owelly
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| posted on 24/11/09 at 10:56 PM |
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O/T. 50v LED lamps??
Sorry if this is in the wrong section......
At work, we have some big breakers (giant 4160v relays) and on the front of these we have indicator lamps. These are fed by a 50v supply which also
trips the breakers. In the distant past, somewhere in the 1960s, all the 50v lamps were changed for 110v lamps because the 50v ones made the lamp
holders/lenses too hot. At the moment, these lamps are pulling 3amps off the battery chargers that supply the batteries, that supply the tripping
coils and lamps.
I'm trying to find some lower consumption lamps. The lamps are a crazy size. A bit like small edison screw (SES) but smaller. I believe they are
CES (candalabra?) lamps.
However, I can't find CES lamps rated at 50 or 110volts. I can't find any LED replacements.
We can't change the voltage and we can't change the lamp holders.
So, my question is, if I was to make my own lamps, out of LEDs and resistors, what LED would I need and what resistor?
I've looked through the RS catalogue and got so confused, my eyes fell out.
Any suggestions are welcomed with open legs............
http://www.ppcmag.co.uk
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RichardK
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| posted on 24/11/09 at 11:03 PM |
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If nobody can help on here drop me a line and I'll have a word with a mate who is an led design engineer who maybe able to help. I'll
obviously have to check with him first before giving you his email!
Still chuckling about the size of that boat you've just bought  Did you think you were getting a little 4 seater?  ? ?
Cheers
Rich
Gallery updated 11/01/2011
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owelly
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| posted on 24/11/09 at 11:07 PM |
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The boat looks smaller from far away. I need to make sure Miss O doesn't get too close.......
http://www.ppcmag.co.uk
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tegwin
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| posted on 24/11/09 at 11:08 PM |
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I assume the feed for the bulbs is AC?
In which case something like this would be ideal:
http://www.simplecircuitdiagram.com/2009/05/08/led-circuit-for-ac-powerline-indicator/
You would obviously have to size your capacitor and resistor to suit your voltage, but the theory is simple enough!
------------------------------------------------------------------------------------------------------------------------
Would the last person who leaves the country please switch off the lights and close the door!
www.verticalhorizonsmedia.tv
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Madinventions
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| posted on 24/11/09 at 11:14 PM |
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Would these do the job?
RS link
Failing that, to work out the resistor value required is quite simple. A red LED has a forward voltage drop of about 1.8V (green is about 2V
normally) so the first thing to work out is how many LEDs you're going to use for each 'lamp'. Let's assume 1 for now.
Subtract the forward voltage drop from the supply voltage, 50V - 1.8V = 48.2V. Now use ohms law to work out the resistor value required to pass about
10mA. (LEDs can normally take up to 20mA, but 10mA is normally just as bright).
V / I = R, so the resitor = 48.2 / 0.01 which is 4820 ohms. So a 4.7K resistor should be fine.
To be on the safe side, you should work out the power dissipated by the resistor which is V*I = 48.2 * 0.01 = 0.48W, so you'll need a 1W
resistor.
For red leds, here's a list for multiple leds:
1 to 5 leds = 4K7, 1W
6 to 8 leds = 3K9, 0.5W
9 to 10 leds = 3K3, 0.5W
For green leds, the values are pretty much the same.
The LEDs you'll need for this are standard 3mm or 5mm radial types.
Hope this helps,
Ed.
Mojo build diary: http://www.madinventions.co.uk
Solo music project: Syrrenfor http://www.reverbnation.com/syrrenfor
View my band website:
http://www.shadowlight.org.uk
http://www.eastangliankitcars.co.uk/
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owelly
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| posted on 24/11/09 at 11:27 PM |
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Tegwin, we're 50v DC.
Ed, thats exactly the info I wanted! The MES is too small and because of the nature of the lamp holder, I can't use the MES bulbs. And
they're £5 each! I need about 150.
I'll order up some LEDs, a bag of resistors and some 12mm dia plastic rod and make my own lamps!!
Cheers.
http://www.ppcmag.co.uk
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trikerneil
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| posted on 25/11/09 at 04:56 AM |
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There's a useful LED circuit design tool HERE.
HTH
Neil
ACE Cafe - Just say No.
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02GF74
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| posted on 25/11/09 at 07:41 AM |
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quote:
Originally posted by owelly
The MES is too small and because of the nature of the lamp holder, I can't use the MES bulbs. And they're £5 each! I need about 150.
I'll order up some LEDs, a bag of resistors and some 12mm dia plastic rod and make my own lamps!!
woo hoo someone else making their own LED lamps - check out how I did mine
Use the old bulbs, smash the glass* and fitthe LED/resitor to it. Wrap cellophane (or whatever the stuff is) and than pour in glass fibre resin to
shape and keep it all together.
You may be able to saw off the glass bulb, fit the dubbind inside and glue the bulb back on.
if you choose components wisely, they should last many many years.
try 10 mA to see if it is bright enough then 15 and 20 mA.
decide what colour you want, size and if you want clear or coloured lens.
ebay has loads of LEDs, probably cheaper to get a bag from Honk Gonk, that is where I got my white LEDs from.
[Edited on 25/11/09 by 02GF74]
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owelly
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| posted on 26/11/09 at 09:10 PM |
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The holders for the lamps are 12mm so I've ordered a bundle of LEDs, some resistors and a length of 12mm clear acrylic tube. I'll let you
all know if it works!!
http://www.ppcmag.co.uk
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MikeRJ
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| posted on 26/11/09 at 11:40 PM |
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Don't enclose a resistor which is dissipating 1/2 watt, it will get ridiculously hot.
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02GF74
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| posted on 27/11/09 at 11:18 AM |
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ne more thing you may need to consider is the type of blub fitting and how to install them.
if they are bayonet tye, you are better off drilling the contents out from the rear and then hold the bulb so you can twist it into position.
my lamps were held in place by the lens and a spring.
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owelly
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| posted on 27/11/09 at 09:11 PM |
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The 1960s lamp holders use an adjustable (threaded) brass rod, fitted with a spung plunger in the end, to wind up against the lamp to push it into the
glass lens so as long as my 'lamp' is around 45mm long, it should be OK.
http://www.ppcmag.co.uk
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owelly
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| posted on 28/11/09 at 11:17 PM |
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I had a package waitng for me at work today so I flopped out the slobbering iron....
I couldn't understand why a couple out of the ten I made didn't work. Then I checked the polarity on the lamp holders and found due to the
way the panels were wired, they were the wrong way round. So I made some with the negative in the centre!
http://www.ppcmag.co.uk
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