Making a long wharehouse with multiple sections, would like to get LED`s, can they run on low voltage?
Tom h
LED are current devices. White ones usually run around 3 volts at 20 mili-ampres. They can run at even lower voltages, its the current that is most important to LEDs
The “specified” voltage of LEDs varies by color.
They will often “run” on a lower voltage, but I’d stick to the recommended voltage.
Most important, is what David said, they are controlled by the current flowing, exceed that current and they burn out. So you need enough voltage available, and then normally a properly calculated resistor in series to control the current.
Greg
Many ebay sites have strip LEDS that run on 12 volts, can be cut to length and leads soldered on. The ones I use are warm light “Dimable” They will still light up wwith current as low as 5volts. I have used them one Aristro heavy weights and a 9 volt battery.
The 12 volt strips I have seen have 3 leds in series and these come in rolls.
A 1 amp a DC 12 volt power source would be fine for running 50 sections (due to 3 in series that is 150 leds) assuming 20 ma of current flow.
Double this if the leds are 10 ma.
And in several weeks one can get discounted outdoor led Xmas lights, but I hesitate to place line voltage lights near my trains.
For a lot of LEDs, the 12v strips are pretty inefficient, since they use current limiting resistors.
I’d use a string of LEDs and the highest voltage power supply you feel comfortable with the CL2 current limiting IC.
24 or 48 volts, and the CL2 would be the least wiring, and lowest cost.
See my page, look for CL2:
http://elmassian.com/trains/dcc-battery-rc-electronics/misc-electronics/led-lighting-basics
Greg
oops!
Ross Mansell said:
I have several 5m reels of these flexi strip leds for my aeromodeller customers and their drones…and they light up on 12v/ 1.5 amp gell battery no probs and darn bright as well.
The aeromodellers just plug them into their 12v lipo cells.I have cut off a couple of 3 led strips and mounted them in coaches and power them from a small 9v NiMh rechargheable via a simple push on/off switch mounted under the coach… Amber coloured…look great. The flexi leds have their own BUILT -IN resistors on each segment of three… A 5metre (about 15ft 300 led reel) cost me approx. $8 post free from China.
Thanks Tom, good explanations.
Going to build a long wharehouse and would like to light inside and have lamps outside on deck that will have over hangs.
Noel did one about 6-8 months ago I think, will be similiar.
Tom H
Greg Elmassian said:
For a lot of LEDs, the 12v strips are pretty inefficient, since they use current limiting resistors.
I’d use a string of LEDs and the highest voltage power supply you feel comfortable with the CL2 current limiting IC.
24 or 48 volts, and the CL2 would be the least wiring, and lowest cost.
See my page, look for CL2:
http://elmassian.com/trains/dcc-battery-rc-electronics/misc-electronics/led-lighting-basics
Greg
Thanks Greg. The CL2 looks like a wish come true. I’m going to have to try them.
FYI: I like the CL2N3’s and they do a great job, but there is two packages used from two different MFG’s. The Surface mount and the To-92 package. I have used both.
For some reason the surface mount package is not regulating properly for me, but do not have that problem with the TO-92 package.
Has anyone else had this problem?
Dennis
No the surface mount package works fine, BUT remember if you hook it up backwards once, you fry it, and then no regulation…
Greg
p.s. it comes in three different packages: http://www.supertex.com/pdf/datasheets/CL2.pdf
I used a CL2 for an LED headlight and after a couple of direction changes the LED no longer functioned. I was advised at that time to add a diode to the circuit, other than the LED, to protect the CL2.
That is good advice… LEDs do not have a high reverse voltage capability like regular diodes.
Many people run LEDs like they are a diode as well… technically they are, but they are not designed to rectify AC or protect from reverse bias.
Of course every time I mention this, tons of people who never have had a failure contest the idea. I build stuff to work and not break.
Greg
Greg, yes a protection diode is cheap insurance and a good idea. I was surprised, in tech school, when the instructor showed us that some LEDs will conduct in the opposite direction. This usually damages the LED.
A rectifier in front of the CL2 will restrict the current to only low in one direction. I use a rectifier, a large capacitor and a CL2 to run any number of LEDs from one to a dozen or more. Voltage in is variable track, or fixed DC, or AC from a power supply.
Even made my own printed circuit board to make them easy to build.
You NEED to restrict the current direction through a CL2, it will be destroyed passing current in the other direction.
So, I’m not sure of the intent of your first sentence… and what does “restrict current to only low in one direction” intend? … the CL2 limits current to 20 ma in one direction, current flow in the other direction can destroy the CL2.
If you are trying to just agree with all the points raised so far, ok, gotcha, I know you use these… if there is some other message, I’m not getting it.
The cap will smooth the half wave power if running from AC, but you would do better with a full wave bridge from the track, that will give you full wave power to the cap, better filtering, and reduction of flicker, and protect the CL2 from reverse polarity.
A further note: adding the diodes does reduce the number of LEDs that can be powered in series by a bit.
Greg