Propane Weigh Scale Hack

Description

The Flame King Propane Tank Scale is a great idea.....but poorly implemented. The battery compartment is on the bottom and so is the On-Off switch. So in order to turn it off, you have to remove the tank. I initially added a toggle switch on the side to fix this issue. But the App is Horrible....almost always reading 80% and is not linear at all. Had so many connection issues....that I decided to update all the electronics inside and also add an iPhone app connected via BLE. So here is my progress to date.

Project Logs

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Working on an update
Steve Smith • 12/06/2023 at 23:48 • 0 comments

Have been using my propane weight scale hack for over a year and it is awesome! Life caught up to me and I didn't get to finish my hack logs, but I will have more time now to make more entries about the software in the last few weeks of December....so stay tuned.! In the mean time...here's a shot of one of the iPhone screens that I designed using RemoteXY application....it's amazing...!
HX711 wiring and the TinyPico ESP32
Steve Smith • 06/03/2022 at 18:06 • 0 comments

Now that I had the Wheatstone thought out, I connected it to the HX711 and wired it as per the example schematic. I had to add the two fixed 1000 ohm resistors per the diagram to make the Wheatstone a full four cell bridge. I added in the color codes of the load cells to the sketch and it is wired internal just like this really Ugly hand sketch shows. Having found the HX711, I went looking for an ESP32 type chipset that was the smallest unit that I could find that was in stock and available. I stumbled into the TinyPico.....it is a full ESP32 with WiFi and BLE and extremely small. I will take more pictures of the installation in future log entries. But I was able to wire it up and tested it and it worked with the example sketches...!! A lot of software work needed to be done....and I was still on the lookout for a way to communicate with an iPhone. The hunt for that continued......
The TinyPico ESP32 Super Small Chipset
Drawing out the Wheatstone Bridge with Resistors. Amplifier selection.
Steve Smith • 06/03/2022 at 16:46 • 0 comments

Having drawn out the main PCB portion....I measured the load cells and did another Ugly Sketch of just the Strain Gauges and how they configured into a wheatstone bridge. Knowing this would allow me to add my own load cell amplifier to this circuit and then output to an AVR type microprocessor. Since I didn't need to recreate the wheel here....I ended up using the HX711, which already had libraries that were well documented and were usable in ESP32 type chips.....which I wanted to use because of their WiFI and Bluetooth capabilities. Wiring diagrams are on the SparkFun page....but I will do a full diagram when I am done with the project.

Sparkfun HX711 Load Cell Amplifier
Decipher and Sketch PCB Strain Gauge Connections
Steve Smith • 06/03/2022 at 16:11 • 0 comments

I started off this project by trying to understand how the existing scale platform was electronically connected. So I just started drawing a sketch based on iphone pictures that I took of the PCB and load cell wiring. It was an UGLY view into basically a 3 way Strain gauge wired as a WheatStone bridge of sorts. The big ah-ha moment was that there were few 3 strain gauge load cell wiring diagrams on the internet......but after deciphering their PCB, I noticed that they filled in the fourth strain gauge with just passive resistors that were trimmed to equal the series resistance of the other 3 strain gauges. So I had a VERY UGLY but preliminary sketch and that was a good start!