Author Topic: LED Filament clock display  (Read 9394 times)

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Online mikeselectricstuff

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LED Filament clock display
« on: April 06, 2015, 05:33:09 AM »
Messing with filament strips from LED lamps.
Clock design page : http://electricstuff.co.uk/ledfilclock.html

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Offline Lightages

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Re: LED Filament clock display
« Reply #1 on: April 06, 2015, 06:39:09 AM »
Those LED filaments look like they have lots of potential uses and also fun to play with. Thanks for sharing.
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Offline PeterFW

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Re: LED Filament clock display
« Reply #2 on: April 06, 2015, 07:37:26 AM »
Messing with filament strips from LED lamps.

Very interesting, thanks for posting and making a video about them!
 

Offline davidf2281

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Re: LED Filament clock display
« Reply #3 on: April 06, 2015, 07:52:52 AM »
Love the look of the clock.

Just had a quick gander on ebay but no immediate hits for filament LEDs under 99p -- any recommendation for sellers?

David.
 


Offline davidf2281

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Re: LED Filament clock display
« Reply #5 on: April 06, 2015, 08:01:09 AM »

Lovely, thanks Mike.

David.
 

Offline davidf2281

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Re: LED Filament clock display
« Reply #6 on: April 06, 2015, 08:08:26 AM »

Also, keep up the excellent work with the YouTube vids -- they're v entertaining.

David.
 

Offline jimon

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Re: LED Filament clock display
« Reply #7 on: April 06, 2015, 08:33:43 AM »
Ordered some of them, will see what is possible with them :)
 

Offline IanB

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Re: LED Filament clock display
« Reply #8 on: April 06, 2015, 09:37:56 AM »
Strangely, I've been looking for those "filament" style lamps here in the USA and I have not seen any yet. Also, it seems (from watching Clive) that Poundland sells many more interesting items than I have seen in the likes of Dollar Tree here. I guess when it comes to bargains the greater value of the pound leads to more options than a lowly dollar permits.

As far as driving those filaments, would a VFD driver like the MAX6291 be of any use? It seems the voltages are similar.
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Online mikeselectricstuff

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Re: LED Filament clock display
« Reply #9 on: April 06, 2015, 09:48:22 AM »
Strangely, I've been looking for those "filament" style lamps here in the USA and I have not seen any yet. Also, it seems (from watching Clive) that Poundland sells many more interesting items than I have seen in the likes of Dollar Tree here. I guess when it comes to bargains the greater value of the pound leads to more options than a lowly dollar permits.

As far as driving those filaments, would a VFD driver like the MAX6291 be of any use? It seems the voltages are similar.
probably - not looked at it, but it's Maxim, so expensive, if you can even get it.
TPIC6B595 is cheap - you can also use the slightly cheaper TICP6C595, which ISTR has a slightly lower clamp voltage, but still useable.
Hell if you get the voltage spot-on you could probably even drive them direct from a PIC output, tough that would  be a rather bad idea.
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Offline DanielS

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Re: LED Filament clock display
« Reply #10 on: April 06, 2015, 09:59:18 AM »
Strangely, I've been looking for those "filament" style lamps here in the USA and I have not seen any yet.

As far as driving those filaments, would a VFD driver like the MAX6291 be of any use? It seems the voltages are similar.
They might not be available in NA (at least not through official channels) due to not meeting safety requirements: no fuse, no resistor to limit current if the diode bridge shorts out, possibly nasty stuff if the current-limiting capacitor shorts out too and likely more.

As for the driving, as Mike said, you could probably drive those using regular 5V TTL chips by tweaking the supply voltage since most of the voltage gets dropped across the LED string: simply set your supply voltage to NxVF + 3V, then set RS to 2.7V/IF allowing 0.3V VCEsat on TTL outputs, this way the outputs should not get pulled much beyond VCC.
 

Online mikeselectricstuff

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Re: LED Filament clock display
« Reply #11 on: April 06, 2015, 10:05:11 AM »
Strangely, I've been looking for those "filament" style lamps here in the USA and I have not seen any yet.

As far as driving those filaments, would a VFD driver like the MAX6291 be of any use? It seems the voltages are similar.
They might not be available in NA (at least not through official channels) due to not meeting safety requirements: no fuse, no resistor to limit current if the diode bridge shorts out, possibly nasty stuff if the current-limiting capacitor shorts out too and likely more.
But no reason they couldn't be made safe with minimal extra cost -just a fuseable resistor and maybe a bleed resistor across the cap.
I don't recall having seen them in shops in the UK yet, though quite a few on Amazon
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Offline IanB

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Re: LED Filament clock display
« Reply #12 on: April 06, 2015, 10:16:28 AM »
I don't recall having seen them in shops in the UK yet, though quite a few on Amazon
That was the reason for my Poundland comment. I thought Clive had found some in there, though I may be thinking of something else.
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Offline Hero999

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Re: LED Filament clock display
« Reply #13 on: April 06, 2015, 08:05:30 PM »
I thought these LED filaments require a relatively high voltage >50V so powering directly from a MCU pin is out of the question.

I don't believe Clive found an LED filament lamp in Poundland. I think there's some confusion over a video he did about a cheap LED lamp from Poundland, with a light sensor on it, which is very inefficient because it used a big resistor and consumed just as much power, whether it's on or off.
« Last Edit: April 06, 2015, 10:50:51 PM by Hero999 »
 

Offline Psi

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Re: LED Filament clock display
« Reply #14 on: April 06, 2015, 08:23:56 PM »
Could use this dcdc module to generate 72V from a more reasonable voltage
They're $14 each from digikey and come in 5V input and 12V input versions.
$14 isn't that cheap but it saves you needing to make a HV supply yourself for a one-off project.

Output is -72V @ 42mA  (42mA if only loading one output, it also has -24V and -48V  output).
You could drive 42 of these led strings at 1mA each with one module
They're isolated so you can easy use them around the other way for +72V instead of -72V

http://www.digikey.com/product-detail/en/NMT1272SC/811-1584-5-ND/1927145
http://power.murata.com/data/power/ncl/kdc_nmt.pdf
« Last Edit: April 06, 2015, 08:34:35 PM by Psi »
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Online mikeselectricstuff

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Re: LED Filament clock display
« Reply #15 on: April 06, 2015, 10:21:38 PM »
Could use this dcdc module to generate 72V from a more reasonable voltage
They're $14 each from digikey and come in 5V input and 12V input versions.
$14 isn't that cheap but it saves you needing to make a HV supply yourself for a one-off project.

Output is -72V @ 42mA  (42mA if only loading one output, it also has -24V and -48V  output).
You could drive 42 of these led strings at 1mA each with one module
They're isolated so you can easy use them around the other way for +72V instead of -72V

http://www.digikey.com/product-detail/en/NMT1272SC/811-1584-5-ND/1927145
http://power.murata.com/data/power/ncl/kdc_nmt.pdf
72V is a bit marginal,but you could stack it on top of the 5V rail  for 77V which would be ideal

Some cheap ones here - $6.88 - presumably surplus
http://www.componentsdirect.com/murata-manufacturing-co-nmt1272sc.html?utm_source=supplyFrame&utm_medium=buyNow
« Last Edit: April 06, 2015, 10:25:11 PM by mikeselectricstuff »
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Offline ConKbot

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Re: LED Filament clock display
« Reply #16 on: April 06, 2015, 10:45:28 PM »
I thought these LED filaments require a relatively high voltage >50V so powering directly from a MCU pin is out of the question.

Diodes always drop a forward voltage drop, it just drops as diode current drops. It certainly wouldnt be robust, or even good design practice, but if you're only feeding them a few mA, and if the Vf @ 1mA of the string was 70V, and the vF at 0-100nA (whatever the leakage of the uC pin is) is 66V, with a 71V supply, and 1V across your dropper resistor when its on, then the MCU should only see 5V on its input pin.  But you're relying on a whole lot to go right there. Could it work with a bit of luck in the voltages of the diode string working out and tweaking your supply just so? Maybe. And dont count on much surviving if a few of the dies on the LED string short out  ;D
 

Offline Hero999

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Re: LED Filament clock display
« Reply #17 on: April 06, 2015, 10:52:06 PM »
I thought these LED filaments require a relatively high voltage >50V so powering directly from a MCU pin is out of the question.

Diodes always drop a forward voltage drop, it just drops as diode current drops. It certainly wouldnt be robust, or even good design practice, but if you're only feeding them a few mA, and if the Vf @ 1mA of the string was 70V, and the vF at 0-100nA (whatever the leakage of the uC pin is) is 66V, with a 71V supply, and 1V across your dropper resistor when its on, then the MCU should only see 5V on its input pin.  But you're relying on a whole lot to go right there. Could it work with a bit of luck in the voltages of the diode string working out and tweaking your supply just so? Maybe. And dont count on much surviving if a few of the dies on the LED string short out  ;D
Oh I see.

I agree it's not good design practise and LEDs have a negative temperate coefficient which makes it worse.
 

Offline amyk

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Re: LED Filament clock display
« Reply #18 on: April 06, 2015, 11:10:14 PM »
I feel like the Chinese are going to start selling a version of this that runs everything off a capacitive dropper... and uses an ASIC that integrates the HV constant-current drivers and clock logic.
 

Offline Hero999

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Re: LED Filament clock display
« Reply #19 on: April 07, 2015, 02:48:47 AM »
How about using a mains transformer and a capacitive voltage multiplier to power the LED filaments?
 

Offline DanielS

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Re: LED Filament clock display
« Reply #20 on: April 08, 2015, 10:29:31 AM »
I agree it's not good design practise and LEDs have a negative temperate coefficient which makes it worse.
Depending on how many mA you want to put through the string and how many volts that resistor might need to drop, it should be possible to replace the current-limiting resistors with a JFET as a single component (roughly) constant current element.
 

Offline TerminalJack505

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Re: LED Filament clock display
« Reply #21 on: April 08, 2015, 10:58:02 AM »
If you're just needing to boost a DC voltage and don't need a lot of current (< 30mA) then you could probably use the scavenger boost converter to drive the filaments.  Just swap-out the 5V Zener for a ~75V Zener.

I've only played around with it in the simulator but it should work.
 

Offline Hero999

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Re: LED Filament clock display
« Reply #22 on: April 09, 2015, 12:27:43 AM »
I agree it's not good design practise and LEDs have a negative temperate coefficient which makes it worse.
Or you could add an emitter resistor to the driver transistor.
Depending on how many mA you want to put through the string and how many volts that resistor might need to drop, it should be possible to replace the current-limiting resistors with a JFET as a single component (roughly) constant current element.
 

Offline PedroDaGr8

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Re: LED Filament clock display
« Reply #23 on: April 09, 2015, 02:06:29 AM »
Strangely, I've been looking for those "filament" style lamps here in the USA and I have not seen any yet.

As far as driving those filaments, would a VFD driver like the MAX6291 be of any use? It seems the voltages are similar.
They might not be available in NA (at least not through official channels) due to not meeting safety requirements: no fuse, no resistor to limit current if the diode bridge shorts out, possibly nasty stuff if the current-limiting capacitor shorts out too and likely more.

As for the driving, as Mike said, you could probably drive those using regular 5V TTL chips by tweaking the supply voltage since most of the voltage gets dropped across the LED string: simply set your supply voltage to NxVF + 3V, then set RS to 2.7V/IF allowing 0.3V VCEsat on TTL outputs, this way the outputs should not get pulled much beyond VCC.

I've seen these used all over the place here in San Diego, starting mid last year. I have even seen them for sale in a few stores but usually at around $5-10/bulb.
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Offline cimmo

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Re: LED Filament clock display
« Reply #24 on: April 09, 2015, 07:31:59 AM »
This looks like it'll do the job:
http://www.ebay.com.au/itm/321664475968
"100W DC-DC Boost Converter 10-32V to 60-97V Step Up Power supply module" - ($5.36USD incl ship)

And Aliexpress has "10pcs/lot 1W COB LED Filament Lamp Bulb Globe Candle Light Source Warm White Pure White DIY" for $4.69 USD (incl ship)
http://www.aliexpress.com/item/10pcs-lot-1W-COB-LED-Filament-Lamp-Bulb-Globe-Candle-Light-Source-Warm-White-Pure-White/32274032926.html

« Last Edit: April 09, 2015, 07:54:36 AM by cimmo »
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