{"id":6,"date":"2010-12-19T10:38:31","date_gmt":"2010-12-19T10:38:31","guid":{"rendered":"http:\/\/www.emtronics.co.uk\/wp_blog\/?p=6"},"modified":"2017-04-16T15:38:17","modified_gmt":"2017-04-16T15:38:17","slug":"compass","status":"publish","type":"post","link":"http:\/\/www.emtronics.co.uk\/wp_blog\/?p=6","title":{"rendered":"Compass Belt"},"content":{"rendered":"<h3>Introduction<\/h3>\n<p>Last year I saw an article on Engadget on the Haptic Compass Belt, since then I have wanted to make one. Finally a year after having half the components, I decided to design and build one.<!--more--><\/p>\n<p>For those intersted in what this project is, and more importantly what the point of it is, see these links:<\/p>\n<p><a title=\"Engadget Article\" href=\"http:\/\/www.engadget.com\/2009\/02\/09\/haptic-compass-gives-you-sense-of-direction-not-style\/\" target=\"_self\">http:\/\/www.engadget.com\/2009\/02\/09\/haptic-compass-gives-you-sense-of-direction-not-style\/<\/a><\/p>\n<p>This is the original Wired article which goes into more detail:<\/p>\n<p><a title=\"Wired Article\" href=\"http:\/\/www.wired.com\/wired\/archive\/15.04\/esp.html\" target=\"_self\">http:\/\/www.wired.com\/wired\/archive\/15.04\/esp.html<\/a><\/p>\n<h3>Features<\/h3>\n<p>All of the Compass Belts I have seen build so far have been quite large and intrusive, normally with separate battery, I wanted to design one which was as small as possible, internal power and easy to charge.<\/p>\n<p>I decided to build around the AT90USB162 AVR from Atmel, this allows code update via USB, which I can also use for charging.<\/p>\n<ul>\n<li>Small size (45mm x 35mm x 10mm)<\/li>\n<li>Light weight (electronics + battery)\u00a0 &#8211; 30 grams<\/li>\n<li>AT90USB162 AVR @ 16MHz (clocked to 2MHz)<\/li>\n<li>960 mah Lithium Ion Battery<\/li>\n<li>Li-Ion charging through USB<\/li>\n<li>HM55B Compass module<\/li>\n<li>2 LEDS<\/li>\n<li>RS232 connection<\/li>\n<li>Support for 8 motors<\/li>\n<\/ul>\n<h3>Design<\/h3>\n<p>Below is the circuit design. I decided to use the &#8216;1.5 layers&#8217; technique,\u00a0 this means all the traces are on one layer, with only Ground on the bottom layer &#8211; this make it much easier to etch as you don&#8217;t have to worry about printing\/developing\/aligning 2 sides.<\/p>\n<table>\n<tbody>\n<tr>\n<td>\n<p><figure id=\"attachment_13\" aria-describedby=\"caption-attachment-13\" style=\"width: 300px\" class=\"wp-caption alignnone\"><a href=\"http:\/\/www.emtronics.co.uk\/wp_blog\/wp-content\/uploads\/2010\/12\/main.png\"><img loading=\"lazy\" decoding=\"async\" class=\"size-medium wp-image-13\" title=\"Compass Belt Schematic\" src=\"http:\/\/www.emtronics.co.uk\/wp_blog\/wp-content\/uploads\/2010\/12\/main-300x166.png\" alt=\"\" width=\"300\" height=\"166\" srcset=\"http:\/\/www.emtronics.co.uk\/wp_blog\/wp-content\/uploads\/2010\/12\/main-300x166.png 300w, http:\/\/www.emtronics.co.uk\/wp_blog\/wp-content\/uploads\/2010\/12\/main-1024x567.png 1024w, http:\/\/www.emtronics.co.uk\/wp_blog\/wp-content\/uploads\/2010\/12\/main.png 1326w\" sizes=\"auto, (max-width: 300px) 100vw, 300px\" \/><\/a><figcaption id=\"caption-attachment-13\" class=\"wp-caption-text\">Compass Belt Schematic<\/figcaption><\/figure><\/td>\n<td>\n<p><figure id=\"attachment_10\" aria-describedby=\"caption-attachment-10\" style=\"width: 300px\" class=\"wp-caption alignnone\"><a href=\"http:\/\/www.emtronics.co.uk\/wp_blog\/wp-content\/uploads\/2010\/12\/main_brd.png\"><img loading=\"lazy\" decoding=\"async\" class=\"size-medium wp-image-10\" title=\"Compass belt board\" src=\"http:\/\/www.emtronics.co.uk\/wp_blog\/wp-content\/uploads\/2010\/12\/main_brd-300x213.png\" alt=\"compass_belt_board\" width=\"300\" height=\"213\" srcset=\"http:\/\/www.emtronics.co.uk\/wp_blog\/wp-content\/uploads\/2010\/12\/main_brd-300x213.png 300w, http:\/\/www.emtronics.co.uk\/wp_blog\/wp-content\/uploads\/2010\/12\/main_brd-1024x727.png 1024w, http:\/\/www.emtronics.co.uk\/wp_blog\/wp-content\/uploads\/2010\/12\/main_brd.png 1170w\" sizes=\"auto, (max-width: 300px) 100vw, 300px\" \/><\/a><figcaption id=\"caption-attachment-10\" class=\"wp-caption-text\">Compass belt board<\/figcaption><\/figure><\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<p>Notes: The values of components on the schematic may not be accurate. The Data+\/- for the USB are not routed, these were wired up.<\/p>\n<p>These are the main components:<\/p>\n<ul>\n<li><a href=\"http:\/\/uk.farnell.com\/jsp\/search\/productdetail.jsp?SKU=1455073\">AT90USB162<\/a><\/li>\n<li><a href=\"http:\/\/www.robotshop.com\/eu\/parallax-hitachi-hm55b-dual-axis-compass-module.html?utm_source=google&amp;utm_medium=base&amp;utm_campaign=GoogleUK\">HM55B <\/a>compass module<\/li>\n<li><a href=\"http:\/\/uk.farnell.com\/jsp\/search\/productdetail.jsp?SKU=1628221\">MAX1551<\/a> &#8211; Li-Ion charger<\/li>\n<li><a href=\"http:\/\/uk.farnell.com\/jsp\/search\/productdetail.jsp?SKU=1652419\">ULN2803 <\/a>&#8211; NPN transistor array<\/li>\n<li><a href=\"http:\/\/uk.farnell.com\/jsp\/search\/productdetail.jsp?SKU=1469641\">16 MHz chrystal<\/a><\/li>\n<li><a href=\"http:\/\/uk.farnell.com\/jsp\/search\/productdetail.jsp?SKU=1135395\">TPS73033DBVT <\/a>3.3 regulator<\/li>\n<li><a href=\"http:\/\/uk.farnell.com\/jsp\/search\/productdetail.jsp?SKU=1608080\">Switch<\/a><\/li>\n<li><a href=\"http:\/\/www.pagermotors.com\/\">Pager Motors<\/a><\/li>\n<\/ul>\n<table style=\"height: 317px;\" width=\"336\">\n<tbody>\n<tr>\n<td>\n<p><figure id=\"attachment_19\" aria-describedby=\"caption-attachment-19\" style=\"width: 300px\" class=\"wp-caption alignnone\"><a href=\"http:\/\/www.emtronics.co.uk\/wp_blog\/wp-content\/uploads\/2010\/12\/DSC01204.jpg\"><img loading=\"lazy\" decoding=\"async\" class=\"size-medium wp-image-19\" title=\"Compass Belt printed PCB\" src=\"http:\/\/www.emtronics.co.uk\/wp_blog\/wp-content\/uploads\/2010\/12\/DSC01204-300x225.jpg\" alt=\"\" width=\"300\" height=\"225\" srcset=\"http:\/\/www.emtronics.co.uk\/wp_blog\/wp-content\/uploads\/2010\/12\/DSC01204-300x225.jpg 300w, http:\/\/www.emtronics.co.uk\/wp_blog\/wp-content\/uploads\/2010\/12\/DSC01204-1024x768.jpg 1024w\" sizes=\"auto, (max-width: 300px) 100vw, 300px\" \/><\/a><figcaption id=\"caption-attachment-19\" class=\"wp-caption-text\">Compass Belt printed PCB<\/figcaption><\/figure><\/td>\n<td>\n<p><figure id=\"attachment_20\" aria-describedby=\"caption-attachment-20\" style=\"width: 300px\" class=\"wp-caption alignnone\"><a href=\"http:\/\/www.emtronics.co.uk\/wp_blog\/wp-content\/uploads\/2010\/12\/DSC01206.jpg\"><img loading=\"lazy\" decoding=\"async\" class=\"size-medium wp-image-20\" title=\"Compass Belt PCB developing\" src=\"http:\/\/www.emtronics.co.uk\/wp_blog\/wp-content\/uploads\/2010\/12\/DSC01206-300x225.jpg\" alt=\"Compass Belt PCB developing\" width=\"300\" height=\"225\" srcset=\"http:\/\/www.emtronics.co.uk\/wp_blog\/wp-content\/uploads\/2010\/12\/DSC01206-300x225.jpg 300w, http:\/\/www.emtronics.co.uk\/wp_blog\/wp-content\/uploads\/2010\/12\/DSC01206-1024x768.jpg 1024w\" sizes=\"auto, (max-width: 300px) 100vw, 300px\" \/><\/a><figcaption id=\"caption-attachment-20\" class=\"wp-caption-text\">Compass Belt PCB developing<\/figcaption><\/figure><\/td>\n<\/tr>\n<tr>\n<td>\n<p><figure id=\"attachment_21\" aria-describedby=\"caption-attachment-21\" style=\"width: 300px\" class=\"wp-caption alignnone\"><a href=\"http:\/\/www.emtronics.co.uk\/wp_blog\/wp-content\/uploads\/2010\/12\/DSC01209.jpg\"><img loading=\"lazy\" decoding=\"async\" class=\"size-medium wp-image-21\" title=\"Compass Belt PCB etching\" src=\"http:\/\/www.emtronics.co.uk\/wp_blog\/wp-content\/uploads\/2010\/12\/DSC01209-300x225.jpg\" alt=\"Compass Belt PCB etching\" width=\"300\" height=\"225\" srcset=\"http:\/\/www.emtronics.co.uk\/wp_blog\/wp-content\/uploads\/2010\/12\/DSC01209-300x225.jpg 300w, http:\/\/www.emtronics.co.uk\/wp_blog\/wp-content\/uploads\/2010\/12\/DSC01209-1024x768.jpg 1024w\" sizes=\"auto, (max-width: 300px) 100vw, 300px\" \/><\/a><figcaption id=\"caption-attachment-21\" class=\"wp-caption-text\">Compass Belt PCB etching<\/figcaption><\/figure><\/td>\n<td>\n<p><figure id=\"attachment_22\" aria-describedby=\"caption-attachment-22\" style=\"width: 300px\" class=\"wp-caption alignnone\"><a href=\"http:\/\/www.emtronics.co.uk\/wp_blog\/wp-content\/uploads\/2010\/12\/DSC01216.jpg\"><img loading=\"lazy\" decoding=\"async\" class=\"size-medium wp-image-22\" title=\"Compass Belt PCB\" src=\"http:\/\/www.emtronics.co.uk\/wp_blog\/wp-content\/uploads\/2010\/12\/DSC01216-300x225.jpg\" alt=\"Compass Belt PCB\" width=\"300\" height=\"225\" srcset=\"http:\/\/www.emtronics.co.uk\/wp_blog\/wp-content\/uploads\/2010\/12\/DSC01216-300x225.jpg 300w, http:\/\/www.emtronics.co.uk\/wp_blog\/wp-content\/uploads\/2010\/12\/DSC01216-1024x768.jpg 1024w\" sizes=\"auto, (max-width: 300px) 100vw, 300px\" \/><\/a><figcaption id=\"caption-attachment-22\" class=\"wp-caption-text\">Compass Belt PCB<\/figcaption><\/figure><\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<p>I produced the board using Photo Etching FR4, briefly the steps involved are:<\/p>\n<ul>\n<li>Print onto translucent paper using a laser printer (print inverted!)<\/li>\n<li>Exposed the PCB using UV light<\/li>\n<li>Develope the PCB using special solution<\/li>\n<li>Etching in acid<\/li>\n<\/ul>\n<p>I used a 2 layer board, but as mentioned above the bottom layer is only a ground layer, so does not need to be etched (leave protective plastic on).<\/p>\n<table style=\"height: 317px;\" width=\"336\">\n<tbody>\n<tr>\n<td>\n<p><figure id=\"attachment_43\" aria-describedby=\"caption-attachment-43\" style=\"width: 300px\" class=\"wp-caption alignnone\"><a href=\"http:\/\/www.emtronics.co.uk\/wp_blog\/wp-content\/uploads\/2010\/12\/DSC01224.jpg\"><img loading=\"lazy\" decoding=\"async\" class=\"size-medium wp-image-43\" title=\"Compass Belt board soldered\" src=\"http:\/\/www.emtronics.co.uk\/wp_blog\/wp-content\/uploads\/2010\/12\/DSC01224-300x225.jpg\" alt=\"Compass Belt board soldered\" width=\"300\" height=\"225\" srcset=\"http:\/\/www.emtronics.co.uk\/wp_blog\/wp-content\/uploads\/2010\/12\/DSC01224-300x225.jpg 300w, http:\/\/www.emtronics.co.uk\/wp_blog\/wp-content\/uploads\/2010\/12\/DSC01224-1024x768.jpg 1024w\" sizes=\"auto, (max-width: 300px) 100vw, 300px\" \/><\/a><figcaption id=\"caption-attachment-43\" class=\"wp-caption-text\">Compass Belt board soldered<\/figcaption><\/figure><\/td>\n<td>\n<p><figure id=\"attachment_44\" aria-describedby=\"caption-attachment-44\" style=\"width: 300px\" class=\"wp-caption alignnone\"><a href=\"http:\/\/www.emtronics.co.uk\/wp_blog\/wp-content\/uploads\/2010\/12\/DSC01225.jpg\"><img loading=\"lazy\" decoding=\"async\" class=\"size-medium wp-image-44\" title=\"Compass Belt board soldered 1\" src=\"http:\/\/www.emtronics.co.uk\/wp_blog\/wp-content\/uploads\/2010\/12\/DSC01225-300x225.jpg\" alt=\"Compass Belt board soldered 1\" width=\"300\" height=\"225\" srcset=\"http:\/\/www.emtronics.co.uk\/wp_blog\/wp-content\/uploads\/2010\/12\/DSC01225-300x225.jpg 300w, http:\/\/www.emtronics.co.uk\/wp_blog\/wp-content\/uploads\/2010\/12\/DSC01225-1024x768.jpg 1024w\" sizes=\"auto, (max-width: 300px) 100vw, 300px\" \/><\/a><figcaption id=\"caption-attachment-44\" class=\"wp-caption-text\">Compass Belt board soldered 1<\/figcaption><\/figure><\/td>\n<\/tr>\n<tr>\n<td>\n<p><figure id=\"attachment_45\" aria-describedby=\"caption-attachment-45\" style=\"width: 300px\" class=\"wp-caption alignnone\"><a href=\"http:\/\/www.emtronics.co.uk\/wp_blog\/wp-content\/uploads\/2010\/12\/DSC01226.jpg\"><img loading=\"lazy\" decoding=\"async\" class=\"size-medium wp-image-45\" title=\"Compass Belt board soldered 2\" src=\"http:\/\/www.emtronics.co.uk\/wp_blog\/wp-content\/uploads\/2010\/12\/DSC01226-300x225.jpg\" alt=\"Compass Belt board soldered 2\" width=\"300\" height=\"225\" srcset=\"http:\/\/www.emtronics.co.uk\/wp_blog\/wp-content\/uploads\/2010\/12\/DSC01226-300x225.jpg 300w, http:\/\/www.emtronics.co.uk\/wp_blog\/wp-content\/uploads\/2010\/12\/DSC01226-1024x768.jpg 1024w\" sizes=\"auto, (max-width: 300px) 100vw, 300px\" \/><\/a><figcaption id=\"caption-attachment-45\" class=\"wp-caption-text\">Compass Belt board soldered 2<\/figcaption><\/figure><\/td>\n<td>\n<p><figure id=\"attachment_46\" aria-describedby=\"caption-attachment-46\" style=\"width: 300px\" class=\"wp-caption alignnone\"><a href=\"http:\/\/www.emtronics.co.uk\/wp_blog\/wp-content\/uploads\/2010\/12\/DSC01228.jpg\"><img loading=\"lazy\" decoding=\"async\" class=\"size-medium wp-image-46\" title=\"Compass Belt board soldered protected\" src=\"http:\/\/www.emtronics.co.uk\/wp_blog\/wp-content\/uploads\/2010\/12\/DSC01228-300x225.jpg\" alt=\"Compass Belt board soldered protected\" width=\"300\" height=\"225\" srcset=\"http:\/\/www.emtronics.co.uk\/wp_blog\/wp-content\/uploads\/2010\/12\/DSC01228-300x225.jpg 300w, http:\/\/www.emtronics.co.uk\/wp_blog\/wp-content\/uploads\/2010\/12\/DSC01228-1024x768.jpg 1024w\" sizes=\"auto, (max-width: 300px) 100vw, 300px\" \/><\/a><figcaption id=\"caption-attachment-46\" class=\"wp-caption-text\">Compass Belt board soldered protected<\/figcaption><\/figure><\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<p>Above shows the components soldered to the board. I removed the pins to the compass module and attached it to the pads on the board.<\/p>\n<p>The HM55B is supposed to be powered by 5v, the circuit is 3.3v so I bypassed the onboard regulator.<\/p>\n<h3>Software<\/h3>\n<p>The software is written in assemblyon the AVR. It needs to read data from the HM55B, perform calibration, calculate the angle,\u00a0 control motors.<\/p>\n<figure id=\"attachment_49\" aria-describedby=\"caption-attachment-49\" style=\"width: 171px\" class=\"wp-caption aligncenter\"><a href=\"http:\/\/www.emtronics.co.uk\/wp_blog\/wp-content\/uploads\/2010\/12\/compass_belt_soft_flow.png\"><img loading=\"lazy\" decoding=\"async\" class=\"size-full wp-image-49\" title=\"Compass Belt Software\" src=\"http:\/\/www.emtronics.co.uk\/wp_blog\/wp-content\/uploads\/2010\/12\/compass_belt_soft_flow.png\" alt=\"Compass Belt Software\" width=\"171\" height=\"445\" srcset=\"http:\/\/www.emtronics.co.uk\/wp_blog\/wp-content\/uploads\/2010\/12\/compass_belt_soft_flow.png 171w, http:\/\/www.emtronics.co.uk\/wp_blog\/wp-content\/uploads\/2010\/12\/compass_belt_soft_flow-115x300.png 115w\" sizes=\"auto, (max-width: 171px) 100vw, 171px\" \/><\/a><figcaption id=\"caption-attachment-49\" class=\"wp-caption-text\">Compass Belt Software<\/figcaption><\/figure>\n<p>In order to calculate the heading arctan needs to be calculated, to do this on the AVR I made a lookup table. The table only needs to cover 0 to 45 degrees.<\/p>\n<p><strong>I created the table so the heading would be calculated 0 &#8211; 255, instead of 0 &#8211; 360<\/strong>. This make its much easier to perform calculations on an 8bit micro.<\/p>\n<pre>For n = 0 to 255\r\n    ARCTAN_LOOKUP[n] = arc-tan(n\/255) * (180\/pi) * (255\/360)\r\nNext<\/pre>\n<p>This makes a lookup table of 256 elements covering 0 to 45 degress (values 0 to 32).<\/p>\n<p>To calculate the angle:<\/p>\n<pre>ARCTAN_LOOKUP[(Y * 256) \/ x] (for Y less than X)<\/pre>\n<pre>64 - ARCTAN_LOOKUP[(X * 256) \/ Y] (for X less than Y)<\/pre>\n<p>Then use the sign of X and Y to find the quadrant. Notice I use a 16bit divide routine, this is the only expensive operation.<\/p>\n<h4>Calculating the offsets.<\/h4>\n<p>When using the compass module, I found there was often an offset on the X and Y values, this makes the heading calcuation very inaccurate and must be removed.\u00a0 Also, the module is very senstive to angle, and it would give wild results if not calibrated. I found finding the X and Y offsets for a given angle increased the accuracy.<\/p>\n<p>For this reason, when the belt is turned on, you need to do some calibration. This works by going into a loop monitoring X and Y from the HM55B, and continually updates the Max and Min values of X and Y it sees, the user must spin round about 2 or 3 times so the Max and Min can be established.<\/p>\n<h3>The Belt<\/h3>\n<table style=\"height: 317px;\" width=\"336\">\n<tbody>\n<tr>\n<td>\n<p><figure id=\"attachment_50\" aria-describedby=\"caption-attachment-50\" style=\"width: 300px\" class=\"wp-caption alignnone\"><a href=\"http:\/\/www.emtronics.co.uk\/wp_blog\/wp-content\/uploads\/2010\/12\/DSC01220.jpg\"><img loading=\"lazy\" decoding=\"async\" class=\"size-medium wp-image-50\" title=\"Belt Construction\" src=\"http:\/\/www.emtronics.co.uk\/wp_blog\/wp-content\/uploads\/2010\/12\/DSC01220-300x225.jpg\" alt=\"Belt Construction\" width=\"300\" height=\"225\" srcset=\"http:\/\/www.emtronics.co.uk\/wp_blog\/wp-content\/uploads\/2010\/12\/DSC01220-300x225.jpg 300w, http:\/\/www.emtronics.co.uk\/wp_blog\/wp-content\/uploads\/2010\/12\/DSC01220-1024x768.jpg 1024w\" sizes=\"auto, (max-width: 300px) 100vw, 300px\" \/><\/a><figcaption id=\"caption-attachment-50\" class=\"wp-caption-text\">Belt Construction<\/figcaption><\/figure><\/td>\n<td>\n<p><figure id=\"attachment_51\" aria-describedby=\"caption-attachment-51\" style=\"width: 300px\" class=\"wp-caption alignnone\"><a href=\"http:\/\/www.emtronics.co.uk\/wp_blog\/wp-content\/uploads\/2010\/12\/DSC01221.jpg\"><img loading=\"lazy\" decoding=\"async\" class=\"size-medium wp-image-51\" title=\"Belt Construction 1\" src=\"http:\/\/www.emtronics.co.uk\/wp_blog\/wp-content\/uploads\/2010\/12\/DSC01221-300x225.jpg\" alt=\"Belt Construction 1\" width=\"300\" height=\"225\" srcset=\"http:\/\/www.emtronics.co.uk\/wp_blog\/wp-content\/uploads\/2010\/12\/DSC01221-300x225.jpg 300w, http:\/\/www.emtronics.co.uk\/wp_blog\/wp-content\/uploads\/2010\/12\/DSC01221-1024x768.jpg 1024w\" sizes=\"auto, (max-width: 300px) 100vw, 300px\" \/><\/a><figcaption id=\"caption-attachment-51\" class=\"wp-caption-text\">Belt Construction 1<\/figcaption><\/figure><\/td>\n<\/tr>\n<tr>\n<td>\n<p><figure id=\"attachment_52\" aria-describedby=\"caption-attachment-52\" style=\"width: 300px\" class=\"wp-caption alignnone\"><a href=\"http:\/\/www.emtronics.co.uk\/wp_blog\/wp-content\/uploads\/2010\/12\/DSC01231.jpg\"><img loading=\"lazy\" decoding=\"async\" class=\"size-medium wp-image-52\" title=\"Compass Belt\" src=\"http:\/\/www.emtronics.co.uk\/wp_blog\/wp-content\/uploads\/2010\/12\/DSC01231-300x225.jpg\" alt=\"Compass Belt\" width=\"300\" height=\"225\" srcset=\"http:\/\/www.emtronics.co.uk\/wp_blog\/wp-content\/uploads\/2010\/12\/DSC01231-300x225.jpg 300w, http:\/\/www.emtronics.co.uk\/wp_blog\/wp-content\/uploads\/2010\/12\/DSC01231-1024x768.jpg 1024w\" sizes=\"auto, (max-width: 300px) 100vw, 300px\" \/><\/a><figcaption id=\"caption-attachment-52\" class=\"wp-caption-text\">Compass Belt<\/figcaption><\/figure><\/td>\n<td>\n<p><figure id=\"attachment_53\" aria-describedby=\"caption-attachment-53\" style=\"width: 300px\" class=\"wp-caption alignnone\"><a href=\"http:\/\/www.emtronics.co.uk\/wp_blog\/wp-content\/uploads\/2010\/12\/DSC01232.jpg\"><img loading=\"lazy\" decoding=\"async\" class=\"size-medium wp-image-53\" title=\"Compass Belt 1\" src=\"http:\/\/www.emtronics.co.uk\/wp_blog\/wp-content\/uploads\/2010\/12\/DSC01232-300x225.jpg\" alt=\"Compass Belt 1\" width=\"300\" height=\"225\" srcset=\"http:\/\/www.emtronics.co.uk\/wp_blog\/wp-content\/uploads\/2010\/12\/DSC01232-300x225.jpg 300w, http:\/\/www.emtronics.co.uk\/wp_blog\/wp-content\/uploads\/2010\/12\/DSC01232-1024x768.jpg 1024w\" sizes=\"auto, (max-width: 300px) 100vw, 300px\" \/><\/a><figcaption id=\"caption-attachment-53\" class=\"wp-caption-text\">Compass Belt 1<\/figcaption><\/figure><\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<p>I used a black leather belt to attach the motors and wires, admittedly it does not look very neat, but because it is mostly black other people would not notice it on! I used velcro for the circuit and battery, so it can easily be removed.<\/p>\n<h3>Files<\/h3>\n<p><a href=\"http:\/\/www.emtronics.co.uk\/wp_blog\/wp-content\/uploads\/2010\/12\/compass.rar\">Compass Belt Eagle files<\/a><\/p>\n<p><a href=\"http:\/\/www.emtronics.co.uk\/wp_blog\/wp-content\/uploads\/2010\/12\/compass_belt_asm.rar\">Compass Belt AVR Studio files<\/a><\/p>\n<h3>Results<\/h3>\n<p>It works as expected, I have only been wearing it for a couple of days, so will need to give it longer for proper results.<\/p>\n<p>Please feel free to ask any questions you may have!<\/p>\n","protected":false},"excerpt":{"rendered":"<p>Introduction Last year I saw an article on Engadget on the Haptic Compass Belt, since then I have<\/p>\n","protected":false},"author":1,"featured_media":43,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[3],"tags":[],"class_list":["post-6","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-projects"],"_links":{"self":[{"href":"http:\/\/www.emtronics.co.uk\/wp_blog\/index.php?rest_route=\/wp\/v2\/posts\/6","targetHints":{"allow":["GET"]}}],"collection":[{"href":"http:\/\/www.emtronics.co.uk\/wp_blog\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"http:\/\/www.emtronics.co.uk\/wp_blog\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"http:\/\/www.emtronics.co.uk\/wp_blog\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"http:\/\/www.emtronics.co.uk\/wp_blog\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=6"}],"version-history":[{"count":21,"href":"http:\/\/www.emtronics.co.uk\/wp_blog\/index.php?rest_route=\/wp\/v2\/posts\/6\/revisions"}],"predecessor-version":[{"id":309,"href":"http:\/\/www.emtronics.co.uk\/wp_blog\/index.php?rest_route=\/wp\/v2\/posts\/6\/revisions\/309"}],"wp:featuredmedia":[{"embeddable":true,"href":"http:\/\/www.emtronics.co.uk\/wp_blog\/index.php?rest_route=\/wp\/v2\/media\/43"}],"wp:attachment":[{"href":"http:\/\/www.emtronics.co.uk\/wp_blog\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=6"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"http:\/\/www.emtronics.co.uk\/wp_blog\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=6"},{"taxonomy":"post_tag","embeddable":true,"href":"http:\/\/www.emtronics.co.uk\/wp_blog\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=6"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}