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Topic: Woes and Color Mixing Lamp Trouble (Read 1 time) previous topic - next topic


Jan 13, 2017, 07:30 pm Last Edit: Jan 13, 2017, 10:00 pm by WWWLibrarian
I'm a librarian learning Arduino with the goal being to create a youth program for disadvantaged pre-teens and teens.

Howerver, I am having a lot of trouble with Arduino components. It's too the point of getting frustrated with the entire project; I'm ready to look for another starter kit.

The problem is the hardware more than the coding. The instructions could be more explicit in putting things together, but I've been able to follow the directions for the physical and coding parts. But putting the breadboard together seems to be much harder than it should be.

In general, the wire sizes don't quite match the illustrations.

On project 2 (Spaceship Interface), the resistors are too "tall" for the card cover to sit flush against the breadboard. I considered trimming them, but finally bent them. Then, the LEDs were too "short" to stick out the cover! I ended up having to create a spaceship interface cover with shorter folds, so it would fit over the breadbox, but the LEDs would come through.

On project 4 (Light Mixing Lamp), I had so much trouble with the gels. They barely fit into the wood parts, and that's if the wood doesn't slight down the photosensor leads! The slightest movement sets them flying across the room. But I finally got it all together, wrote the code, checked, plugged it in and ran it...nothing.

After some playing around, I noticed that when moving the ground (black) wire--which already has a lot of wiggle room--the LED does flash on, then off. It happens during the movement to connect the pin to the board; once in, nothing happens.

Any thoughts?

See my setup here: http://imgur.com/gallery/NgsJh

First photo is the setup, second photo is my attempt to get the light to flash on as I put in the ground wire. It flashed just before I took the photo; you can see the pin is not "in."

***EDIT: Please check me if this solution is correct. The instructions have the phototransistors backwards. The instructions say that "attach the long end of each photo transistor to power. On the other side [meaning the shorter end], attach a 10k ohm resistor to ground."
I took this to mean that the long piece should be placed on the F column of the breadbox, on the side where a small red wire connects to the positive column (and thus the 5V), while the shorter side should be placed in the E column, the side of the breadbox that has the resistor.
HOWEVER, this project only works when the instructions are reversed. The long side of the phototransistor needs to be in E, on the same row with the resistors; the short side needs to be in F which has the connection to power.

Are the instructions incorrect? Is this fix (turning the photo transistor opposite) correct? Or am I missing something?


Regarding Project 2, you can bend a lot of the wires around to make room for the cardboard. You could also use shorter jumper wires.

For Project 4, I don't see anything wrong with your circuit. It's strange that putting the photo transistor in reverse makes it work, because usual that would prevent the circuit from working. It might be something wrong with your code. Maybe you can post your code?

I'm a newbie myself, but I tried to add some input to help you out.



WWWLibrarian, I just attempted to put together the same project (Project 4) and had nearly identical issues. I realize I'm a bit late to the party, but maybe it will help somebody. After a bit of research, here's what I learned:

It looks like at some point, Arduino was shipping a different kind of phototransistor in their kits. Specifically, a shorter one (instead of the ones I have, which look more like a transparent LED with a flat end). This other style was a lot thinner, and as such I imagine the gels would have fit a bit better into the wooden tabs. With the patience and delicate touch rivaling that of a safe-cracker, I managed to get them slotted in where they belong, and mostly covering the tops of the phototransistors (although as these are a lot taller than the other ones, I don't even know if the gels do anything, because the sides are completely uncovered). So it seems like they changed the hardware and didn't update the "accessories."

Additionally, allegedly phototransistors are not polarized (i.e. - unlike LEDs, there isn't a positive + negative leg), however the ones I have feature one leg that is slightly longer than the other (like an LED's cathode/anode legs). When I put everything together and programmed it, my RBG LED didn't switch on at all, and I wondered if I'd gotten the legs mixed up. No, I hadn't, the "anode" leg was connected to "+", and the "cathode" leg was connected to "-". So I didn't try turning them around, but I did get a flashlight and shine it directly on one of the phototransistors (the red one), and lo and behold, the RGB LED immediately glowed red.

So I wonder if perhaps these new phototransistors somehow have a more narrow "viewing angle" (probably the wrong term but hopefully you get my meaning) than the old batch, or if they are somehow less sensitive. Because the Serial port logger showed them reading 0 the entire time, until I put the flashlight 1 inch away. And admittedly the room I was in wasn't extremely bright, but I could certainly see what I was doing!

Alright, sorry for the long response, hopefully this is of some use to someone! Will reply again if I learn anything else useful.

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