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1500 questions
34
votes
8 answers
Power rating on Zero Ohm resistor
I was ordering some resistors online, and I saw that 0 Ω resistors have a power rating. Why is that? Power through a resistor is calculated with the equation \$P = UI\$ or \$P = RI^2\$. Since \$R = 0\ Ω\$, \$P=0\ W\$.
According to this post (How to…
M.Ferru
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34
votes
12 answers
Should I be worried about electro-static discharge?
Doing mostly micro-controller work, I have never bothered with grounding myself with a wrist-strap or any other implementation.
Should I be worried about this?
How serious is ESD when working at my workbench on projects?
stbtra
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34
votes
5 answers
Safe temperature for desoldering SMD components w/ hot-air rework gun?
What is a reasonably safe temperature to use for desoldering SMD components using a hot-air rework gun? I have a new-to-me rework station from Xytronic and the documentation clearly assumes you know what you're doing… It tells you what temperature…
Kaelin Colclasure
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34
votes
13 answers
How can I make connection on pcb (circuit board) holes without solder (for prototyping)?
I have a Pro Micro board (very small -- see pic below) and it has connector holes in the printed circuit board.
Best Non-Solder Connection (Easy and Removable)
I'm wondering the best way to make non-solder connections for doing my prototype work. …
raddevus
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34
votes
7 answers
Optimize heat sink design - connect cooling pad on PCB backside by vias
In one of my current projects I'm using an MC7805 in a D2PAK package to generate my logic supply of 5 V from an available 24 VDC supply. The current required by the circuit is 250 mA. This results in a dissipated power of the MC7805 of:
\$P=(24\…
KarlKarlsom
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34
votes
6 answers
Voltage regulator vs. voltage reference
I need a cheap, somewhat accurate (~0.5%) voltage reference for some DACs. At first I was going to use a LDO voltage regulator (a TC1223 specifically) for this, it seems to fit the bill looking at the datasheet. Then I saw there is a separate…
GrixM
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34
votes
8 answers
Two black boxes display the same impedance at all frequencies. Which has the single resistor?
Two black boxes display the same impedance at all frequencies. The first contains a single 1 Ohm resistor. Each end is connected to a wire, so that two wires protrude from the box. The second box looks identical from the outside, but inside there…
Paskualino
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34
votes
10 answers
Looking for a good freeware/open source PCB design software equivalent to Altium
I am familiar with Altium PCB design software in my workplace.
But thats an expensive suite to maintain. Is there any decent enough free software which I can use at home for my pet projects? I have tried ExpressPCB but not satisfied with it. Any…
scorpiokid
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34
votes
7 answers
Linux on ARM Cortex-M3 series
I'm new to ARM and a bit confused with all the diferent series.
I need to build a low power gateway (ethernet, wifi...), so I guess a cortex-M or cortex-R will be the good starting point.
But it didn't find any dev board with say a cortex-m3 (wich…
jojo l'abricot
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34
votes
3 answers
Whats inside a resistor?
How does a resistor "resist" current/potential?
I know it's an elementary question, but I'm sure others are wondering too.
Shubham
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34
votes
3 answers
Design for long term reliability?
I need to design a small board that will go into a large piece of public infrastructure intended to last many decades. I am looking for papers and the like that give guidance on such design based on real research.
This board will be much bigger for…
Olin Lathrop
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34
votes
2 answers
How to calculate battery life
How do I calculate how long a battery operated product will run?
Here's what I've got:
2 AA, 1.5V, 2700mAH batteries
Voltage Regulator with a Iq of 25 uA
Voltage Regulator Eff = 80%
Active Current = 50mA
Sleep Current = 1uA
Duty Cycle = 99.9%…
Robert Deml
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34
votes
5 answers
Choosing resistor values for inverting amplifier and why?
The gain here is A = -Rf/Rin. However, lets say I want a gain of 10 V/V. Which resistor value would you choose and why?
I know that you could have infinite number of combinations for these resistors but why would some one use specific value. i.e Rf…
dr3patel
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33
votes
4 answers
Building a hobbyist oscilloscope
I have a project that I've been thinking about for a little while, and I've come to the realization that at some point during its development, I'm going to need an oscilloscope. Okay, not a problem.
Instead of purchasing an oscilloscope, I've…
kestrel
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33
votes
3 answers
Arduino pin spacing
How do you get around the annoying pin spacing on the Arduino?
Where pin 7 and pin 8 are not standard spacing.
Why is it set up like this?
mad_z
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