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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 ...
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  • 951
8 votes
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Is there a component out there that can push a button i.e. will extend a rod about 1 inch and then retract it?

Have a look here: How to have a Raspi trigger a Remote Control physically Needs some ideas to trigger silicone rubber buttons A solenoid with a moveable pushrod can be driven fairly quickly and ...
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8 votes

Is there a component out there that can push a button i.e. will extend a rod about 1 inch and then retract it?

I believe the most appropriate device would be a solenoid. They are quite common. For a simple button pressing solenoid, something like this might work well. I would recommend that you put a soft ...
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8 votes
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Reversed LED in GPIO Output

As shown this circuit cannot drive two LEDs the way you want it. Consider GPIO-pin high: L2 lights up, L1 does not. GPIO-pin low: no LED lights up as there is no (significant) potential difference ...
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6 votes
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How to add isolation between raspberry pi and relay board?

Relays are pretty safe to use without any special isolation like optocouplers. The reason people recommend optocouplers in DIY projects... well because its DIY and an optocoupler is safer in case of ...
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  • 17.1k
6 votes
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Do I need a current limiting resistor in series with a magnetic door sensor?

Logic levels are detected by input pins. The difference between an input pin and an output pin is that an output pin has a specific voltage applied to it. An input pin does not, and when not ...
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  • 55.6k
6 votes

Easy way to switch on and off of 12V DC current

You'll need just two things: Make use of the GPIO pins Using the GPIO port of the Pi is possible with numerous libraries for all significant languages. Finding one that interfaces well with Python ...
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  • 15.5k
6 votes

Is there a component out there that can push a button i.e. will extend a rod about 1 inch and then retract it?

It's easy enough to find solenoids, servos etc with the power to push a button. The tricky bit is the mounting. Humans are really very good at pressing buttons on arbitary things, compensating for ...
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  • 5,393
6 votes
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Common ground with 9V?

There is no risk in connecting the GND of the power supply and the RPi together - actually, to create useful circuits most of the time this is required so that the +9V from the power supply and the +...
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  • 4,993
5 votes

reverse engineering: Transcend digital photo frame display to Raspberry Pi

The manual on the Trancend Website (see pjc50's answer) suggests that the unit will be recognised by a PC if a USB lead is connected to the mini-USB connector (C) on the SIDE of the case (not the full ...
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  • 3,583
4 votes

Circuit to safely power-down Pi

The best solution on my opinion is to use the UPS Pico , a specially designed for Raspberry Pi UPS, that offer a plenty of other features. It is low cost, includes battery, no need for any extra ...
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4 votes

Powering a 3-12V water pump on raspberry pi

It will be best to power the Raspberry Pi using a good 2Amp power supply. You will still need a transistor to drive the relay. But really relays are for high power, 24volts up to 220volts and heavy ...
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  • 17.1k
4 votes

Can I control this ESC/Brushless Motor with a Raspberry Pi and/or Arduino

ESCs (Electronic Speed Controllers) are typically controlled just like you would control a hobby servo -- with a PWM signal. There are many guides to controlling a servo that should be applicable to ...
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  • 2,984
4 votes
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How can I combine many inputs on one pin?

The B+ has 26 usable gpios. In that context 8 doesn't seem a lot. In effect you are trying to trade off the number of gpios used against complicating the circuit. Have you considered a port ...
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  • 66.3k
4 votes

I am getting ghosting/bouncing on my digital input

I had exactly the same problem with these interrupt events under Python. I believe this is a sofware bug in the lib. I do not use these Interrupts anymore, but now I am polling the GPIO. This works ...
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4 votes
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Is it safe to drive a current between a GPIO output at 0V (LOW) and the 3.3V supply?

Yes. In fact this is normal engineering practice, although for the Pi it probably makes no difference as the outputs are symmetrical. Having said that the amount of current you can supply from 3.3V is ...
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  • 53.3k
4 votes

reverse engineering: Transcend digital photo frame display to Raspberry Pi

The AM7338 is a dedicated Digital Picture Frame System on Chip (DFP SOC). It is a all in one single chip solution for DFPs, handling typical functions of buttons, IR remote, memory card and flash ...
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  • 301
4 votes

How to read values from an clamp-on ammeter with an raspberry pi?

The first thing I would do is plug it into your multimeter and see what readings you get. Note that current clamps (with very few exceptions) have to be clamped round the live wire only. Clamping ...
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  • 5,393
4 votes
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Use 3.3V regulator on 5V rail with GPIO

Apparently, the Pi's 3.3V rail can't (or shouldn't) source more than 50mA of current I'm shamelessly taking this from a recent Piversify post, "Exploring the 3.3V Power Rail", by one of our other ...
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  • 55.6k
4 votes

How to control 12V DC motor with a NPN transistor, a GPIO pin and a 12 V DC power supply

The 2N2222 is rated for a continous collector current of 600 mA only (that could be issue 1). To drive this current however a higher base current is required than is possible in this setup with the 1k ...
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  • 15.5k
4 votes
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Recording landline phone calls

My approach to this would be to do everything I possibly could to avoid interfacing the Pi directly with the phone line. It's definitely achievable, but it sounds a lot harder than I like my spare ...
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  • 10.5k
4 votes

Can I connect 5V to an OUTPUT GPIO pin?

You should never feed more than 3V3 into a Pi GPIO - that's the official line and that is unlikely to ever change. However lots of us have done so by mistake and on purpose. If you do so try to put ...
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  • 66.3k
4 votes

Did I destroy my GPIO board?

You need to checkout this tutorial that covers controlling a DC motor using a Raspberry Pi. The Pi's GPIO pins are for very low current applications such as controlling a transistor or controlling an ...
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  • 3,050
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 ...
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  • 53.3k
4 votes
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Powering an element that draws more current/voltage than GPIO can supply?

first thing first, you cant extract that much power from the pi, you need an extra batery and mosfet for that. heres the deal, in order to heat your pad you need and extra batery conected to the pad, ...
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4 votes

Can a relay be on for 16 hours continuously?

To add to @Ghanima's excellent answer, you may also wish to consider a latching relay. Briefly, a latching relay has two stable states (i.e. it is a bistable device, similar to a flip-flop). This ...
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  • 17.4k
4 votes

Simple pushButton circuit causes errors

There are numerous errors in the script. time module is not imported PIRinPin is not defined. AmountMotionsDetected is not defined, set as a global, or incremented. Once those errors are corrected ...
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  • 66.3k
4 votes
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Can I use HDMI 1 instead of HDMI 0?

A fully updated Raspberry Pi 4 will boot up properly and show the desktop, regardless of which hdmi port was used. Now I faintly remember this not being the case at some point, but Forum moderator &...
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  • 1,574
4 votes
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What is this 8-pin fpc place On RPi 4?

This is a JTAG connector used for development and testing. Here's a picture of an old Pi B+ featuring the signal names printed on it: AFAIK it's useless unless you have VideoCore documentation and ...
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