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I have a remote controller for a portable heater, and working on a small project to be able to control the fan on/off from an arduino with Bluetooh HM-10 module. I thought a solenoid might work by mounting on top of the remote but it doesnt have enough force, I want to remove/desolder the mechanical button and figure out a way to control it without the switch but kind dont really know what circuit I should use, kind of just learning how to use arduino.

Images of remote and button traces below.

Any idea how I could wire this up to arduino via some switch/relay circuit? Any circuit design / schematic would be helpful

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  • Is that a battery powered remote control? Often a opto-coupler is possible, but for this I would use a mechanical contact. Some small 5v reed relays require only 20mA. The arduino uno can drive that directly (without transistor). – Jot Jan 26 '19 at 13:27
  • Would I solder the relay or remove the button and solder on to the pads? – condo1234 Jan 26 '19 at 13:52
  • 1. Don't forget to edit your original question if you have additional thoughts to make the question better. 2. Caution, try a much safer project. A heater project may go wrong and start a fire. Try a low voltage light. 3. With out knowing the voltage and current handled by the part your are replacing it is difficult to make recommendations. That said, if the switch is N.O. then likely you could simply solder the N.O. contacts of the relay across the switch. – st2000 Jan 26 '19 at 14:22
  • I would not remove the button, but solder two wires. To prevent that the wires break, attach them to the board. For example drill a hole and use a cable tie. I often also use hot glue to stick the wires to the board so they don't move where they are soldered. – Jot Jan 26 '19 at 16:59
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I would unsolder the switch then solder in a FET in the configuration shown below. The FET will act as a switch and may be controlled with any digital output from your Arduino board. When selecting a FET makes sure you find something that will fit the foot print you have to work with on your board, and the gate-source threshold voltage is rated to handled 5V.

circuit

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  • Great thanks! Would a BJT NPN transistor work aswell? – condo1234 Jan 27 '19 at 3:07
  • @condo1234 yes...a BJT NPN would accomplish the same task but the FET is less of a load on your Arduino board and more efficient than the BJT. When you have 5vdc on the base of your BJT you will have a constant base-emitter current (BJT load). With the same 5vdc on the FET gate you only need to initially drive the FET capacitance (FET load). – fijismart Jan 27 '19 at 18:22
  • Thanks, would an IRF540n work ok?Also with the 10k resistor can I just link that directly to an arduino ground pin? – condo1234 Jan 28 '19 at 2:50
  • @condo1234 Yes, that could work as long as you don't exceed Vds and Vgs (data sheet specs). That it a pretty beefy FET for what otherwise looks like a low power application. Conceptually you have the idea; now you just need to go through some trial-and-error (design iteration) to get the circuit to do what you want it to do for you. The grounds should be tied together on your Arduino board and the circuit board if they are sharing a circuit (in this case the switch). This is to ensure both circuits are referencing the same ground potential. – fijismart Jan 29 '19 at 15:34
  • @condo1234 If you want to get into circuit design I would advise you to download a Orcad Lite (Free Version of Orcad). This will allow you to layout your circuits and run simulations to help determine how the circuit will behave. Heres the link: orcad.com/resources/download-orcad-lite – fijismart Jan 29 '19 at 15:35

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