Arduino + LEDs + fan = POV "APPLAUSE" sign

 

I saw these POV(Persistence of Vision)  devices on other Instructables and thought I would like to make one and I have always wanted my own "APPLAUSE" sign.  Next improvement will be to make it go on whenever I enter the room.  :)  Maybe have it say, "And here's Charlie !" But that is for another time.

So I got a fan at a garage sale, did some reading , found some code and below is a video of my machine in action.

I started with nice code from an Instructable by Scott Mitchell - "Arduino Bike POV" but what I ended up with is his code greatly parred down.  I could not get it to work at first and so I keep changing the code .  Turned out my problem had nothing to do with the code. So I am going to go back to his code and try again as his is much more generic and would work more easily with different phrases.   But that is for later also.

The video below shows the POV in action. It does not seem as broken or disconnected in real life as it does on the video.

Step 1 Get stuff

Items used in this project:
small fan - garage sale - 2.00
misc lumber - my basement - 0.00
a length of plastic  15 by 2.5 inches  - my basement - 0.00
an Arduino - I use a Ardweeny from SolarBotics - about 10.00
7 red LEDs -  already had -  1.00
7 - 330 ohm resistors - 3.00
Halls Sensor - I got from Adafruit - US5881LUA - 2.00
1 10k resistor to be used with the Halls sensor - 1.00
2 magnets from local hobby store - 1.00

also will need : wire, 9v battery , screws, Loctite 5 min epoxy, small PCB from Radio Shack

 

Comments

[dchurch24]

Hi, does the hall effect sensor have to be at the other end (opposite the LEDs)? I have designed a PCB with the hall sensor just in front of the 1st LED. Would I need to change the code (the delay part) for this to work?

[duboisvb]

I have not worked with the hall sensor much but what I found was that it acts like a switch and so i have one sensor 180 degrees from the other because I just wanted the word to appear at the top of the circle. With just one sensor it would turn on the first time around and then off the second time around , etc. You could produce images all the way around the circle. You would have to play with the delay time to get good spacing . hope that helps.

[dchurch24]

Are both of your sensors plugged into the same Arduino pin? Reading through the code it seems like that might be the case.

[duboisvb]

There is only one Halls sensor. It is attached to the part that spins. As it reaches the first magnet, it will be turned on and the software will detect that and then start the LED's . When it reaches the second it is turned off ( the lower half of the cycle)

[dchurch24]

Thank you. That makes much more sense now. For some reason I thought you were using two sensors!

[dchurch24]

Excellent, thank you for the reply. I have ordered 10 sensors (I couldn't find anywhere that only sold singles, but I have no complaints ;-) ).

I've just made a small home-printed PCB (following instructions from here and elsewhere) with 7 LEDs on and the holes ready for the hall sensors.

I'll keep you posted on my progress. Keep up the good work. Thanks for an easy to understand Instructable (it's actually the first that I've tried to put into practice).

[dchurch24]

Hi, well, I'm still waiting for my hall effect sensors from China - so I went ahead and made it anyway. I changed the code and guessed at the rotation speed instead of using the sensors (I will change it back when they arrive). However, it only bloody works! The text spins sightly, especially as the motor battery discharges, but there is text spinning and is readable!

My kids love it! So, thanks once again for making an easy to understand 'able.

[duboisvb]

thanks. I am glad it is working for you.

[bears0]

what about hacking one of those little handheld fans that are pre-made POV's. i wanna learn how they make those.

[Blackice504]

hi mate i copyed the code into my arduino software and it comes up with this error

sketch_aug16a.cpp:28:19: error: font.h: No such file or directory
sketch_aug16a.cpp: In function 'void printLetter(char)':
sketch_aug16a:103: error: 'font' was not declared in this scope
sketch_aug16a.cpp: At global scope:
sketch_aug16a:129: error: expected unqualified-id before '--' token

i am very new to programing with microcontrollers so i not sure how to fix this any ideas?

[duboisvb]

Hello,
I think this may be the problem:
I did not spell it out in the instructable and that is my fault but ....

In the instructable the code is actually 2 files. I get the same error if I copy and paste the whole code listing into an Arduino sketch but if you do the following it does verify:
copy and paste from the top of the file to the point where font.h is started ie the last 2 lines of the copy will be :
delayMicroseconds(2500);

}

Then in the arduino sketch you need to click on the arrow that is in the box on the right near the top and select "new tab" , name this font.h , copy and paste the font.h code from the Instructable into this sketch.

I just tried this again and it worked but after doing the copying and pasteing, I did need to go back and delete a couple of lines that were not commented out properly eg
------------------------------------- this line
and

*/ this line


So in summary:
you need the font.h to be a seperate file (or tab)


Hope that helps

[Blackice504]

i shall try this.
thank you for pointing this out.

[Blackice504]

oh yeah i was thinking of using a PC fan and the sensor wire i think i can find the code for that from the examples from the arduino website but i think that should work.

[nmvb]

What is a Halls Sensor?

[godofal]

a hall effect sensor if a chip that detect magnetic forces and electric current :)
here its used to know when a certain point is reached on the circle, so the arduino knows when to start blinking the LED's

[duboisvb]

It is a electronic component that senses the presence of a magnet field. There are different types but the one I used changes states when near the north pole of a magnet and then changes back when near the south pole. This change of state can be "read" by the arduino and used as a signal to do something.

The following URL is to the Adafruit item that was used and a more detailed explanation can be found there.

http://www.adafruit.com/products/158

[nmvb]

oh, thanks :D