Hello, my current setup is as per the attached image
, i.e. I have a Sonoff SV connected to a switch (I found out afterwards that the Sonoff SV is actually a switch but this works), which is then connected to a remote control that controls the gate to my residence. Sonoff SV is powered by a repurposed iPhone power cable, i.e. 5v power adapter. The remote control is powered by 2x 3v lithium coin batteries. This all works fine but I’m wanting to now power the remote control from the Sonoff SV or alternatively from a Raspberry Pi. Any suggestions on how I could do this? Many thanks in advance.
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One idea I had was to connect the positive and negative contacts for the batteries to 5v Power and Ground GPIO pins but given that the positive would be 5v and not 6v, I didn’t think this would work. One comment on the web mentioned that the circuit board should be able to accept 5v power as the battery power output would drop as the charge in the batteries lessened.
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Hey Tim,
Using a voltage converter would probably be your best bet, something like this Pololu voltage regulator will provide will allow you to adjust your voltage output from the module and still give you a fair amount of current to work with (depends on the difference between voltages).
Compared to a battery this regulator will provide quite a noisy signal being a switching regulator so depending on how the transmitter is constructed the noise might propagate through to the signal.
Most boards that use batteries have some sort of regulation and protection on board to be able to accept a range of voltages down to a point then it will cut power, it’s definitely possible that it could handle 5V.
Let us know how you go!
Liam.
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Just FYI I plugged the remote into one of the 5v power pins on an RPi and the negative into the ground and it worked like a charm! So glad I don’t need to buy batteries for the remote control anymore.
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Hi Tim,
Cool to hear you got it working with just the Pi. It’s worth double checking how much power the Sonoff switch will draw as you definitely don’t want to draw more than the adapter your Pi is connected to can handle.
https://pinout.xyz/pinout/pin2_5v_power
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I actually decided to get rid of the Sonoff altogether and just use the Pi so no issues with drawing too much power 
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After all that, the distance from the gate remote transmitter and the gate seems to be a bit too far as it doesn’t work 100% consistently. When I had the transmitter closer it worked 100% of the time. So it looks like I’ll need to go back to my Sonoff SV setup and try using the Polulu voltage regulator you suggest.
How would I connect that to a Sonoff SV board, though? Thanks.
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Hey Tim,
You should be able to wire that one up in place of the battery. GND to negative and Vout to +. Be sure to set the voltage to a safe one before plugging it in though! The low end of the button cells voltage would be a safe bet.
Liam.
Sorry, I don’t think I understand. So I wire it up as you suggest but then where’s the power for the gate remote coming from?
It may not be too clear from my photo but if I take the button batteries out of the gate remote the only power is the power coming from the Sonoff SV to the switch to turn the gate remote on and off.
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Hey Tim,
Oooh, I think Liam thought you were trying to power the module itself.
To short the switch and emulate a button press you’ll need atleast 5 wires all up. A relay is perfect here although they are usually used for something a bit higher power, a logic level alternative would be an analog switch: 74HC4066 Quad bilateral analog switch IC | Jaycar Electronics
To get it connected you’ll have to wire the Vcc and GND to the Pi’s power pins and the other to a GPIO pin that you want to control it with
I’m still a bit unclear on the final setup.
This is how I envisage it. Firstly, with the relay module: 
And secondly, without it, i.e. using the switching functionality on the Sonoff SV itself (my preferred setup): 
Is this possible?
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Hey Tim,
I’m still a little bit confused as to what you are looking to do. I had a look over the Sonoff again and it looks as if it’s a WiFi controlled relay.
The voltage regulator will take some voltage and convert it to some other one so you can use it as a source of power. i.e. take a 10V input and convert it to say 5V(you will only be able to get some amount of current out of it as well, the relation for that can be found in the product page).
Putting the Sonoffs relay between the voltage source(regulator) and the device you are looking to switch on and off will be no worries.
In the end it will sound like you’ll have a couple “power loops” as a relay can isolate different systems (isolate here should be taken very loosely here).
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Thanks for that and sounds like my 2nd diagram will be fine, then. Putting it simply I’m just trying to power the gate remote so I don’t have to keep on buying the button batteries.
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Just an update. I ended up using a long network cable to move the RPi closer to the gate and now it works 100% of the time without a problem.
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