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Thread: Hydro powering Teensy + screen

  1. #1

    Hydro powering Teensy + screen

    I'm trying to get a project going that involves a Teensy 3.2 running a simple game, displaying on a 2.2" TFT display (this one). The catch - I'd like to make it fully hydro powered (and self contained, i.e., not connected to mains water supply).

    After trying to make my own water mill system I've been experimenting with simple water turbines from amazon like this. They work really well when hooked up to a garden hose, and I've managed to get the teensy up and running the sketch that way. There's plenty of water pressure and I get the voltage/current required. It's pretty hilarious.

    I've since tried to make the water system self contained, using water bottles and piping. I've learned that in order to get the right water pressure I need some pretty serious height, which is also pretty fun.

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    Anyway, with that height the turbine is running nice and fast and giving me a reading of around 9v, though it is pretty shaky of course. When I hook up the Teensy/screen to the turbine using this system the sketch doesn't launch properly. The screen turns on and the LED on the Teensy flickers, but the sketch just doesn't get going. I would guess it's stuck loading the firmware or something.

    My suspicion is that the power supply needs to be cleaned up somehow before sending it to the Teensy. I tried putting in a 7805 voltage regulator but it didn't work (the Teensy didn't turn on at all).

    My questions are: does that suspicion seem correct? Does anyone have tips to do that? I'm imagining that I should put a capacitor across the turbine, probably with a diode? Or am I barking up the wrong tree? It does work when hooked up to the main water supply, so do I just need to generate more pressure?

  2. #2
    Senior Member+ MichaelMeissner's Avatar
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    Nov 2012
    Ayer Massachussetts
    I am a software guy, so this is more of a guess than anything else. I suspect that you probably want to have a battery in between the raw hydro power and the Teensy. The hydro power would recharge the battery and the battery would smooth out the power draw providing enough power when the teensy needs a bit more juice, particularly during startup and to cover over temporary gaps in power supply.

    I would probably want to use a 5v step-up/step-down voltage converter between the hydro power and battery. While a pure step-down converter would be more efficient, I tend to err on not trusting that my power supplies will always produce the voltage they say they will.

    You would feed this 5v into the battery charger, which then connects to the Teensy. One that comes to mind is this product from Adafruit. There are various other options, but this is fairly simple. You would add a standard USB to micro-B cable to connect from the charger to the Teensy, and when you wanted to program the Teensy, you would just disconnect the USB cable and plug it in the computer. You wouldn't have to worry about cutting the VIN/VUSB connection, providing power blocking diodes, etc. You should be able to solder the output of the voltage regulator to the 5v/ground pins (or convert it to a micro-B usb plug):

    You would need to connect a Li-poly battery. There are many different ones. With the various rules and regulations about batteries, it is probably best to use a distributor in your country:

    I do see solar power setups, so perhaps look those up, and just substitute the hydro power for the solar panels.

  3. #3
    oh yes, I should have mentioned that I'm trying to avoid the battery route. for various reasons I'm hoping to make something that *only* runs when the water is running, and I figured the best way to enforce that is to just use the raw power being generated by the turbine.

    I recognize this is fairly silly, but I'd like to try doing it that way for conceptual reasons more than anything else!

  4. #4
    A bit of an update, on the microscopic chance that anyone wants to attempt this in the future...

    I bought a voltage converter and added this into my circuit - I went for this multipack from Amazon, which appealed to me mainly because of the variable control of the voltage output.

    Long story short, I got it working! It turns out, unsurprisingly, that the screen I was using was drawing much more power than the Teensy. So I've rigged up a circuit where I'm connecting the turbine to the voltage converter, which is set to the lowest amount of voltage output required to get the sketch running on the Teensy (I think this is around 4v, though I haven't checked exactly). However I'm taking the voltage from the turbine *before* it gets to the converter, and sending that to power the screen, via a diode and a 7805 voltage regulator. I don't pretend to understand exactly why this combination works, or even whether it's a correct way of doing it, but it seems to do the job.

    If anyone's interested I can knock up a rough schematic and measure the voltages and so on.

  5. #5
    thanks for your help, Michael! fingers crossed I've worked out a solution now...

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