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12

A 555 doesn't have to generate a 50% duty cycle. Even if you do want to use a 50% duty cycle, the edge can be RC coupled into the interrupt to reduce the pulse width. An Arduino can use a slow clock like a 32kHz watch crystal, then it's very low power indeed. This slow one can be used to wake-up your more power-hungry Arduino. The lowest power and tidiest ...


10

The best solution for you is to use LowPower library which does not require any external parts. It supports up to 8 seconds sleep. If you need exactly 10 seconds you can write a loop with 5 cycles and call powerDown with 2 seconds sleep. If you still want to use external interrupt, see this for some chip options. Also, see this article for some good ideas ...


9

You are already using a differential signalling system that doesn't care about ground levels, so you don't need to worry about that side of things. As for power distribution - a strategy known as point of load regulation is what you want. That is where you supply a higher voltage (but lower current) power feed to one, or in this scenario more likely a group ...


6

This sketch is almost identical to the powerDownWakeExternalInterrupt.ino sketch that comes with the LowPower Library. I'm using INPUT_PULLUP and a N.O. push button switch to trigger it to wake up and turn an LED on. #include "LowPower.h" const byte wakeUpPin = 2; // Just a handler for the pin interrupt. void wakeUp(){} void setup(){ // Configure wake ...


5

Level logic converting for level shifting is different from powering a device. Logic level is the state of a digital input/output. No voltage (or very little of it) is considered LOW. Over the threshold voltage is HIGH. On a 3.3V system, if you set pin to HIGH, it has 3.3 V. On a 5 V system, HIGH is 5 V. A digital input pin reads HIGH once the ...


5

From your schematics it looks like: you connected the power supply backwards (on both schematics actually, I wonder how come you did not fry your Arduino) the external supply and the Arduino do not share a common ground as they should. Edit: about the orientation of the power supply: the (−) side of the supply (and GND of the Arduino) should be connected ...


5

1A coming in thru the barrel jack connecor, then you risk blowing the 1A rated reverse polarity protection diode. The 5V regulator will overheat at high currents above 7.5V. The chip itself can have 800mA put thru if if properly cooled and the IO limits of current per port are respected. So 1.6A, no way.


4

At times like this it is useful to refer to the datasheet. You can, in that document, find this paragraph: 4. Power and Pin DHT11’s power supply is 3-5.5V DC. When power is supplied to the sensor, do not send any instruction to the sensor in within one second in order to pass the unstable status. One capacitor valued 100nF can be added between VDD ...


4

If your sensor draws less than 40mA to operate, then you can safely "power" it from an GPIO pin. The related question also asks how long the sensor must be powered in order to get a stable reading. For a sensor such as this one, it appears to be a simple resistive voltage divider, with the moisture sensor itself providing one leg of the divider circuit. The ...


4

Technically you can use any arduino for that purpose with some modifications. I recommend to go with an arduino Pro Mini and remove the LED and the voltage regulator. But if you don't need so much I/O you can go with a digispark Attiny board.


4

You do not need a DAC. In this 'regulation cases' PWM on digitalPin is used. See analogWrite Arduino function. I use Grove MOSFET module to have PWM of desired voltage. The MCU generates a 3.3 V PWM. MOSFET module gets in my case 5 V as input voltage. You would use 10 V as Vin. MOSFET switches the 10 V line on and off at 'PWM speed' resulting in 10 V PWM. ...


4

100 Meters of 5050 SMD strip LEDs will require roughly 120-200 amps. However, you cannot drive a 100 meter strip from a single power supply. The thin copper traces in the LED strip can only handle so many amps before they become too hot (your LED strip would melt like ice cream on a hot summer day). This is why led strips are usually limited to 5 meters (~5A)...


4

I put this code into the IDE, and for n>=2, I got 99, 999, 9999 etc. The catch is that Arduino uses floating point arithmetic to implement the pow() function, and some of your values are being truncated as ints. If you change: int multiplier = pow(10,power); to float multiplier = pow(10,power); The results should be as expected. (The brief reason ...


4

As you have noticed, measuring voltages is the first step. Here's some voltages for you and what they mean if they aren't there. These are all assuming precisely 12V in through the barrel jack. They are in order of "priority" - start at the top and work down, the first one that fails is your culpret (i.e., the barrel jack feeds VIN through the diode, VIN ...


4

The VIN pin goes to a 5V voltage regulator on the Arduino and needs at least about 7V minimum to work properly. If you want to supply 5V to an Arduino do it either on the 5V pin or via the USB connector. The VIN pin should receive 7V to 12V.


3

First you want to take a regulated 24V supply. To that you want to add a switch-mode ("Buck") regulator to drop you down to 5V. You don't want to try using an LDO for this unless you are happy to have a heat sink the size of a small car. A good cheap choice is a "UBEC" that can take 24V in and give 5V out (I use these). That 5V can then be fed direct into ...


3

Yes, activating low power does disable the UART - but only while it's sleeping. To use serial you just need to ensure that you only use it while it's not sleeping - and due to the interrupt and buffered nature of the Serial driver it's not as easy as just printing. However, it's simple to achieve: just flush the serial before sleeping. This ensures that ...


3

Datasheet for MAX232 Section 7.3 Recommended Operating Conditions VCC Supply voltage MIN=4.5, NOM=5, MAX=5.5 (V) The MAX232 has a minimum supply voltage of 4.5V, typically expecting 5V. There are other alternatives, such as the MAX3232, which supports either 3.3V or 5V supply voltage.


3

The ADM660, link below, is a charge-pump voltage converter that can be used to either invert the input supply voltage giving VOUT = -VIN or double it (ADM660 only) giving VOUT = 2 x VIN. It accepts an input range between 1.5V-7V so if you use the 5V from the Wemos USB power you'll be able to reach the desired 10V for your application, and it's cheap :) ...


3

pow() works with floating point numbers. Floating point numbers are just an approximation. You will very rarely get precise results using floating point numbers. Instead you could write your own little integer-based ipow() function.


3

I think it is not a good idea to power the LED strip via USB. Normally USB delivers a maximum of mA (see below). Assuming you have 30 LEDs (minimum for a normal LED strip), and each LED gives 40 mA (maximum), this is already more than what most USB ports can deliver. This can ruin your USB port. For the Arduino Nano you can use the 5 V, and you should ...


3

The power consumption is part of the exchange with the PC when it is plugged in. You can change that. Find the file USBCore.h in your Arduino install directory. In my case (under Linux) it was: ./hardware/arduino/avr/cores/arduino/USBCore.h Inside that file, at around line 269 (depending on the distribution) you should see these lines: #define D_CONFIG(...


3

The old circuit will not work as you expect. While the ATtiny85 can run happily with 2.7 to 5.5V in this setup it expects 5V. I assume this is due to the high CPU clock setting. To run stable at a high CPU clock it requires 4.5V. The VIN pin is connected to a linear regulator that has a 2V drop-out. Thus the supplied voltage has to be at least 2V about the ...


3

Assuming you are using a 9V block battery: They don't deliver the current you need for the esp32 to run/create an access point/act as a client. What you can do is connect 6 AA batteries in a row (6*1.5V = 9V) and they will deliver a higher current than the 9V block.


3

You can make -5 V if you use an external power source, like in the circuit below (untested). Connect the GND (-) from the Arduino to the +5V from the External (5V) source, than 0V will be the GND (with respect to the Arduino), but the GND of the external source will be -5V with respect to the Arduino. I only used the resistors to get no short circuits, you ...


3

While it may be possible to bend one of those to your proposed usage, it's far from ideal, for a number of reasons: It's far more expensive than the single P-FET that you need to get the job done It's risky: you can easily reverse the current through your components and blow them up It imposes a ground offset which can cause you communication problems. All ...


3

Expanding on my previous comment... I need a way to keep an array of memory ignored by the C initializer You can achieve this by instructing the compiler to store the array in the “.noinit” memory section: int my_array[ARRAY_LENGTH] __attribute__((section(".noinit"))); Your array will end up sitting somewhere between the .bss and the heap (if any), and ...


3

You have an N-channel MOSFET. That is not suitable for switching the 12V supply of an Arduino. Instead you need a P-channel MOSFET which has the gate pulled up to 12V using a resistor, and then an N-channel logic level MOSFET which is used by the Arduino to pull the gate of the P-channel MOSFET LOW to turn it on. Something like: simulate this circuit &...


3

No. You must connect AVcc even if you're not using the ADC. According to the datasheet: AVCC is the supply voltage pin for the A/D Converter, Port C (3:0), and ADC (7:6). It should be externally connected to VCC, even if the ADC is not used. If the ADC is used, it should be connected to VCC through a low-pass filter. Note that Port C (5:4) use digital ...


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