For soldering at home, I use a Hakko hot air rework station. This has a hot air gun, and a standard Hakko soldering pencil (24v, 50W).
My current soldering station is bulky, not portable, and has very poor temperature control (bang-bang rather than PID). I would like to design and build a new controller to be used with Hakko soldering irons. This should provide much better control to the iron, allow more features and customization, and be much more portable.
The current specifications:
- 240v AC mains input (rear IEC socket)
- Internal 60W, 24v toroidal transformer
- Support for virtually all 24v soldering irons
- Able to read the temperature of K-type thermocouple and PTC thermistor irons (selectable via an internal jumper)
- Full PID control of temperature
- Auto standby mode if left in the stand for a certain time (able to tell that from monitoring tip temperature/power requirement)
- 'Turbo mode' activated by a button (increase temperature by 50 degrees for 30 seconds)
- Variable temperature
- Multiple preset temperatures
- All in a neat, compact, aluminium case
Most of those are pretty standard features for a soldering iron driver - including both thermistor and thermocouple sensing sections on the PCB mean I'll be able to carry on using this driver whatever soldering iron I want to use (in other words, when I can afford something nicer than Hakko pencils!).
I'm doing this project as building things is my hobby and it'll be a fun process, rather than a real need for a better iron. I'm hoping to come up with a controller that looks great and controls temperature better than my current station's bang-bang control.
So - the really important bit - the front panel! This is the bit the user (me) will really see, so I want something that looks nice and cool.
I'm currently planning to manufacture the entire front panel of the box out of dark tinted plastic, with the display behind it. In the centre of the front will be three 7 segment displays, showing the set temperature. In a circle around this there will be a circle of 40 red/green bicolour LEDs, which will act as a circular LED bargaph. The set temperature will be shown in red, and as the iron heats up, the LEDs will fill the bar up with green. Sorry if that's a poor description, it looks good in my head!
Presets/turbo would be selected with illuminated tactile buttons - or standard tactile buttons surrounded by LEDs if low profile SMD illuminated switches are too hard to find. Possibly (blue sky thinking here!), use non-contact capacitive sensing for all front panel functions?
I'm having mixed thoughts on what the temperature input should be:
Potentiometer- + Very fine control
- + Very fast control
- + Easy to read in software
- - Will be changed/knocked if station is transported elsewhere
- - Harder to adjust presets etc
Rotary encoder- + Easy to make adjustments to presets
- + Very versatile (can change software)
- - Most of the time you want big steps, other times small changes
- - Requires interrupts in software
- - Very few soldering stations use them - probably a reason for that
Up/Down buttons- + Easy to make adjustments to presets
- + Looks neatest on front panel
- + Can implement fast changing if held down
- + Most digital irons have buttons!
- - Requires interrupts in software
- - Could be a fiddly interface if done poorly
My current view is up/down buttons are the best solution - they're least obtrusive, don't stick out at all, and probably work best with adjusting presets. Capacitive buttons could work really nicely here! A rotary encoder seems unsuited for this - most of the time you want to be able to change temperatures without having to turn a knob multiple times.
Any thoughts or comments would be very welcome. Got any feelings about what the ultimate soldering iron controller should have? Can the front panel be made any cooler than having a circular red/green bargraph around the LED readout?
Looking forward to hearing your views!
Andy