Andy48 Posted December 26, 2016 Share Posted December 26, 2016 OK, I know you plug the transformer into the mains and away they go... I bought some icicle lights which work in alternate banks, switching on, off and dimming. Both banks can be on or just one. Using my simplistic electrical knowledge it would appear that you need 3 leads, a power lead to each bank and a common return. However these lights only have two leads, just one live and one return, so how does the system activate each bank? Quote Link to comment Share on other sites More sharing options...
Gary Manuel Posted December 26, 2016 Share Posted December 26, 2016 Everyone knows fairy's are magic. Quote Link to comment Share on other sites More sharing options...
Martin Harris - Moderator Posted December 26, 2016 Share Posted December 26, 2016 Changing polarity of the supply with blocking diodes? Quote Link to comment Share on other sites More sharing options...
Gary Manuel Posted December 26, 2016 Share Posted December 26, 2016 Posted by Martin Harris on 26/12/2016 21:08:47: Changing polarity of the supply with blocking diodes? I think they use NPN transistor in one leg and PNP in the other, but that's basically it. Quote Link to comment Share on other sites More sharing options...
Shaunie Posted December 26, 2016 Share Posted December 26, 2016 I strongly suspect it will be two strings of LEDs back-to-back (known as inverse parallel). Apply voltage in one direction and one string will light, reverse the polarity and the other string will light. For effects, the controller is probably generating a square wave ac waveform and controlling the brightness of each string by varying the duty cycle of each half (positive for one string and negative for the other). Shaunie. Quote Link to comment Share on other sites More sharing options...
Chris Walby Posted December 26, 2016 Share Posted December 26, 2016 Martin is right... the give away is in the name L.E.D's Light Emitting Diodes....so if you run all of the LED's in parallel, but half are one way around & the other lot the other, you can control them independently depending on which half cycle of the ac supply you change... I liked the "old" filament ones in series....you get 240V ac across the faulty lamp...! What do the say " if it didn't kill you it made you stronger wiser! Quote Link to comment Share on other sites More sharing options...
Andy48 Posted December 26, 2016 Author Share Posted December 26, 2016 Ok thought about that but how do you get both strings to light at once? I wonder if the switching is fast enough to ensure each string remains lit? Edited By Andy48 on 26/12/2016 21:25:50 Quote Link to comment Share on other sites More sharing options...
John Privett Posted December 26, 2016 Share Posted December 26, 2016 I started to reply to this, then got distracted, and somehow lost my reply! Anyway Shaunie has said pretty-much what I was thinking - and probably summarised it a bit more concisely than I was doing in my lost-reply! Quote Link to comment Share on other sites More sharing options...
John Privett Posted December 26, 2016 Share Posted December 26, 2016 Posted by Andy48 on 26/12/2016 21:24:42: Ok thought about that but how do you get both strings to light at once? I wonder if the switching is fast enough to ensure each string remains lit? You don't need to keep the LEDs 'lit' - just switch them fast enough to fool the human eye into thinking they're lit. A lot of LEDs used in displays are not actually on permanently even when they look as if they are. Quote Link to comment Share on other sites More sharing options...
Chris Walby Posted December 26, 2016 Share Posted December 26, 2016 Shaunie, I don't think you can back to back them as the reverse bias current is too small to get the other one to light up. It would be possible to do that with three wires or as I suggested run them in parallel just some facing one way and the others the opposite way. Of course depending on the applied voltage you could have a string of LED's in one direction and another string in them in the other... that way you could control each alternate string as Andy48 suggested. Personally I was more concerned that I was at the top of a ladder that my wife was footing while hanging them on the gutters than thinking how they worked... Quote Link to comment Share on other sites More sharing options...
John Rudd Posted December 26, 2016 Share Posted December 26, 2016 In electronics there's a technique called 'charlieplexing' where leds connected back to back can be lit alternately, as Shauni suggested earlier..... Quote Link to comment Share on other sites More sharing options...
Former Member Posted December 26, 2016 Share Posted December 26, 2016 [This posting has been removed] Quote Link to comment Share on other sites More sharing options...
Shaunie Posted December 27, 2016 Share Posted December 27, 2016 Chris, two strings of LEDs placed in inverse parallel will work fine. The blocking voltage of an LED is not great but is better than the forward voltage (Vf), if in doubt place a diode in series. I know that's how I would do it. Shaunie. Quote Link to comment Share on other sites More sharing options...
Gary Manuel Posted December 27, 2016 Share Posted December 27, 2016 THIS explains one way of how the circuitry works, with driver circuitry and oscilloscope waveforms. Your lights are type 2 as shown at the bottom of the page. Quote Link to comment Share on other sites More sharing options...
Stephen Jones Posted December 27, 2016 Share Posted December 27, 2016 LOL , I have been ask that same question many years ago, By the bin men, Taxi drivers, or anyone who passed my house "how do you make you're lights flash like that". LOL i replied i plug them in. But in fact i made a opto isolator board and wired it to my 8 bit printer port of my Sinclair computer wrote a small basic program to switch the outputs in sequence . The eight sets of lights where of course the 240 volt daisy chain type. I was the talk of the neighborhood with taxi drives often stopping to watch them. My partner whom i was courting at the time was embarrassed to be dropped of by taxi, so asked that she be dropped off at the end of the street , Steve Edited By Stephen Jones on 27/12/2016 01:24:45 Quote Link to comment Share on other sites More sharing options...
Max Z Posted December 27, 2016 Share Posted December 27, 2016 Posted by Stephen Jones on 27/12/2016 01:22:26: and wired it to my 8 bit printer port of my Sinclair computer Wow, that IS many years ago Steve! Max. Quote Link to comment Share on other sites More sharing options...
Don Fry Posted December 27, 2016 Share Posted December 27, 2016 Posted by Tom Sharp 2 on 26/12/2016 23:04:44: Mine have stopped working today. Can't understand it they are only 30 years old. That's cos yer fairy has died. Quote Link to comment Share on other sites More sharing options...
Geoff Jackson Posted December 27, 2016 Share Posted December 27, 2016 Everyone knows that Fairies dont die - that would be cruel! Quote Link to comment Share on other sites More sharing options...
Andy48 Posted December 27, 2016 Author Share Posted December 27, 2016 Thanks everybody. It confirms one thing though, I ought to buy myself a decent fast oscilloscope one day. Quote Link to comment Share on other sites More sharing options...
cymaz Posted December 27, 2016 Share Posted December 27, 2016 Posted by Donald Fry on 27/12/2016 09:07:16: Posted by Tom Sharp 2 on 26/12/2016 23:04:44: Mine have stopped working today. Can't understand it they are only 30 years old. That's cos yer fairy has died. Don't sneeze as well. Every time you sneeze a fairy dies....Tinkerbell told me that! Quote Link to comment Share on other sites More sharing options...
Gary Manuel Posted December 27, 2016 Share Posted December 27, 2016 Posted by Andy48 on 27/12/2016 11:32:23: Thanks everybody. It confirms one thing though, I ought to buy myself a decent fast oscilloscope one day. I bought a "scrap" Telequipment D54 scope from work a few years. Cost me £5 plus a couple of hours of my time to fix the fault. Still going strong. Quote Link to comment Share on other sites More sharing options...
Don Fry Posted December 27, 2016 Share Posted December 27, 2016 Posted by cymaz on 27/12/2016 12:45:43: Posted by Donald Fry on 27/12/2016 09:07:16: Posted by Tom Sharp 2 on 26/12/2016 23:04:44: Mine have stopped working today. Can't understand it they are only 30 years old. That's cos yer fairy has died. Don't sneeze as well. Every time you sneeze a fairy dies....Tinkerbell told me that! Only if you pass wind at the same time. Something to do with sitting on Christmas trees. Quote Link to comment Share on other sites More sharing options...
Focae Posted December 27, 2016 Share Posted December 27, 2016 Posted by Geoff Jackson on 27/12/2016 10:13:31: Everyone knows that Fairies dont die - that would be cruel! Only if you pull their wings off!! Quote Link to comment Share on other sites More sharing options...
Geoff Jackson Posted December 27, 2016 Share Posted December 27, 2016 Bet you did that to flies too! Quote Link to comment Share on other sites More sharing options...
Gary Manuel Posted December 27, 2016 Share Posted December 27, 2016 I've never really understood why people string masses of fairy lights across the front of their houses. BUT this is really amazing - I would even go so far as to call it an art form. Quote Link to comment Share on other sites More sharing options...
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