Got a set of Xmas lights. Gawd knows how they do them at the price. Blue and White. PS/controller gives a variety of programmes. Including flashing the blue and white alternately, or all on together. But only two wires from the PS. I can see reversing the polarity could have one colour or the other, but how both at once with no apparent flicker? Fast switching?
Yup pretty much... Throw a bit of PWM into the mix as well, and you should be able to get dimming and fading effects as well.
Simple digital oscillator in a chip driving a transistor on and off I'd imagine. it need only be small as little dissipation all on or all off. Brian
and quite a lot of radio interference I noticed a few years ago when messing around with a radio near a shop with them round the window. Brian
Julian Ilett explains two-wire pulse-controlled RGB LEDs here. Not sure if your blue/white is exactly the same.
That was interesting, thanks, I have some of those.
His video makes me wonder if they could be 'randomised' by first sending lots of low pulses of ever decreasing length between say 500us and
100us, then switching to a fixed 20us pulse regime.I think that would make a more interesting display.
Cheers
Fascinating devices. Googling for NorthLight products (as seen in the videos) suggest Clas Ohlsen but the site say discontinued maybe sold out until next Xmas perhaps? Anyone found a supplier with stock?
It's more than just PWM it's IC2 which uses atmel contollers to control e ach individual LED is possible .
we have this sort of thing on our lab christmas tree it has a remote contro l I can set almost any colour and slow of fast transitions. Last time when two studetns were doing selfies with my tree I used teh remote to turn it o ff, they looked worried as they thought they'd broken the lights. :-)
So it might be that a dedicted xmas tree light setup uses the above and pos sibley even cheaper.
The RGB LED strips are a somewhat more sophisticated setup than many of the cheap two wire sets of lights though. However the posh versions of them can do quite impressive lighting effects.
Wouldn't expect Amazon to provide any real details, but the pic shows a four pin connector. Which would allow three different colour LEDs to be driven in any way you can think of.
That wasn't what I was asking about.
Yes I know and that was brought last year. I can't think of why they don;t multiplex the control signals with the power, simialtr to the way old mians wireless intercomms work. Maybe that should be a studetn project.
That seems to be the type with GND and a separate power to all the R/G/B in parallel, i.e. no individual control of LEDs, but with PWM you can drive the whole string to any colour.
Some of the new ones available this year seem to do just that, just a GND and +5V rail, with colour data sent as brief pulses to 0V on the 5V rail.
Fairy lights are a well known cause of poor ADSL connections.
A neighbour seems to have a set which are RF synchronised. They have a set in a ground floor window and an identical set in a first floor window at the opposite corner to the first set. Both flash at the same rate, showing the same colours etc. at the same time.
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