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Questions tagged [resistor]

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

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LED brightness variations

I'm using two different types of code and noticing that in the first set up the last LED is dimmer than the rest. Then in the second set up, the first LED is brighter than the rest. I would like to ...
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1 vote
2 answers
73 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 ...
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6 votes
2 answers
104 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 ...
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1 answer
112 views

What resistor should I use when using a photo-resistor?

So I'm trying to use a photo-resistor and I learned that you should have a "fixed" resistor in the circuit. So my question is, what resistor should I have be the fixed resistor? My photo-...
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1 vote
2 answers
80 views

How to hook up a HC-06 to Arduino Nano

So I have an arduino nano hooked up to hc-06 however every diagram of the hookup wires shows some kind of resistors (1K and 2K, rather high resistances to ignore), and I completely overlooked them. I ...
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-2 votes
1 answer
158 views

Do I use an LED or a pullup resistor for stopping "floating" or "ghosting" for a matrix keypad?

I know this sounds simple, but I have an Arduino Mega 2560 and I am making a matrix keypad for a claw machine. It's a 3*4 matrix keypad. Let's just say, I am making this keypad for the claw machine to ...
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  • 101
1 vote
1 answer
46 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 ...
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1 vote
1 answer
98 views

Arduino H-bridge for rc car

I've got an old rc car laying around, of which i would like to swap the insides, but re-use some of the parts that are already in there. The car runs 2 dc motors: one for steering, one for throttle. ...
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4 votes
4 answers
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 ...
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0 votes
2 answers
49 views

Why does a pull down resistor configuration not destroy the pin it's connected to?

I don't understand why a pull-down resistor connected to ground would prevent a pin connected to 5V through a button would not destroy the pin as the current does not need to go through the resistor ...
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  • 1
2 votes
1 answer
166 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 ...
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0 votes
2 answers
56 views

Resistor - Correct value for optocoupler, but dont have that size

I am making a shutter for my camera using a Arduino and an optocoupler. I understand most of most parts, but unsure about the resistor because I don't have the correct size. 5V will be coming from the ...
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0 votes
1 answer
47 views

Are these GND connected resistors on the Arduino Due redundant?

Does anyone know why these 4 resistors are there (attachment)? It seems like they are useless since connected in a loop to GND. Full schematics here: https://store.arduino.cc/arduino-due
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3 votes
1 answer
636 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 ...
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1 vote
4 answers
473 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 ...
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1 vote
1 answer
76 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-...
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1 vote
3 answers
2k 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 ...
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0 votes
1 answer
247 views

ISR Issue: Arduino Pro Micro

I'm trying to do a small test where I am using the ISR on the Arduino Pro Micro it up from sleep mode. I'm using a Force Sense Resistor (FSR, a resistor that changes it's resistance depending on how ...
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1 vote
1 answer
127 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?
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  • 201
0 votes
1 answer
167 views

Is this circuit properly made?

I can't get to work a circuit that doesn't look that hard to copy. This circuit was done for an Arduino extension of my DSC HS2032 system. I was trying the example "Status" on the Arduino's ...
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  • 37
0 votes
1 answer
322 views

i2c high speed and pull-up resistors

hello guys i want to ask about 2 things first one is i'm connecting and arduino uno attached to a usb host sheild and transferring data of a mouse coordinates to 10 arduino leonardo i'm using the ...
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0 votes
2 answers
2k views

How do I know if I need to use a resistor in a circuit?

I have been trying to find answers on Google to this question but cannot seem to find any answers that actually pertain to what I am wanting to know. I would consider myself a beginner in the area of ...
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1 vote
0 answers
57 views

Button example: resistor vs wire

I am playing with this basic example: Arduino: Button There're a lot of existing questions about why to connect button to the ground. I get the idea more or less. Is done to avoid "noise" during ...
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1 vote
2 answers
1k views

multiple RC522 RFID on arduino yun

I was trying for one month to make multiple RC522 rfid readers work together on SPI on an arduino yun, one works fine, but if I plug 4, each with a specific slave select, only one, sometimes 2, ...
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  • 143
0 votes
1 answer
47 views

Generate number

I wanna make some sketch to generate number to represent sensor value, with range from high (900) to low (670), that number decrease with range between 1-10 and with some delay of switching number ...
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1 vote
0 answers
51 views

Control 12V power with 3 transitors to 3 seperate consumers

I have this shematic. With one electrical Pump and two solenoid valves I want to control via the arduino. Here are the specs for the parts: Pump: 12V max. 250mA Valve 1: 12V max. 160mA Valve 2: ...
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  • 121
0 votes
1 answer
184 views

Menus not changing when button is pressed TFT 128 x 128

I've just followed a tutorial so that when a button is pressed it goes through a menu. Click once, next slide. Only issue is it isn't appearing on my screen at all. It has uploaded but I'm a total ...
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2 votes
0 answers
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 ?
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  • 121
1 vote
5 answers
1k 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 ...
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2 votes
2 answers
223 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 ...
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0 votes
2 answers
247 views

Why does current flow along a wire instead of a resistor right next to it? [closed]

I am having trouble understanding exactly what is going on in a circuit where when a button is pressed an LED goes on. Also, I have the Arduino UNO. The schematic can be seen at: 2:36 of this video: ...
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1 vote
3 answers
262 views

Arduino Uno with 6x 5V solenoids + 9V battery - Not enough power?

I have 6 5V solenoids connected to an Arduino Uno, each of them with a TIP120 transistor, diode and resistor. Exactly like https://core-electronics.com.au/tutorials/solenoid-control-with-arduino.html ...
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  • 111
-2 votes
1 answer
397 views

What should the cut-off frequency be? [closed]

To convert a PWM signal to a DC voltage it must be filtered with a low pass filter. How can you know which cut-off frequency should be used and how do you calculate the values for the resistor and ...
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  • 1
0 votes
1 answer
164 views

Connecting DAC output from Arduino Due to another arduino

I have an Arduino Due and I want to connect the output from the DAC as an input to an Arduino Uno's analog input pin. From this link http://forum.arduino.cc/index.php?topic=164763.0, user DuaneB ...
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  • 105
0 votes
1 answer
61 views

Do all pins of Arduino Uno output 5V?

I am currently working on a project which uses PIR motion sensor and 5V relay. Since you might be familiar that both the motion sensor and the relay requires a 5V connection. My problem is, I don't ...
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0 votes
2 answers
358 views

Would a 100KΩ resistor connected to ground pull an open analog line down to 0

I have a project that has a photoresistor wired into a voltage divider and connected through a 3.5mm “stereo mini plug”. When nothing is in the mini plug, the analog line is an open circuit, and ...
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1 vote
0 answers
20 views

Arduino Uno Force-Sensitive Resistor

Would any one know how many Force-Sensitive Resistors that a Arduino Uno can handle being hooked up to at one time?
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0 votes
3 answers
3k views

Multiple I2C slave devices on Arduino - Pull-up values

This question is asked a lot and I've found many usable details on different forums regarding adding pull-up resistors on SDA/SCL lines. I know that only one resistor should be added on these lines ...
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1 vote
1 answer
237 views

Sanity check for dual IR LED circuit [closed]

If the intent is to drive the two LED's with 200-400mA (using PWM @ 38Hz), is there anything wrong with this solution? Perhaps this is a better solution, as it ensures the current is exactly the same ...
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0 votes
1 answer
2k views

Preforming impedance termination for UART Communication (TX and RX) pins

I need two Arduino devices (Arduino Mega and Nano) to communicate with each other via UART. The two Arduino devices are long distance apart from each other. The distance is 1.5 meters. The Arduino 1 ...
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2 votes
2 answers
6k 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); ...
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  • 157
3 votes
2 answers
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 ...
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-1 votes
1 answer
2k views

Pulse counter to measure flow-rate: 0 Pulse issues

I am using a Netafim M-Series flow meter interfaced with a UC-32 Arduino. The goal of this is to create a pulse counter than in turn will allow us to determine flow rate in the meter. (1 US gallon per ...
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0 votes
2 answers
52 views

Schematic interpretation, where to put resister?

I'm new to schematics, trying to figure out where to put a resistor (no instructions other than the schematic) I'm told I need: 10K variable Resistor x 1, 4.7K Resistor x 1, 100 Resistor x 1 But I ...
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0 votes
1 answer
59 views

Does blinking an LED with no resistor for a few seconds harm my Arduino?

I am new to Arduino and I just made my first LED blink. I connected the LED to ground and digital pin 13 without resistance (for only a few seconds). Does this harm my Arduino? Hilmi
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  • 19
2 votes
2 answers
6k 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: ...
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  • 21
-1 votes
1 answer
996 views

Minimum value of a pull-down resistor

I've just started working with the Arduino UNO SMD edition and I'm also quiet new to electronics in general. Recently I wanted to try out this tutorial https://www.arduino.cc/en/Tutorial/Button and I ...
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1 vote
1 answer
44 views

Button isn't working properly

I am new in arduino trying to make race game. My problem is that my button (all buttons) is working sometimes and sometimes not. I am pretty sure that it's because of my code. Could you please help me ...
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0 votes
1 answer
102 views

Coding force sensitive resistor to give output based on time used?

I have a basic set up of having a force sensitive resistor being used to power an LED as can be seen below. I am wondering how I can code it so that the LED is lit after a pressure has been applied to ...
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8 votes
1 answer
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 ...
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