Why? reasons. mostly fox-related reasons. makes a nice light though! as you may be able to tell, I'm looking forward to this Film!
its what I'm guessing is life size at about 25CM across and uses 101 white LEDs. If anyone else wants to make one for whatever reason just ask and I can post the design files I made for it, its mostly Printed but the black part is just a drilled ABS sheet.
EDIT:- all files needed to make this can now be found here http://www.thingiverse.com/thing:1298643
its what I'm guessing is life size at about 25CM across and uses 101 white LEDs. If anyone else wants to make one for whatever reason just ask and I can post the design files I made for it, its mostly Printed but the black part is just a drilled ABS sheet.
EDIT:- all files needed to make this can now be found here http://www.thingiverse.com/thing:1298643
Category Photography / All
Species Vulpine (Other)
Size 1280 x 1054px
File Size 882.5 kB
well, its sort of easy, most of the parts are printed so you'd either need a 3D printer or to go to one of the various services that will do that for you, after that you just need a drill for the faceplate several M4 screws and either the ability to solder 101 LEDs together on the back of the plate so you'd need a soldering iron to do that part or find a ready made string of 5mm white ones, which could probably be found on ebay somewhere (or some place still selling Christmas lights!), its not really something you could get all the parts in a shop but it should be possible to get them all on-line without needing any special tools, of course if you didn't care about the yellow surround or could make one another way then it might be possible to get all the parts from a shop
Unfortunately it's more likely that the way you wired up your LEDs is what killed them, opposed to manufacturing quality.
You can't use a single current limiting resistor for that many LEDs in parallel. Slight variations in the construction of every LED in a batch means that current through that circuit won't be constant. The LEDs which see the most current will have shorter lifespans than the rest in the circuit. Over time, as each burn out the current through the other strands will see more and more current until they've all failed.
I've designed a boost converter with a 555 timer to use for my rendition of this to overcome this problem. Boosted to ~70VDC, three strands in parallel will make current-mode failure less likely.
I'll post details once completed, if you're interested =3
You can't use a single current limiting resistor for that many LEDs in parallel. Slight variations in the construction of every LED in a batch means that current through that circuit won't be constant. The LEDs which see the most current will have shorter lifespans than the rest in the circuit. Over time, as each burn out the current through the other strands will see more and more current until they've all failed.
I've designed a boost converter with a 555 timer to use for my rendition of this to overcome this problem. Boosted to ~70VDC, three strands in parallel will make current-mode failure less likely.
I'll post details once completed, if you're interested =3
You are perfectly right, wiring that many LEDs in parallel would normally be a bad idea however, it should be ok here as I am running the LEDs at nowhere near their full current, to actually get them to a level of brightness where you could look at them without it being painfully bright I ended up running them at only 75uA each when they are rated at 30mA (that gives a current for all 101 of around 2mA! and I have measured this and it is close) so yes some will still have more current than others BUT to be over their rating the current would need to be over 50 times greater in one rather that another.
the LEDs in question cost 99p for 1000 white LEDs so phenomenally cheap and I have commonly seen them fail even in single operation with their own resistor off a microcontroller pin (and that's run at about 10mA instead of the full 30) their not very good, I just have a lot of them. (and I can't find a reputable electronic components supplier that stocks 5mm white LEDs for less than 15p each) and in this specific case, well it was sort of strange, the LED was flickering on and off but not effecting the others in that chain so it must have been going short and after a few days it actually fixed itself, its working again now.
I would be interested in seeing your circuit however!
the LEDs in question cost 99p for 1000 white LEDs so phenomenally cheap and I have commonly seen them fail even in single operation with their own resistor off a microcontroller pin (and that's run at about 10mA instead of the full 30) their not very good, I just have a lot of them. (and I can't find a reputable electronic components supplier that stocks 5mm white LEDs for less than 15p each) and in this specific case, well it was sort of strange, the LED was flickering on and off but not effecting the others in that chain so it must have been going short and after a few days it actually fixed itself, its working again now.
I would be interested in seeing your circuit however!
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