maelli01 74 Posted June 23, 2014 Share Posted June 23, 2014 Hello,Oh no, not another clock...My first standalone MSP430 project and also my first project tobe programmed "in circuit", and a soldering exercise for the TSSOP housingA tiny LED clock. It is minimalistic by all means:-a TSSOP G2452, no other IC-only one button to set the time-a dumb 4 digit white LED 7 segment display, https://www.sparkfun.com/products/11409-a PCB size of 25mm x 25mm-extremely low powerWanted to find out whether I can use the TSSOP with my usual home made setup,that is Eagle, Deskjet printer, photosensitive base material, UV-lamp, develop,the ugly FeCl3 etching, and then hand-solder.The PCB is single sided of course.I use the lauchpad for programming.The white LEDs of the display are pretty bright at their nominal current.I wanted something low power and just enough brightness to see the time in themiddle of the night with darkness-adapted eyes.So at 4:30 in the morning, the display is much more useful than an LCD.The whole thing draws around 0.3- 0.5mA, LEDs included.CPU runs at 1Mhz, but is in LPM3 most of the time, even though the poor thing hasa restless sleep: it has to wake up 512 times a second, to do the multiplexing.At this low current there are quite a few options for a power supply, I considered- 2 AA cells; would run around half a year- something solar, with supercap- I ended up with direct AC supply via a capacitive dropper, 4700pF mains rated filmcap. Where I live, plugs are polarized, so I know which one if life and which oneis neutral. Still I think that this would not be street-legal without double insulationhousing.Overall I calculated 2milliwatt total power consumption, probably the lowest ofany mains powered clock.If anybody is interested, I might bring schematic and software intohuman-readable form. RobG, dubnet, bluehash and 5 others 8 Quote Link to post Share on other sites
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