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More LED Festive Lights

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dave_g
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Username: dave_g

Post Number: 916
Registered: 05-2005

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Posted on Saturday, 03 December, 2016 - 09:41 pm:   Edit Post Delete Post Print Post    Move Post (Moderator/Admin Only)

Getting a habit this.

The usual thing of a plug in adaptor, which includes a controller, running an LED string. Wires passed through window frames, 4 way extension leads, etc.

ENOUGH! Outside socket installed, controlled by a Double Pole Switch inside. Trouble is, the plug in adaptor won't fit.

30v, 6VA. Two strings.

Of course, PIC controlled, 30v, 15VA toroidal to run both strings. Built LM317T board from Rapid, bit of Vero with Acrylic spray, waterproof enclosure from the Rapid "sell off" bin, and a PIC18F2550 (yes, over the top) to get 2 x PWM outputs. Couple of MOSFETS and Bob's yer Santa Claus.

Too much time, too much effort - but no wires through the window frames and two identical patterns of LED lights across the front of the house. Wife walking around saying "everything you do is over-engineered, it was fine as it was...". Typical. She just doesn't get it...

(OK, couple of hours making a 4mm aluminium backplate. Nylon M3 bolts, standoffs, etc., transformer bracket, use of jigsaws and bench grinder, but not OTT at all...)

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twintub
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Username: twintub

Post Number: 414
Registered: 02-2007

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Posted on Saturday, 03 December, 2016 - 10:03 pm:   Edit Post Delete Post Print Post    Move Post (Moderator/Admin Only)

What, no earth (looks like flat 2-core mains cable)?
Or does the alleged OTT engineering render the unit as Class II double insulated!
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dave_g
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Username: dave_g

Post Number: 917
Registered: 05-2005

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Posted on Sunday, 04 December, 2016 - 09:18 am:   Edit Post Delete Post Print Post    Move Post (Moderator/Admin Only)

Well, it does.

On first glance I would agree, but earth what?

The enclosure is double skinned. The incoming supply goes straight to an enclosed toroidal transformer inside the double skinned box.

There are no exposed metal parts, indeed the backplate could be earthed but that is all. The output is, of course, nicely isolated by that transformer and I neither need or want to earth the output.

Happy to hear views on this (easily changed) but that was my logic.

Just checked Wikipedia:

"A Class II or double insulated electrical appliance is one which has been designed in such a way that it does not require a safety connection to electrical earth (ground).

The basic requirement is that no single failure can result in dangerous voltage becoming exposed so that it might cause an electric shock and that this is achieved without relying on an earthed metal casing. This is usually achieved at least in part by having at least two layers of insulating material between live parts and the user, or by using reinforced insulation.

In Europe, a double insulated appliance must be labelled Class II or double insulated or bear the double insulation symbol (a square inside another square).

Insulated AC/DC power supplies (such as cell-phone chargers) are typically designated as Class II, meaning that the DC output wires are isolated from the AC input. The designation "Class II" should not be confused with the designation "Class 2", as the latter is unrelated to insulation (it originates from standard UL 1310, setting limits on maximum output voltage/current/power)."

(Message edited by dave_g on 04 December, 2016)
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twintub
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Username: twintub

Post Number: 415
Registered: 02-2007

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Posted on Sunday, 04 December, 2016 - 05:47 pm:   Edit Post Delete Post Print Post    Move Post (Moderator/Admin Only)

Ah, it's a plastic enclosure! I made an assumption that it was heavy duty diecast alluminium (that's what it looks like at first glance) but now that I've opened my eyes I can now see that there are tell-tale brass inserts for securing the lid!

as an outward going earth is not needed, then a Class II design is a safer option that having an earthed metal enclosure. Good choice!
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dave_g
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Username: dave_g

Post Number: 918
Registered: 05-2005

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Posted on Monday, 05 December, 2016 - 02:47 pm:   Edit Post Delete Post Print Post    Move Post (Moderator/Admin Only)

Thanks, no worries. I was going to use an Aluminium enclosure from the same "sell out" bin but it was a tad too small.

This one is a tad too big, which just fuels the fire of the "OTT" squad...

Heyho, better get it wired up tonight/tomorrow or we'll be behind the neighbours!!
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dave_g
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Username: dave_g

Post Number: 919
Registered: 05-2005

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Posted on Saturday, 10 December, 2016 - 03:09 pm:   Edit Post Delete Post Print Post    Move Post (Moderator/Admin Only)

All installed. Works. Brilliant.

Wifes comment - "they're not flashing fast enough". The implications are get it off the wall, into the study, PIC out, reprogram, and, as the Haynes manual would say, "refitting is the reverse of removal".

I get told this while do some other electrical work in the house, like a contortionist, head in the ceiling, etc....

Yes dear.

Now you're being sarcastic. Oh, I give up.

Bloody marvellous, off to the next job.

Fast enough. 20Mhz PIC18F, you wanna see fast??!!
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hackinblack
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Username: hackinblack

Post Number: 733
Registered: 09-2006

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Posted on Thursday, 15 December, 2016 - 07:13 pm:   Edit Post Delete Post Print Post    Move Post (Moderator/Admin Only)

"they're not flashing fast enough"
Visions of a family strobing their way through christmas like some wierd charlie chaplin remake...

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