![\"TINI](\"http:\/\/www.logicalzero.com\/blog\/images\/tini+socket_thumb.jpg\")
The heart of the beast is an older model TINI<\/a>, a little Java computer with Ethernet and loads of I\/O, all in the shape of a 72-pin SIMM — roughly the height, width and maybe a third the thickness of a pack of gum (although newer models use the DIMM form factor). This sits in an extremely simple breakout board, which basically just provides a RJ45 network jack and a breadboard-compatible set of DIP pins for all 72 conductors on the SIMM. The meters I bought in a lot of ten on eBay. They are all from different sources, are different sizes, and have different units and scales displayed.<\/p>\n![\"The](\"http:\/\/www.logicalzero.com\/blog\/images\/Meters_thumb.jpg\" "\\"The")
The first challenge is to generate the analog signal for the meters. My original idea was to use 1-Wire digital potentiometers. The TINI supports 1-Wire exceptionally well, which is not surprising, as it has invented by the same people. 1-Wire would let me add meters as needed, just attaching them to the 1-Wire bus; I could then direct data to them by the unique ID of each 1-Wire potentiometer.<\/p>\n
The problem with the digital potentiometers is the lack of range. Using the potentiometers to drive the analog meters directly did not give me the even coverage I need. The meters, regardless of their displayed units, are ammeters. Adjusting the resistance gives me a reciprocal curve (if I’m using the term correctly): x\/1, x\/2, x\/3, et cetera.<\/p>\n
I need some sort of ‘real’ digital\/analog conversion; either PWM or some more sophisticated DAC chip. 8 bits of resolution are probably enough; if a meter has an arc of 60 degrees, that gives me increments less than half a percent. I have a couple of candidates in mind.<\/p>\n
More background on this project and its current status to come.<\/p>\n","protected":false},"excerpt":{"rendered":"
The ‘Meter Thing’ — to be granted a better name when one occurs to me — is a project to display on a set of vintage analog meters several numeric data (or data that can be turned into numbers) scraped from the Internet. The heart of the beast is an older model TINI, a little […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":[],"categories":[6,7],"tags":[30],"_links":{"self":[{"href":"http:\/\/www.logicalzero.com\/blog\/index.php?rest_route=\/wp\/v2\/posts\/8"}],"collection":[{"href":"http:\/\/www.logicalzero.com\/blog\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"http:\/\/www.logicalzero.com\/blog\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"http:\/\/www.logicalzero.com\/blog\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"http:\/\/www.logicalzero.com\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=8"}],"version-history":[{"count":1,"href":"http:\/\/www.logicalzero.com\/blog\/index.php?rest_route=\/wp\/v2\/posts\/8\/revisions"}],"predecessor-version":[{"id":42,"href":"http:\/\/www.logicalzero.com\/blog\/index.php?rest_route=\/wp\/v2\/posts\/8\/revisions\/42"}],"wp:attachment":[{"href":"http:\/\/www.logicalzero.com\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=8"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"http:\/\/www.logicalzero.com\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=8"},{"taxonomy":"post_tag","embeddable":true,"href":"http:\/\/www.logicalzero.com\/blog\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=8"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}