While it was not planned, most of the completed circuits did not work the first time around.  This presented a perfect opportunity for some impromptu troubleshooting practice.  A couple of days after the workshop I breadboarded the circuit at home and made a couple of observations.  If the voltage is applied in the correct polarity, the LED must be installed in the correct polarity for it to work.  If the voltage is applied in reverse polarity, the LED will be very dim when installed correctly, and normal brightness when it is installed in reverse.  I also discovered the small green LEDs handed out for the practice circuit seem to be fairly dim in comparison to the other LEDs available.  I was also able to run 15 LEDs off of a single AA battery if I didn’t use those smaller LEDs, but only a few if I did.  I was going to try more but it was way past my bedtime and my desire for a horizontal position overrode my desire to push the circuit any further.  I want to work with Gillian to use a multimeter to determine the output voltage of the circuit, and show her how the current increases as more LEDs are added to the circuit.  I’m also curious to look up the specs of the transistor and see how many LEDs it should be able to safely drive before exceeding its safe operating current, is 15 pushing it?

Gillian’s lamp she made currently only has 5 LEDs installed, but if we replace those smaller green LEDs out with the larger green, and some more orange/red LEDs, we should be able to run at least 10 LEDs since her battery compartment holds 3 AA batteries in parallel.  We did notice the transistor tends to warm up a bit even with the 5 current LEDs, so we may be limited more by the tolerance of the transistor rather than the capacity of the power supply.

All in all we had a great time and Gillian learned quite a bit.  While she hasn’t grasped the full concept of electronics work yet, she does now know how to do basic soldering, and understands that different parts do different things, and that combining those individual components makes larger components.  We’re currently working on a basic walker robot built out of cardboard, so she’s learning how the electronic world (Arduino) can interact with the physical world.