1. Home
  2. Electronics Design
  3. 120 VAC (in-and-out) - Compliance

120 VAC (in-and-out) - Compliance

Last one for tongight. Figured I'd get it out there while I'm Use-Netting.

My project needs to know if two separate 120 VAC circuits are "hot". I'm using a simple MID400 circuit for this.

This information is used by the rest of the product, but the rest of the pr oduct is typically powered by DC and need not be powered directly from eith er of these 120 VAC circuits being measured. Each 120 VAC circuit arrives on a separately fused and switched "power entry module", such as DigiKey Pa rt# 1144-1033-ND.

On the PCB itself, all the 120-volt stuff (which is just in-and-out connect ions) is segregated to one dedicated portion of the board. Mechanically, t he MID400's are positioned so that only their optical output side continues on to the rest of the circuit. In short, the "120 in-and-out" is opticall y isolated from the rest of the product.

Now -- What kind of trouble am I likey to be in when it comes to "convincing" a UL examiner that this arrangment is totally safe, etc... (Ignoring for the m oment all the other "hassles" with UL approvals, and the like.)

Surely there are products like this already -- but I can't recall any offha nd.

There are other ways to accomplish the goal, of course, including using low

-voltage CT's, but my primary objective with this design is to ELIMINATE a significant amount of production labor (as is the case with our current des ign). Which design, sucks for many other reasons I won't get in to.

Mostly just interested in any "hurdles" with sampling 120 VAC lines by brin ging them into my product, testing their state with opto's (MID400's) and t hen sending them right out of the box on their merry way.

Reply to
mpm
Loading thread data ...

If you need to sense line voltage, and not current, you could do what some scopes do for line trigger pickoff: twist an insulated sense wire with the hot wire, and use the wire-wire capacitance as the pickoff. Both wires are UL rated for the voltage, so compliance is basically free.

I've also see a UL-good wire pressed against a PC trace to make the coupling, but that was in a box that did not have a UL or CE sticker, so that may be harder to get away with.

--

John Larkin         Highland Technology, Inc 
picosecond timing   precision measurement  

jlarkin att highlandtechnology dott com 
http://www.highlandtechnology.com
Reply to
John Larkin

product is typically powered by DC and need not be powered directly from ei ther of these 120 VAC circuits being measured. Each 120 VAC circuit arrive s on a separately fused and switched "power entry module", such as DigiKey Part# 1144-1033-ND.

ctions) is segregated to one dedicated portion of the board. Mechanically, the MID400's are positioned so that only their optical output side continu es on to the rest of the circuit. In short, the "120 in-and-out" is optica lly isolated from the rest of the product.

UL examiner that this arrangment is totally safe, etc... (Ignoring for the moment all the other "hassles" with UL approvals, and the like.)

hand.

ow-voltage CT's, but my primary objective with this design is to ELIMINATE a significant amount of production labor (as is the case with our current d esign). Which design, sucks for many other reasons I won't get in to.

inging them into my product, testing their state with opto's (MID400's) and then sending them right out of the box on their merry way.

Why not see what safety standard your current product is certified to and then look at that standard for guidance on isolation clearances etc.

John

Reply to
jrwalliker

ElectronDepot website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.