Tagged Questions
3
votes
1answer
330 views
Measuring almost 1 volt between Raspberry Pi input pin and ground, why?
I'm trying to use a switch to to provide input to software running on the Raspberry Pi. I have software running right now that continually reads the input pin and prints the result. Problem is, even ...
0
votes
3answers
299 views
Use transistor to auto swap power source
Basically I'm looking to use a simple transistor circuit to diconnect one V+ (or ground) when another is connected and automatically switch back when the switching source is removed.
Like having a ...
2
votes
2answers
1k views
Driving a large 7 segment display using a micro-controller
I need to drive a large seven segment display (segment length is a about 2 inches) using a micro-controller (PIC 16F877). I've driven normal seven segments directly from PICs without issues, but I ...
4
votes
4answers
397 views
Replacing a switch with a transistor
I am working on a project on the Raspberry Pi, it is a bit experimental as I am learning the electronics side as I go along... please edit out any problems with terminology.
My aim is to replace a ...
1
vote
1answer
143 views
Voltage problem in printed circuit with switches
I've got a simple circuit consisting of a 74157 MUX, whose entries come from switches. These entries have also 10k pull-up resistors, so when the switches are open (default), inputs are at 5V. When ...
4
votes
4answers
2k views
how to build a low-voltage disconnect switch for DC 12.4V 70A?
How can I make a device that will make the power connected as long as the voltage of the power-supply keeps over 12.4 V (adjustable) and disconnect it if it falls below?
It also must connect the ...
8
votes
3answers
1k views
Need help operating a transistor
I have a relay operated by an NPN transistor that needs some voltage applied to the base. I'm working with an arduino and if I give it a digital port, all's well. The circuit looks like this one:
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