...
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2answers
1k views

How to use a logic level shifter for 1602 LCD

please bear with me as I am very new to electronics. I am trying to connect a NodeMCU dev kit (ESP8266) with a 1602LCD. I am using an i2c converter to interface with the LCD. The LCD requires 5V. I ...
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1answer
3k views

Is it possible to use a simple diode and pullup resistor to level shift down in one direction?

I'm working on a circuit that involves interfacing with a 3.3v microcontroller (ESP8266) and I'd like to be able to program it using my existing FTDI which operates at 5v. I'm new to level-shifting ...
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1answer
310 views

Max rx input voltage on FT232rl

The data sheet states: "Integrated 3.3V level converter" on the UART and CBUS pins. (https://cdn.sparkfun.com/datasheets/BreakoutBoards/DS_FT232R.pdf). I just want to confirm that means it's rx pin ...
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1answer
915 views

Noise margin calculation for schmitt and non-schmitt input signals

The noise margin is defined as: Noise Margin High = VOH - VIH Noise Margin Low = VIL - VOL Is the noise margin calculated the same way for schmitt and non-schmitt buffers? If so then why? This ...
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1answer
1k views

5V to 3.3V Level shifting circuit

I am interfacing an SD card to the Z80, one of which uses 5 V logic (Z80) and the other uses 3.3 V logic (SD). I believe the 3.3 V to 5 V level shifting will be taken care ...
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1answer
9k views

Help understanding 3.3v logic vs 5v logic with Raspberry Pi GPIO

This will probably be an extremely easy question for the seasoned EE's of you in the community. My question is this, I have 5v and 3.3v devices I want to interface with my Raspberry Pi's. I'm paranoid ...
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3answers
497 views

What design decisions must I make to select a suitable P-Channel MOSFET

I need a PFET with a logic level gate to trigger a power connection to a hobby servo that pulls more current than my MCU pin can handle. The requirement is simple but I'm trying to understand how to ...
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2answers
543 views

analog level conversion in ADC circuit

I'm trying to feed a 3.3V ADC from a gas sensor that operates at 5V. I know I can use a voltage divider, but am a bit confused how it would apply here. Datasheet: https://cdn.sparkfun.com/datasheets/...
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2answers
259 views

Logic family for 3.3 V microcontroller interface

I need to generate a bunch of chip selects for a SPI bus that I want to use on a project. I will use a 36 position (similar to PCIExpress = cheap) card edge connector and etc. The bus is simple : <...
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1answer
70 views

What characteristics of a MOSFET should I be looking at? [duplicate]

I'm trying to determine a MOSFET for a circuit I'm building which will drive the gate of an N-channel MOSFET at 3.3v with an available current 40mA (**this will be driven using PWM at 4MHz), the ...
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1answer
683 views

What's the purpose of this diode in this level-shifter?

look at this circuit: I don't get that what's the usage/purpose of the BAS316 in this circuit?
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1answer
658 views

How to turn a DIP switch into an array of logical values

Is there a better way to turn a open/closed switch into a logical value (capable or sinking or sourcing current) other than: simulate this circuit – Schematic created using CircuitLab I'm ...
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1answer
1k views

Interfacing 12V logic with 5V circuitry

I'm trying to build a simple circuit to control a church lampadary for an escape room game. I don't know if you've seen these but they're fairly common in catholic churches where I live: You input ...
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1answer
92 views

Question about Logic Level MOSFET's [closed]

In this schematic i thought i was connecting the 19v in to Q1 the source of the MOSFET and continue out the drain. however in eagle the default connection shows it supposed to connect the 19v in to ...
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1answer
829 views

How to connect a CD40109BE Voltage Level Shifter

I have a circuit requirement using a Texas Instrument CD40109BE Voltage Level Shifter. This chip incorporates 4 low to high level shifting circuits. I plan to use two of these circuits, A and B with ...
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2answers
1k views

How to drive power MOSFET by logic level signal without inverting phase?

I struggle yet another day with very simple problem (circuit). This challenge seems to be very common, but nowhere I can find a complete solution: I have a heavy load (12v / 1 Ohm peltier = 12A max) ...
0
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1answer
103 views

Upper and lower bound - Digital electronics

A logic signal is transmitted in a logic circuit with positive logic, where \$V_{IL}=2.3 V\$, \$V_{IH}=4.5 V\$, \$V_{OL}=1.4 V\$, and \$N_{MH}= 1.8 V\$ . Recall that when using positive logic, the ...
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1answer
811 views

Multiple SPI devices with different logic levels

I'm going to use one of the PIC32MX795F512L SPI peripherals (master), 1 to 4MHz, to communicate with multiple devices (slaves): Wi-Fi module MRF24WG0MA (3.3V); uSD card (3.3V); 9 modules with sensors ...
3
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3answers
868 views

Interfacing open-collector optoisolator to 3.3V microcontroller

I have a bit of a puzzle on my hands trying to interface a Fairchild MID400 optoisolator (popular "logic level" optoisolator for mains detection) to a 3.3V GPIO pin. The MID400 is a 5V part [*] and ...
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2answers
230 views

2 state converter, from -24VDC [ON] - +5VDC [OFF] to 5VDC [ON] - 0VDC [OFF]

So as the header says, I would like to take a 2 state signal (ON/OFF) where the on state is -24VDC and it's off state is +5VDC and make that/convert to a 0-5VDC 2 state signal, where 0 is the ...
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2answers
171 views

MOSFET-N as a switch for several ICs

I want to use MOSFET-N (MTM232270LBF) as a power switch for several ICs in my project. It should poweron the devices when logic level is high (3.3V) and poweroff when 0V. I want to ask you if ...
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1answer
128 views

why use 2 diodes when shifting from 3.3 to 5v? [closed]

for the question "how do I go from 3.3 to 5v" people point to the microchip cheat sheet. The Diode option has one between the data line and 5V so it pulls it almost to zero, the other one seems to ...
2
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1answer
184 views

Large range input single level shifter

I have an application where I will be taking serial signals will need to level shift the signal to 3.3V. The input signal will be from 15 to 5V for a high input and I need them all shifted down to 3....
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1answer
720 views

What is the explanation with shorting vcc and gnd to power up the whole circuit in a breadboard? [closed]

I was building a logic circuitry that performs 8 bit multiplier 16 bit divider using decoders as finite state machine in breadboards. the circuit is a bit large and i wonder why grounds or low voltage ...
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2answers
2k views

How to output 5V from 3.3V MCU?

Big picture: I want to control a LUXdrive 3023 BuckPuck LED driver (3023-D-E-1000) from a Particle Photon (essentially an ARM Cortex M3 microcontroller). The MCU runs at 3.3V. I have tried a few ...
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3answers
148 views

MOSFETS +/- Voltages? Which to use?

I've been trying to get into some low level electronics to explore to "Internet of Things" and still struggling a little with MOSFETS. I'm trying to make a single push button act as a latching power ...
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1answer
474 views

Level Shifter Issue with Ground

I am using this level shifter spark fun breakout board: https://learn.sparkfun.com/tutorials/using-the-logic-level-converter My goal is to interface a 5V logic SPI LCD with a 3.3V logic micro ...
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1answer
68 views

Whats happenning with my logic levels?

I'm using a 3.3 MCU and a 5v logic RS-485 IC. I'm trying to send out some data to another controller. I don't have a logic level shifter as of now. So I decided to use resistor divider, to get it to a ...
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2answers
13k views

7400 series CMOS vs 4000 series logic IC

I understand the traditional difference between the 7400 series and the 4000 series logic ICs, but since there are CMOS versions of the 7400 series, is there an advantage to use the 7400 CMOS version ...
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3answers
1k views

Does powering a module with 5v instead of 3.3v affect it's logic level? [closed]

I bought a NEO-6 u-blox 6 GPS Module (datasheet, pages 9 and 14), which has a standard serial connection. I have a USB to serial converter, which is 5v logic. This board says it can be supplied 3v-5v, ...
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3answers
755 views

Do bi-directional level converters connect either input directly to ground?

So I have the following circuit, which is a bi-directional level converter: I am using it to convert a 5v logic signal (which at high is actually 4.2v and low is ~0.2v) to a 3v3 logic signal. I have ...