Open source f/stop enlarger timer

[BetterSense]

Even still, all those requirements were too much for the typical hobbyist who just wanted some basic project.

I use AVR ATMEGA 128 microcontrollers in tons of my own projects, including my enlarger meter, my panoramic camera, my beer fermentation chamber, my automatic fish feeder, and abunch of other things I've long since disassembled.

[nolindan]

The AIM and KIM were $500-ish for a circuit board with a hex keypad, I think.

My firm had a Tek-Lab and a DECWriter, then a couple II's & III's, then it was beige IV's and I^2ICE; finally Intel released PC hosted compilers and ICE. The typical listing book for a single product was 6" thick. Remember green-bar paper, CDC Hawk drives [10MB, 300lbs, 2 minute spin-up time, sound like a 727 taking off]?. How about PL/M-86 & PL/M-51?

Before that it was cross-assemblers running on assorted minis, paper tape, Data I/O programmers and ROM emulators.

[We are showing our ages, we are showing our ages, we are showing our ages...]

[polyglot]

The Arduino is based on the AVR series of microprocessors (uP). The uP alone sells for $3 or so, and for may applications that's all you need.

It used to be that developing software for a uP involved writing a check to Intel for $50,000 for a 'development system'. With the development of uP with Flash memories and JTAG debuging interfaces all that is needed is the uP chip and a $39 interface cable.

You can find an AVR DIY community at http://www.avrfreaks.net/

Indeed it is even easier again than that. The arduino comes with a bootloader which listens on its serial port, plus it has a USB/serial converter. All you need to program it is a USB cable. If someone talks to the bootloader within 1s of reset, it will suck a new application over the wire, write it to program-flash and boot it.

I've been through the whole JTAG/ICSP dance when I used to write PIC assembler but this is so much easier. Of course, you can use ICSP to overwrite the arduino bootloader, reclaim that extra 2kB (1/16 of the total!) program space and not have the bootloader wait for 1s on restart to see if someone is talking to it. But that bootloader is what makes arduino so nice for prototyping; you can go from "board in mailbox" to blinkenleds in about 10 minutes tops using zero additional hardware. After that, it's gcc behind the scenes so you can write whatever C(++) you want.

Avrfreaks is an excellent forum, though you will find plenty of arduino-haters there because it's "too easy" and lets filthy stinky hippie types (who might even be building something arty for Burning Man!) play with microcontrollers instead of just hardcore electrical engineers.

Personally I like to do some code prototyping on the Arduino (Atmel ATmega328) and then if the USB interface is not required, just transplant the 328 into some veroboard. It's also nice for debugging software (since you have a serial port, plenty of IO, etc) before recompiling it for a smaller chip and programming that up with ICSP. For the f/stop timer though, the Arduino will go into the project whole - I will make use of the USB and power supply parts on the board.

If you like the idea of these things but the AVR is too small, slow or otherwise limiting for what you're pondering, have a google for "Cortex M3". 72MHz 32-bit ARM thumb, bucketloads of everything, lightning fast and still available for under $20 on a development board. These are interesting times we live in, for sure.

Anyway, the timer is on pause while I wait for the aluminium enclosure (I splurged to the tune of $20) to arrive from China and for me to have a massive holiday. Once I get back, I'll finish the hardware off and document its construction on my webpage. I posted this on the arduino forums and to some friends and all I got back was "WTF is an fstop timer?". So I'll have to document that a bit more too.

[philipmorg]

Could Arduino be used to make a DIY temperature-controlled faucet similar in function to the Hass Intellifaucet?

[polyglot]

Could Arduino be used to make a DIY temperature-controlled faucet similar in function to the Hass Intellifaucet?

Certainly, but the cost is mostly in the electrically-actuated valves (hardware), not the controller.

[philipmorg]

True, and I can't really tell from the data sheets I'm seeing whether the less expensive solenoid valves offer variable flow rates or just a simple on/off. I imagine a good used Hass Intellifaucet would be the easier route, but those aren't too readily available. Hmmm...

[nolindan]

less expensive solenoid valves offer variable flow rates or just a simple on/off

Simple on-off.

Search for 'motorized valve' to find a flow control valve.

The cheapest are 'zone valves' made for home heating systems. These aren't strictly speaking flow control valves: there isn't any position feedback and valve opening Vs. motor position isn't necessarily linear. However, they may be 'good enough'. You will have to use motor on-time to estimate valve position. When the system turns the water off it would over-drive the valves to the off position to zero their position. Antenna rotators use the same logic with a motor in the set-top control box that mimics the motor in the antenna mast.

Someone who has opened their Intellifaucet may be able to shed some light on the valves therein.

[philipmorg]

Thanks for that information, Nicholas!

[Robert Hall]

Great project. Thank you for your generosity in posting the code and design.

[polyglot]

Update posted on APUG and schematic now available on the website. Now supports a rotary encoder for exposure adjustments.

PCB is designed and will be sent off for manufacture this weekend, which means a small number of them will be available in November if they work.