Practical beginner questions

Relying on old memories: Using the Netduino with the USB. I have a separate 5VDC 1 amp supply, encapsulated, very solid and used in older TTL days on production equipment. WHy? Because I have a box of them ! A CD4069, output of one gate to a 2N2222A, running a small DC motor. Motor draws 95 ma running, don't know startup draw. Playing with stuff like this, trying out motors, gearing, just playing. It's been a long time ! int x; for (x = 0; x < 10; x++) { led.Write(false); Thread.Sleep(20); led.Write(true); Thread.Sleep(100); } Question: Tie my grounds together? Both from the Netduino board and the separate 5VDC supply? Question: Base resistor for the 2N2222? Not using one, and if I run the motor steady the 4069 gets a little toasty. Runnning the loop from above, and it goes all night not getting warm. For the amusing part, I spent too too long yesterday before I noticed the pinout from the Radio Shack package for the RS 4069 was different than the normal pinout from Google searches. This is a part from 30 years ago. I'm amazed the 4069 took the abuse and grief I subjected it to, before I noticed the pinout difference and changed it.

Ok, answering one of my own questions, a little thought and I added a 1k resistor from the 4069 and the base. Was not a problem, except when the gear bound up a bit, and the motor draw and I assume the base emiter current got too high.

Frank, You sound just like me. I used to a very good electronics engineer but years ago a took a different path in life. Now I am digging out all the old stuff and getting some new stuff. Very exciting I must say. You should always have a common ground unless the supplies are isolated. Look at the spec for the 2N2222. Take the collector current rating (Ic) divide by the gain of the tranny and that should tell you what the maximum base current should be. Divide 0.7v by the base current and that should give you the base resistance that you need. Good luck

Thanks for the answer ! Feels funny to be messing with transistors after many years. I suppose I can throw way all my ceramic tube sockets, eh ?!

Frank, Not if you are in the music industry. We still prefer valve amps and almost every decent amp maker has at least one in the range. I wont play with a 100% solid state amp, they just don't have what it takes.