Shower timer

content/post/2024-03-24-Show Timer.md

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+---
+title: 'Shower Timer - aka Embedded RP2040 with Rust'
+date: '2024-03-24'
+layout: post
+slug: showertimer
+summary: Reduce water usage, and play with Rust on RP2040
+tags:
+    - hardware
+    - rust
+keywords:
+    - echo
+    - rust
+    - embedded
+    - rp2040  
+---
+
+
+Self-powered shower timer - inspired by teenagers spending ages in the shower; along with an excuse to build something. 
+
+Saw something similar in a random catalog years ago.
+
+Features:
+
+- Uses water flow generator to create the power needed
+- Compact-ish design to screw into the shower feed
+- RP2040 as the micro-controller
+
+![](/showertimer/IMG_20240318_081910.jpg)
+
+## Generator
+
+Search for Water Turbine, and lots of different things turn up on Amazon and eBay.
+
+Decided to take a chance on [this one](https://www.amazon.co.uk/dp/B07WXK59MK?psc=1&ref=ppx_yo2ov_dt_b_product_details)
+
+- Voltage was 12v - had no idea what type of current/voltages would actually come out. Knowing wthat something in 5-3.3v would be needed seemed that opting for 12v would give some room to drop this and get some current.
+- The connectors were 1/2" threaded which is the UK standard for showers.
+
+### Practical Experiments
+
+On testing it seemed that with only a modest water flow it could get to 12v; taking it apart later determined that there was a regulator and capacitor inside that help to regulate the voltage.   Current to power a couple of LEds was quite sufficient.
+
+This was witih a decent mains-level water pressure.
+
+
+
+## Hardware
+
+There's a 5mm tri=colour LED, driven with 3* 2n2222 transistors from the GPIO pins.
+
+For power I had one these very small boards available [SparkFun BabyBuck Regulator Breakout - 5V](https://thepihut.com/products/sparkfun-babybuck-regulator-breakout-5v-ap63357?variant=42391014506691)
+
+The controller I had available was a [Seed XIAO RP2040](https://thepihut.com/products/seeed-xiao-rp2040?variant=41181796335811)
+
+To address the 'elephant-in-the-room' - a dual core processor is way too much; an embedded arduino, or a PIC controller would have been far better. Even smaller and even less power. 
+
+But for 2 reasons; one the only controller that was small enough was the XIAO; plus after I'd managed to unsolder some of the pads previously it wasn't really up for anything needing SPI or I2C. 
+
+Second reason is you can use Rust!
+
+### Additional parts
+
+Note that the brass converter which is internally threaded to 1/2".  so this was needed to connect to the shower outlet - with washer as well. 
+
+The white outer casing a small plastic container from aquarium fish food; cleaned, label removed and cutdown. Glued with circuit inside. 
+
+![](/showertimer/IMG_20240318_081917.jpg)
+
+## Software
+
+Contained in this repo based on this [tutorial](https://tutoduino.fr/en/tutorials/programing-in-rust-the-xiao-rp2040-board/)
+
+When the power is connected; the software works through using 3 GPIO pins to control the LED. It'll move through Green-Blue-Red-Flashing Red. Moving ever 4 minutes, and ending on the flashing red.
+
+To build the software please see the tutorial mentioned above, the two main commands I used where
+
+```
+cargo build --release
+elf2uf2-rs target/thumbv6m-none-eabi/debug/xiao_rp2040_rs op2.uf2
+```
+
+Rather than `cargo run` which would to try and download the code to the XIAO, I was running this on WSL2 so the transfer was a manual step.
+
+## Does it work?
+
+![](/showertimer/IMG_20240318_082328.jpg)
+![](/showertimer/IMG_20240318_082603.jpg)
+
+Bascially Yes; does it reduce the shower time - well maybe it won't long term when the novelty wears off. 
+
+The big issue is if you turn on the water slowly; the XIAO doesn't start properly. This will be connected to the power; and could be fixed by a hardware reset at some point. 
+
+And really it would be so much better to use a different microprocessor (PIC probably) and also use a proper PCB. 
+