![\"Components](\"https:\/\/i0.wp.com\/www.recantha.co.uk\/blog\/wp-content\/uploads\/2023\/08\/PXL_20230819_111355247_sm.jpg?resize=560%2C422&ssl=1\")
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Hi everyone. It’s been a little while! I’ve been horribly busy with various things, including work, so it’s been difficult to keep up with blogging. I have been posting Pi stuff over on Twitter\/X<\/a> (how I hate that new name!) so if you follow me there, you’ll see I’m still active in the community.<\/p>\n Today, I’d like to show you a project I put together over the weekend of 19th-20th August 2023. I decided I wanted to create a temperature sensor, but a portable, battery-powered one.<\/p>\n I went shopping in the Pimoroni sale and bought the following components:<\/p>\n I chose the LiPo Amigo Pro<\/strong> because I wanted the functionality of it being able to charge and supply power to the Pico at the same time. It means I have the choice between plugging it in or leaving it portable.<\/p>\n With the compilation of components laid out, I mentally worked out what I wanted to do.<\/p>\n First of all, I knew that I would need to create a kind of “sandwich” with the Display Pack, the Pico Proto and the Pico W. It was therefore vitally important to work out what to solder, and in what order.<\/p>\n The first thing to do was to put it together “dry” and make sure it would all work together, and that I had the Proto on the right way up! Then, I soldered the BME sensor to the Pico Proto.<\/p>\n As you can see in my slightly-blurred photos (!), I bridged between the 3v3 pin and a vertical rail. This was just in case I needed to add anything else that needed power. As it turned out, I didn’t need this after all, but I’m glad I did anyway. As you can see, the wire wrap split when I soldered it, so I used a pair of tweezers to close it again. Not totally successful, but again, a good idea. You’ll see that I used pins 8 and 9 on the Pico for the I2C connections of the BME. In the event, this was a mistake<\/span> because the Pico Display Pack uses one of the pins for the RGB LED. Never mind!<\/p>\n I dry-assembled it again and realised that if I used the standard pin headers in the project, because of the soldering of the pins through everything, I’d come up a little short. So, I dug out some extended headers from my parts box and soldered those to the Pico instead.<\/p>\n This gave me enough length to go through the Pico Proto and into the Pico Display Pack with solder in between. I did have to trim all the pins to length, though. I took about half a centimetre off of each pin with a pair of side cutters.<\/p>\n I had looked up which pins I needed to solder the JST lead wires to – VSYS and GND. This sends the battery power directly into the Pico, which can take between 1.8V and 5.5V. The battery pack has a nominal voltage of 3.7V, so that’s bang in the middle. The Pico takes care of converting that into the appropriate voltage for its components. I soldered the wires to the Proto board as well and then set about assembling the sandwich again.<\/p>\n As you can see, there is a fair amount of space for the wires. I think this was before I snipped the pins down to size. The finished article has less space, but not so little as to squash the wires or ground anything out.<\/p>\n I then realised that by doing that, it was impossible to tell if the Pico was working or not because I hadn’t programmed it to do anything! I quickly knocked up an LED blink script in MicroPython using the Pimoroni firmware for the Pico W<\/a>. To my delight, as you can see above if you look closely, the LED started blinking when powered from the battery. Marvellous! I also added a sensor read-and-print. To my dismay, the sensor failed to initialise! \ud83d\ude41 After an inspection using a multimeter, I worked out that everything was wired correctly. So what was the problem? It turns out there was a tiny sliver of wire between SDA and SCL on the Proto. I took a big breath and blew, and off it went into the distance. I ran the script again and it worked!<\/p>\n I programmed the full code at this point, but more on that later.<\/p>\n The final thing to do was to assemble everything into a nice, near package. Out came the trusty glue gun. First of all, I glued the LiPo Amigo Pro to the bottom of the battery with the USB-C port on the end. Then, I glued everything else together as you can see below:<\/p>\n And, yes, I did clear the glue strands off afterwards!<\/p>\n First things first: Thank you to whoever at Pimoroni (and I think it was Phil “Gadgetoid” Howard) who did the code for the Pico Display Pack and the BME280 sensor library. I stood heavily on the existing code, and I don’t mind admitting that!<\/p>\n I programmed reading the BME280 sensor then fed the readings into the graphing function, slightly adapted to cope with the multiple sets of data. I also coded in a button handler so that I could switch between temperature, humidity and pressure. You can see the results in the demo video below.<\/p>\nThe project<\/h2>\n
The components<\/h2>\n
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Putting it together… Bit by bit…<\/h2>\n
![\"\"](\"https:\/\/i0.wp.com\/www.recantha.co.uk\/blog\/wp-content\/uploads\/2023\/08\/bme280_top.jpg?resize=560%2C297&ssl=1\")
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<\/p>\n![\"\"](\"https:\/\/i0.wp.com\/www.recantha.co.uk\/blog\/wp-content\/uploads\/2023\/08\/pico_long_headers_sm.jpg?resize=560%2C302&ssl=1\")
<\/p>\n![\"\"](\"https:\/\/i0.wp.com\/www.recantha.co.uk\/blog\/wp-content\/uploads\/2023\/08\/sandwich.jpg?resize=560%2C201&ssl=1\")
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<\/p>\n![\"\"](\"https:\/\/i0.wp.com\/www.recantha.co.uk\/blog\/wp-content\/uploads\/2023\/08\/Assembled-1.jpg?resize=560%2C262&ssl=1\")
![\"\"](\"https:\/\/i0.wp.com\/www.recantha.co.uk\/blog\/wp-content\/uploads\/2023\/08\/Assembled-4.jpg?resize=560%2C258&ssl=1\")
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<\/p>\nThe code<\/h2>\n
![\"\"](\"https:\/\/i0.wp.com\/www.recantha.co.uk\/blog\/wp-content\/uploads\/2023\/08\/adafruit_io_graph.jpg?resize=520%2C627&ssl=1\")
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