557Views16Replies

Author Options:

What could be wrong with my led light box? Answered

Hey you guys I did everything correctly but its still not working. Here's a pic of mine. I know its not the leds because they light up when I plug them up to a 12v source.Also thats a brand new tip31 and im using 8 Triple A batteries?

Discussions

0
None
iceng

Best Answer 5 years ago

Re-drawn and if 12V battery that 100 ohm resistor increases to 350 ohms.

With the darlington  configuration a 1uF capacitor in series  with the signal will also work !

A

again.GIF
0
None
tramonticeng

Answer 5 years ago

do i really ned to buy another transistor

0
None
icengtramont

Answer 5 years ago

No you don't, but do follow steveastrouk's advice !

You non-EE people should know how we buy parts.
  • One to Smoke
  • One to Lose
  • One to Use
  • One for the second version
  • One for another reason
  • And add 10% for good measure
Get at least SIX next time.
0
None
tramonticeng

Answer 5 years ago

Okay but does he want me to put a 100ohm resistor on each led? Also how would I go about wiring that up

0
None
icengtramont

Answer 5 years ago

Here is the circuit that Steve described.

a gain.gif
0
None
icengiceng

Answer 5 years ago

Oops one correction change the 47K to a 4.7K ( yel-viol-red ) resistor

0
None
tramonticeng

Answer 5 years ago

Im only using 6 leds, so is it still wired the same?

0
None
icengtramont

Answer 5 years ago

Which six ? ...... :-)

a6 gain.GIF
0
None
Josehf Murchison

5 years ago

Why are you using a 40 watt transistor when a 2N3904 1/2 watt will do?
Also you need resistors you may have connected this up and the LEDs flashed once and died from to much current.

0
None
icengJosehf Murchison

Answer 5 years ago

And he only acquired a single one ! ...................... :-P

0
None
steveastrouk

5 years ago

Diodes in backwards ?
No base resistor ?

Take a resistor (4k7 will do), and connect it to the base of the transistor and the 12V supply. The LEDs should light. If they don't, mak sure they are the right way round. If they STILL don't light, you have a dead transistor.

0
None
icengsteveastrouk

Answer 5 years ago

+ you may have too many LED in series and a transistor forward forward drop to light up.

0
None
steveastroukiceng

Answer 5 years ago

Hmm. Yes, 6, and on 12V.

Try 3 in parallel with 3 and put a 100 ohm series resistor in each leg

0
None
tramontsteveastrouk

Answer 5 years ago

Okay im going to try that thanks for your help

0
None
steveastrouk

5 years ago

Wot, no current limit resistor ?

0
None
icengsteveastrouk

Answer 5 years ago

Late night muddy brain non-engaged :-)