Then why not just buy this resistor pack. from Sparkfun.

If I were to put 3 less together in series would it need a max of 6.6v? Or would it still be 2.2?

 

It's quite simple.
If the Ans and Select probes go to the same horizontal wire (correct answer) the Green LED is illuminated and the relay is energized from the battery.
This opens the normally-closed contact on the relay, preventing the Red LED from also illuminating.
This current flow is shown by the red lines on the left schematic.

If the Select probe (green wire) is connected to a different wire then Ans (incorrect answer), than the relay and Green LED are not energized, and the Red LED is illuminated through the diode of the wire the Ans probe is connected to.
This current flow is shown by the red lines on the right schematic.

View attachment 131473

Ok I have set this up exactly the same as in the diagram but for some reason when the answer is wrong the red light activates, but when it is correct both lights activate... Do you know of any reason why?

 

I am happy to see my project sparked some other similar designs!

Just wanted to pop in and say after three years of operation everything is still working great! The only issues have been the wearing down of the "answer" and "selection" pen magnets due to excessive use.

I have replaced the magnets a couple times but they are very easy to swap out so its no issue at all.

Thanks for all the help again!

 

Thanks for the feedback!
It means a lot to all of those who participated in the solution.

 

It would be nice to summarize the content here, in a “Completed Project” post? Any chance of that happening?

 

It would be nice to summarize the content here, in a “Completed Project” post? Any chance of that happening?

Sure, what specifically would you like to know?

 

Sure, what specifically would you like to know?

Hello Gable,

If you weren’t aware, there is a separate forum called The Completed Projects forum. It’s for posts on s completed project that serves as a guide on how to build that project yourself. As such, questions on how to build a project typically are not included. Statements on how the project was built are included.

There is a sticky post on how the requirements for a completed projects thread. I believe if you read that link, it will answer the question you asked of me!

Hope you can do this. It’d be s good contribution to AAC.

 

Ahh, got it and thanks for the heads up. I will try to do this later today!

 

@GopherT where from you got the logic table posted above for CD4063/74LS85 I was not able to find such datasheet showing 4 outputs, what i found has only 3 outputs,
thanks

 

@GopherT where from you got the logic table posted above for CD4063/74LS85 I was not able to find such datasheet showing 4 outputs, what i found has only 3 outputs,
thanks

Which post is the logic table in?

 

You only posted one way.
But you need one diode on each line to isolate the lines.

 

Okay, I see how it works now which is a very simple design. Just had a little brain freeze.
I've given it some thought but so far, I can't think of a simple way to light the light with a wrong selection.
The problem is, it's simple to detect one right selection, but not so simple to detect umpteen wrong selections.
It you dedicated one probe as only for selecting the question, and the other dedicated for only the answer, then that might simplify the problem.
Would that be acceptable?
Edit:
Below is my take on a way to do it with one relay, diodes, and dedicated probes.
It requires one 1N4148 diode (or similar) per answer line (two lines shown).
I didn't show a resistor in series with the LEDs which are needed.
Note that a diode is also required across the relay coil, as shown, to suppress inductive transients.

When the Ans probe and the Select probe are connected to the same wire (correct answer) then the relay is energized and only the Green LED lights.
If The Ans probe and the Select probe are connected to different wires (wrong answer) then the relay is not energized and the Red LED is activated through the diode from the incorrectly selected answer line.

Edit 2--Simplified schematic:
View attachment 103084

Thank u in advance. If I use simple wire instead of diode will there be any problem?