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Individually control ~200 LEDs

I am planning to build a LED polar clock, so it will need about 181 LEDs (12 Month, 31 Day, 7 Day-of-week, 12 Hour, 60 Minute, 59 Second) and I need to control each one individually. I will be buying everything from scratch so I ask for help…
dylan p.
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Ideas for setting I2C device IDs

I am using I2C to communicate between a collection of ATtiny85s that are acting as controllers for various parts of a system and the "Main Brain" -- a RaspberryPi. Most of the ATtiny85s only have a couple of free pins left (usually Pins 1 and 2 --…
ThatAintWorking
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How to measure the supply voltage of Arduino without using an analog pin

I'm using Arduino Nano to measure temperature with a 10 kohm thermistor and a voltage divider. My problem is I'm getting only 4.2V on the 5V pin. The power is supplied via a USB cable from a desktop PC. I measured the output voltage of a USB port…
dixhom
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Does porting code to different MCU clock frequency affect serial baud rate?

Tried to upload my Arduino Uno sketch that writes to serial UART at 9600 baud rate onto my ATtiny2313 running at 1MHz. Not getting the signal on the ATtiny, does this have to do with my clock frequency of the MCUs being 16 vs 1MHz?
Nikola
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Can Arduino control 8 solenoids?

I know very little about Arduino and even less about programming one. Before I purchase a board, and learn how to program it, I was wondering if my idea is feasible. I want to program the Arduino to sequentially open one after another irrigation…
Tim Christensen
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Wire.h library works on Uno but won't compile for ATtiny85

TL;DR: Arduinos are current hungry so I want to switch my microcontroller code works on Uno, I change upload to ATtiny85, code doesn't compile Wire.h breaks at the TWBR input Should I keep trying to fix this or should I just use ATmega328P without…
auphynne
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Can I use a spare Darlington Pair on my ULN2003A to drive a DC motor?

I'm successfully running a stepper from my Arduino via a ULN2003A and a secondary power supply. It uses the first four of the seven Darlington Pairs on the chip, leaving three spare. A) Is there any reason I wouldn't be able to use one of the…
RickMeasham
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Why would the resistor be after the LED in this project?

This is project 2 of their official arduino projects book called "Spaceship interface". I understand resistors normally reduce voltage so the LEDs don't burnout but here 5v is coming from either digital 3, 4, or 5 and it seems like it goes right…
Nick D
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DFPlayer Noise: Researched, Tried, and Bep Bep Bep Bep Bep

Spent an entire day researching and attempting to fix the DFPlayer noise problem. The amp works as expected, so it is not the problem. I have made a video to help you better understand the sound produced:…
Joshua Roehrig
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Assuring an unsigned long int?

Basic question: How far do I have to go to assure that integer math is done correctly? For example, this is probably overdone: unsigned long burnTime = 0UL; unsigned long curBurnTime = 0UL; // Do some stuff that sets the above variables to millis()…
bluesmoke
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Is the arduino hackable when using communication shields?

Let's say I have an arduino Uno connected to a W5100 ethernet shield. The arduino communicates with the ethernet shield using the tx0 and rx0 pins. When I upload a new script to the arduino using USB, it uses the same tx0 and rx0. So that made me…
Orry
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Digital Potentiometer not fading LED

So I am trying to test what will eventually be a Arduino controlling 3 110V motors that are currently controlled by an analog pot. But more on that later. I am trying to test out using a digital pot (never have before) and am running into some…
cgaubuchon
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Is it possible to extract a hex file via UART from an Arduino?

Right now I am tinkering on my 3D printer that has an Arduino mega as a brain. I need to update the Marlin firmware but in case of an error I want to create an backup of the firmware. And because it is assembled using a shield on top have no access…
Coder_fox
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Fool Proofing My Arduino IC Checker

I am creating an IC checker for some high school juniors since a faulty IC can be a nuisance of a bug to find when bread-boarding. These ICs are all simple TTL gating from the 74LS series; the set I am using are all 14-pin and have VCC and GND at…
Benjamin Brownlee
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Does the tone() generates unwanted signal?

I was trying to use the tone function for another project but I found that it also generates an undesired frequency (not the harmonics above of square wave it generates) but a lower frq square wave. Is this normal or somethings wrong with my…
user174174
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