Recently I bought an almost brand new Yihua 858D on Kijiji, a site similar to Craigslist, for $55 CAD. Overall decent quality, the fuse and switch are on the live wire, the wand is properly grounded, no complains. I tried to calibrate it, it works pretty well for the temperature you calibrate at , but the other end is not really accurate. Therefore I calibrated it around 380C, the temperature that I will probably use most of the time to solder/desolder parts. Close to the lower end 200C it is lower by about 10C, and close to the upper end 450C it is higher by about 5C, so no big deal. It does overshoots when changing the temperature by about +/- 30C, but it stabilizes in about 30 seconds to a minute and is reasonably stable after that, about +/- 2 - 3C.
One issue that I found was that one wire that goes to the triac was reversed, so the triac was on the neutral line rather than live. I swapped the contacts in the connector housing as I want the heater in the wand to be at zero volts when it is in the cradle.
When I bought it I hoped that it is similar to Youyue and I can hack it, and it is but also has some differences:
1. The display is common anode.
2. The optocoupler that controls the triac is drived through an NPN transistor, rather that directly from MCU port, so the control is inverted.
3. The thermocouple amplifier (LM358) is supplied with 5V only, there's no negative voltage on the board.
4. There's no fan voltage sense to the MCU.
5. UP and DOWN buttons inputs are shared with the LED display segments B and F.
The MCU map is:
Pin Function
1 GND
2 LED E
3 LED D
4 NC
5 LED DP
6 LED C
7 LED G
8 LED A
9 LED F shared with DOWN SW
10 LED B shared with UP SW
11 Triac Drive (positive logic)
12 REED SW
13 TC Temp
14 CON7 Pin (Not sure what this is for)
15 NC
16 FAN ON/OFF
17 DIG3 +
18 DIG2 +
19 DIG1 +
20 +5V
@ madworm
If I make an adapter from S3F94C4EZZ to Mega328P, could you help with the SW changes? Display and triac polarity is easy, I may need some help with the temperature measurement and buttons.
Thanks,
Miti