A second helping of Pumpkin Pi

25 Oct 2012

Want to build this project?

In my last post, I introduced the Pumpkin Pi: a Raspberry Pi project for Halloween. It puts a Raspberry Pi inside a jack-o'-latern to provide web-controlled lights and sound:

(click to enlarge; screenshot of latest version as of 2012-Oct-26)

The Pumpkin Pi software was written in Python with generous assistance from Bonnie King and can be found on GitHub under my account "pdp7" in the punkin_pi repository.

Install dependencies:

To run punkin_pi on your Rasperry Pi, you'll first need to install these dependencies. The following commands were run on the current Raspbian 2012-Sept-18 image:

sudo apt-get update

sudo apt-get install git-core mplayer python-setuptools

sudo easy_install bottle

sudo easy_install RPi.GPIO

If running an earlier image, then you may encounter an error on when installing the RPi.GPIO in that last step ("couldn't find Python.h"). To resolve the error, run this command: sudo apt-get install python-dev and then sudo easy_install RPi.GPIO again. Thanks to Joel Dunn for the advice!

Install sound clips:

Next, sounds clips that the pumpkin will play need to be installed. I downloaded a few .wav files from a site with a nice collection of Halloween sound clips and placed in /home/pi/files as punkin_pi expects:

pi@raspberrypi ~ $ mkdir files

pi@raspberrypi ~ $ cd files

pi@raspberrypi ~/files $ wget http://www.countessbloodshalloweenhorror.com/sounds/howl.wav

pi@raspberrypi ~/files $ wget http://www.countessbloodshalloweenhorror.com/sounds/scream.wav

pi@raspberrypi ~/files $ wget http://www.countessbloodshalloweenhorror.com/sounds/ghostgigl.wav

Any files that mplayer can play can be put into /home/pi/files such as .wav, .mp3 & .ogg.

Install & run punkin_pi:

Next, I installed the punkin_pi software project via git:

pi@raspberrypi ~ $ git clone https://github.com/pdp7/punkin_pi.git

The web server (built on the bottle framework) can be started via:

pi@raspberrypi ~ $ cd punkin_pi

pi@raspberrypi ~/punkin_pi $ sudo python ./control.py

It will be available at the Pi's IP address on port 8081. Here is a video of the web interface in action:

(The LEDs happen to be connected to the Raspberry Pi via the Adafruit Pi Cobbler in this video clip as my Adafruit Pi Plate featured in my previous post wasn't handy at the time)

Audio troubleshooting:

If you want to check if punkin_pi will be able to play a particular file in /home/pi/files, then try to play it with mplayer:

mplayer /home/pi/files/howl.wav

Sometimes the sound system may become unstable and produce errors. Restarting ALSA should resolve this:

sudo /etc/init.d/alsa-utils restart

If your speakers lack a volume control, then the ALSA mixer can be used to adjust volume:

alsamixer

Cheers,

Drew

element14

Product Name*	Description	Buy All Parts
Raspberry Pi Model B with SD Card	Raspberry Pi model B and 8GB SD Card with NOOBS preinstalled
Optical mouse	Basic USB optical mouse
Keyboard	Basic USB keyboard
Adafruit Pi Plate	Breakout and expansion board for Raspberry Pi
Tiny Breadboard	Small breadboard sized to fit Pi Plate
Adafruit Pi Box	Clear acrylic enclosure for Raspberry Pi
(2) NPN BJT	NPN bipolar transistor
(2) 1k ohm resistor	1k ohm, 250mW carbon film resistor
(4) Red LED	5mm red LED
(4) 220 ohm resistor	220 ohm, 250mW carbon film resistor
(4) 180 ohm resistor	180 ohm, 250mW carbon film resistor
(4) Yellow LED	5mm yellow LED
20AWG Red Hook Up Wire	20AWG solid copper hook up wire - red
20AWG White Hook Up Wire	20AWG solid copper hook up wire – white

Additional Parts

Product Name*	Description
Rechargeable USB Battery Pack	4000 mAh Li-Ion battery pack with USB outputs and included cables
Mini Speaker	Small rechargeable mono speaker with integrated amplifier

*Products and resources listed are listed to help members build their own Pi Projects. They are suggestions and listed for educational purposes. For substitutions of any parts, please post a question asking the original author.

Top Comments

fustini over 13 years ago in reply to fustini

I think typically PWM would be used to vary the intensity of the LED. When PWM duty cycle changes randomly, it gives flicker effect. The Pi's only hardware PWM pin is used by the analog audio, so software PWM is the only option. Gordon Henderson has written a C library called WiringPi which offers software PWM: https://projects.drogon.net/software-pwm-on-the-raspberry-pi/. Gordon has a nice halloween raspberry pi project using WiringPi: https://projects.drogon.net/halloween-pi/

This is a software PWM library in Python: https://github.com/aboudou/pizypwm. It looks promising and was used for a project by its author: https://goddess-gate.com/dc2/index.php/pages/raspiledmeter.en. I'd like to see if it will play nicely with the bottle framework in punkin_pi. I think blinken.py would be the most likely place to integrate it.
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Former Member over 13 years ago in reply to fustini

Drew,

Yeah, what I'm gonna do is go back to basics (what I should have done in the first place!) and try it with a breadboard and/or a DMM. I ordered one of the little breadboards from Adafruit like in the picture in your example, should be here soon. I may miss Halloween, but I'll have it ready by Thanksgiving ;-)

Thanks for the encouragement and link to the Adafruit tutorial. Probably should'a started there first, but your project ID got me interested in actually doing something with the GPIO, so that's good!

-Joel
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fustini over 13 years ago in reply to Former Member

Flicker effect is a great idea. I'd be very interested to see your results and feel free to send me a pull request on github if you'd like any changes to be pulled into my repo.
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Former Member over 13 years ago

I'll experiment with the different audio files and amixer later. I want to look a the code now to see if the blinking and duration can easily be randomized, to resemble more of a candle flicker, and maye even break it up ino four sets of lights.
Next year, we will have one that also blinks with the sound too.
Regardless, this was a great start. Thanks again!
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fustini over 13 years ago in reply to Former Member
re: the pop - yeah, I get that too and didn't find any way to eliminate it yet. If I remember right, then I think there was less of a pop for mp3 files than wav files. I'm thinking it might be something to do with the immaturity of the sound driver. It doesn't occur on my x86 Linux desktop.

Good to know that it plays analog audio when HDMI isn't connected. I think it should be possible to switch the audio output with amixer. From the eLinux wiki:

http://elinux.org/R-Pi_Troubleshooting#Sound_does_not_work_at_all.2C_or_in_some_applications
```
sudo amixer cset numid=3 <n> 
where n is 0=auto, 1=headphones, 2=hdmi.
```
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