This page helped me a lot when I started out with transistors: http://www.mcmanis.com/chuck/robotics/tutorial/h-bridge/bjt_theory.html
Yeah, but with that freaking fritzing program you can't tell that - have to go look up the parts and see which pins are B, E, C - which was totally obviouse in the original post.
The way to deal with this is to calculate the"nominal" base current required for the app, and then about double it, by using a value for base resistor R2 of about 1/2 the nominal value.
Also, your values above may be wrong. Normally, the hFE value is "lower" for largercollector currents.
I'm curious why OP chose to switch the high side instead of using the original circuit. With this setup, the transistor is operating in the linear region and will never reach saturation.
QuoteThe link goes to a CircuitLab page that makes it easier to evaluate.That's even more confusing. If you didn't know any better, you'd thing the 5V supply on the collector was upside down, ;-). Possibly confusing to a noobee.I'm not crazy about that schematic capture browser app.Also, this is not good, pinouts between NP2222 plastic case and 2N2222 metal caseare backwards, oof! Murphy strikes again.http://www.stanford.edu/class/ee133/datasheets/2n2222.pdfhttp://www.jameco.com/Jameco/Products/ProdDS/38237ST.pdfhttp://www.fairchildsemi.com/ds/PN/PN2222A.pdfThey look right to me. The base is in the middle where I expect it and the plastic part would fit in the standard TO-18 triangular PCB layout without having to cross the legs.I congratulate OP for going through the design process. The first circuit is more common though, in my opinion.
The link goes to a CircuitLab page that makes it easier to evaluate.
So, there is actually a difference if the LED is in the collector side or the emitter side ??
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