"Jon Slaughter"
** Geeez - now that explains everything !!!ROTFLMAO ...
.... Phil
Is this legal?
Mar 13, 2008
29 Replies
Looks like he's been "promoted" to "Technical Fellow".
Dave.
That's impressive.
Not in any positive sort of way, but it is impressive.
Tim Wescott
Control systems and communications consulting
http://www.wescottdesign.com
Need to learn how to apply control theory in your embedded system?
"Applied Control Theory for Embedded Systems" by Tim Wescott
Elsevier/Newnes, http://www.wescottdesign.com/actfes/actfes.html
"David L. Jones"
** Being a " technical fellow " is a position of high honour in firms like Microchip and Microsoft.Means one is considered to be a learned individual and a leading light in the firm.
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....... Phil
Ok, so now the fuse is blown. But what difference does that make? Leave the fuse out - what difference does it make?? The fuse does absolutely nothing to protect anything.
Ed
Hmmm... OK.
First, let\'s look at an unisolated, ungrounded power supply
connected across the mains properly:
+--------+
LINE
That makes sense thanks for thethorough explanation.
Oops... I put the fuse in the wrong place:
Here\'s how Microchip has it wired:
+--------+
LINE
Right. It should never have been proposed for any case in which the load will be exposed to the user's world. In principle, it is OK when the PIC can float on the line, and any external I/O is done with opto-isolators or similar devices. And in such a case, the connection of line or neutral does not matter, the fuse is not necessary, and the safety GND will only connect to the user's enclosure.
I think I will discuss this on the Microchip forum:
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This circuit is in their "Tips and Tricks" document, and I think their tricky engineer was a bit tipsy when he proposed this in this way.
Paul
It's still unsafe to depend on the fuse and the GND wire. The worst case is when the outlet is wired wrong so that Neut and Line are reversed AND the GND is not connected (Think about a two-wire outlet with a three-prong adapter.) In that case, the fuse will not blow, and any part of the circuit which the user can touch is live. This circuit would need a double-insulated case and a GFCI to be safe, in which case the fuse would be unnecessary.
Ken Fowler, KO6NO
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