OK, here is the first draft.
I mentioned the power supply voltage, but I'm not sure you picked up on it. A 9V battery will not work well for this application. You also need a really stable voltage, there isn't much room either way. 12V would have been much better, but the regulated voltage requirement still exists. 12V will reduce the total max current by a third, maybe more.
The transistor will get warm, but not hot. This circuit will draw in the neighborhood of 240ma total (another reason a 9V battery will not work well).
If the Vf of the Green and Yellow transistors is different than I assume let me know and I will recalculate the resistors.
Chapter 1 of my article explains how the values were calculated, if you are curious. I also included the 0.6V base emitter drop of the transistor Q1.
I mentioned the power supply voltage, but I'm not sure you picked up on it. A 9V battery will not work well for this application. You also need a really stable voltage, there isn't much room either way. 12V would have been much better, but the regulated voltage requirement still exists. 12V will reduce the total max current by a third, maybe more.
The transistor will get warm, but not hot. This circuit will draw in the neighborhood of 240ma total (another reason a 9V battery will not work well).
If the Vf of the Green and Yellow transistors is different than I assume let me know and I will recalculate the resistors.
Chapter 1 of my article explains how the values were calculated, if you are curious. I also included the 0.6V base emitter drop of the transistor Q1.
