Questions tagged [resistor]

Passive electronic component which reduces current flow in a circuit, dissipating power as heat.

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26
votes
3answers
6k views

What happens to the Arduino if you don't use a resistor with an LED?

Making a blinking light seems to be one of the most common beginner projects with Arduino. A typical approach is to connect an LED + resistor (in series) to an IO pin, and connect the other end to ...
21
votes
2answers
4k views

Can two LEDs attached to different pins share their resistor?

I'm designing an Arduino style board with built-in LEDs for several of the pins. To simplify assembly of the board and save on components, I was wondering whether it would be safe for those LEDs to ...
10
votes
3answers
2k views

Digital Read Serial tutorial - calculating the resistor value

The Arduino Digital Read Serial tutorial guides you through the wiring of a simple button. My questions are centered around the resistor. Why is the resistor necessary? I think I understand this, ...
9
votes
2answers
5k views

Use Higher Resistance Than Instructed in a Circuit

I'm following the "Get Started with Arduino" Guidebook, and I'm at the part where pulse width modulation (PWM) is discussed. The instructions say to create a simple circuit with a breadboard, red ...
8
votes
1answer
16k views

Resistor pull-ups for ESP8266

I'm using 4.7kOhm resistor as pullups for GPIOs 2,0,2,16, CH_PD and RESET, and also 4.7kOhm pulldown for GPIO 15. The ESP8266 boots and works fine. Would it be okay for a long shot? Should I use ...
8
votes
2answers
2k views

Performance of internal vs external resistors

Is there any significant performance trade-off between buttons wired with the internal vs external pull-up/down resistors? I see a lot of tutorials demonstrating the use of external resistors when ...
6
votes
2answers
97 views

Do you actually NEED external resistors for switch connecting IO pin to ground?

Years ago, I encountered a fairly long debate at AVRfreaks.net about whether or not it's OK to directly connect AVR pins that are configured as inputs with internal pullup enabled directly to ground ...
4
votes
4answers
2k views

Why am I receiving random input values in my Arduino?

I want to use a switch for my Arduino using digitalRead(), but I keep receiving random inputs. Whenever I connect energy to that pin, it always returns HIGH, but otherwise it goes completely random. I ...
4
votes
4answers
2k views

Importance of resistor

I'm new to Arduino and also new to electronics. I'm following the tutorial here. I'm not understanding the importance of the resistor in this schematic diagram. Can someone please help me on this?
4
votes
5answers
12k views

Stop Led's from blinking

My code: // Pin 13 has a LED connected on most Arduino boards. // give it a name: int led = 13; const int buttonPin = 2; // the setup routine runs once when you press reset: void setup() { // ...
4
votes
4answers
12k views

Can I change VCC pin to 3.3V on a 5V Arduino Pro Micro?

I'm using a 5V Arduino Pro Micro (schematic). For my project, I'm using the VCC pin to output power to an external device. I need VCC to output 3.3V to the external device. Can I open jumper SJ1 to ...
4
votes
3answers
361 views

Unexpected Delay Between For Loops

I made some arduino code for leds that blink down a row and then back again, but when the program is run, there is an approximately 2 second delay in between the first for loop and the second. This is ...
3
votes
3answers
11k views

What difference makes resistance of thermistors?

Following this thermistor tutorial i used 1k thermistors (and resistors) instead of 100k as in video. What difference does it make? What about 10k thermistors? Is it good idea to use 1k/10k/100k ...
3
votes
2answers
4k views

Why all blink tutorials use 330 ohm resistor

When I do the led calculation I found 150 ohm resistor is enough for 3mm red led. If so why all arduino tutorials, like this one, are suggesting 330 ohm resistor? I assume V = 5 Volt, diode forward ...
3
votes
2answers
1k views

Newbie Arduino DC motor problem

So I am new to Arduino and new to electronics in general. I've looked up a few tutorials and they all have a simple early tutorial that turns on a DC motor and turns it off again. Something like this: ...
3
votes
3answers
4k views

What is the minimum wattage of resistors for breadboarding with Arduino Uno?

I'd like to buy new resistors for breadboarding with my Arduino Uno. There are 0.25W, 0.4W, 0.6W, 1W, 2W, 3W, 5W, 10W resistors in the shop. What is the most suitable for this operation?
3
votes
1answer
448 views

Why is it i need transistors and resistors to turn a dc motor with an Arduino but i can connect it directly to a battery

As the question says im building a circuit to run a DC motor whenever motion is detected on a motion sensor. Now as this image suggests I need a diode + resistor + transistor to get this thing to ...
3
votes
2answers
2k views

Resistors on LCD - does a small difference matter?

I recently have tried to connect an LCD to my Arduino Uno. The tutorial tells me I need a 220 Ohm resistor, but the only ones I have are 330 Ohm. Does it matter? Here's the Fritzing diagram by the ...
3
votes
1answer
934 views

Getting the DS18B20 detected and temperature read

I'm quite new with the electronics part of Arduino, but I thought that this was the basic way to get the DS18B20 temperature device hooked up. However, I can't detect it in my program using OneWire ...
3
votes
2answers
9k views

Purpose of this resistor in Arduino Nano schematic

I was looking at the Arduino Nano's schematic and noticed a resistor that seems to be pointless (RP2C on this picture). Also there is numbers 6 and 3 on it, does it mean that resistor is connected to ...
2
votes
1answer
135 views

What is micro C in a circuit diagram?

This is probably a simple question but I am a beginner with these things. What does the micro C part of the circuit diagram mean? The diagram is from the datasheet of the tssp77038 IR receiver. Does ...
2
votes
1answer
828 views

what is the importance of the resistors that connect to push buttons ? can i replace them by wires?

Please, iam a junior in arduino and i want to know what is the importance of the resistors that connect to push buttons? can i replace them by wires? thanks in advance.
2
votes
3answers
2k views

does INPUT_PULLUP uses power?

When using a digital pin as input, one has the option of using the internal arduino resistor, which is connected to VCC; that is setting the digital pin as INPUT_PULLUP, and then the pin reads HIGH. ...
2
votes
2answers
13k views

10k ohm Potentiometer vs 10k ohm Resistor on LCD Display

I'm trying to use a LCD Display with my Arduino, but I don't have a potentiometer and all of the guides I find always require one, usually a 10k ohm potentiometer. The point is that I'm not very good ...
2
votes
2answers
303 views

Source power with 2 V and LED with forward voltage of 2 V

I have a source power with 2 V and 100mA. I have an LED that has a forward voltage of 2 V and a max current of 20mA. Should I use a resistor to reduce the current? I see many formulas in the internet ...
2
votes
1answer
141 views

Arduino Mega Clone CH340G Capacitor Values

I'm making my own Arduino Mega board with ATmega2560-16AU and CH340G. Jump to the end of the post to find the real question. I have already ordered a PCB before and it didn't work when I soldered ...
2
votes
1answer
171 views

Self made microphone burns Arduino

I'm very new to electrical engineering and I'm trying to read microphone input with Arduino Nano. I've made a separate microphone module (based on this example) and plugged it into Arduino like this: ...
2
votes
2answers
222 views

measure +3V and -3V through resistor divider and switch on/off by digital pins

I've seen that resistor dividers can be used to read negative voltages, but I'ld like if there is a way to accomplish this with less components and having a way to turn this off. I was thinking if ...
2
votes
2answers
5k views

How can I tell the resistance of an internal pull-up resistor?

I have a SparkFun ESP8266 Thing Dev board, to which I want to perform a digitalRead() on one of the GPIO ports. I'm using D15, and I'm configuring it for input like this pinMode(15, INPUT_PULLUP); ...
2
votes
2answers
5k views

Minimum value I2C-pull up resistor for arduino

I'm trying to determine the minimum value of pull resistor for Arduino Uno The datasheets says for arduino; VOL = 0,4 for IOL = 20 mA. (VDD = 5V) For formula for calculation of minimal pull-up is: ...
2
votes
3answers
129 views

What is the most Inputs on An analog Pin with a specified Accuracy on the Resistors Used?

I am asking about the technique were switches and resistors in series are used on the analog pin, so it creates a voltage divider when one of the switches is pressed, it a well known technique it is ...
2
votes
0answers
30 views

Why do we need this resistor? [duplicate]

What is the purpose of it and on what bases its value is calcuated in ohms ?
2
votes
0answers
495 views

How to use Honeywell NBP Series Sensor with Arduino

I am trying to use a HONEYWELL NBPDANN100PAUNV Pressure Sensor. I found an example here http://www.circuitstoday.com/interfacing-pressure-sensor-arduino As this example says as instrumentation ...
1
vote
5answers
876 views

Why does the transistor burn out

I have an arduino uno which turns on a water pump (12V, 3.6W) once every 10 hours for a few minutes (I've followed this tutorial on how to connect the water pump). To turn on the water pump I used a ...
1
vote
4answers
402 views

Can I control LED brightness with potentiometer without any code, as well as reading the potentiometer value?

I am just getting back into electronics and have started to play around with making my own button box. I am trying to control an LED's brightness using a potentiometer, while also reading the ...
1
vote
1answer
13k views

Reading 4 to 20ma pressure sensor using uno

I have a OsiSense™ XMLP pressure sensor that I want to read from my Arduino uno. This is the circuit I am looking at building for measure 4 to 20 milliamp. I've read online to find out how to build ...
1
vote
3answers
5k views

How to select which resistor is required for my curcuit to reduce voltage

I am trying to connect arduino and esp8266 as like this I know arduino runs at 5V and RX of ESP8266 should not have voltage more than 3.5V. If you see my diagram there voltage is large than need on ...
1
vote
2answers
65 views

Why analogRead's value decreases when I decrease the value of resistor?(I use digitalWrite(high) to positive terminal of resistor)

Basically, my circuit contains only 1 resistor(like the basic LED circuit). I tried to know what is the actual voltage of digitalWrite(High). I don't understand why the value of analogRead does not ...
1
vote
1answer
73 views

How can I measure maximum range of my ohm meter?

Hello everyone I am working on a project that will measure ohm value of a resistor . Schematic / article link https://create.arduino.cc/projecthub/iasonas-christoulakis/how-to-make-an-arduino-ohm-...
1
vote
3answers
1k views

How to determine what resistor value to use for LED strip

I'm trying to use an ESP8266 powered by my computer through USB cable to control a WS2812B LED strip. I've read online that you're supposed to put a resistor before the data channel to help prevent ...
1
vote
1answer
97 views

Do I need a resistor to control a servo with a PWM signal?

I working with Arduino Nano Every that has several analog PWM pins. I want to use one to control a small servo. Do I need to put a resistor between PWM pin and the servo signal?
1
vote
2answers
5k views

8Ω speaker, what resistor values to use?

I want to connect 2 speakers of 8 ohm to 2 (different) pins of the Arduino. However, for this example one speaker is enough. I came across a lot of circuits without or with a single resistor which on ...
1
vote
1answer
189 views

digitalPin giving lower voltage than Vcc

I am using an ATTINY88 for a project that requires to turn on an LED. Right now I am using pin PA1(ADC7/PCINT25). I noted, however, that when the pin is ON, I get about half the voltage that is ...
1
vote
2answers
923 views

Use LDR with 220 ohm resistor

I have read many tutorials on LDR(Light dependent resistor) with Arduino which includes a 10 kilo ohm resistor but can i use it with 220 ohm resistor or even without resistor.
1
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2answers
590 views

How to interface DS1801 digital resistor with Arduino DUE SPI interface? What clock rate so use?

I am trying to program a digital resistor and set it's wiper resistance. The general circuit looks a little like this where "pot" represents the Maxim DS1801 digital resistor and DUE is, of-course the ...
1
vote
1answer
316 views

how to calculate correct resistor value to use with LEDs Potentiometer and other devices?

I have been following http://arduino.cc/en/Tutorial/Fade to fade and LED. But I don't know why they are using a 220 Ohm resistor. According to Ohms law if LED is of 2.2 V and it runs on 0.025Amps and ...
1
vote
2answers
182 views

Which side should I connect the resistor on?

I understand that when connecting an LED and a resistor in series; the resistor can be placed on any side of the LED as the current will remain same in a series connection. Please correct me if I'm ...
1
vote
2answers
104 views

What does the datasheet information for a switch mean?

I'm clueless when it comes to the information on datasheets for switches. When I see a datasheet for LEDs or servos, I'm used to seeing a fairly straightforward call out for the required volts and ...
1
vote
4answers
2k views

Setting a Pin to HIGH to simulate a button with a "pull up" resistor

in the below Fritzing diagram, I have a button that has a pull-up resistor, which when pressed, sets the GPIO Pin 23 to HIGH. On the Raspberry Pi, when the button is released, the GPIO goes LOW. The ...
1
vote
1answer
42 views

LEDs not lighting up even though current is flowing through them, problem with ground?

I'm using a 74HC595N shift register to light up 8 LEDs but for some reason they won't turn on even though current is flowing through all of them. I provided an image of my circuit below, there is a ...