0
votes
1answer
52 views

Should AC voltage supplied to an external device through a relay be electrically isolated from the main power source of the enclosure?

Given a power supply in an electrical enclosure powered by 120 VAC. An I/O device will trigger a relay with a 24 VDC control. The signal from the I/O device will enable the relay for a set duration. ...
11
votes
2answers
955 views

Why AC points on PCB are separated by a hole

I want to find out why, in professional PCB's, they separate between the AC (220 VAC) points on the PCB with a hole in the PCB: Is it for more isolation between the AC lines? Is leaving a distance ...
3
votes
1answer
107 views

AC leaks to laptop, cellphone surface. Feel by finger! [closed]

I've accidentaly discovered that several mains+battery-powered devices with metallic casing like cellphones, laptops and mp3 players, exhibit a special kind of friction when stroked with a finger. But ...
4
votes
1answer
211 views

How do AC and DC hipot tests compare?

Suppose I have a DC/DC converter, Recom RPP30 for an example to hand. It lists an isolation voltage of 3000 VDC. How does this translate to an AC isolation voltage? Would this be equivalent to 3000 ...
5
votes
1answer
703 views

How should I isolate AC and DC on a small PCB?

I am designing a small PCB (1"x1") and it will have some DC logic traces (5V and GND) and some high frequency AC power traces (100V 1000Hz 50mA). Are there any special considerations I need to take ...
3
votes
3answers
317 views

Sensing signal on a power line from high side

I have a circuit design as above. I'm trying to sense the voltage difference accross the \$ 0.1 \Omega \$ resistor. I physically connected the sensory circuit to the low side of the AC line, and saw ...
5
votes
3answers
1k views

Why is power supply from electrical utility referenced to earth?

In response to the question Basic Training for working with 120V AC zebonaut had replied that "A regular wall outlet is referenced to earth" and this provides the close loop for the circuit to ...