My mother has a washing machine (LG WFS65A01DCT) and randomly I got a feeling to search for it's service manuals and to find why these boards are too expensive to replace?(We cost 1/3rd of the machine's worth 6 years ago)
And surprisingly, it was not complex. But I think the IC TMP87CH46N is hard to source now!
And I thought how can I use this with an Arduino and an old LG washer pressure switch!
Is it doable? And because the MC14069 is hard to source, can I use 74HC14 instead?
In this application the HC14 would be functionally identical to the 14069. Probably much better actually, since those old CMOS parts had some weird failure modes.
That said, have you looked for the boards outside the manufacturer's supply? My 5 year-old washer died due to a bad control board and I found a perfectly working one on eBay for $30.
Thanks! But after I made it, it seems not working(or maybe the Arduino can't pick it's output)
What kind of an output it will output? A square, sine or a triangular wave? and how can I use it on the Arduino to detect the water level of a machine with a similar sensor? (6601EN1005A)
Looking more closely at that circuit I notice that they are feeding an output back to an input so it is going to oscillate. The HC14 has a schmitt trigger input so it will not switch at the same voltage levels, so might not oscillate in the same way this circuit would.
You would need more data on the pressure sensor to determine how else to interface it to an arduino.
The HC14 probably will not work, try a HC04. The input to the micro is integrated with the external filter. Switching that input from VCC to Ground will suffice. Try it at the junction of R24 & C22.
The sensor appears to be a capacitance sensor. It has an oscillator built in and material getting close to it changes the duty cycle of the oscillator. This appears to be what is being detected.
