Final project critique

[freeskier89]

For a science project I need to turn on and control two motors and turn on and off two lasers via the computer. The motor control was already covered in the thread "Help: Digital Polarity Inverter". It would be absolutely awesome if someone could look over my circuit with the lasers/an led added for a final time. Any assistance would be great since Im still a newbie for this subject. One of the major questions I had was when adding resistance so the 12V doesnt fry the 3V lasers, do you add the resistance after the NPN BJT, before the laser, or does it really matter?

Well thanks again in advance!
-Brandon

 

[evandude]

well, for starters, it looks like your DC supply is backwards in that diagram...

the resistors are fine right where they are.

I presume that the bottom pin on each of the logic input pin pairs is logic ground?

 

[freeskier89]

Oh duh on the dc supply I thanks for the tip! On the bottom pins of the logic if you see on the last thread I made (https://www.electro-tech-online.com/threads/plz-help-me.16832/). Adding the logic GND was not liked (or at least to my knowledge) Should I make them GND? Or keep them the way they are?

Thanks for the reply!

 

[evandude]

well they do all appear to be connected to (what should be) the negative terminal of the DC supply, and they would have to share a ground with the controlling circuit anyway...

 

[freeskier89]

Alright then. Thanks for all your help! So the consensus is that it will theoretically work. right?

Thanks,
Brandon