Bypass touch button on fan

Danster · Jul 1, 2023

Hi there,
I have ask how can I bypass the touch button on fan Sencor SFE 2340WH, please? I want to of/off fan with smart momentary switch. Below is componets names, maybe with reading errors and photos of con board. Thank for all suggestions.

PS: The best solution will be if i will be able to bypass it by two wires (NO/COM). Like in this post.

Components:
TR1-TR5: HSDQ / BT134-800 / A2040D
MCU1:SOC / SC93F8333M (datasheet link)
U1: PN6007 / M35A17

Diver300 · Jul 22, 2023

Danster said:
Yeah, I know but it can be plugged into outlet upside down, so L can be plugged into N…

That is the same for most circuits connected to the mains.

The fan circuit contains a low voltage supply, which runs the processor, labelled MCU1. That supply will most likely be 3.3 V or 5 V, so there is 3.3 V or 5 V between the +ve (Vdd) and -ve (Vss) of that supply. The voltage between the -ve of that supply and ground could be a wide range of voltages, and it may depend on which way round the plug is connected.

The voltage between the -ve of the supply and ground doesn't really matter because nothing is connected between those two points. The 3.3 V or 5 V is important because that processor runs from that supply.

I think that the relay...

Danster · Jul 12, 2023

Diver300 said:
How long is the wire that operates the detection circuit?

As i said, like 5cm

Diver300 · Jul 12, 2023

Danster said:
As i said, like 5cm

If that 5cm wire isn’t connected to or close to anything, it will be quite difficult to create a switch circuit that doesn’t permanently trigger the circuit.

You could try connecting normally open relay contacts between the switch input and the circuit ground that connects to all the big transistors. Tell us if that triggers the circuit.

Danster · Jul 22, 2023

Diver300 said:
If that 5cm wire isn’t connected to or close to anything, it will be quite difficult to create a switch circuit that doesn’t permanently trigger the circuit.

You could try connecting normally open relay contacts between the switch input and the circuit ground that connects to all the big transistors. Tell us if that triggers the circuit.

I am not sure where is the ground that connects to all big transistors, as the fan have two pin plug european (Live and Neutral) and it can be reversed when plug in to power socket. I am worried that I connect 230v to the touch button.

Danster · Jul 22, 2023

rjenkinsgb said:
Try adding a resistor from the touch input to the MCU VSS pin.
That should reduce the touch sensitivity.

Like this?

Diver300 · Jul 22, 2023

Danster said:
I am not sure where is the ground that connects to all big transistors,

I meant the wider pcb track that is at the top of your photo. That track connects to each of the transistors TR1 ... TR5. It is the ground for the circuit, even if it isn't connected to mains earth.

(I now think that they may be triacs, not transistors)

Danster · Jul 22, 2023

Diver300 said:
I meant the wider pcb track that is at the top of your photo. That track connects to each of the transistors TR1 ... TR5. It is the ground for the circuit, even if it isn't connected to mains earth.

(I now think that they may be triacs, not transistors)

Yeah, I know but it can be plugged into outlet upside down, so L can be plugged into N…

Diver300 · Jul 22, 2023

Danster said:
Yeah, I know but it can be plugged into outlet upside down, so L can be plugged into N…

That is the same for most circuits connected to the mains.

The fan circuit contains a low voltage supply, which runs the processor, labelled MCU1. That supply will most likely be 3.3 V or 5 V, so there is 3.3 V or 5 V between the +ve (Vdd) and -ve (Vss) of that supply. The voltage between the -ve of that supply and ground could be a wide range of voltages, and it may depend on which way round the plug is connected.

The voltage between the -ve of the supply and ground doesn't really matter because nothing is connected between those two points. The 3.3 V or 5 V is important because that processor runs from that supply.

I think that the relay has a better chance of working if connected to the -ve (Vss) instead of Vdd in your post #24. Also I suggest common connected to Vss and the touch pin connected to NC.

Danster · Jul 23, 2023

Diver300 said:
That is the same for most circuits connected to the mains.

The fan circuit contains a low voltage supply, which runs the processor, labelled MCU1. That supply will most likely be 3.3 V or 5 V, so there is 3.3 V or 5 V between the +ve (Vdd) and -ve (Vss) of that supply. The voltage between the -ve of that supply and ground could be a wide range of voltages, and it may depend on which way round the plug is connected.

The voltage between the -ve of the supply and ground doesn't really matter because nothing is connected between those two points. The 3.3 V or 5 V is important because that processor runs from that supply.

I think that the relay has a better chance of working if connected to the -ve (Vss) instead of Vdd in your post #24. Also I suggest common connected to Vss and the touch pin connected to NC.

Nice, thank you, it worked! VSS pin to COM on momentary switch and TOUCH BUTTON pin to NO on momentary switch.

Danster · Jul 24, 2023

Diver300 said:
That is the same for most circuits connected to the mains.

The fan circuit contains a low voltage supply, which runs the processor, labelled MCU1. That supply will most likely be 3.3 V or 5 V, so there is 3.3 V or 5 V between the +ve (Vdd) and -ve (Vss) of that supply. The voltage between the -ve of that supply and ground could be a wide range of voltages, and it may depend on which way round the plug is connected.

The voltage between the -ve of the supply and ground doesn't really matter because nothing is connected between those two points. The 3.3 V or 5 V is important because that processor runs from that supply.

I think that the relay has a better chance of working if connected to the -ve (Vss) instead of Vdd in your post #24. Also I suggest common connected to Vss and the touch pin connected to NC.

It can be used without resistor when its working with wire? Like post #28?

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