Making a Hakko 470 work with an 807

[KnuckleheadFlow]

(Actual problem in the last paragraph)

On a whim I bought a working Hakko 470 for a good price. Not having looked into it beforehand, I found it hard to find an 802 for a good price. On another whim, figuring "how different could they be?", I bought an 807. At first I was going to try to adapt the 470's board but realized pretty soon it'd be easier to just build a control board from scratch based on an Arduino Nano. I now know that I probably just should've bought a 47x control board compatible with the 807, but I've actually learned a bit so far and I've got the sunk cost fallacy going in full effect. Besides, I've got some nice Osram DLR2416 displays, it'd be nice to put one to use here. Having read the 470 and 473 manuals, and a bunch of Arduino based soldering iron (starting here) and dot matrix LED interface projects, I've got most of it planned out. Of course constructive criticism will be appreciated.


I figured out the display pretty quickly and I'll reuse the original pot to set the temperature. I figured out the sensor in the 807 is a PT50 RTD, found a resistance/temperature table for it and I've sorted out a voltage divider and op-amp circuit that should give me pretty accurate readings (±1°, way better than I need). I've also read up on getting accurate voltage reference for analog measurement with the Arduino.
(P1 and P2 here is to and from the sensor. A7 is on the Arduino Nano)


I was originally going to use PID and a MOSFET to control the heater, but I believe it'll be simpler to leave it AC and have it simply be turned on and off as needed (cycles on the order of seconds) with an optocoupler and TRIAC. There's a couple TRIACs on the 470's board I can reuse, the second would activate the pump.

What I really need help with is figuring out how the 807's button works. I had a look at the board in the 807 and when pressed, the trigger line has continuity with the heater's H2 line. I've found some useful photos of the 473's board on ebay and I've been using them to try to figure out how the IC reads a button press. To my DC-centric mind, the diodes seem to be going in the wrong direction! And if the heater is not on, how would the button press be detected?


Any help would be appreciated.

[floobydust]

You can easily convert a Hakko 802 gun into an 809 gun.  This adds life to the 470 stations

The 802 heating element (A1029) is obsolete and not worth finding.
I bought a 809 heating element A1313, B1723 element cover, B1724 cover nut, and B2073 filter-pipe kit for 809. and I think a A1319 packing. Total $100.

Here is Hakko doc on doing the conversion, it's hard to find on their website.


Hakko 470 schematic I drew here: https://www.eevblog.com/forum/repair/hakko-470-471-de-soldering-station-schematic/msg1296987/#msg1296987

[rtsmith54]

Thanks for the idea, I'm going to look into this as well with some older weller/ungar base units a different irons