Multiple Bluetooth Endpoints

As mentioned in the last post, one of my winters project was to output the multiplexed NMEA signals from Raspberry PI to 2 different Bluetooth transceivers. Before hooking my Bluetooth creation to the Raspberry PI, I wanted to confirm that this setup would work. All this to share data across android devices using a custom NMEA app.

Last night I tested to see if the custom UART converter design could handle multiple Bluetooth transceivers on the same output circuit. I was worried that splitting 1 NMEA output across 2 Bluetooth devices could result in a depleted signal. Because the length of wire connecting the 2 Bluetooth transceivers is so short (and will be short when installed) I was hoping to see little to no reduction of signal quality going to either Bluetooth transceiver.

From the picture below, you can see the breadboard prototype and the 2 Bluetooth transceivers receiving a split NMEA output. 

Testing showed little to no signal depletion (measuring both volts and amps) after hooking the Bluetooth outputs to a voltmeter and comparing the main signal. The entire system, wind instrument + 2 paired Bluetooth transceivers draws 0.12 Amps, that's a whopping 1.44 Watts! Now I know why my 70 aH battery was still partially charged when mistakenly leaving this system on for 2 weeks.

Next I wired up my wind instrument to the breadboard prototype.

Now realizing that the length/distance of wire from the masthead to the electrical panel on Santeria is about 35 to 40 feet, I went ahead and uncoiled a 35 foot length of speaker wire and connected the data output wire of the wind instrument (to mimic the height of the mast). After connecting the speaker wire to the breadboard, I went ahead and paired 2 different Android devices, one to each Bluetooth transceivers. I turned on the fan to get the wind instrument moving, then started the custom Android app.

The results:

Tablet output:

Phone Output:

Giddie Up!

This should work quite nicely aboard Santeria. This double Bluetooth scenario significantly reduces the amount of redesign effort.

Next.....the Raspberry PI!