Formation and strobe light installation

Grouncontrol · Post by **Grouncontrol** » Thu Feb 24, 2011 3:26 pm

Let me preface this by saying that since joining starship modelers I've read so many great posts and great advice to help out some of us less skilled and/or experienced modelers. My dilemma is this: through alot of research and trial and error, I now have my circuits designed for the formation lights and the strobes on the enterprise. What I need some advice on is this, how to get a 3mm led to show through a hole designed for the clear model part which is significantly smaller. Do I drill the hole and make it bigger, or do I try and shave the led to fit.

en'til Zog · Post by **en'til Zog** » Thu Feb 24, 2011 11:27 pm

You can flatten the domed end of your 3 mm LED and superglue the clear model part to it, using the model part as a "light pipe".

You can also shorten the LED itself as long as you don't damage the actual LED crystal or the TEEEENY little gold wire that bridges between the top of the crystal and the lead next to it.

You can turn down a 3 mm LED to fit. (Get several "sacrificial" LEDs in case of problems.)

Or look for 2 mm LEDs, maybe at Super Bright LEDs.

robiwon · Post by **robiwon** » Fri Feb 25, 2011 5:24 am

You could also use fiber optic as well. How big is the hole?

USS Atlantis · Post by **USS Atlantis** » Fri Feb 25, 2011 5:42 am

en'til Zog wrote:You can flatten the domed end of your 3 mm LED and superglue the clear model part to it, using the model part as a "light pipe".

You can also shorten the LED itself as long as you don't damage the actual LED crystal or the TEEEENY little gold wire that bridges between the top of the crystal and the lead next to it.

You can turn down a 3 mm LED to fit. (Get several "sacrificial" LEDs in case of problems.)

Or look for 2 mm LEDs, maybe at Super Bright LEDs.

Unique LEDs carries 1.8mm

Else use the fiber optic trick

Grouncontrol · Post by **Grouncontrol** » Thu Mar 17, 2011 12:01 pm

USS Atlantis wrote:
en'til Zog wrote:You can flatten the domed end of your 3 mm LED and superglue the clear model part to it, using the model part as a "light pipe".

You can also shorten the LED itself as long as you don't damage the actual LED crystal or the TEEEENY little gold wire that bridges between the top of the crystal and the lead next to it.

You can turn down a 3 mm LED to fit. (Get several "sacrificial" LEDs in case of problems.)

Or look for 2 mm LEDs, maybe at Super Bright LEDs.
Unique LEDs carries 1.8mm

Else use the fiber optic trick

just recieved my order of 1.8 mm leds from unique-leds. they should do the trick! thanks for the advice!

Grouncontrol · Post by **Grouncontrol** » Sun Mar 20, 2011 11:33 am

I have one more question regarding these lights. I've got 1.8 mm leds that will work perfectly in the model, but they are all white. Will painting the ends with clear red and clear green for the port and starboard formation lights do anything bad to the leds?
Probably a stupid question, but where I'm trying to build this on a budget, I'd really hate to ruin any of my led's.

USS Atlantis · Post by **USS Atlantis** » Sun Mar 20, 2011 1:41 pm

All whites?

I would have ordered the colored ones - ya, they all are "water clear", which means when off they look like white ones, but the "doping" of the diode determines color

Otherwise, ya - you can use transparent paints (Tamiya Acrylics, MM Acryl or even clear art paint from Michaels

Grouncontrol · Post by **Grouncontrol** » Sun Mar 20, 2011 4:33 pm

Thanks Ken. The only reason I decided to go all white, is because I've read that different colored LEDs run at different voltages and would require different current limiting resistors than the clear ones do.

USS Atlantis · Post by **USS Atlantis** » Sun Mar 20, 2011 4:49 pm

There is that, though you can "cheat"

My strobe circuit for the TOS has a Red and a Green - different voltages, but I run them in series, since they use the same current draw

9v->Red(2.2v)->Green(3.2v) = 180ohm

Where as

9v->Red = 390ohm
and
9v->Green = 330ohm

So, one resistor, of a lower value results in less power waste and less heat generated

Realize that each resistor you have in there generates heat - and the higher the value, the more heat it generates

So the trick is to keep the resistors low in both number and rating

Grouncontrol · Post by **Grouncontrol** » Sun Mar 20, 2011 7:30 pm

I'm running my LEDs in parallel. I seem to remember reading in one of the other threads that LEDs run in parallel use less current. I've also seen on a wip somewhere else where a person was using only 1 current limiting resistor on a parallel string of LEDs. So, I soldered my clr's directly onto my pc board which will be in the base stand and am planning on running the wires from there to the LEDs in the model.

USS Atlantis · Post by **USS Atlantis** » Sun Mar 20, 2011 7:46 pm

Grouncontrol wrote:I'm running my LEDs in parallel. I seem to remember reading in one of the other threads that LEDs run in parallel use less current.

I dunno where - here's how you always calculate for voltage/current

series = voltages add, current remains the same
parallel = voltage remains the same, current adds

So running in parallel, you're drawing more current, which will heat up not only the resistor, but the power supply as well

Always better to use as much voltage as possible from PS and reduce current draw to minimum

Grouncontrol wrote:I've also seen on a wip somewhere else where a person was using only 1 current limiting resistor on a parallel string of LEDs. So, I soldered my clr's directly onto my pc board which will be in the base stand and am planning on running the wires from there to the LEDs in the model.

So long as all the LED's are of the same specifications, yes, you can do that - I do it myself with my rotating warp-bussard controller - which looks pretty neat

Grouncontrol · Post by **Grouncontrol** » Sun Mar 20, 2011 8:25 pm

Ya, all the LEDs in my parallel circuits are exactly the same, for the reasons stated above.
Just re-read your post and am slapping my forehead. You're right, I'm way wrong. It was because I was using a 9v battery as my power source I needed to run my LEDs in parallel and not in series because of the voltage draw. Thanks again!

USS Atlantis · Post by **USS Atlantis** » Mon Mar 21, 2011 3:56 am

Grouncontrol wrote:Ya, all the LEDs in my parallel circuits are exactly the same, for the reasons stated above.
Just re-read your post and am slapping my forehead. You're right, I'm way wrong. It was because I was using a 9v battery as my power source I needed to run my LEDs in parallel and not in series because of the voltage draw. Thanks again!

If there's still time - here's how I would run those

Run the LED's in strings of 3

So if there's 9 total, you'd have 3 parallel runs of 3 in series

Advantages

1) Each white LED uses 2.8-3.5v - so say it uses 3.0 - now you only need a minimal resistor - 10ohms or so - even if your draw voltage matches the source voltage, it's still a good idea to put a small-value resistor in there

2) Current draw is reduced to the minimum possible, there-by extending battery life - 9 LED's in parallel will draw 180 Ma, 3 strings of 3 will draw 60 Ma - 1/3 the current draw extends the life of the battery by 3x - look at the MaH rating of the battery - divide that by the Ma draw of the circuit - that's your battery life (don't forget that any IC's are gonna take some of that power too)

Disadvantage

1) If one LED in a string goes out, the entire string will be dark

So you have to decide what the best course for you is

Grouncontrol · Post by **Grouncontrol** » Mon Mar 21, 2011 10:30 am

thanks ken. You.ve certainly given me plenty of options! I'm looking forward to actually building this beast now.