High sensitivity Bluetooth antenna?

Hey Everyone,

I have an issue stemming from this thread where I put tire pressure sensors on my spare tires so I know when they need to be refilled. It works, but just barely.

Even though I have an ESP32 as a Bluetooth proxy about 12 feet away from the sensor, the spare tire is essentially sitting in a Faraday cage that is the trunk of my car. The signal strength is about -100 dBm at that distance.

What are some options to improve connectivity? A high sensitivity Bluetooth antenna for the ESP32? Put something in the car to send the signal outside? Something else?

Thank you for your help!

Just leave your spare in the garage :slight_smile:

But seriously…

You may see an improvement from a large antenna like this: How to add an external antenna to an ESP board - #14 by tom_l

But it may still not be enough. Can you move the proxy closer?

How did you generate the graph?

Like I mentioned in that other thread, the sensors just don’t broadcast very ‘loudly’ nor very frequently. Even with a BT Proxy in the vehicle and using an external antenna like Tom mentioned, the sensors spent most of their time in the ‘unavailable’ state during my testing, hence why I went the template sensor route.

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@stevemann I turned on the signal strength entity for the sensor and viewed the graph there.

@brooksben11 Yeah, my brain was just twirling on what could improve the readings and “Faraday cage” sprung to mind since the devices are in the car rather than outside as expected.

@tom_l Good to know external antenna are an option. Do you have suggestions for ESP boards that have built-in antenna connectors and the antenna themselves so I can avoid soldering?

Thanks again!!

Unfortunately the US store is out of stock, https://www.drzzs.com/shop/quinled-esp32/

Are they usually out of stock or is today just a bad day? Where else can they be found?

There are two links in my post. The first one is for the global store (China) where they are in stock.

Ooohhh… It looked weird (different) on mobile when I checked it. Makes sense now. But, getting one from China puts it at $23 delivered. I tried finding it on Amazon but didn’t get any results. What key words should I use (or are they not available on Amazon)?

Thanks again!!

I know this point is not to your goal of using a ESP device as a BLE collector and I don’t have any quantifiable data to go with this. That said, you might explore using USB Bluetooth dongle with a RPI or other lightweight Linux machine. In my playing around with various USB bluetooth dongles and ESP32’s I find the reception of the dongles to be better. Unfortunately, you have to figure out which of the newer Bluetooth dongles are supported by Linux, however, these newer bluetooth 5.x radios do seem to have better reception characteristics over ESP32 boards. In my experience, even ESP32’s with external antennas. Back to my lack of science on this, it might be just that putting the bluetooth radio even a short distance from the MCU board and WiFi antenna via a USB cable that makes most of the difference ¯_(ツ)_/¯ .

Good hunting!

@dproffer Oh, that is an interesting angle. I could use an old Pi3, get a USB Bluetooth dongle with a long antenna, and install some kinda version of Bluetooth Proxy on it. I’ll see what I can find on that.

@tom_l Would either of these work to get a solid Bluetooth signal out of a standard ESP32 Bluetooth proxy setup?



I drive an EV. It doesn’t have a spare tire. Problem solved…

I am seeing a lot of Rube Goldberg solutions here, but can’t you put the USB Proxy closer to the rear of the car? Line on the ceiling of the garage?

At any rate, here is an ESP32 with external antenna. $16 at Amazon.

@stevemann Bold of you to think I have a garage. :wink: I don’t. :disappointed_relieved: Wait, you don’t have a spare tire? :open_mouth:

Is the antenna on your suggestion better than the two cheaper ones I linked to in my post? How is yours powered?

Well, that explains the distance to the nearest proxy…
I don’t have the board, I was just responding to the comment that one of the suggestions was out of stock.

Power? Probably 3.3V. I don’t see a 5V regulator in the photos.

Pick up boards with an usb port. It will be easier to flash.

Done. I ordered the first one I linked. Should be here Wednesday. Thanks!!

Hey Everyone,

I’ve installed the new Bluetooth proxy with the better antenna in the same spot as the previous proxy and removed all other proxies from the area. Here are the results:

As you can see, there is a significant visible improvement in the signal strength by using a better antenna. The signal goes from a -90 to -100 range to a -80 to -90 range with some readings being better than -80.

I hope this information helps other folks here in case you have similar issues.

Good luck and have fun!!

Most EV’s don’t have a spare tire. Less weight means better mileage. Surprisingly, most people never need their spare tire, and look at all the space they would occupy.

Interesting. I wouldn’t have thought the spare would have made a noticeable performance difference, especially compared to the mass of humans. I know I have needed my spare tire a few times (I clipped a sharp curb and blew a tire, hit a random nail on the road causing a slow leak, that kinda thing). Each time it happened, I was back on the road in 10-15 minutes as if nothing had happened.

CSB: I was in a friend’s car when he hit something on the highway that punctured his tire. He had the “free emergency service included” thing instead of a spare tire. We called them and they said, “Yup, you’re covered. We’ll be there to help you in about 3 hours.” A real spare tire would have been greatly appreciated.

Back to EVs, I’m now shocked and disappointed to hear there’s no spare spot. I keep hearing, “There is so much more room in my EV since there is no motor. Check out my fronk!” In my cars, they’ve only come with donuts, but they had room for a full-sized spare, and I have always swapped my donut for a spare with a matching rim. I can understand not including a spare and basing performance metrics without a spare in place, but I had no idea that removing the spot for a spare was a thing. I’m not sure what to think.

Now I’ll have to add, “Does it come with a spot for a spare tire?” to my list of new car requirements since I was assuming there would always be a spot. I’m still flabbergasted at the car industry about this concept of removing… space. What will they do next? “The back windows don’t roll down because we took the window motors out to save weight since most people didn’t roll down the back windows anyway.” Geez!

Or the mass of the battery.

Yeah I’m not buying a car without a spare.