Issue with general griecous econ board

[Baboon]

Hi all. I'm having an interesting issue with one of these, . I'm making two lightsabers for two kids, using the board from that saber. One has a green LED and one has a amber LED. The green one lights up fine (the LED is a little dim, but I'm not using fresh batteries just so I can test), the amber one however will not light up all the way.

I was thinking that maybe I'm using the wrong resistor, but with the resistor I have on it and plugging directly into a battery pack it's much brighter, and no matter how I wire the board up the amber LED just will not get full power, but the green LED on either board lights up fine. I have tested the amber LED on both boards and it's the same. So I'm not 100% sure whats going on, and was hoping someone has experience with this board and can tell me I'm being a n00b and have it wired wrong.

Thanks in advance.

[Baboon]

I just tested both LED's on a saber that I know works just fine, and both LED's lit up as bright as could be, so I don't know whats going on

[Obi1]

Did you try to measure the voltage on the amber LED with a multimeter? Dim means, either voltage is low or too high. Most of the case it's too low. Which is quite interesting in this case, since a gree die has a higher forward voltage than the amber and the gree you had worked fine with the same board... But we will know more once you have that voltage reading.

[Baboon]

I think it has to do with the negative leads for the LED not giving enough amperage? (not sure if amps or voltage). With both LEDs hooked up to either board if I have the negative from the LED going to the board, it has the amber LED dim and the green one slightly dim, if I take the negative from the LED and go directly into the negative on the battery pack, both are full brightness. I'm thinking that the board just can't provide enough from the negative contacts. One way I can think of to get around this would be to add a second latching switch to control just the LED, but that would have the side effect of no FoC (which wouldn't be that bad, I have another saber set up like that).

I'll have to get my hands on a voltmeter to see whats what.

[Sevinzol]

Sounds like you need a relay to bypass the low power coming from the board.
check the sticky threads here:
Cutaway-views-and-wiring-schematics
a power extender might do that same trick but I've not done either yet.

[Obi1]

From the small pic in the first post I see that you have the kind of saber with a few small LED's at the base of the blade, and the blade is foldable, is that correct?
I think in this case that Sevinzol is right, you need a power extender/external Transistor (bipolar or MOSFET, check the link above). From you description the picture gets clearer: the board negative goes through a transistor to GND acting as a switch itself. but since in the orignal setup this transistor needs to switch small currents (or loads), it is a cheap one (rather high resistance over the channel, you can think about it like a resistor in the path limiting the current to your LED).
Only Thing still confusing me: according to theory the green (having a higher threshold voltage) should be more dim than the amber (lower threshold). But it could be that the green you perceive as more bright due to the fact that green LED's are the rbightest ones (mcd values) and red-likes are the dimmest generally (that is, if you drive a green, a blue and a red/amber with the max voltage allowed, the green one will appear to be the brightest, same types of LED's assumed).

OMG, I again could not resist writing too much. So in short: that board probably cannot supply enough current through your LED, Sevinzol already put you on the right track.

[Baboon]

Thanks a lot for the reply's. Interesting thing happened last night when I was playing with it, I happened to have a transistor laying around so I wired it up with that. When I have it wired up according to diagrams I've found, the LED is on nice and bright...... when the board is off. When I turn the board on the LED blinks off and when I turn it off the LED blinks on. I'm trying to see if I can wire it differently to get my brightness when the sound is on lol.

[Obi1]

Sound like you mixed up the drain and the source of the transistor. That is, if you use a MOSFET. Do you know which type, n- or p-channel? Or bipolar?
Anyway, you are definitely and irreversibly on the right track

[Baboon]

Lol, thanks for the help. I'll have to check on the transistor type when I get home, unfourntatnly the fun of saber smithing can't follow me to work (all the time)

[Baboon]

Looks like the transistor I'm using is a TIP120 Darlington Transistor. Looking at the transistor I used in a previous build, looks like I used a TIP42 PNP silicon transistor. I kinda have a funny feeling that the TIP120 is the wrong one.