Hello, I have 2 different circuits on the same page of tinker cad. One is an LDR base driven NPN transistor, that turns on an LED and the other is the same circuit but with an PNP transistor instead. I noticed that with the NPN circuit that no matter how much i change the resistance on the LDR, the transistor is always biased ON. Both circuits also have 1k resistors in series with the LDR.
When i change the resistance on the LDR on the PNP circuit i am able to bias it to where it is only delivering 230uA (turning the led off) to about 8ma with full light (turning the LED on),
But with the npn circuit, it ranges from about 3ma to about 9ma.
Ahh, that's what we call in the business, a Fritzing mess.
My biggest problem, how do I know the layout of the transistors? And all those sharp wire bends of this low resolution doesn't make it more readable either...
Tip, just grab a piece of paper and a pen(cil) and just draw it
Looking at the horrible fritzing diagram its seems to be the same polarity of circuit for both transistors, whereas PNP
and NPN require completely complementary circuits.
NPN common emitter circuit needs emitter to GND
PNP common emitter circuit needs emitter to Vcc.
This is really a case where people are given a tool... with no rules or guidance so they are pretty much guaranteed to use it wrong.
The drawing, as is, really doesn't convey much useful information. This is one of the main reasons we actually use Schematic Diagrams, not Pictorial Diagrams, to discuss issues with designs. and one is not as good as the other for many reasons.
Many people who get the absurdity in that image will still use a spreadsheet for completely
wrong purposes which is actually worse (at least the picture shows a drill being used to drill a hole).
