Velleman mk 186 help?

[doomdecibel]

I tried to build the Velleman mk 186 kit (sound activated LED) and I can't get it to work. I am somewhat of a newbie when it comes to electronics construction so if I did anything glaringly wrong please tell me! I am eventually gonna hook it up to a LED display that will pulse with a kick drum for a live band.

I attached a picture of the component side, solder side, and the edge on.

 

[CocaCola]

Double check polarity of the microphone and LED, and then check again...

Take a Q-tip (cotton swab) and using isopropyl alcohol clean the bottom of the board of the excess flux... Acetone can be used as well (will work faster) but care should be taken as the acetone will attack the plastic parts in no time flat...

 

[doomdecibel]

The polarities were correct, I just didn't the solder the mic on very well. The LED now turns on when I clap, however I can't seem to get an LED connected to the output to turn on.

I am using a 24V AC/DC transformer for my input, this gives the the output a 120W max. I am using 10mm blue LED with the following stats:
8000 mcd, 20mA, 3.2V (typical), 3.8 V (max).

I tried both using an single LED and 3 LEDs connected in series. Do I need additional resistors to make it work right?

 

[CocaCola]

You need current limiting yes, if you pumped 24V into the LEDs with no current limit they you are lucky they didn't pop like popcorn, but they did pop...

For this application and testing you can use one LED and about 1.2K resistance, NOTE that you will need at least a 1W resistor doing it this way...

May I suggest for testing you use a multimeter or a 24V device, even an automotive 12v bulb will work in a pinch, but life will be shortened significantly...

See Steve's sticky post on LEDs...

 

[doomdecibel]

Thanks for the help, I am going to have to rethink the design I want to do.