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arduino uno has 5v output in gpio when it enabled to drive high. but, most of the home appliances require 230v single phase power to energise them. therefore, we need the following unit to drive 230v device using 5v capable gpio

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Mohammed

Guys, does anyone know the answer?

get arduino uno has 5v output in gpio when it enabled to drive high. but, most of the home appliances require 230v single phase power to energise them. therefore, we need the following unit to drive 230v device using 5v capable gpio from screen.

Arduino UNO digital output voltage (5V)

Hi folks. When the arduino (eg UNO) gets its power from USB cable only, how does the digital output pins get 5V? The outputs are really at about 5.0 V (from multimeter measurements) when the output pins are high. If USB…

Arduino UNO digital output voltage (5V) - how it gets the 5V from USB power?

Using Arduino General Electronics Southpark Jun '16post #1

Hi folks. When the arduino (eg UNO) gets its power from USB cable only, how does the digital output pins get 5V?

The outputs are really at about 5.0 V (from multimeter measurements) when the output pins are high. If USB voltage is 5V, then I was thinking that there would be voltage drops internal to the arduino that would result in less than 5V output. Thanks in advance.

Jun '16

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3 3 3 Grumpy_Mike Karma: 2500+ Jun '16post #2

If USB voltage is 5V, then I was thinking that there would be voltage drops internal to the arduino that would result in less than 5V output.

Why would you think that? It is not the case.

There is no voltage drop if there is no current flow. You put a 220R resistor from a high input to ground and measure the voltage again you will then see some voltage drop from the 5V.

Southpark Jun '16post #3 Grumpy_Mike:

Why would you think that? It is not the case.

There is no voltage drop if there is no current flow. You put a 220R resistor from a high input to ground and measure the voltage again you will then see some voltage drop from the 5V.

Arduino Official Store

Arduino Uno Rev3 53

Arduino Uno is a microcontroller board based on the ATmega328P (datasheet). It has 14 digital input/output pins (of which 6 can be used as PWM outputs), 6 analog inputs, a 16 MHz ceramic resonator (CSTCE16M0V53-R0), a USB connection, a power jack, an...

"Each of the 14 digital pins on the Uno can be used as an input or output, using pinMode(), digitalWrite(), and digitalRead() functions. They operate at 5 volts."

Ok..... this will mean operating at around 5V, but pin output won't necessarily be at 5V.

Thanks again Mike. Grumpy_Mike Karma: 2500+ Jun '16post #4

Ok… this will mean operating at around 5V, but pin output won’t necessarily be at 5V.

Yes that is correct. If you look at the data sheet for the Atmega328, in section 28 there is what the voltage output of a logic high can be with a current of 20mA.

Here is an extract of the appropriate page.

It means that when you power the chip with 5V and take 20mA out of the pin the voltage can drop to 4.2V. This is the worst that can happen and it is often more than that. It also tells you what will happen if the chip is powered by 3V and you take 10mA out of it.

Southpark Jun '16post #5

Thanks very much Grumpy Mike! That helped me a lot. Greatly appreciated.

westfw Karma: 1200+ Jun '16post #6

(The output driver transistors of the AVR are MOSFETs, so they behave pretty much like low-value resistors when “on”, rather than having an inherent Vce voltage drop like a bipolar transistor might…)

2 YEARS LATER dipido Oct '18post #7

Hi guys, sorry if I revive this old thread. So, in this scenario:

The unexpected voltage drop (I get 4.7V between the digital pin and GND - instead of 5V - when I put an LED and a resistor into the circuit) is due to the internal resistance of the Arduino. Moreover, this happens only with digital pins (not with the Arduino 5V source). Am I right?

One more question: is it possible to avoid this behaviour? :

Grumpy_Mike Karma: 2500+ Oct '18post #8

is it possible to avoid this behaviour?

No. Unless you add a transistor or FET to the output pin and take the voltage from that.

The unexpected voltage drop (I get 4.7V between the digital pin and GND - instead of 5V - when I put an LED and a resistor into the circuit)

It is not unexpected, it is entirely expected.

is due to the internal resistance of the Arduino

Given that the output impedance is caused by a mixture of things then yes. Note it is not internal resistance.

this happens only with digital pins (not with the Arduino 5V source

The Arduino 5V pin is not driven by the processor so you can’t predict what will happen from the processsor’s data sheet.

In practice the voltage will drop with increasing current due to the impedance of the source feeding it. This could be from the USB connector, there is a 500mA thermal fuse on that or from the regulator if powered from the power jack.

dipido Oct '18post #9

Thank you for your answer Grumpy_Mike and sorry for the "obvious" question. Could you please suggest me some documentation to better understand the problem?

pwillard Oct '18post #10

While people groan... a good place to start is the DATASHEET.

I think that the most important thing to understand is that PINS are "flexible". They can be OUTPUTS or INPUTS... but they are not "power" pins... they should neither be used to POWER the chip (which they can do in a destructive manner parasitically) or as power sources for other things.

Digital PINS are "designed" to be senders or receivers of logic level "signals". Logic signals have a wide range of what is acceptable as a LOGIC "1" or LOGIC "0" so a pin outputting a voltage between 3V and 5V is STILL a perfectly acceptable LOGIC "1" signal. Its NOT broken if it delivers 4.7V.

स्रोत : forum.arduino.cc

5V Relay Module : Pin Configuration, Circuit, Working & Its Applications

This Article Discusses an Overview of What is a 5V Relay Module, Pin Configuration, Circuit Diagram, Working, Advantages & Applications

Relay is one kind of electro-mechanical component that functions as a switch. The relay coil is energized by DC so that contact switches can be opened or closed. A single channel 5V relay module generally includes a coil, and two contacts like normally open (NO) and normally closed (NC). This article discusses an overview of the 5V relay module & its working but before going to discuss what is relay module is, first we have to know what is relay and its pin configuration.

What is a 5V Relay?

A 5v relay is an automatic switch that is commonly used in an automatic control circuit and to control a high-current using a low-current signal. The input voltage of the relay signal ranges from 0 to 5V.

5V Relay Pin Configuration

The pin configuration of the 5V relay is shown below. This relay includes 5-pins where each pin and its functionality are shown below.

Relay Pin Diagram

Pin1 (End 1): It is used to activate the relay; usually this pin one end is connected to 5Volts whereas another end is connected to the ground.Pin2 (End 2): This pin is used to activate the Relay.Pin3 (Common (COM)): This pin is connected to the main terminal of the Load to make it active.

Pin4 (Normally Closed (NC)): This second terminal of the load is connected to either NC/ NO pins. If this pin is connected to the load then it will be ON before the switch.Pin5 (Normally Open (NO)): If the second terminal of the load is allied to the NO pin, then the load will be turned off before the switch.

Features

The features of the 5V relay include the following.

Normal Voltage is 5V DC

Normal Current is 70mA

AC load current Max is 10A at 250VAC or 125V AC

DC load current Max is 10A at 30V DC or 28V DC

It includes 5-pins & designed with plastic material

Operating time is 10msec

Release time is 5msec

Maximum switching is 300 operating per minute

5V Relay Module

The relay module with a single channel board is used to manage high voltage, current loads like solenoid valves, motor, AC load & lamps. This module is mainly designed to interface through different microcontrollers like PIC, Arduino, etc.

5V Relay Module Pin Configuration

The pin configuration of the 5V relay module is shown below. This module includes 6-pins where each pin and its functionality are discussed below.

Relay Module Pin Diagram

Normally Open (NO): This pin is normally open unless we provide a signal to the relay modules signal pin. So, the common contact pin smashes its link through the NC pin to make a connection through the NO pinCommon Contact: This pin is used to connect through the load that we desire to switch by using the module.Normally Closed (NC): This NC pin is connected through the COM pin to form a closed circuit. However, this NC connection will break once the relay is switched through providing an active high/low signal toward the signal pin from a microcontroller.Signal Pin: The signal pin is mainly used for controlling the relay. This pin works in two cases like active low otherwise active high. So, in active low case, the relay activates once we provide an active low signal toward the signal pin, whereas, in an active high case, the relay will trigger once we provide a high signal toward the signal pin.

However, these modules generally work on an active high signal which will strengthen the relay coil to make contact with the common terminal with the normally open terminal.

5V VCC: This pin needs 5V DC to work. So 5V DC power supply is provided to this pin.Ground: This pin connects the GND terminal of the power supply.

5Volts 1-Channel Relay Module Components

The components in a 5v relay module with a single channel include a relay, output terminal, status LED, power LED, freewheeling diode, input connector & switching transistor.

Relay Module Components

Relay

A 5V relay is coated with blue color plastic material. For both AC & DC loads, the utmost operating voltage & current are also displayed on the relay. This relay operates with 5V, so it is called a 5V relay.

Output Terminal

The output terminal of the relay module is located at the left-hand side, used to fix an AC/DC load & AC/DC i/p power source. Every o/p connector’s terminal is connected through NC, COM pins & NO of the relay.

The relay module consists of screws that are used to connect wires & cables. The max current supported by this module is 10A & the max contact voltage is 250V AC & 30V DC. Thick main cables are mainly used whenever high voltage & current load is used.

Status LED

Status LED is connected by using a current limiting resistor that is located on the top right side of the relay module. So this LED illustrates the relay status by activating the relay & coil through a signal pin. The DC supplies throughout a relay coil.

स्रोत : www.elprocus.com

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Mohammed 3 day ago

Guys, does anyone know the answer?