That Samsung matches the pinout for power/gnd, and the fact that pin 4 is input-only also matches how it's used in the circuit. ADC is also available on the right pins.
A little more searching on the Internet about how to read/write those MCUs (the phrase "tool mode" in particular) lead to a forum about programmable remote controls, and eventually a patent and programming software and utilities (written in Visual Basic, it seems) for them... anyone want to do some more RE'ing with all this info?
Anyone have a source for the adapter boards to suit Samsung S3F94C4EZZ ic's ? I PM'ed wguibas a while ago but haven't heard back from him, and he seems not to have been active on this forum for a few months.Tried the attachment under this post: https://www.eevblog.com/forum/reviews/youyue-858d-some-reverse-engineering-custom-firmware/msg782035/#msg782035
Thanks DGM, that's an excellent summary this thread has been lacking!
The important bit you're missing from me is the name of the 'unknown name board' - as shown in the attached picture, it is marked AF858D, and dated 20161212.
In case you want to add it, the details of the adapter board I developed for this PCB are below:
- Schematic: attached
- PCB: https://oshpark.com/shared_projects/NQGwEEH0
- Features:
- TL431 reference
- Vfan and current sense support
- ISP header
- MLF-32 ATmega package
The ADC scaling factor for this board when used with a 2.5v reference was 2.4 in my case.
Thanks everyone for looking at the Rev. A sch and pcb and giving feedback. I corrected the LED digits (misread the F/W assignments) so PCB Rev. B now....
This tach circuit works very well. But it needs a MCU timer/counter or an interrupt becuase of the 1/F relationship to RPM.
The fan curve has RPM/speed and airflow as a complex relationship that is non-linear.
This tach circuit works very well. But it needs a MCU timer/counter or an interrupt becuase of the 1/F relationship to RPM.
The fan curve has RPM/speed and airflow as a complex relationship that is non-linear.
Hmm. Ok. I was thinking that I was going to read the output of the circuit as a voltage on the ADC. I suppose it would make sense to count the pulses. But that confuses me a little... Madworm's original circuit also pulses, but is read on the ADC.
I suppose that the ADC would show higher voltage if more pulses are seen during it's sample period??
Is there any issue with just reading the voltage at the ADC vs counting the pulses?
The "data slicer" I use to pick off fan speed, gives a pulse-width and frequency that changes with the fan speed.
I didn't try turning it into an average DC signal for an A/D.
I found that fan speed is not so useful....
For safety, the temperature climbs very fast if the fan is not working. The original 858D+ firmware looks at this rate of change and will shut down if it climbs too quickly. Take a look at the derivative of temperature term.
You could take fan speed and model airflow for super precise control, but as I said earlier you still don't know what nozzle (restriction) is being used. Each nozzle could get characterized and put on a menu. But you still could be close/far away from the part being heated, so end temperature is not precise here.
That's a really interesting topic. Since I'm able to measure rpm, fan voltage and temperature derivative, together you should be able to characterise nozzle restriction. The fan voltage vs rpm curve would yield different flow (lpm) along the curve at different backpressures. I think the voltage vs rpm curve itself would also change with backpressure. As the temperature derivative would modulate with flow, all together you should be able to deterimine backpressure, and hence nozzle size. You wouldn't need to enter the nozzle size manually I'd imagine.
One big problem with the 858D+ is AC mains noise on the thermocouple signal.
The hand-wand cable has the thermocouple conductors (mV) right next to the heating element conductors (100's V).