Questions tagged [raspberry-pi]

The Raspberry Pi is a credit-card sized computer that plugs into your TV and a keyboard. There have been several generations of the device with improved performance, more memory, and more connectivity. This tag should be used for electrical engineering questions that involve the use of a Raspberry Pi. For questions about the Raspberry Pi itself see the raspberrypi.stackexchange.com Raspberry Pi specific forum.

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37
votes
8answers
3k views

Add a passive hardware token using a 3.5mm jack

I have a box that I made for my niece, which allows her to exchange voice messages with me. It is powered by a Raspberry Pi and features two buttons, a LED, a microphone and a speaker. Now, for ...
31
votes
6answers
45k views

Embedded Programming for Beginners: Arduino or Raspberry Pi? [closed]

I'm a computer science student and I'm eager to expand my knowledge on embedded programming and electrical engineering. I've read here that using tools like the Arduino microcontroller is a good way ...
25
votes
1answer
21k views

Understanding an 'ideal' diode made from a p-channel MOSFET and PNP transistors

The Raspberry Pi B+ models have a protection circuit between the USB connector and the 5V net on the board. They recommend putting a similar protection circuity on a Pi HAT before 'backpowering' the ...
24
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3answers
3k views

What does “no fit” mean in electronics?

I have found at some places, especially: Raspberry Pi Forums eLinux RPi Hardware page the following wording: S2: DSI interface. 15-pin surface mounted flat flex connector (possibly no-fit) S5: ...
14
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4answers
24k views

Shutdown Controller for Raspberry Pi in a car

Following on from my previous question I'm trying to create a shutdown controller for my Raspberry Pi. The Raspberry Pi needs to be powered from the battery, but should power-down after the Pi ...
13
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6answers
5k views

Is a pull up/down resistor really necessary?

Logical reading (1 or 0) of a micro-controller input GPIO pin may float if it is neither connected to VCC nor GND; someone said it is because of surrounding RF interference. When a floating GPIO ...
12
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5answers
9k views

Control the hardware of an old phone using a Raspberry PI

I have a very old phone (60 years old) and I want to control its part using a Raspberry PI: Microphone & speaker from the head set The bell The dial wheel I have the electric circuit but don't ...
12
votes
1answer
8k views

Plugging a LDR into GPIO pins of a Raspberry Pi

I want to connect a LDR into the GPIO pins of my Raspberry Pi, I know that Raspberry Pi doesn't have an analog-to-digital converter so what I want to do is to signal a HIGH signal (3.3v) on the GPIO ...
12
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2answers
7k views

Using a microcontroller to turn on LED strip

I have 60 leds that came in a led strip. One meter length of the led strip requires the following: 400 milliamps 12 volts I want to control these LEDs with micro controller. I'm thinking of using a ...
11
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2answers
14k views

Using a 5v voltage regulator - Capacitors necessary? Better options?

I am very new to electronics. I am learning as I go, and I haven't quite found the answers I need; when it comes to programming, I'm not afraid of mistakes as they happen constantly. With electronics, ...
10
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2answers
14k views

Is the Raspberry Pi a microcontroller or a motherboard? [closed]

I had quick question regarding Raspberry Pi: is it a microcontroller or a motherboard? It looks like a motherboard, but considering that it has its own dedicated memory and processor, it should be a ...
10
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1answer
2k views

I connect a 5 volts to a low resistance, but I measure a much lower current than I expect

I cannot understand why the current I expect is so different from what I am measuring. I found a very low resistor, 15 ohm and connect it to 5 volts. Why is the current I measure so low? Shouldn't it ...
10
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4answers
11k views

shorting a remote control pushbutton with GPIO and a transistor

I'm trying to control my garage door remote with a GPIO pin from my Raspberry Pi. Instead of driving a relay, it would be much easier to just short the pushbutton on the remote. Is this how I should ...
9
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3answers
4k views

Detect 220 VAC with a Raspberry Pi

I want to build a simple device to check if the light is on or off. I found some schematics but I need to be sure that it is safe. Source : How to detect 220 VAC voltage using an opto-isolator My ...
9
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5answers
15k views

Raspberry PI without OS on it?

I've been doing a lot with Arduino recently. It's very simple because you can directly execute C++ code on it without the need of operating systems or drivers. I've done some research and AFAIK, you ...
8
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8answers
13k views

Sending I2C reliabily over Cat5 cables

I am considering implmenting an home automation system around my Raspberry Pi but I found the price and space requirement of inserting a Pi every place some control is required too much but the Cat5e ...
8
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3answers
2k views

Breadboarding a Raspberry Pi

Ok, long time reader first time asker on this parcticulair stack-exchange. I am rather new to electronics, I've done some simple projects like Blinking Lights, alarms that go on when its dark and a ...
8
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3answers
4k views

Miniature Traffic Light with Raspberry Pi: Wiring many LEDs

Background: I am a Civil Engineer specialized in traffic control devices and I have a small hobby project to build a scale model traffic light system. I can manage and control the traffic light ...
8
votes
1answer
7k views

How to properly use a relay module with JD-VCC from Arduino/Raspberry?

I got two 4-relay-modules and I am probably doing something wrong because none of them seems to work: My first try was using a breadboard 5v power supply, connecting VCC and In1 to 5V and GND to GND. ...
8
votes
4answers
16k views

Circuit to safely power-down Raspberry Pi

I want to use a Raspberry Pi as an XBMC server in the car. The XBMC docs say that you should always use the shutdown command before disconnecting the power. I don't want to have to (tell my wife to) ...
8
votes
3answers
9k views

Raspberry Pi as JTAG programmer?

Other than obviously non-trivial problem of writing the software, is there any practical reason why the GPIO port of a Raspberry Pi couldn't be used as a JTAG programmer? I ask because I'm doing some ...
7
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6answers
1k views

How to read 0 -10V analog voltage with lower voltage tolerant ADCs without a voltage divider

Background Information I want to implement an ADC as an extension to a Raspberry Pi, so that it has the capability to read analog signals. I will be using the MCP3004/3008, as I got lost in the ...
7
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3answers
8k views

Using larger resistor values

I'm connecting a Raspberry Pi to an LED and this video tutorial says that I need 270 Ω resistors. I only have 100 Ω, 1 kΩ, and 10 kΩ resistors with me. Is it okay if I use the 1 kΩ resistor?
7
votes
2answers
1k views

Understanding 74LVC245 datasheet and current source/sink

I'm using a SN74LVC245A (datasheet) to shift 5V TTL down to 3.3V so I can read the signals with a Raspberry Pi. However I am getting really weird results (a 60Hz input signal is picked up by the Pi ...
7
votes
2answers
8k views

Switching MOSFET from Raspberry Pi GPIO

I'm trying to drive a STP16FN06 from a Raspberry Pi GPIO pin but I'm a bit lost. The schema below represent (I think) how it is currently wired, on the left the RPi pin + ground and on the right a 5V ...
7
votes
4answers
2k views

Using a digital potentiometer in a voltage divider

I'm using an MCP3008 ADC and an MCP4131-103 (10k) digital potentiometer to try and create a sort of "adjustable voltage divider." For the project, the resistance I'm measuring will vary, and I hoped ...
7
votes
4answers
5k views

Wheatstone bridge sensitivity and accuracy

From my earlier question I was able to wire up 2 SEN-10245 weight sensors (each forming one half of a wheatstone bridge) with an AD620 InAmp & 47 Ohm resistor (to set the gain to ~1000). I then ...
6
votes
3answers
3k views

Is it normal to have SPI Clock with varying duty cycle?

I am working to get an SPI interfacing radio module on embedded Linux system. This particular module (RFM12B) is already ported onto Raspberry Pi. Now I am working on OMAP4 based systems. I noticed ...
6
votes
5answers
24k views

Simplest uni-directional level shifter (3.3V -> 5V)

I want to drive a WS2801 LED strip from a Raspberry Pi GPIO. I have connected the MOSI and CLK pins directly to drive the LED but it is not working as the WS2801 datasheet says that a high level is \$...
6
votes
3answers
702 views

Can I do this tutorial without a potentiometer?

I am trying out online tutorial to practice python and Raspberry Pi. I am currently following this tutorial. It says a potentiometer is needed, but I don't have one. The lcd I have is JHD162A What ...
6
votes
3answers
673 views

Is this an acceptable circuit for debouncing a Raspberrry Pi input pin?

I am trying to design a circuit to debounce an input switch on a Raspberry Pi. The switch is for a doorbell, so it doesn't need to register multiple valid presses that are close together in time. ...
6
votes
4answers
22k views

Control 5v relay through 3.3v GPIO using NPN transistor

I'm not very pratical as I just started learning electronics and I'm planning to make some experiment with Raspberry Pi. I'm trying to control a 5v relay board that, I think, is made for Arduino, as ...
6
votes
4answers
9k views

Proper usage of a MOSFET to control USB

On the RaspberryPi.SE it was suggested that one can use MOSFET BS170 to switch a USB device on and off by a GPIO pin (3.3V). I need to get 500mA to power a GSM dongle; the voltage drop should ...
6
votes
2answers
997 views

Voltage regulator misbehaves under certain conditions

Okay guys, this one has me baffled. Take these two circuits: Typical stuff; Power in goes to the + rail, GND to the - rail. This is a 19V power supply going in. It goes through the voltage regulator (...
6
votes
2answers
1k views

Microcontroller vs FPGA to DAC and ADC [closed]

I searched multiple forums about microcontrollers and FPGAs but I couldn't find the answer were I was looking for. I have to make a choice of whether I'm going to use a microcontroller/minipc like a ...
6
votes
5answers
9k views

Safety of using microcontrollers such as Arduino

I have been learning how to work with Arduino Uno R3, and it seems very intuitive and exciting for me. As many agree, I see lots of benefits of learning to use it at a young age. I would like to ...
6
votes
5answers
5k views

Do you need to UL Certified the enclosure with the board inside?

I want to use the RaspberryPI in an industrial environment that requires all devices have UL certification. The RaspberryPI board has UL certification but there is currently no enclosures that are ...
6
votes
1answer
482 views

How does the Nintendo 64 detect a controller is connected?

To give some context, I am trying to emulate controller input to the N64 via a GPIO pin on the Raspberry PI. In an attempt to accomplish this, I have one of the PI's GPIO's in a pull-up configuration ...
6
votes
2answers
266 views

Why can't I trigger my relay?

Solution This issue was caused by the choice of SOT-23 symbol when creating my PCB in KiCAD. As you can see in the picture below, there are a number of symbols associated with transistors in the KiCAD ...
6
votes
2answers
9k views

Raspberry Pi stereo camera frame synchronization/genlock (video or still image)

I need to frame synchronize a stereo camera for a computer vision application. The synchronization should the best possible, hopefully on a millisecond level. I would like to get about 10 FPS either ...
6
votes
2answers
8k views

transmit data wirelessly under water?

I am looking into constructing a small submarine with a Raspberry Pi. This is just for a hobby project but my idea is to have it communicate with the surface wirelessly. I know that normal radio waves ...
6
votes
2answers
2k views

Odroid XU4 and Olimex MOD-IO by I2C via level converter

Long version Like some of you, I do electronics as a hobby and I'm relatively now to this, so I have a few questions regarding the communication between my Odroid XU4 and a nice I2C module from Olimex ...
6
votes
1answer
2k views

How to fix RaspberryPi HDMI-DDC/CEC issue while keeping ESD protection?

The RaspberryPi (Type B, all revisions before B+) shows a more or less well-known issue with the CEC/DDC of connected HDMI devices. When powered down CEC between the connected TV set and other devices ...
6
votes
3answers
882 views

Determining Capacitor Discharge Rate

First time poster, apologize if I accidentally missed any rules. I've built a circuit that keeps a relay closed that is attached to battery power for a specific amount of time so my Raspberry Pi has ...
6
votes
0answers
579 views

Cheapest Raspberrypi (or MCU) power supply with both toggle *and* momentary switches? [closed]

TL;DR/main question: How would one modify this PCB to add an extra toggle switch that does not just abruptly cut the power to a load and that still allows enough time for a clean shutdown of, i.e, a ...
5
votes
4answers
2k views

Powering a Fan with Raspberry Pi

I have a 12V computer fan that I want to hook up to my Raspberry Pi. It has a 7V sensor, 12V power and ground. I know that the Pi can only supply 5v so I’m just wondering how to hook it up to the Pi ...
5
votes
5answers
8k views

How do I reverse my electric motor?

For a pet project I am doing (trying to fly a kite using my computer) I need to move and reverse an electro motor to my liking (I took the motor from an old hand-held vacuum cleaner). I need to ...
5
votes
5answers
5k views

Looking to build signal level converter to reduce 20V input to 3.3v out. Am I on the right track?

I'm working on a small pet project with my RaspberryPi and I'm looking hook it up to some sensors. The output from the sensors is normally at 0v but when the sensor is triggered, goes high to 20v. ...
5
votes
3answers
1k views

Can I screw up my board by guessing which RS232 pins are which?

I have a Raspberry Pi that I want to hook up to a serial (RS232) cable. I've found and read some information about this, so I know what pins on my RPi are Rx/Tx/3.3V/Gnd... Now the cable I'm hooking ...
5
votes
3answers
888 views

SPI and multiple devices

I'm planning out hardware for a project and would like to drive at least 2 displays, each using the SPI interface. What I dont understand is why there are dedicated pins for the CS line (at least on ...

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