Bypass touch button on fan

[Danster]

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]

I would probably bypass the entire circuit board.

The fan will most likely run when mains power is connected between "L" and one of "LOW", "MID" and "HI". If you pick a speed, and connect the remote switch in series, then the fan can be turned on and off remotely using the remote in its latching mode. The remote must be rated to the mains voltage and the current that the fan takes to work like that.

If you want to keep the control board, connect the remote to the ON/OFF connection with a capacitor in series, and the other side of the remote to ground. You should use a small, mains rated capacitor, maybe 100 pF. That should simulate someone pressing the button. The remote would be used in its momentary mode.

 

[Danster]

I would probably bypass the entire circuit board.

The fan will most likely run when mains power is connected between "L" and one of "LOW", "MID" and "HI". If you pick a speed, and connect the remote switch in series, then the fan can be turned on and off remotely using the remote in its latching mode. The remote must be rated to the mains voltage and the current that the fan takes to work like that.

If you want to keep the control board, connect the remote to the ON/OFF connection with a capacitor in series, and the other side of the remote to ground. You should use a small, mains rated capacitor, maybe 100 pF. That should simulate someone pressing the button. The remote would be used in its momentary mode.

Thank you for your idea, but i want find way, how i can baypass only button, because that fan have remote control, and i want to use it as well.

 

[Diver300]

Thank you for your idea, but i want find way, how i can baypass only button, because that fan have remote control, and i want to use it as well.

Well the method with a capacitor and connecting to the button connection is likely to work. It might not, as it is not clear what the original circuit is actually measuring from the buttons.

 

[Danster]

Well the method with a capacitor and connecting to the button connection is likely to work. It might not, as it is not clear what the original circuit is actually measuring from the buttons.

Can you please draw me where i have to connect capacitor and momentary switch? And there is way to bypass it on MCU1 (microcontroller) componet?

 

[Diver300]

This is what I am suggesting. You should keep the smart switch close to the fan, like a few cm away.

I don't know what you mean about bypassing it on the MCU. You could send a signal to the MCU, you can make the output device turn on without the MCU turning it on, or you can change the way that the MCU works by changing its programming or replacing it. Which one do you mean?

My suggestion is trying to fool the input into thinking that someone has touched the ON/OFF button. The ON/OFF button connects directly to the MCU via R34 which is 560 Ohms.

The MCU controls the five transistors TR1 to TR5 via five resistors, each of 270 Ohm. They are R6, R10, R11 and two that I can't read, but the resistors are all labelled "271". You might be able to turn the transistors on with some circuitry other than the MCU.

 

[Danster]

And capacitor in that circuit will be 100pF yeah? And where i can connect ground (i mean can i find it on pcb board?).

Yeah, I mean send signal to mcu like in this post (without any capacitor or anything else). Will by that possible?

PS: Sorry for my bad english.

 

[Diver300]

The capacitor will be 100 pF. Ground should be the mains ground. It may not be on the board at all.

When those touch switches work normally, they are measuring the capacitance to ground through whoever touches them. That is what you are trying to simulate.

 

[Diver300]

I think that the wire that connects to all five of the big transistors is the negative of the circuit, but I am not sure if connecting the ground of the relay to that point will work.

That whole circuit is not isolated from ground. You should consider any part of it to be as dangerous as the mains electrical supply.

 

[christinescoms]

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 countertop resurfacing dallas

How do eliminate the touch switch so the machine comes on when given power? R23 is the switch.

 

[Danster]

How do eliminate the touch switch so the machine comes on when given power? R23 is the switch.

How it can be switch? It’s only resistor. I don’t understand what your idea is. Please can you explain more detail?

 

[Danster]

The capacitor will be 100 pF. Ground should be the mains ground. It may not be on the board at all.

When those touch switches work normally, they are measuring the capacitance to ground through whoever touches them. That is what you are trying to simulate.

That capacitor can have capacity more or less than 100pF or it have to be exact value 100pF? And for what voltage that capacitor should be?

According to datasheet for MCU ground should be at MCU1 at VSS pin, or am I wrong?

 

[Diver300]

That capacitor can have capacity more or less than 100pF or it have to be exact value 100pF? And for what voltage that capacitor should be?

100 pF is my guess based on the capacitance of a person to ground. You should have a capacitor rated to mains voltage.

 

[Danster]

100 pF is my guess based on the capacitance of a person to ground. You should have a capacitor rated to mains voltage.

I tryied it. And it can be simulate with piece of wire without capacitor. The new problem is so it simulate touch everytime when you touch it with wire. So it somulate touch when it disconnected in momentary switch.

 

[Diver300]

I tryied it. And it can be simulate with piece of wire without capacitor. The new problem is so it simulate touch everytime when you touch it with wire. So it somulate touch when it disconnected in momentary switch.

For that approach to work , you need to get the capacitance of the switch to a very low value. If they are any suppression devices on the switch circuit you will have to remove them.

As I mentioned in post #6, the switch needs to be close to the fan. That is to minimise capacitance to ground.

You could also try a capacitor smaller than 100 pF in series. The fan circuit detects a person through the plastic, so the maximum capacitance it will normally be connected to is very small.

 

[Danster]

For that approach to work , you need to get the capacitance of the switch to a very low value. If they are any suppression devices on the switch circuit you will have to remove them.

As I mentioned in post #6, the switch needs to be close to the fan. That is to minimise capacitance to ground.

You could also try a capacitor smaller than 100 pF in series. The fan circuit detects a person through the plastic, so the maximum capacitance it will normally be connected to is very small.

But when you touch contact of touch button with simple 5 cm wire it also trigger touch button

 

[rjenkinsgb]

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

 

[Diver300]

But when you touch contact of touch button with simple 5 cm wire it also trigger touch button

The system is detecting the capacitance of you to ground, via the wire. If you attach the wire and then let go, it will no longer detect anything.

 

[Danster]

The system is detecting the capacitance of you to ground, via the wire. If you attach the wire and then let go, it will no longer detect anything.

Untouched connected wire blocked touch button it act like you holding touch button

 

[Diver300]

How long is the wire that operates the detection circuit?

Untouched connected wire blocked touch button it act like you holding touch button