Receiving 433mhz signal from remote

I am trying to get an esp32 (3.3v board) to receive signals from a fan remote I have to control something else.
I am currently using the cheap super-regenerative receiver. RCSwitch detects the signals at a range of about 5cm away from the receiver, which is WAY too small for practically anything at all. I need at least a few meters of range. I did add an approx 20cm antenna made of some thin wire to the receiver. I find it amusing that the range is so small you might as well just use a wire.

Would using a super-heterodyne receiver give me an acceptable range?

Are you sure that the remote is transmitting at 433 MHz and using a recognized RCswitch protocol? Many are not using either, and for example, a 433 MHz receiver will respond weakly to a 315 MHz remote.

Here is a tutorial on how to analyze the signals from arbitrary 433 MHz remotes and sensors:
https://rayshobby.net/wordpress/reverse-engineer-wireless-temperature-humidity-rain-sensors-part-1/

I agree. You don't have enough evidence to convict the receiver. If there was no antenna on it at all, that explains a lot. Radios need antennas like cars need tires.

It did have an antenna

I did open the remote, the only labled thing inside was a 13.506 crystal, not sure if that means anything. I will try that tutorial.

Try multiplying it by 32, and you will see! The local oscillator frequency.

I've tried a few different receivers, some IC based as well as the superregen. My impression was that the superhets are better (for obvious reasons), but that antenna tuning and placement, and isolation from local EMI especially from the MCU board and any peripheral modules like LED displays actually make most of the difference. Signal path as well.

After making an rf sniffer like in that tutorial, I have found the problem to be... my massively noisy RGB keyboard on my desk (which won't be near the device for what I am using it for, so it's not an issue)


My keyboard was on from 0 to 5 seconds.

After turning it off, it actually works at an acceptable distance, it's not perfect but it detects the signals most of the time. I was testing it with an arduino mega, but using bluetooth on a 3.3v eps32 board might not work so well, I will test it.

Thanks for letting us know! The "real world" has many interesting surprises in store.

I get a bit of noise from using bluetooth LE on an esp32. I have to use bluetooth le. It usually detects only about 50% of the remote's signals. Are there ways to reduce the impact of it on the receiver?

It's 98% about physical layout. So you have to provide images and schematics to help understand the images...

This is my board. The board in the middle is a level shifter from 5v to 3.3v

That coiled antenna is nearly worthless. 17 cm of straight wire is what you need. It will be most effective if it is perpendicular to a grounded, conductive surface ("ground plane").

First of all, in spite of maybe awkwardness with the USB cable, I would rotate the Sparkfun 180 degrees and all the way to the end, so that the antenna protrudes past the proto board. As is, the antenna is far too close to unconnected strips, and also actual digital circuitry.

Remember also that with the 433MHz type of receiver, the ground isn't RF passive, it's an active counterpoise because the antenna is a monopole. That also makes RX sensitive to noise on the ground. Only with an RF balun, can you decouple RF from the circuit. I suggest using a rigid antenna, like 22 or 24 AWG insulated wire, I loop and twist it at the end for eye protection...

The ground conduction problem is why almost all commercial versions of this use loop or FIFA (a folded type) antennas, because the RF ground is decoupled very well. Look on the ESP. :slight_smile:

On my own protoboards, I have permanent extra jumpers joining all the power and ground connections in multiple places, making a solid grid (as much as possible on those boards). I'm sure it does help with noise.

I've mentioned before, for unknown reasons, I've not had much trouble with RX interference except from some LED displays. I'm sure the casual wiring had something to do with that as well. In conclusion, another nice thing about an antenna tuned for resonance, or as close as possible to it, also filters out of band noise a bit. But not a lot. I think turn the Sparkfun, cross connect the power and ground wires, change the antenna, and add some bypass capacitors on the power rails for good measure. Maybe you can move the receiver further away from the ESP.

Oh, and... I'm almost sure I've seen receivers that will run on 3.3V.

I have moved the receiver and the esp as far away as possible on the breadboard, and changed the antenna as recommended. Without the BT radio on, the receiver works well, but with the BT on it just refuses to work properly.

I'm not really sure what you mean by "cross connecting the power and ground wires".
I have tried waiting for a signal, turning bluetooth on, connecting, etc, then disconnecting but it's too slow.

At this point, I don't think what I'm trying to do is going to work. Thanks for the help though.

Please show an image of the update... By "cross connecting", I mean this... for example, consider the ground. It makes a kind of "U" shape because it runs down one proto strip side, through the power converter, and then back down the other proto side strip. Imagine adding a wire in the middle of the board, connecting the two supply strip grounds. Now it's like an upside down "A" and the electrical length to get from one ground conductor end to the other, is much shorter. Now add another at the opposite end... Now it's like an "8" and the path is even shorter... in your case the power runs different voltages on each side (I think) so you can't do it with those.

Left over stuff... did you add the bypass caps? Did you rotate the Sparkfun? Try putting a layer of foil under the board and grounding it.

Agree on the antenna points made. For 433mhz you will need about 173mm, but you can shorten in (wind it around a pencil, removing the pencil after winding) to make a short antenna.

But back to the OP. If you just trying to control a fan (like ON/OFF), you might fins using something designed for that sort of application. I have used garage door type controller modules for such things. Search ebay for EV1527 and you can see that you can get a receiver and transmitter modules at low cost. You can also get nice looking pre-built remotes for a very small cost.