![\"rocket_lcd1\"](\"http:\/\/int03.co.uk\/blog\/wp-content\/uploads\/2015\/11\/rocket_lcd1.jpg\")
<\/a><\/p>\nI decided to have a round LCD gauge display. This is actually a rectangular 1.8″ TFT display with 160×128 resolution, mounted behind a circular 32mm diameter hole. To make a circular mask to hide the edges of the backlight, I printed a black circular frame onto an Inkjet Transparency, and sandwiched this between the LCD and the front panel. It also serves as a protective film for the LCD.<\/p>\n
The display I’m using is the Hobbytronics TFT Serial<\/a>, largely because I had one spare from another project. This display is unusual in having an on-board Arduino ATmega328 to control the display in response to a basic set of drawing commands sent over 9600 baud serial.<\/p>\n For this application, I wanted to have an analogue gauge effect, which meant filling circular arcs. To achieve this, I wrote a scanline polygon filling routine, which is used to draw small quads, for each 10 degree segment of the arc. To get good performance, I added this polygon fill to the LCD firmware, so that only the polygon coordinates need to be sent via serial.<\/p>\n The gauge is only selectively redrawn (only the parts that change) to improve performance. With these tweaks, the display is fast enough to produce a smoothly animated gauge.<\/p>\n The brains of the operation is a small Arduino Nano board (actually a cheap clone). This has a serial output to drive the display, and various analogue and digital I\/O pins to control the rocket.<\/p>\n There are several switches used to operate the launcher:<\/p>\n There’s a 2-channel relay board<\/a> used to switch a 12V car tyre compressor (100psi maximum pressure) to pressurise the system, and a 12V solenoid valve to launch. These are controlled by two active low GPIO pins.<\/p>\n Pressure is measured using a car oil pressure gauge (rated 0-100psi and 18-126ohm). This is connected to an analogue input, with a 1K resistor to the 5V rail forming a potential divider. ADC raw values were recorded at several 10psi increments, and a straight line fitted in Excel to get the (hard coded) parameters needed to approximately convert ADC values to PSI.<\/p>\n All the connections between the controller and the main launcher go over a long 4 core screened cable, with 5-pin DIN connectors at both ends (5V, \/Fire, \/Pump, Pressure, Ground=Screen).<\/p>\n The code for the controller is up on Github here: nano-launcher<\/a>. The TFT display firmware isn’t yet committed, pending a bit of clean up.<\/p>\n","protected":false},"excerpt":{"rendered":" I’ve basically finished my rocket control panel, except for a few software tweaks I have planned. It now has an LCD display to display pressure and status! I decided to have a round LCD gauge display. This is actually a rectangular 1.8″ TFT display with 160×128 resolution, mounted behind a circular 32mm diameter hole. To make a … Continue reading Rocket control panel finished!<\/span><\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[3],"tags":[],"_links":{"self":[{"href":"https:\/\/int03.co.uk\/blog\/wp-json\/wp\/v2\/posts\/501"}],"collection":[{"href":"https:\/\/int03.co.uk\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/int03.co.uk\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/int03.co.uk\/blog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/int03.co.uk\/blog\/wp-json\/wp\/v2\/comments?post=501"}],"version-history":[{"count":3,"href":"https:\/\/int03.co.uk\/blog\/wp-json\/wp\/v2\/posts\/501\/revisions"}],"predecessor-version":[{"id":776,"href":"https:\/\/int03.co.uk\/blog\/wp-json\/wp\/v2\/posts\/501\/revisions\/776"}],"wp:attachment":[{"href":"https:\/\/int03.co.uk\/blog\/wp-json\/wp\/v2\/media?parent=501"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/int03.co.uk\/blog\/wp-json\/wp\/v2\/categories?post=501"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/int03.co.uk\/blog\/wp-json\/wp\/v2\/tags?post=501"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}\n