# Spaceship Interface circuit not working

I work at a k-8 school and am currently working on some arduino projects for afterschool. One of the kids is excelling very well and built his circuit correctly, and started to help some of the other kids that were going a little slower.

As he helped them after he successfully put his together, he followed the instructions(arduino starter kit with arduino uno rev.3) as they are in the book to help the students.

He said he couldnt figure out what was wrong with the other students projects because they looked exactly like his. So the class ended and i started to look over the students work to see why they werent working.

As far as i can tell they are exactly as the student that got his to work. I even took apart theirs and tried to get them to work bu couldnt.

Out of a set of 6 i built the circuit the same exact way as it is described in the book and cannot get the other students 4 projects that look EXACTLY the same to work.

I have even had two other teachers follow the instructions in the book to the T and they cannot get it to work either.

Try to imagine that we don't know what a k8 school is, or what book and circuits you're referring to.

Back to you.

Can you post a clear photo of one that works and one that does not?

One thing that I can think of has to do with solderless breadboards. On some the top and bottom (power) rails are split in the middle so the split must be bridged for the rails to be continuous.

working one

nt working

I wonder if your current limiting resistors are plugged in to the wrong place.
On the working one, the green LED is plugged in to rows 16 and 17.
The yellow wire from one of the arduino pins (cant tell which one) is plugged in to row 17. The current limiting resistor is plugged in to row 16.
Similarly the 2 red LEDs are in rows 20/21 and 24/25 with the yellow wires from the arduino pins in 21 and 25, and the current limiting resistors in 20/24.
On the non-working one, some of the current limiting resistors are plugged in to the same row as the yellow wire.

EDIT: never mind. I zoomed in more. It was just a trick of the angle of the picture.

Next thought. Are the 5v and ground wires in the wrong rows on the power rail? I cannot see where those are plugged in to the arduino. Typically, the red gets plugged in to the power or 5V on the arduino. The black gets plugged in to the ground or GND on the arduino.
Then on the breadboard, the red wire gets plugged in to the power rail nearest the red line. The black gets plugged in to the power rail nearest the blue line. It looks to me like these 2 wires are reversed on the non-working model.

I never trust those little square switches. If you turn them 90 degrees your connections are incorrect. Did you check with a meter that you have the correct pins?

Looks like the not working one has the power reversed from the Uno to the breadboard if the red wire is +5v.

So ive tried a few of the suggestions that the above users had said.

Im still not getting any luck. Ive taken apart the two boards and put the back together 3 times now and still am not having any luck.

Are you testing each time expecting the green led to light as per working example? What happens if you swap one of the red leds into its place? Just a thought.

Are all the codes the same? Can you post the code.

The green light on the working one isnt running any code, its just plugged into the computer.

When I plug in the other board the green light doesnt work.

Ah a clue. So are the boards all new and virgin? If they have been programmed before then the pin state is unknown at startup. Likewise when new.

Program both boards with working code then report back.

justone:
Looks like the not working one has the power reversed from the Uno to the breadboard if the red wire is +5v.

+1

If the OP can't tell the difference then what can the OP be told twice now? Red, black, hey they're just wires!

There's also the which pins does the button switch as a potential problem that can be worked out.

first, remove power.

then make sure the LED goes out on the board.

Check to make sure there is no power.......

======================

red wire goes from the Arduino V plug
to the RED line on the board
red to red

============

# black wire goes to ground and to the blue line on the board.

tasmod:
Ah a clue. So are the boards all new and virgin? If they have been programmed before then the pin state is unknown at startup. Likewise when new.

Program both boards with working code then report back.

The boards were virigin. And the kids said they coded them, which i found out they didnt.

So after coding the boards they all work fine now.

Ah glad it worked out. Usually something simple when it's like that.

GoForSmoke:
+1

If the OP can't tell the difference then what can the OP be told twice now? Red, black, hey they're just wires!

There's also the which pins does the button switch as a potential problem that can be worked out.

As for you. If you see the new picture posted they are both fine (newest post with picture attached). I can tell the difference between red and black thank you. I was just seeing if I reversed them if something differently would work (in the second picture i posted).

No need to be rude about it.

You never clairified that you were using the corrected configuration. Don’t confuse frustration with rudness.

Reversing supply polarity is something that’s shows a complete lack of common sense. Would you hook up your car battery backwards if it wouldn’t start?

Reversing polarity can irreversiblely damage both components and the Arduino. Do it with circuits that have more power available can result in things exploding in your face.