Power Blinkie

I world think that the whole point of Darlingtons would be to have ability to power much more than 2mA. Maybe something in the 200-500mA range (I don't remember the exact specs for a 4401 of the top head, but they should able to handle that). Going with the Darlington configuration, each pair will have a gain of about 10,000. That means you don't need big caps and small resistors to drive large loads. Normally, with just two BJTs, too push enough current the bases drive big loads, you would have to use small resistors and big caps. Thus limiting the operating frequency to some pretty slow speeds. With the Darlingtons, you aren't limited such slow speeds with large loads, because you don't need such small resistors and/or large caps to keep the base current high enough. There's a flipside to that, though. You could drive relatively small loads a few mA at really fast frequencies, because you could get away with huge resistors and tiny caps, and still be pushing enough current at the bases to switch the loads. Those the two reasons I would see for a Darlington setup. But just to drive a 9V 2mA load at around 1Hz, I don't see any real advantage over single BJTs. Anyhow, that's just my two bitcoins.

Basically, the way this circuit is biased right now, you could easily drive 1A. Now, 9W would fry a 4401, but what are they good for? 600mW? Something like that? Crank those bulbs up to 450mW, and push 50mA through there. That should be child's play for those Darlingtons. Better yet, use a 4401 for the low current stage of the Darlington, and a TIP31 for the high current stage. Then a 9W 9V load is no big deal. Moar power!

There ya go @rky- that enough juice in ur lunchbox?..

Ya the schematic called for lamps @9V, 300mA. The math on that is V•I=P right? So 20 mW- or did I miss a decimal point? Yeah that value didn't work or so well here..

9V x .3A = 2.7W

And yes, now you're taking advantage of the darlingtons. ;)

If you have to build a blinkie then yes build a smoking ass high power one!!!! :-D

Use mosfets! I'll post a circuit

Yeah I posted a power MOSFET multivibrator for Facebook a ago. I'll republish it. It's 2 weeks old. "For Faceblast and Sine_eyed" is title. But if you don't have suitable MOSFETs available, knowing how to use Darlingtons is handy.

Hey, you two have been great about this power blinkie thing and I appreciate it I do- but I really didn't have any intention to build a real one. Not yet anyway. I need to learn how to use darlingtons and mosfets properly, absolutely. But one thing I hold myself to is not to try and take on a project or learn something that's outside the breadth and width of my understanding of electronics thus far. The more you wanna learn- the more you gotta learn to learn it! That's what I've learned lol..

And honestly, I started looking into and trying to figure out the whole transistors as amplifiers thing only about...... wait for it........ 2 months ago! So yeah, I really wanna have a handle on a little 2222, or a 2907 before I jump into all that other stuff!