1A – Basic Circuits Project – Heated Jacket

maddy — Wed, 10 Sep 2014 06:18:05 +0000

Group Members: Ronald Chang, Bryan Gardiner, and Maddy Varner
Roles: Ronald as Scribe, Bryan as Designer, and Maddy as Tutor

Introduction

The purpose of this project was to create a functional heated jacket that warmed up as you buttoned it up. By using the buttons already in the jacket, we could make the technology seamlessly integrate into something we use every day. Also, the technology is used in a logically consistent way (buttoning up your jack makes you warmer) so that the jacket’s warming feature is intuitive.

Video

Technical Notes

The circuit in the jacket is actually two separate, identical circuits with a battery, a switch and a resistor. The switches in our circuits are the two buttons on our jacket, and the resistors are each 50 ft of 30 grade PTFE High Temperature Stranded Wire. The batteries we used are 11.1V 2.2A lipo batteries.

In order to provide heat, the resistors must be discharging enough Wattage, which can be found using the equation P=V2/R. Since V=11.1 and R=5, the Wattage generated by each circuit is 24.64 W. Therefore, if both circuits are running, the total Wattage warming the user’s body is 49.28W. Heated clothing on the market is usually around 48 W, so ours is only slightly warmer (an added bonus in Pittsburgh winters). Fortunately, due to the control the user has, if this is too warm, the wearer only needs to unbutton a button to reduce the heat.

Our circuit diagram

Photos

How To Set A Cron Job

maddy — Thu, 28 Aug 2014 20:32:55 +0000

Sometimes you need your Raspberry Pi (or other computer) to run a repetitive task. Maybe you want it to take a picture every five minutes, or recite a protection spell every Friday the 13th. To do this, we can use a cron job, or a scheduled task.

To add a cron job, type nano crontab -e into the terminal. A job is formatted as such:

minute hour day month day-of-week command-line-to-execute

You must use this order, and you may not have any missing fields. The acceptable values for each field is as follows:

Field	Range of Values
minute	0-59
hour	0-23
day	1-31
month	1-12
day-of-week	0-7 (note that 0 & 7 is Sun, 1 = Mon, 2 = Tue, etc)
command-line-to-execute	the command to run along with any parameters you may use

You may also use *, a wildcard character for any given category. This indicates every possible value for the field. So, if you wanted to run a command every day at 1:20pm, your time portion would look like this:

20 13 * * *

Note that we’re using “13” instead of “1” for the hour slot, because we’re using a 24-hour clock. If you wanted to run something every five minutes, you would simply do:

*/5 * * * *

Using the slash, we can divide the wildcard symbol by any number, causing the job to run whenever it’s evenly divisible. And if you’d like to run a script every Friday the 13th at 11:11am and 11:11pm (usually lucky times, even on a very unlucky day), you’d simply write:

11 11,22 13 * 5