## 2014 Community Moderator Election

The community moderator election is currently in the election phase.

## Top new questions this week:

### What reasons are there to avoid vertical through-hole resistors?

I'm working on a layout for a PCB and I need to include a handful of pull-up resistors. The board I'm working on will be a proof of concept, and it is likely I will only need one (and order two). That …

pcb resistors pcb-design

### Firmware protection on AVR and PIC controllers

Can someone extract the HEX file that I burn in a microcontroller I provide them? If that is possible, how can someone ensure that their code is secured in embedded systems? In the case of PIC and …

pic avr embedded firmware

### What is this type of flexible contact strip called?

The LCD below is from a cheap digital clock which was (obviously) damaged (broken glass). The electrical connection between the PCB and the display was realized with this pink strip. Its …

connector display flexible

### 555 saw tooth generator diodes purpose?

I'm given this 555 timer based monostable saw-tooth generator. This is a known arrangement for this part. The difference from other circuits I've seen is that the bias network of the external …

diodes 555

### Should ventless electrolytic capacitors be mounted upside down?

I understand that electrolytic capacitors with vents should not be mounted upside-down. I read that the vent may not function properly and the electrolyte may leak out. Smaller electrolytic …

capacitor electrolytic-capacitor mount

### How do the streetcars in Toronto draw power from the lines?

I've tried googling this but to no avail. I've been trying to figure out how streetcars can draw power from a short circuit. For reference: If I imagine the power lines simplified as a shorted …

power automotive

### What happens when plates of a fully charged capacitor are isolated from each other?

I'm a mechanical engineering student and I'm working on a project that involves a high voltage capacitor. I understand that when the separation between the plates of a charged capacitor is …

capacitor

## Greatest hits from previous weeks:

### What do the PCB markings mean?

On a printed circuit board, I see lots of tiny letters and numbers. Is there some kind of standard that dictates what letter indicates what type of component?

pcb pcb-design markings

### When to use Capacitors?

This is probably the dumbest question ever, but I am an electronics nublet. I understand what capacitors do, and I've been reading beginner Electronics books and such, but I don't quite understand …

capacitor

### USB Clamping for OV protection

For our current design we require overvoltage protection on USB D+ and D-. I am aware that for USB, the total line capacitance of the line should be less than 10pF. We are planning to use a circuit …

usb

### How is the formula for the base current value derived in a three-phase per-unit system?

When analysing a power system using the per-unit system for a three phase system, why is \$S_b = \sqrt{3}*V_b*I_b\$, where as shown in the link, \$S_b\$ is the base power value, \$V_b\$ is the base …

power current