PPAC Fixes, Minimalduino, Timer

I've been busy lately and haven't had as much time as I'd like to tinker, but I've gotten things moving in the last two weeks and am overdue to post.

Hoping to show off the alarm clock a little, I brought the PPAC (including power block, valve tree, and tank) to the Make:SF Meetup last month, and while talking and hooking it up at the same time, plugged the AC supply into the DC power socket! The voltage regulator fizzled but the power board seems fine otherwise. Strangely, of all things, the LCD display was dead as well... though I may have killed it when disassembling the can..:o I ordered a better looking LCD replacement which I'll install in the next few days-- green-on-black instead of black-on-green: Newhaven NHD-0216K1Z-NSPG-FBW-L.

The minimalduino project is still moving forward: I'm using a test board I made at home a few weeks ago, populated with as little as possible: chip, caps, resonator, female headers, reset and male FTDI header. I'll move a few traces around but it's pretty much there, and hope to get three test boards made through the DorkbotPDX PCB order, deadline noon on March 29. I've built a spreadsheet with costs, and it seems like I could make a batch of 25 kits at just under $15 each. I'm not sure if it's worth the trouble though.

A few weeks ago, I built a new coffee grinder timer with a re-worked sketch and single board, then handed it off to fellow coffee fiend HF for ideas on how to make the ideal grinder timer. One thing we agreed on is that tenths of a second would be cool, so last night I had a great time working out a sketch to drive a common anode 3-digit 7-segment display using an SAA1064 IC. Of course having a sketch to start with made things straightforward-- thanks Alessandro Saporetti! I reworked the code to make it more general purpose, using all of the chip's functions including multiplexed (versus not) and changing the constant current output (7 output levels possible, from 3 to 21mA). [Video to come]

Getting Out Of Bed: PPAC Major Components

The "Princess and the Pea Alarm Clock" (PPAC) has been working beautifully, waking me up with "buzz" alarms and literally getting me out of bed with "inflate" alarm functions! I will post more photos and videos soon, but first to outline the alarm clock's major components:

• Alarm clock: LeSueur peas tin can containing the main circuit board, jog/shuttle dial and button input, 16x2 character LCD display, modular handset cord jack, and female 6-pin FTDI cable jack.
• Power block: Power input/output circuit mounted in a plastic iPod Nano box, with input DC power jack and regulator, relay input power jack, two relay-switched output jacks, modular handset cord jack, status LEDs, and main power switch.
• Valve tree: Brass and plastic fittings around the main trigger solenoid-controlled sprinkler valve, with quick-release fittings on both ends, manual safety valve before the trigger valve, and manual release valve.
• Air pressure source: 10-gallon (red) or 5-gallon (yellow) air tanks, both with pressure gauges and female quick-release connectors, usually filled to 110-120psi.
• Air bladder, aka "Pea": Green exercise ball between my mattress and box spring, with a hose ending in a male quick release fitting.

LCD difficulties

After putting together a schematic in EAGLE for the shower control circuit, I tinkered a bit trying to get a scrounged Powertip PC1602-G character LCD working. Serial LCDs from SparkFun are easy to use but expensive, in addition to hogging the serial port and being available only in 16x2 and 20x4; I'd like to be able to use cheapo 8x2 or other displays.

I soldered on a pin header and got to breadboarding it with an iDuino, but quickly discovered that the tutorials are pretty haphazard, and I wasn't able to get any output using the LiquidCrystal library in spite of quadruple-checking my schematic and breadboard connections.

I tried Limor's tutorial but got no result, and I think editing the library to set the pins is an odd (wrong?) way for a library to work. I even used the exact same pins-- no dice. I wonder if the scrounged LCDs I'm using have custom commands that makes them incompatible with the library-- I need to try a different LCD, and maybe use Massimo's raw example.

Update: In a comment, Al asked if the LCDs I was trying weren't HD44780-compatible at all and... oops, thats the problem! I got it working fine with an LCD scrounged from an old Brady Labelmaker, which contains an actual Toshiba HD44780.