{ "metadata": { "name": "2013-09-28-cloud-chamber-physics" }, "nbformat": 3, "nbformat_minor": 0, "worksheets": [ { "cells": [ { "cell_type": "markdown", "metadata": {}, "source": [ "# Cloud Chamber Physics\n", "\n", "At [Science Hack Day SF](http://sf.sciencehackday.com/about-shdsf/) 2013 there was a project to build a thermoelectric cooled [cloud chamber](http://en.wikipedia.org/wiki/Cloud_chamber). These are some notes about the hardware.\n", "\n", "\n", "## Thermoelectric Cooling\n", "\n", "The typical [thermoelectric cooler](http://en.wikipedia.org/wiki/Thermoelectric_effect) (TEC) will typically produce a maximum temperature difference of 70°C. The amount of heat that can be absorbed is proportional to the current and time.\n", "\n", "$$\$$\\dot Q = k_PI\$$$$\n", "\n", "where $\\dot Q$ is heat flow rate, $k_P$ is the Peltier coefficient of the TEC, and $I$ is the current.\n", "\n", "\n", "### Power\n", "\n", "So for a given heat rate and a known TEC we can guess the electrical power requirements.\n", "\n", "$$\$$I = \\frac{\\dot Q}{k_P}\$$$$\n", "\n", "\\begin{align}\n", "P &= IV \\nonumber \\\\\\\n", " &= \\frac{V\\dot Q}{k_P}\n", "\\end{align}\n", "\n", "We can computer how big of a power supply we need for each TEC:" ] }, { "cell_type": "code", "collapsed": false, "input": [ "# Define TECs\n", "TEC_12 = {\n", " 'v': 12, # 12 volt version, TEC1-12710\n", " 'kp': 9.6, # pelter coef\n", "}\n", "\n", "TEC_5 = {\n", " 'v': 5, # 5 volt version\n", " 'kp': 9.6, # pelter coef\n", "}\n", "\n", "# calc power\n", "def power(Q, tec):\n", " v = tec['v']\n", " k = tec['kp']\n", " return (v*Q)/k" ], "language": "python", "metadata": {}, "outputs": [], "prompt_number": 1 }, { "cell_type": "markdown", "metadata": {}, "source": [ "We want to suck the maximum power from both, which according to the datasheets is about 90 Watts(thermal)" ] }, { "cell_type": "code", "collapsed": false, "input": [ "print \"Power supply for bottom TEC: \", power(90, TEC_12), ' Watts'\n", "print \"Power supply for top TEC \", power(90, TEC_5), 'Watts' " ], "language": "python", "metadata": {}, "outputs": [ { "output_type": "stream", "stream": "stdout", "text": [ "Power supply for bottom TEC: 112.5 Watts\n", "Power supply for top TEC 46.875 Watts\n" ] } ], "prompt_number": 2 }, { "cell_type": "markdown", "metadata": {}, "source": [ "Luckily we have two ~100 watt power supplies.\n", "\n", " - [Download this notebook](https://raw.github.com/natronics/natronics.github.com/master/notebooks/2013-09-28-cloud-chamber-physics.ipynb)\n", " - [View on nbviewer](http://nbviewer.ipython.org/urls/raw.github.com/natronics/natronics.github.com/master/notebooks/2013-09-28-cloud-chamber-physics.ipynb)" ] } ], "metadata": {} } ] }