Tagged Questions

3
votes
2answers
286 views

Do I need to use a resistor with a microswitch to limit current for an Arduino Uno?

I'm using an Arduino Uno to control a small robot and I'm starting to add micro-switches as bump-sensors. I know that when I'm creating a circuit with LEDs I need to use resistors to limit the current ...
1
vote
1answer
222 views

Alternative to optocoupler? Other switching devices?

I have a part that classifies what kind of power I get on ethernet by presenting different loads. For example, the part needs to have a 100 Ohm resistor across two of its pins, and the part will ...
4
votes
4answers
932 views

Pull Down Resistors

In my quest to understand electrical engineering, I have stubmled across this tutorial: http://www.ladyada.net/learn/arduino/lesson5.html I have understood the diagrams until I got to switches. I am ...
26
votes
5answers
2k views

Why do you need 2 resistors when hooking up a transistor as a switch

What is the point of R2 in the following diagram: I get that R1 controls the current to the Base, but what does R2 do? Thanks!
1
vote
2answers
334 views

Not use current limiting resistor for switching device on off using TIP122 possible?

I wanting to control MP3 player and amplifier box through PIC board. My project is doing announcement when person standing in near PIC board with proximity sensor. When proximity sensor detecting ...
1
vote
1answer
138 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 ...
1
vote
1answer
370 views

What kind of resistors do I need to use in this Canon remote switch, if it is possible at all with the P2N2222A transistor I have?

I'm a total electronics n00b set out to create an intervalometer for my Canon EOS 350D camera which seemed super simple from the outset, but I got a bit blocked with creating a switch using a ...
22
votes
7answers
5k views

Why does a resistor need to be on the anode of an LED?

Please be kind, I am an electronics nub. This is in reference to getting an LED to emit photons. From what I read (Getting Started in Electronics - Forrest Mims III and Make: Electronics) electrons ...
2
votes
4answers
565 views

How many resistors do I need for an 8 switch DIP switch block?

I was thinking of giving each switch it's own pull-up resistor, but this seems like it would be expensive and a little bit of overkill. But using just one pull-up for the entire block seems like it ...