5ma smd leds

[cteno4]

Anyone have ideas for sources of 5ma smd leds cheap? they are like 5x or more as expensive (thru mouser and the like) than the standard 20ma smd leds. They are not the norm so reason why they are not available thru the usual cheap channels, but thought i would check.

 

thinking of moving to using them in a lot of projects as many times im dimming smd 20ma quite a bit and thus wasting most of the power via the resistor, seems silly. plus some things that i was thinking of doing requiring 100 or more leds were going to be a chunk of power, so anything to cut the power usage down would be great.

 

cheers

 

jeff

[marknewton]

G'day Jeff,

 

DCC Concepts have a good range of LEDs, perhaps they have what you're looking for.

 

http://www.dccconcepts.com/index_files/DCCwhiteled.htm

 

All the best,

 

Mark.,

[cteno4]

Mark,

 

Thanks. Didn't see any 5ma smd leds LEDs, they are a rare beastie. Mouser is looking the best right now at about 15 cents each.

 

Jeff

[E6系]

Hello Mr Jeff,

 

I am wondering why you wish to draw such a low current?

[kvp]

100 x 20 mA = 2000 mA = 2 A (@12V = 24 watts)

100 x 5 mA = 500 mA = 0.5A (@12V = 6 watts)

 

Of course connecting 3 in series with a single resistor and a 12V source would mean better economics, so 100 x 20 mA in groups of 3 is just 0.66 A or 8 watts. From the 5 mA type the result is 166 mA or 2 watts.

 

Not to mention if a normal led at 20 mA is too bright, then a 5 mA led at 5 mA will be too bright too, so it can be dimmed down further and can also be connected in series to reduce wasted power even further. Also less power used means less heat and less chances for the plastic structures to melt.

[cteno4]

i normally run small lighting projects at 3-5v to reduce power waste (5v power supplies are very cheap and easy to come by in many ways). many situations i dont want to run series sets. I was finding i was dropping many of the 20ma smd leds down to less than 5ma for what i wanted. hence the idea of just starting with 5ma to save on power and just less heat dissipation as well on the project ideas i had with larger numbers of leds.

 

I realized most of my power was going into the resistors and just a waste. 20ma are normally used as thats just the standard out there and 99% of the small leds out there are 20ma.

 

also wanted to play with the idea of putting 6 5ma leds into carriages for lighting and keep the overall current draw down (lit 16 car train with 2 20ma leds in each car is .64amps and tough to do with smaller power packs especially with multiple motor cars.

 

going to get a small set to mess with.

 

jeff

[Ochanomizu]

Hello Mr kvp,

 

I am curious to know how much you pay per kW/h for electricity in your country?

 

100 x 20 mA = 2000 mA = 2 A (@12V = 24 watts)

100 x 5 mA = 500 mA = 0.5A (@12V = 6 watts)

[miyakoji]

Ochanomizu, this wikipedia page has an interesting chart: http://en.wikipedia.org/wiki/Electricity_pricing .  I also found this for US prices: http://www.eia.gov/electricity/monthly/epm_table_grapher.cfm?t=epmt_5_6_a .  The costs in Hungary and Japan are very similar, although the data is 2 years apart.  It's interesting how much this varies from country to country.

[cteno4]

Not worried about the cost, just keeping the amps down for projects that have a lot LEDs in a small price.

 

Something in me does not like trimming off most of the power in heat.

 

Jeff

[kvp]

The biggest problems are heat which can damage/warp plastic buildings and vehicles over time, getting the right power supply and getting the power to the leds. It's easier to get a 0.75 A regulated adapter and use standard computer ribbon cables than getting a 2 A adapter and using heavier cables. Also when someone is running everything off the auxiliary output of a transformer or lighting a train with a 750 mA throttle, then using more than half the power for lighting instead of moving the train can be a problem.

 

The same problem was clearly visible in 1:1 scale in the 1930-ies when the first hungarian AC electric locomotives begin operation (with electromechanical VVF drives!). The railroad traction and household network is shared in the whole country, so the same power is used for lighting and running the trains. The result of these early 1.6 MW high speed locomotives were that they dimmed the city lights when they went past a city. The timetable had to be coordinated that when one locomotive was accelerating in an area, another one had to be braking, so the regenerative feedback into the network cancelled out the power draw. We finally got rid of the problem in the 1960-ies with the first solid state AC locomotives. They pretty much look and work like a japanese ED75.

 

ps: Electricity prices in Hungary are tied to the political weather. One party supports the free market, which means monopolistic prices from a single provider, while the other one is for state regulated nonprofit prices. Currenty the second one (the democrats) is in power and they are trying to get the price down by building more government owned power stations, while the other party (the 'socialists') is campaigning for a capitalistic market. (yes, they are only called socialists, they are actually liberal capitalists) So depending on the outcome of the next election we could end up with 120% self sufficient generating capacity from local fuels (nuclear/geotermal) or 80% foreign import (with some coal based local power added). The +20% percent in the current government's plan is allegedly needed for export and/or electric car charging. In short, yes, the hungarian politics are just like the japanese...  :)

[Melandir]

Not worried about the cost, just keeping the amps down for projects that have a lot LEDs in a small price. Something in me does not like trimming off most of the power in heat. Jeff

 

Jeff,

try this place for your led

It's one of the best place I know to find unusual leds

 

http://stores.ebay.it/ledbaron?_rdc=1

[Ochanomizu]

Hello Mr Jeff,

 

Did you purchase your LED?  I would like to know how you proceed with this idea.

 

Also, I believe that purpose made light kits for N-gauge Japanese models use a single LED per car.  Is the quality of light not meeting your expectations?

 

also wanted to play with the idea of putting 6 5ma leds into carriages for lighting and keep the overall current draw down (lit 16 car train with 2 20ma leds in each car is .64amps and tough to do with smaller power packs especially with multiple motor cars.

[cteno4]

Not yet, I have a couple of little projects that need some parts as well so waiting to order them all together.

 

I want to experiment some more with both car and structure lighting for finer detail.

 

Cheers,

 

Jeff

Edited January 28, 2014 by cteno4