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33

The design assumes USB provides a regulated 5v so no further regulation is necessary. The power connecter is meant to accept a wider range of voltage and regulate it to 5v, and the kind of regulators used on the Arduino board need that much higher voltage to provide regulation. If you already have a regulated +5v source you can supply it to the 5v pin. You'...


18

From page 411 of the ATmega328P data sheet, we have a graph of the output current vs voltage. We can see over the the 20mA range of output currents, we drop ~0.5V, giving an approximate internal resistance of 25Ω. A typical LED has a forward voltage of about 2V. Therefore, we end up in the situation where we will drop 3V over the 25Ω internal resistance ...


15

When booted, the Arduino will run whatever program was put on it last. Solution: Don't turn it on if you don't want it to run. When out of the box, the Arduino usually runs the Blink program. So you can just load that and call it a day if you want to "reset" it. Or have a loop program with a sleep command. If you've been messing with the USB bootloader ...


14

It's not that big of deal. The ATmega 328p datasheet states this: Temperature range: -40 to 85 degrees celsius. The same goes for the USB chip on the Uno (ATmega 16u2 for UNO R3). That's inside your limits. It probably could go a bit colder than mentioned, but it'll shorten the length of the board a little bit. However, there are some things that may ...


13

Not best practices, but an alternative approach: Consider the Ruggeduino instead of a standard Arduino. At a price ($39.95) comparable with the equivalent Arduino, the Ruggeduino offers: Resettable fuse on each GPIO pin, i.e. all GPIO pins are protected from short-circuit to ground or other pins All GPIO pins withstand 24 Volts Reverse voltage protection (...


12

Leaving series resistors out will definitely greatly (exponentially) shorten lifetime of both the controller and the LED. Absolute maximum ratings for most AVRs are (a.o.): max. 40mA per GPIO pin max. 200mA per package. A new Arduino sets you back $20 or more, a fist full 220 ohm resistors sets you back 1$. When treated within spec, an Arduino (and LEDs ...


12

Turning the power off and taking proper static precautions also applies to Arduinos. Anorton's tip about not resting it on a conductive surface is also useful. Some other things to keep in mind: Double check the polarities of any connections you make. Keep a consistent wiring color code. Use red for power and black for ground. Calculate the expected ...


11

I don't know if there's one best practice, but the following might be helpful: Limit the voltage on input pins to 5.5 V maximum. Do not short IO pins. Use pullup or pulldown resistors when conecting switches or pushbuttons. Respect the current limits (for each pin and in total). Use resistors. The Arduino is just the brain, not the power station. If you ...


10

The clock speed selected will affect both delay*() and millis()/micros() as well as the functions in <util/delay.h>, therefore you must use the target system's correct clock speed if you are using any of these functions. This can be easily done by editing boards.txt and copying an existing entry for the Uno and changing the value of the f_cpu parameter ...


9

If safety is a major concern, then you should almost always load a stop* sketch onto the board before calling it a day. This would be a good idea, for example, when your board is semi-permanently a part of a larger system. You could do so by: Upload the Bare Minimum sketch found in File -> Examples -> Basic in the arduino-ide Upload a sketch with a large ...


8

Unfortunately, there isn't much way to really determine "wear" in the context of solid-state electronics. Probably the things that are most likely to fail are the electrolytic capacitors and the connectors. First, if you're using an ATmega CPU for something that could possibly injure someone CONTACT ATMEL AND TALK ABOUT SAFETY PRECAUTIONS. The ATmega CPU ...


8

Processor pins have strictly limited current drive capability. The rated values may vary depending on whether you want a high or low drive. Some processors will supply only a few mA and the most you will usually officially get is in the 20 to 30 mA range. There is usually a total current limit for the processor and only a few pins can provide peak ...


7

Although the controllers on an Arduino are pretty well protected, they can still be damaged by ESD (Electro Static Discharge). The same effect that makes a crispy sound when you pull off your woolen sweater in the winter, or after walking with rubber shoes on a carpet and you touch someone else or a metal and grounded object and you feel a pick. Static ...


7

The recommended output (source or sink) from an I/O pin is 20 mA. The absolute maximum is 40 mA. Your relay coil is likely to consume more than that, particularly when it initially energizes. This will damage your output pin. Then it will eventually fail. Nothing seems to be amiss by far. No, not yet. :) How can one control such components without ...


6

Will it break at < 5V? Not likely. Check the datasheet for the IC's on the board and find the minimum power supply voltage the device works at. At typical ATmega328 Safe Operating Area (under "Speed grades" in the datasheet) specifies approximately 4.1V for 16MHz. If you require to use the USB interface, you'll have to check the datasheet for that chip ...


6

AVRDUDE does not actually perform the write, it merely directs it. The actual writes are performed either by the bootloader or by the ISP firmware/hardware within the MCU itself. With the bootloader it depends on how itself is coded, but at worst it would finish off the flash byte or page or EEPROM page zero- or one-filled and then fail to communicate ...


6

If you are talking about running at 5V, then I doubt there is any safety issue. After all, 9V batteries (the sort you put in your smoke detector) just have bare terminals and no-one tells you not to touch them. There is quite a bit of related information at How much voltage is “dangerous”?. That link seems to have enough information that there isn't a lot ...


5

Arduinos are far from bulletproof but with nothing connected (apart from a power source of course) I doubt it will come to harm. If in doubt, upload Blink to it. There are rugged Arduino-compatibles. One of them has a rather obvious name


5

I would use some sort of epoxy and cover up the exposed circuitry. The major concern would be where the wires connect to the board as flex over time can weaken it. Some options include: 3M™ Scotchcast™ Wet-Niche Potting Kit Hysol US1150™—For electronics, telecommunications, and automotive components. Provides environmental hazard protection. ...


5

It depends on the application. For something like a rechargeable torch, Arduino might exceed the specifications. For a weapons system, NEVER (and this is one of the specific prohibitions in the license agreement - see section 1.5 note: link currently broken). You also have to consider that there's literally thousands of armies in the world and they all have ...


5

First, let's consider the logic of your program. You have two groups of pins: 6 pins connected to the wires and 6 pins connected to the terminals. The first thing I would do is forget that these are two different groups. Consider you just have 12 pins that the user has to connect in a specific fashion. This way most “weird things” the user ...


4

One of the sections of the Arduino that is likely to become unreliable over time is its memory. There are three pools of memory in the microcontroller used on avr-based Arduino boards: Flash memory (program space), is where the Arduino sketch is stored. SRAM (static random access memory) is where the sketch creates and manipulates variables when it runs. ...


4

How does one prepare clothing with embedded electronics for washing? Remove the battery(ies) and other power supplies, and set them far away from the water. Buzzers and speakers also. Gently wash clothing (including the Lilypad, LEDs, resistors, capacitors, integrated circuits, accelerometers, magnetometers, Bluetooth modules, GPS modules, etc.) by hand ...


4

I would make it so the Board has velcro on it so that it can be un attached from the clothing, and then have all the wires have snap terminals that wires from the Arduino connect to. This way you un snap all the wires and remove the arduino. As far as components, I would cover them in an epoxy to protect them.


4

Above is an AA Battery voltage curve. Many people assume that 5* 1.5V AA batterys would be enough to power the Arduino. As you can see the 1.5 is the maximum voltage and it quickly drops. Different brands have different values and sometimes this can drop below the value of the voltage regulator input. I usually tend to aim between 7 and 9 Volts for running ...


4

To make sure all pins are responding you could put all your pins as input with internal pull-up except pin 13 which must be set as output. The on board led is connected to pin 13, so when you put pin13 high it will turn the led on. Connect every other pin 1 by 1 to the GND to see if the led is toggling once you've connected a pin to the GND. Try to use this ...


4

Have a look at the simple circuit on this PDF from the Arduino Playground. It shows a single transistor to drive a small relay. As Russell says in his answer, a ULN2803 or similar is a chip which will allow you to drive several small relays, which is neater than using several transistors, if that's what you want. (Also note the diode "D1" in the circuit I ...


4

You can absolutely use GPIO0 as an output. The ESP will read the state of GPIO0 once at boot (And never again thereafter) to determine what boot mode to enter. During this time it is an input, so, whatever you hook GPIO0 up to must not hold this pin low (Unless you want to enter bootloader mode, of course), at least until the chip boots. As long as you ...


4

This means that if I try to flash the program, ATTiny will start to put PWM power into my Arduino. I don't want that to happen. Why do you think that is a problem? The "PWM power" cannot be any higher than the supply voltage, and that is 5V. The Arduino has no problem with you providing a 5V PWM signal to an input pin. The only time it could be a problem ...


3

Like everyone mentions, as long as you're in the shade, hot temperature probably doesn't matter too much as it's within the limits of the components. I'm more worried about condensation in the mornings. Water vapors will condense on electronics just like it does on grass. You could try electrical epoxy to cover the circuit. The Arduino doesn't run very ...


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