Light Canvas - LEDs 6: Dim power

The previous post demo-ed all the LEDs roughly in place in the frame, running on the dimmer circuit - but not running bright enough. I've figured out (I think) the LEDs aren't getting enough power. Firstly I wanted to establish what is happening in the circuit:

• From it's specifications, the 2N222A transistor has a beta value of about 100
• The current applied to the transistor base (555 chip output current) measured at: 1.16mA
• Taking the above, 100*1.16mA = 0.116A
• This calculation is confirmed by the measured of current going through LEDs (via the transistor): 0.1A
• This 0.1A is a quarter of the current needed to fully light the LEDs - measuring the current when driving the LEDs directly from the power supply gave a reading of 0.39A (pretty close to the calculated value of 0.42A)
• The transistor's peak base current is 200mA, so the max emitter current (base current * beta value) should be 200ma*100 = 20A - considerably more than the 0.4A needed.
• It should be possible to get the 0.4A - I just need to figure out how to get more current into the base.

Answers on a postcard...

Light Canvas - LEDs 5: All the LEDs

Here are all the LEDs running - 12 panels, each with 5 LEDs. They're not fixed in place yet, just taped in the approximate location.

It turns out that the 555 dimmer circuit isn't quite right, as it seems that the LEDs aren't getting a large enough current - 0.16A, rather than 0.45A (when powering all the LEDs without the dimmer).

I guess it's something due to the transistor not putting/allowing enough current through...

Video: