Hot answers tagged

5

Those resistors are in fact too high. Section 4.1 "Analog Inputs" (p. 17) and figures 4-1 and 4-2 (p. 18) of the datasheet are of special interest: For the A/D converter to meet specification, the charge holding capacitor (CSAMPLE) must be given enough time to acquire a 10-bit accurate voltage level during the 1.5 clock cycle sampling ...


5

There is nothing wrong with the GPIO, it just can't supply enough current for your coil. If the coil has just 24Ω, at a 3,3V the GPIO would need to supply 137mA. This source at raspberrypi.org says that the maximum current it 51mA for all GPIOs together and 16mA per GPIO. You can connect the GPIO to a transistor that can supply the necessary 137mA.


4

I use buck converters that convert 12VDC to 5VDC to power most of my raspberry pi computers. There are many available but be sure to check the amperage output. Most come with a USB A 5VDC output and that way you can use the microUSB for power thus having fuse protection My RPi Zero computers for my weather station as well as my RPi3B+ camera are all ...


3

The Pi has 3 "components" the CPU, GPIO and Video Core which are relatively independent. Even when the Pi is shutdown the Video Core continues to run, and the GPIO pins retail their state; only the CPU is not running. The 3.3V is supplied by separate circuitry and will be present while ever the Pi is connected to a 5V supply. The best way to reliably ...


3

This howchoo post shows how to connect an LED to show the status of the Pi. The LED is steady on when the Pi is running, and off after shutdown. Briefly: Add this line to /boot/config.txt, and reboot enable_uart=1 Connect the TxD pin (GPIO pin 8) to the positive lead of a 2 or 3 volt LED. Connect a ground pin (e.g. GPIO pin 6) to a 330 ohm resistor, ...


3

Not entirely. There are two Q&A you should read: 1, 2. The first Answer tells us that the voltage output from the USB supply is regulated iaw the USB standards, and therefore needs no further regulation on the RPi. So, I'd say the answer to your question is, "the 5V pads are regulated iaw the USB specifications and standards". The second Answer is ...


3

Question Use MCP3008 to measure voltage of range 0V to 4.2V. Use a voltage divider with 2.7MΩ / 8.2MΩ to step down value for Rpi but not working. Resistor values too high? How to calculate the resistor values? Short Answer MCP3008 ADC operation is indeed very complicated. You need to go through the long answer below a couple of times, ...


3

You can connect as many wires as you want to a 3V3 pin (pins 1 and 17). Similarly you can connect as many wires as you want to a 5V pin (pins 2 and 4). Similarly you can connect as many wires as you want to a ground pin.


2

Update 2019apr08hkt1109 On second thought, the question can be laser cut to focus on a very specific topic: "How to measure the magnitude of AC current in the range of 0 ~100mA, with a generous tolerance of 20%?" I think we can begin our feasibility study with two current sensors: (1) AC712, (2) INA12x/22x, ... ACS712 (or newer ACS723) 5A full scale ...


2

Get yourself a ADC with a range that suits you(plenty of hats) with enough inputs to measure voltages and currents. You can measure currents multiple ways, with current clamps(that doesn't require another hat) or use a current meter. These hats mostly work with i2c, and come with python / c examples. I expect you to know how to use the voltage and current ...


2

I often power a Pi via the 5V and ground pins on the expansion header. Typically I feed a laptop wall-wart PSU into a 5V UBEC. I connect the 5V UBEC output to the expansion header. Search this site for the advantages and disadvantages. Typically the microUSB socket gives you the polyfuse protection and it's less likely that the power polarity will be ...


2

According to this datasheet for the STC-013, the output voltage ranges between 0 and 50 mV for 0 to 100A. An increase of 2/1023*5 gives a measured voltage of around 0.009 V, or 9 mV, which would suggest a current of around 0.9 A. The readings you're getting seem reasonable, just not terribly helpful. In this sort of situation, I believe you can use an op-...


2

The voltage will fluctuate slightly on the 5v pin due to the protection circuitry built-in to the Raspberry Pi. Mainly the polyfuse, which has a resistance of about 0.2 ohms. When the load increases (LEDs, CPU usage, hard drive spinning), the voltage will drop slightly on the GPIO 5v pin. If that voltage drop is undesirable, you can: Run the chip on a ...


2

Question How to keep (1) 5V DC power supply for Rpi and (2) 5V DC power supply for external circuits, eg, LEDs, relays etc as steady as possible, say, less than 0.02V fluctuation (ie, "slight dip" in Rpi 40 pin connector 5V power, when switching on LEDs)? Solution Use two separate 5V regulated power supplies, one for Rpi, another for external circuit such ...


2

"What should I try?" A PROPER power supply.


2

Pin 1 is 3.3V power, and can supply up to 800mA (although it is inadvisable to connect a pump to the supply - particularly without any protection). Pin 3 is a GPIO - if programmed as an output it can supply a maximum of 16mA. By default it will supply ~2mA (because it has a 1.8kΩ pullup) - neither is capable of running any kind of motor. Also connecting any ...


2

Yeah, it will work, but Raspberry Pi works with 5V, then you'll have to provide it with a 2A USB phone charger. As for me, I would insert a battery bank between charger and Raspberry to avoid the leak of current. Particularly for the Raspberry Pi 4, your need 3A, which doesn't exist in chargers phones, then you'll have to transform 12v in 5V another way.


2

You need to use an interposing relay. This is simply a mechanical or solid state relay that has a 12Vdc coil and at least one contact (typically a form C contact, aka single pole double throw). Wire 3.3Vdc from your Pi to one side of the contact and the other to a GPIO input. Ensure you use a pull down resistor with the relay contact and a current ...


2

On the Pi Zero and Pi Zero W the 5V pins are directly connected to the 5V input from the µUSB connector, as can be seen in the schematics Other models have additional components (polyfuse, ideal diode etc).


2

RPi 4 core voltage scales dynamically with frequency in a range of 0.8V to 1.4V (going above 1.25V requires setting over_voltage in config.txt, and going above 1.35V voids your warranty). For an idle CPU, a value around 0.85V is pretty normal.


2

There is no performance hit. The Pi components, like all electronics, have minimum and maximum voltage ratings. If the voltage is not high enough, it will not boot. If it is at a threshold level, you will get intermittent low voltage warnings. An issue with voltage is that it can fluctuate, particularly under load (current draw), which widely varies for ...


1

You can use the L293D for driving motor. It is possible to use it with L293D IC. you must provide the IC power from external source. Using raspberry pi and L293D with a same adapter is not recommended


1

I'd test first if the Raspberry PI zero is even capable to handle 1080p. The Raspberry PI Zero W with fully loaded CPU and some Wifi utilization is taking about 200-250 milliamps, but there is nothing else. Camera and storage will raise power consumption significantly. About boosting battery voltage to the 5V - Boost converter - one of the modes of ...


1

Answering my own question, so you can tell me if it's a good idea. I already made a working system with an ADC (Analog to Digital Converter) that can convert the voltage to an LED with a potentiometer with some C code. - PCF8591 Can i simply buy an ACS712 and send 4 different analog signals to the PCF8591 ? (It does have 4 analog inputs) And then I should ...


1

@RalfFriedl is right, but I found some relays which are done for raspberry and arduino. https://www.youtube.com/watch?v=My1BDB1ei0E Now the circuit works. @joan do you think that this kind of relay will destroy the board?


1

It's as simple as adding a simple resistor to limit the current flowing to the GPIO. What we shall be carefull is to limit the current flowing "to" the GPIO, worst case when the input is 5V . Three steps: define the GPIO pin as input. Add a pull_down. Thanks the BCM2836 design, each GPIO pin has an internal pull down resistor SW enabled. This pull down has ...


1

This is not an answer but a warning! Your circuitry shows a direct connection to the mains active - this this is potentially LETHAL. Incidentally the first circuit you posted would do nothing (unless some of the diodes are faulty) - there is no potential difference across the meter.


1

did I do right? - NO The values suggested (1kΩ/2kΩ) may be mathematically correct (assuming you could ACTUALLY get 2kΩ resistors) BUT ignore the reality of circuit design which needs to consider the tolerance of the external voltage, the resistor values and the input characteristics of the Pi. An Engineer would design a circuit to provide ≥ 1.8V < 3.3V ...


1

I can't find a clear statement in the MCP3008 spec regarding input current. Personally I suggest trying 27k, 82k and going up from there if it works.


1

Question Rpi3B+ python ADS1115, How? Short Answer I am looking at AdaFruit's demo porgram, ... / to continue, ... Long Answer I am doing some research. Below is the research notes, ... / to continue, ... References Recommending CircuitPython for Rpi to newbies CircuitPython overview - Lady Ada CircuitPython for Rpi - Lady Ada Installing ...


Only top voted, non community-wiki answers of a minimum length are eligible