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24

There is confusion about what is and what isn't possible with this board. This is because there are different versions with different power arrangements. NodeMCU 0.9 In this board the USB's 5V and the 5V pin are directly connected together. The combined result is then fed through a diode before entering the 3.3V voltage regulator. With this arrangement the ...


10

You decide which rails are positive and which are negative when you connect them to the + an - from your power supply or battery. A breadboard isn't polarised per se. It's just a bunch of cross-connections inside a perforated plastic case. No active or passive components inside. Some manufacturers may choose to paint indications regarding where to connect ...


10

The problem is that you are using an NPN transistor as a high side switch. The voltage at the emitter of the transistor will always be about 0.7V below the voltage at the base. The "high" output from the Arduino is 5V. The emitter will be at about 4.3V. Have a look at the Wikipedia "emitter follower" page. The emitter follower is also ...


7

The code you linked to measures the 1.1 V internal reference using Vcc as a reference. The ATtiny13A cannot do that. It does have a 1.1 V internal reference, but it can only use it as a reference for the ADC, not as a measured channel. What you can do, if you don't mind adding extra hardware, is divide Vcc with some resistors in order to get a voltage ...


7

Using the 1.1V internal analog reference to measure a draining VCC source by using a voltage divider on it You could indeed use a voltage divider, and measure a scaled-down Vcc against the internal 1.1 V reference. This is, however, not what the code you posted is doing. It is instead measuring the internal reference against Vcc, as stated in the comment ...


6

Based on your schematic, you need to provide a 3.3v power source to the 3.3v side of the logic level converter. You can use the 3.3v pin on the Arduino. Also, it's really hard to evaluate your soldering with such a shaky picture. Just make sure none of the pins are connected. A visual inspection usually will do, but if you want to be sure, use your ...


6

LVTTL is Low Voltage Transistor-Transistor Logic. In general, the term "TTL" is used for a digital signal. The "Low Voltage" part is special, the ATmega32U4 switches from low to high (and vice versa) at low voltages. Just as it is written. For example, when the ATmega32U4 runs at 5V, then: VILmax = 0.2 * 5 - 0.1 = 0.9 V. VIHmin = 0.2 * 5 + 0.9 = 1.9 V. ...


5

The forward voltage of an LED or diode is the applied voltage of the "knee" in the exponential characteristic at which it starts to substantially conduct, and in the case of an LED, produce light. It is not, under ordinary circumstances of indicator-type LEDs, a voltage that would be produced internally to the LEDs, at least not with any substantial ...


5

my 2 cents: A LoLin NodeMCU V3 when powered via USB in the Vin pin reads 2.2 V (don't know why) but... in the VV pin you can get the 5V coming from the USB; so if you need 5V use that pin. The board if powered via Vin with 5V, the VV pin reads 2 V (don't know why either) in any case you can always get 3V in the 3V pin. Cheeers!


5

You're misunderstanding what you need to drive a transistor. A transistor will allow up to a specific amount of current through the collector depending on the current that flows through the base. If less is needed by the load then less will flow. Think of it like a tap. If there's not much water pressure it doesn't matter how far you turn on the tap, after ...


5

It will not be possible for you to PWM dim your LED with that LED driver (power supply). That is a constant current driver with under/over-voltage protection. It delivers a specific amount of current (1.5A) and varies the voltage to allow that to happen. If the voltage rises too high or falls too low then there must be a fault, so it shuts the power off. ...


5

They read voltage. When you close the pushbutton switch the input should have a 0V or digital "0" on it. When you open the pushbutton the resistor should pull the input to 5V or digital "1". Yes, it is still connected to +5V via the resistor but the nearly 0 Ohm switch pulls the line all the way (or very close) to 0V.


4

No you cannot use a Vin or VU pin as a GPIO pin which can be controlled by a program. Vin can be used as an input for 5V battery or as a 5V output when NodeMCU is powered by USB (except on NodeMCU v3 by LoLin). On the V0.1 LoLin board, there are 2 diodes between the VIN and VU pins. So you cannot get power from one to the other. These diodes isolate the ...


4

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 ...


4

If anyone else is confused by this: Will it hurt your Arduino? No, this is a internal voltage reference between VCC & the 1.1v internal analog reference. Is a voltage divider necessary? Not unless you have something external of the Arduino to measure! Is the internal reference actually 1.1v? No, it seems like each pro mini I have the the 1.1v ...


4

This should be a lot of fun but you might consider doing some research on analog circuits and A/D circuits. You have way too many digits to the right of the decimal, the accuracy is not there. The best you can get is 0.0044 volts per count with a 4.6v reference. What are you using to make your measurements, you need at 5 1/2 digit meter to have the decade ...


4

You are talking about measuring 2kV to 10kV pulses, with about 1J to 5J of energy per pulse. The maximum current may be very low, but the voltages you want to measure are very high, and will very probably damage your Arduino without proper measures. You will at least need a voltage divider to reduce the voltage the Arduino sees to 5V (or 3.3V for some ...


3

You may want to use a boost converter which is a device that can step up voltage. You can get them from eBay for around $US 2. As Chris Stratton pointed out in a comment, the boost converter may run your batteries down quite quickly. Let's say you need 200 mA for your Uno, sensor and LEDs. At 5V power that is 1W of power (0.200 * 5). However to get 1W ...


3

He is describing a boost converter which steps up voltage at the expense of current. To quote from the Wikipedia page on that subject: A boost converter (step-up converter) is a DC-to-DC power converter that steps up voltage (while stepping down current) from its input (supply) to its output (load). It is a class of switched-mode power supply (SMPS) ...


3

Assuming you are asking about digital input pins on an Arduino: Digital logic operates at the saturation and cut off regions of the transistor logic used. Most modern day processors use CMOS transistors. The logic levels are Low: 0 V to 1/3 VDD and High:2/3 VDD where VDD is the supply voltage. This information can be found here. So, if your processor is ...


3

-10uS because of the 10uS delay at the end of the loop, and /128 because he has decided there will be 128 possible dimming levels.


3

Measuring voltage Use the following interfacing circuit for measuring voltage: Resistors R1, R2, R3 (1% tolerance or better recommended) will map the voltage input range (-12 to +12V DC) to an output range that can be read will the Arduino ADC (+0.5 to +4.5V DC, in order to have some slack from the top and bottom end of the ADC range). The actual ...


3

Running an Arduino board with 12V is almost always too much. With only a few leds the voltage regulator on the Arduino boards gets too hot. The best voltage is 7.5V. Then the voltage regulator has only little power dissipation and it is just high enough to turn off the USB 5V power. Or power the Arduino board with a 5V (from a USB charger, or USB power pack)...


3

As gre_gor said. A simple breadboard contains of rows and columns of connections but sometimes for convenience manufacturer marks or prints Positive and Negative symbol along the row as they are usually used to power a circuit


3

Expanding on dannyf's answer, if the pump datasheet does not feature a graph, then you will have to experiment. If a flowmeter is not readily available, an excellent approximation can be calculated by pumping water into a large, known receptacle (e.g. 10 litre bucket) and timing how long it takes. Do this for 20%, 40%, 60%, 80% and 100% Pulse Width ...


3

Is the programming code for A0 to D2 the same as for the other pins ? Then you could put the pin numbers in an array and run them in a for loop. The TP4056 has a CE pin, why don't you use that to turn then on and off ? The accuracy of reading a voltage with an Arduino depends on the accuracy of the voltage reference. You use the VCC 5V as reference. Is ...


3

You have a few options: Use a low-pass filter to round the square wave's edges some so they look more AC-ish. Use a low-pass filter and have your code create steps of voltage that look AC-ish by varying the PWM widths. Use an external SPI DAC chip that you can control with more discrete levels to make smoother looking AC. Look into Direct Digital Synthesis (...


3

wouldnt that then send current through the Vin pin and back to the coin cell battery? Is that what would happen in this instance? Yep, that's right. shouldn't there be a design feature to prevent users from damaging it like that? Fool/fail safe? No. VIN can also be VOUT. You can use it to power other things that want a higher voltage.


3

It's actually very simple, and it indeed does involve using PWM. PWM is just a signal being on for a percentage of a predefined period. That percentage is also, when the PWM signal is averaged out, equivalent to a percentage of the peak voltage of the PWM signal. So if you take a PWM signal and use it to switch a higher power source (say, through a P-...


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 ...


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