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# Tag Info

## Hot answers tagged voltage

13 votes
Accepted

### Calculating resistor value for transistor

There's not quite enough information in your question to give a definitive answer, but let's go through the design steps so that not only can you figure out this one, but you might be better equipped ...
• 961
11 votes
Accepted

### TP1/TP2 equivalent for Raspberry Pi 3 B

The official schematics show that: PP1 and PP2 are 5V input from USB PP35 is 5V after the polyfuse PP7 is 5V after the input circuit PP3 through PP6 are GND They are to be found on the bottom side ...
• 15.9k
11 votes
Accepted

### Get reading of RPI supply voltage

I do not think there is any Pi circuitry to return the current supply voltage. As far as I am aware the under voltage circuitry is a piece of hardware which triggers at 4.65V. So you could ...
• 71.3k
7 votes
Accepted

### Raspberry Pi's reaction to 7.2 Volts applied to a GPIO pin?

No. Take it on the bright side. You have learned one thing never to do to a Raspberry Pi.
• 2,368
7 votes

### FM transmitter antenna length

Welcome to the Raspberry Pi SE site! Your question may be judged as off-topic for this site (not saying it will, but it may be), but personally, I'm happy that you've asked it. I say that only because ...
• 22.4k
7 votes
Accepted

### Raspberry Pi 4 - Booting with 3 USB attached Harddrives causes Crashing

I'm assuming these are USB drives, and are powered from the Pi USB port(s). You're probably exceeding the power supply capacity of the Pi and/or the power supply. Hard drives require a fair amount of ...
• 794
6 votes

### Rpi Reading MCP3008 10 bit ADC Result Problem

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 ...
• 15.9k
6 votes
Accepted

### What happens to the GPIO voltage after shutdown?

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 retain their state; ...
• 60.9k
5 votes

### TP1/TP2 equivalent for Raspberry Pi 3 B

Thanks to @Ghanima's great answer I made markings on those +5V points:
• 519
5 votes
Accepted

### Undervoltage symbol

Powerbanks are not made for powering electronics. They are made for re-charging batteries. This is important because these two tasks have some requirements that are at odds. Most significantly, in ...
• 59.5k
5 votes

### Powering a sensor using an external power supply board

Yes, (in general) in this case you should wire the ground terminal of all devices in your circuit together. This provides the necessary common ground reference voltage for them to interoperate. Your ...
• 22.4k
5 votes

### Get reading of RPI supply voltage

As noted in Raspberry Pi Power Limitations (which you referenced) The newer Pi(3/2/B+) have a voltage monitor chip (APX803) which triggers at 4.63±0.07V. The Pi3B+ Pi3A+ use a MxL7704 chip to manage ...
• 60.9k
5 votes
Accepted

### Rpi Reading MCP3008 10 bit ADC Result Problem

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 ...
• 4,735
5 votes
Accepted

### Voltage dropped significantly on GPIO 4 with a relay coil

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 ...
• 2,188
5 votes

### What happens to the GPIO voltage after shutdown?

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 ...
• 329
5 votes

### Voltage monitoring of battery pack (i.e. before voltage regulation)

The PiCheckVoltage project may be stale for a reason. It strikes me as a bit over-complicated for the situation you've described. However, parts of the code may be useful. Here are some alternatives ...
• 22.4k
5 votes

### Voltage monitoring of battery pack (i.e. before voltage regulation)

In my Raspberry Pi tablet, I use very low frequency PWM to measure the battery voltage. One half of a dual voltage comparator was set up as a sawtooth oscillator operating at approximately 100Hz. The ...
5 votes
Accepted

### RPi 4: What happens when reverse voltage is supplied to the GPIO header?

The expansion header GPIO must not be exposed to a voltage outside the range 0V to 3.3V. The expansion header voltage rail pins have no protection. If you reverse the voltage on the 3V3 or 5V pins ...
• 71.3k
4 votes
Accepted

### GPIO Voltage tolerance for input

There are no formal published data, but the following summarises what I have been able to discover. Electrical Specifications of GPIO I would NOT apply 3.6V to a GPIO pin, but if the voltage does not ...
• 60.9k
4 votes

### Connection of 220V Doorbell to Raspberry Pi GPIO

The statements "220V power" and "I'm very new with electronics" raise concerns. The only responsible advice I can give to anyone who isn't a licensed electical contractor is DON'T. Try something ...
• 60.9k
4 votes

### Supply voltage 5V issue from Raspberry Pi 3

The subject of ADC error is both wide and deep. Engineers have built careers on studying, quantifying, measuring and resolving ADC error. If you "Google" terms such as adc error analysis, or adc error ...
• 22.4k
4 votes

### Why my gpio input changes the internal resistance when running the python code?

Adding a resistor in series will not drop the voltage. It will simply reduce the current. Fortunately you seem to have limited the current to a level which the Pi's GPIO protection circuitry can ...
• 71.3k
4 votes
Accepted

### Powering a sensor using an external power supply board

Everything looks fine. Yes, you need to connect the Pi ground to the ground of any sensors you connect to the GPIO. It doesn't matter if they are powered by the Pi or by an external power source. ...
• 71.3k
4 votes

### How to increase voltage of USB ports on the Raspberry Pi 3 Model B?

Short answer: no way. Long answer: USB ports can only output 5 Volts. It's true that your screen came with (citing the product page you linked) 1 * USB to 3.5 DC Power Cable but that cable is ...
• 41
4 votes
Accepted

### Convert 12V to 5V to power RaspberryPi

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 ...
4 votes
Accepted

### What is the correct (internal) voltage range for a RPi 4?

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 ...
4 votes

### How to add Capacitors to Raspberry Pi

You need the supercaps to be in parallel to the power supply, not in series. However, before fixing your circuit, mind a few things: If you simply connect your supercaps between 0 and 5V, most power ...
3 votes

### Turn a Raspberry Pi into a voltage tester

Question Let me first summarize the OP's question. He has a 220VAC water pump. He knows that a 555 IC can tell AC current on by blinking a LED. His question is how to let Rpi talk to 555 to find ...
• 4,735
3 votes

### Is 5V out on the Pi Zero W unregulated?

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 ...
• 22.4k

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