I am a teacher who has to teach some Digital Electronics to students not knowing much myself. I've admired many of the Digital Logic Trainers I've seen (power connector, input leds, output leds, breadboard, etc) that I've seen, but we can't afford these things which are $60-200. So I decided to copycat and improvise a little. I built a prototype which seemed to work, so I built 10 more. Clearly my testing of the prototype was too simple because once my students tried using it for anything complex (like a full-adder) it was erratic. Multimeter measuring shows the voltages aren't what they should be...
I suspect in my ignorance I've messed up resistor values or some such thing. Which probably means a lot of desoldering and resoldering. At any rate, I was hoping someone might be so kind as to look at a simplified schematic of the design and let me know where I went wrong.
Input LED's are red, Output Green, resistors 1/4 watt. It really is a simple project, or so I thought.
I'd really appreciate any help you can provide.
Mike.
