6 votes

Sainsmart 12V, 16 Channel relay module connected to RpiZW has unwanted triggering when booting

You could use an IO expander module (e.g. PCF8575 or MCP23017) between the Pi and the relay board: those modules don't change pin states unless they receive a valid I2C/SPI command, so they will not ...
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4 votes

What is the maximum / minimum operational temperature?

This is an old question, but there are new answers: The original question will soon be 10 years old, and the "official documentation" quoted in the currently accepted answer has been revised....
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  • 17.4k
4 votes
Accepted

Erratic GPIO event callback

Perhaps it is EMF from something switched on at around 18:00. I suggest you run monitor.py in the background and check its view of the situation. sudo pigpiod python monitor.py 13 If you see ...
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  • 66.3k
4 votes
Accepted

Why did Pi-4's port layout change?

According to the launch announcement it was to simplify routing: Our Gigabit Ethernet magjack has moved to the top right of the board, from the bottom right, greatly simplifying PCB routing. https://...
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  • 6,136
3 votes
Accepted

How to persistent write to registers?

Using openssl and public private keys, You could get the pi serial number and encrypt it with a private key, place it on the sd card along with the public key. If you decrypt the file with the public ...
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3 votes

Make case fans work RaspberryPi4

Some fans supplied with cases are designed to run full-time. If that's what you're doing, you don't need any software - just connect the fan wiring to the appropriate GPIO pins. If you're asking how ...
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  • 17.4k
3 votes
Accepted

Raspberry Pi 3B+ board SMT component identification

I admire what you are doing, that is how I learned. What you learn this way will stick a very long time. Try this link: https://www.etechnophiles.com/wp-content/uploads/2020/12/Parts-of-R-Pi-3B.jpg It ...
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  • 687
2 votes

power the logic circuit of an external component with an external power supply instead of the raspberry pi's GPIO

Yes - you can definitely do that. Two things you must keep in mind: The RPi and the external battery-powered hardware must operate at a common reference potential. This is easily accomplished by ...
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  • 17.4k
2 votes

power the logic circuit of an external component with an external power supply instead of the raspberry pi's GPIO

In general, yes this is possible. You must connect the grounds of both power supplies together at some point. You must also make sure that no 5 V logic signals that come from your 5 V logic are ...
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2 votes

Children: Concerned with lead and other substances in handling a Raspberry Pi without case?

Common sense would be that children who are too young to understand or be responsible for the issues involved with handling a bare board should be closely supervised (or just plain told they are too ...
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  • 55.6k
2 votes

I too have knocked off a component from the underside of my Pi 4 board. HELP

There are no schematics published for the Raspberry Pi. Only reduced schematics are available, which show connectors and parts of the power distribution circuit. You won't find that resistor in there. ...
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1 vote

LPM raspberry pi 4B extinction mechanism

My question: by which signal / pin, the processor sends the order to the PMIC to turn off the regulated outputs? In section 2B of the RPi 4B schematic, you will see a connection to GLOBAL_RESET. This ...
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  • 17.4k
1 vote
Accepted

Raspberry PI B schematics and hw drawings

The Schematics and Mechanical Drawings of most models are available. The Pi Model B did have a reasonably "complete" 5 page schematic (Raspberry-Pi-Schematics-R1.0.pdf), but does not seem to ...
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  • 53.2k
1 vote

Raspberry PI B schematics and hw drawings

The information you seek should be at https://www.raspberrypi.com/documentation/computers/raspberry-pi.html To determine the version of a pi is simple if you have a running linux on it; see https://...
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  • 2,061
1 vote

RPi4 Broken Resistor

What I would consider is purchasing another Pi, removing and measuring the value of that resistor. Then purchase new resistors and install one on each board. If you do not have the skill set to do the ...
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  • 687
1 vote

RPi4 Broken Resistor

Unfortunately, the RPi conglomerate does not publish full schematics, or a parts list. Consequently, unless the part you are interested in is covered on their partial schematics, you will have to ...
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  • 17.4k
1 vote

What sensor can I use for detecting a metal type without the use of magnets?

The simplest of-the-shelf device to do this would probably be a low-resistance meter, using 4-terminal sensing. You could probably create your own version, but the design would be quite tricky, as the ...
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  • 227
1 vote
Accepted

Can I add a second processor to pi 4b 8gb? Is it even possible?

It would be extremely difficult if not impossible. There is no provision on the Pi 4b board for a second chip, and the hardware isn't designed to support a second chip. One reasonable approach to ...
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  • 794
1 vote
Accepted

Network Resillience Options

In raspi-config there is a System Options Network at Boot option which delays boot until there is a network.
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  • 53.2k
1 vote

is it possible to control the Fan from GPIO?

Perhaps the easiest way to do this is to add the one-line dtoverlay=gpio-fan facility to your /boot/config.txt file. You will still need to add some hardware, but the transistor and resistor may be ...
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  • 17.4k
1 vote

What is the name and specs for the RPi CM 4's GPIO connectors?

I understand they are '100pin Hirose DF40JC high-density connectors' and they they don't just carry the GPIO connections they carry all of the Raspberry pi's IO HDMI, USB, Networking etc.
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1 vote

How to persistent write to registers?

All Pi SOC have a One-Time Programmable (OTP) memory block, indeed this is where the Serial Number resides. See OTP register and bit definitions although as goldilocks pointed out security through ...
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  • 53.2k
1 vote

power the logic circuit of an external component with an external power supply instead of the raspberry pi's GPIO

You CAN power external components; indeed for some this is recommended. It is (generally) essential to share Gnd connections (opto-isolated devices are a possible exception). There is actually no need ...
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  • 53.2k
1 vote
Accepted

How to detect low amp AC current with GPIO

It's not clear from your question that you need to measure current. As a practical matter, measuring voltage is often easier. @Dougie comment suggesting an [opto-coupler (a.k.a. opto-isolator)] is a ...
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  • 17.4k
1 vote

I2C communication error: OSError: [Errno 121] Remote I/O error while using PAJ7620 sensor

Errno 121 usually occurs when running an I2C python program with the following situation: 2.1 The hardware wiring connection is bad, eg, 2.1.1 Forget to plug/connect the cable, 2.1.2 Too long cabling,...
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  • 4,184
1 vote

any way to know the real time status of speaker is it playing any sound through cli?

if you use ALSA then this command should help you: cat /proc/asound/card*/pcm*p/sub*/hw_params when nothing is playing the output is "closed" but when something is played it shows i.e. like ...
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1 vote
Accepted

Correct way to wire resistors

It appears you have shorted the two ends of the resistor - this is not what you want to do. Breadboards (a.k.a. "solderless breadboards") are really simple, but like all simple things, you ...
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  • 17.4k
1 vote

Desolder wifi/bluetooth module on a Raspberry Pi 4

I desoldered the wifi chip with hot air gun and Rpi seems to be working just fine. Also disabled wifi and BT in /boot/config.txt (maybe not necessary).
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  • 11
1 vote

How to install a Kuman 7" Touchscreen with Raspberry Pi

Note that matchbox is a standard software which can be installed from the Pi OS repository using apt-get install matchbox-keyboard.
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1 vote

Second WiFi adapter for the Raspberry Pi 4 B

We are successfully using a TP-Link TL-WN722N (Realtek chipset, i.e. v2 or v3) adapter with a Raspberry Pi Zero W running balenaOS 2.54. It was completely plug-and-play; no drivers necessary.
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  • 111

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