LED "bars" not runnig at full power.

[Danz409]

ok. so i'm working on a project. (not a lightsaber) but since its in the same naborhood. i figured id ask for some help here.
the project:
i'm making a battery powered emergency light that can last a day or 2 (only at night)
the problem:
not getting full power to the LEDs.

here is the setup.

http://i.imgur.com/ijCFaJc.png

sorry. apparently the forums are now picky about sizes >.>

but yea. thats the setup. 18 LEDs in parallel with 3x 18650s. this should give the max 20ma per LED right?
i'm only getting 50ma combined on my DMM
oddly if i pull one bar off (bringing it down to 9 LEDs) it jumps UP to 70ma a little odd, anyone have any ideas what the issue is? the sensor is working fine. tested it on other units. and works flawless.
could the TIP42 switch be acting up causing these issues?

[Danz409]

also. the way i have the LEDs wired up is on copper tape found at crafting stores (used for stained glass) this tape is stuck to laxan to make a "cheap circuit board"
think this tape may be more trouble than its worth. its already had sevral cracks and breaks iv had to solder up. would it be better to get copper flashing and just glue that to some laxan instead?
normally id just use perf board but this thing needs to be ~26 inches long

[Forgetful Jedi Knight]

Offhand, I would say you should have all 18 in a parallel setup, not two sets of 9 - which is more of a seriallel setup.
When you split the current draw, you are splitting what you pull from your batteries, PLUS you are probably trying to pull more voltage than your battery can handle. The Vf is what maybe 3.2V for white? The max voltage is 3.7 for your battery solution. ;)

[Danz409]

no they are also set up in parallel

[Forgetful Jedi Knight]

If you have 2 sets of 9 and they are not connected then they are not ALL in parallel. You said you could remove a bar (and I got the impression you did it easily). Let's see a pic of the actual setup please.

[Danz409]

its currently at work. but i can make a diagram if needed.

[Forgetful Jedi Knight]

its currently at work. but i can make a diagram if needed.

A picture of the actual setup would be better. ;)

[Danz409]

ill get that tomarrow and post it

[Silver Serpent]

Verify that the control wire coming off the light sensor is negative. If it's positive, you'll need to use an NPN transistor instead.
You may not be saturating the TIP42 fully, causing it to not send the full amount of power across the line. I've run into that when using a speaker line as a control wire. You just end up with a minimal amount of current being sent across the transistor.
You could also try using a relay. Relays have a slower response time than transistors, but it shouldn't be an issue in this project.

The only other thing I can see is if your copper tape has a significant level of resistance. It's unlikely, but if you have a number of breaks, then it could have poor overall conductivity.

You're not overdrawing the batteries. 20mA * 18 LEDs = 360mA of current flow. Definitely within an 18650s ability to provide. From your diagram, all 18 LEDs appear to be in parallel.

[Forgetful Jedi Knight]

You're not overdrawing the batteries. 20mA * 18 LEDs = 360mA of current flow. Definitely within an 18650s ability to provide. From your diagram, all 18 LEDs appear to be in parallel.

With the diagram he showed, I wouldn't be so sure. If he has 2 sets of 9 in parallel (which is what his diagram indicates), it could be a seriallel situation, depending on how he has the 2 segments connected, which is why I asked to see the actual setup.