Gerrit Niezen

According to the r/hydro reddit, the best value-for-money LED grow lights are the so-called “quantum boards”. These look like a bare PCB with typically Samsung LM301B LEDs, mounted to a metal panel that acts as a heat sink, and with a Meanwell LED driver. They differ from older LED grow light designs that are actively cooled with a fan, being both noisier and bulkier in size.

I found a bunch of the quantum boards on AliExpress/Alibaba, but unfortunately it's always hard to know if you're really getting the original Samsung LEDs, and if you can even return them if something goes wrong.

A couple of Youtubers that specialise in hydroponics mentioned the brand Spider Farmer, whose panels are the typical quantum-style, but have mounted the driver onto the heat sink. They provide an efficacy rating of 2.7 umol/J, and have an after-sales service. At a 10% markup (£126 versus £115 for similar AliExpress boards) that doesn't sound like too bad a deal. They also have a UK warehouse, which means you don't get surprise customs fees on delivery.

£126 sounds like a lot of money for just growing plants, but it's still cheaper than the lights you'll find in a hydroponics shop. After working my way through a mind-numbing amount of conflicting information about grow lights, this does indeed appear to be the best solution at the moment.

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#100DaysToOffload #day60 #hydroponics

For the hydroponics stuff I'm building, I needed to spray some plastic totes. This is so that they don't let any light in that can promote algae growth. Chalkboard spray paint was recommended so that's what I got.

It was only when I got home that I read on the can that plastic needs a primer to go on first. It looked good after spraying it without primer, but you have to handle it very carefully afterwards, otherwise the paint will just crack off.

I also learned that you need to spray from a distance of around 30 cm, otherwise the paint job will look blotchy and very uneven. So there you have it – two tips if you ever need to spray paint plastic containers.

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#100DaysToOffload #day59 #hydroponics

This morning I had a look at the seeds I currently have and started some seeds in rock wool as follows:

1. Placed rock wool cubes (Grodan 36mm SBS) into propagator (Garland Super 7) trays
2. Prepared the cubes with half-strength nutrient solution (5mL Formulex in 1L water)
3. Seeded one or two seeds per cube
4. Labelled each tray
5. Placed trays on heated propagator mat

I planted some “Habanada” sweet peppers (1 seed per cube), “Wild Garden Mix” kale (2 seeds per cube, as well as some lamb lettuce or corn salad (2 seeds per cube).

I also ordered some “Red Robin” tomatoes, which should grow only around 30cm tall, as well as some “Bright Lights” chard, which should be fun to grow.

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#100DaysToOffload #day58 #hydroponics

I'm putting together a spreadsheet of the various requirements to grow different vegetables in hydroponics, e.g.:

• days to first harvest
• pH range
• EC (Electrical Conductivity) range
• Light range
• Temperature

I'm thinking that having something that people could collaboratively edit could be useful. For example, also stating the variety, nutrients, method or grow light that was used. That could lead to creating common “recipes” for specific types of crops. You could even have recipes that change during the growing the period, for example increasing night time temperatures and decreasing daytime temperatures for fruit production in pepper plants after they reach their mature height.

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#100DaysToOffload #day57 #hydroponics

I somehow got stuck on day 55 of #100DaysToOffload in July and suddenly it's September already! Oh well, I guess it's now day 56.

For the month of September I'm taking a sabbatical from work, to work on something different than what I'm usually working on. I decided to work on DIY hydroponics, which I've mentioned a couple of times on this blog in the past. I bought the book DIY Hydroponic Gardens by Tyler Baras, and started to build one of the designs in the book. The one I'm starting with is called a media bed, using a simple “flood and drain” (also called “ebb and flow” or “ebb and flood”) system. It consists of two containers on top of each other, with water pumped up from the bottom container and draining back into it using a pump and a timer.

I've already spray painted one of the containers, and most of the equipment I need have been ordered. I'll post some photos soon.

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#100DaysToOffload #day56 #hydroponics

A couple of weeks ago I mentioned that I was making a simple hydroponics planter on my 3D printer. Well, I just realised that I haven't even posted a picture of the planter, so here we go:

You may notice that the first leaves of the basil seed that I planted just appeared! 🎉️ I started off the seed in a Root Riot cube, surrounded by some clay pellets. I haven't yet put any nutrient solution in the reservoir, but will as soon as the first roots start appearing.

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#100DaysToOffload #day55 #hydroponics

This is the final instalment of my second series of blog posts on MTP. I now have my code working in both the browser and Node.js, where it connects to an Android device, reads the latest file and saves it locally.

First off, I had to write some code to figure out whether we're in the browser, in Node.js or in Electron:

let isBrowser = null;

if (typeof navigator !== 'undefined') {
  const userAgent = navigator.userAgent.toLowerCase();
  isBrowser = userAgent.indexOf(' electron/') === -1 && typeof window !== 'undefined';
} else {
  // Node.js process
  isBrowser = false;
}

I'm sure there are modules out there that do this better, but it works for now. Now we have to load some modules for Node.js when we're not in the browser:

let usb, fs = null;

if (!isBrowser) {
  // For Node.js and Electron
  usb = require('webusb').usb;
  EventTarget = require('events');
  fs = require('fs');
} else {
  usb = navigator.usb; // Yay, we're using WebUSB!
}

We also need to be able to save the file to disk in both the browser and Node.js:

const array = new Uint8Array(data.payload);

if (isBrowser) {
  const file = new Blob([array]);
  const a = document.createElement('a'),
  url = URL.createObjectURL(file);
  a.href = url;
  a.download = this.filename;
  document.body.appendChild(a);
  a.click();
  setTimeout(function() {
    document.body.removeChild(a);
    window.URL.revokeObjectURL(url);
  }, 0);
} else {
  fs.writeFileSync(this.filename, array);
}

We also need to deal with event listeners differently in the browser and Node.js:

const initMTP = () => {
  const mtp = new Mtp(0x0e8d, 0x201d);

  if (isBrowser) {
    mtp.addEventListener('error', err => console.log('Error', err));

    mtp.addEventListener('ready', async () => {
      mtp.addEventListener('data', (e) => mtp.dataHandler(e.detail));
      await mtp.openSession();
    } );
  } else {
    mtp.on('error', err => console.log('Error', err));
    mtp.on('ready', async () => {
      mtp.on('data', (data) => mtp.dataHandler(data));
      await mtp.openSession();
    });
  }
};

And finally, WebUSB requires a user interaction before it will show the permission prompt, so we need:

if (isBrowser) {
  document.addEventListener('DOMContentLoaded', event => {
    let button = document.getElementById('connect');

    button.addEventListener('click', async() => {
      initMTP();
    });
 });
} else {
  initMTP();
}

So, that's it! Over on GitHub I have the full implementation. If you run it in Node.js, it will save the newest file on your Android device to disk. If you run it in the browser, it will do the same after you click the Connect button:

<html>
  <head>
    <title>MTP over WebUSB</title>
    <script src="mtp.js"></script>
  </head>
  <body>
    <button id="connect">Connect</button>
  </body>
</html>

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#100DaysToOffload #day54 #mtp

In the previous post on MTP we looked at how to retrieve the name of a file on an Android device using MTP. Let's see how to decode that filename:

const array = new Uint8Array(data.payload);
const decoder = new TextDecoder('utf-16le');
filename = decoder.decode(array.subarray(1, array.byteLength - 2));
console.log('Filename:', filename);

In short, we need to remove the length byte at the beginning and the zero terminator bytes at the end, and then decode it as UTF-16LE. To retrieve the file itself, we use the following (where CODE.GET_OBJECT.value is 0x1009):

const getFile = {
  type: 1,
  code: CODE.GET_OBJECT.value,
  payload: [objectHandle],
};
await device.transferOut(0x01, buildContainerPacket(getFile));

All that's left to do is to save the data that is returned to a file! (OK, I also need to write some code that handle files that are larger than the buffer we use for transferIn.)

All the code is currently on a branch on GitHub: https://github.com/tidepool-org/node-mtp/blob/pure-js/mtp.js

Once I have it all working, I hope to replace the Node.js-specific bits so that it can run in the browser using WebUSB, and ideally have a proof-of-concept available on the web.

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#100DaysToOffload #day53 #mtp

I've been wanting to build my own hydroponics setup for a while, but up until now I've just been using my commercial grow pod for growing stuff. I actually bought some expanded clay pellets, nutrient solution and grow plugs ages ago, but just never actually built the setup.

I think it's due to a number of reasons, the main one being that the original design I was going to build was to be outside, but I don't have a suitable greenhouse to put it in. So I decided to look around at some other designs, specifically ones that:

• are for indoor use
• can be completely 3D-printed (as I can't just drive to IKEA in Cardiff due to lockdown)
• modular, and
• are very simple to build.

I've been interested in this modular vertical setup for a while, but based on the comments it is prone to leaking and hasn't been updated in a while.

I've been wanting to design a voronoi net cup for fun, and noticed while searching Thingiverse that someone else had the same idea. Not only that, but they have a simple, modular and indoor system to go with it. It doesn't look like the build has been replicated by any other people, but I decided to give it a try and the base is printing right now.

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#100DaysToOffload #day52 #hydroponics

In the previous post I looked at connecting to an Android device over WebUSB and opening an MTP session.

Let's have a look at how to see what objects (directories, files etc.) are available on the device. Before we get started, let's define some of the operation and response codes that we'll need, as well as some possible container types:

const CODE = {
  OPEN_SESSION: { value: 0x1002, name: 'OpenSession' },
  CLOSE_SESSION: { value: 0x1003, name: 'CloseSession' },
  GET_OBJECT_HANDLES: { value: 0x1007, name: 'GetObjectHandles'},
  OK: { value: 0x2001, name: 'OK'},
  INVALID_PARAMETER: { value: 0x201D, name: 'Invalid parameter'},
  INVALID_OBJECTPROP_FORMAT: { value: 0xA802, name: 'Invalid_ObjectProp_Format'},
  GET_OBJECT_PROP_VALUE: { value: 0x9803, name: 'GetObjectPropValue' },
};

onst TYPE = [
  'undefined',
  'Command Block',
  'Data Block',
  'Response Block',
  'Event Block'
];

We also need to be able to parse container packets:

const parseContainerPacket = (bytes, length) => {
  const fields = {
    type : TYPE[bytes.getUint16(4, true)],
    code : getName(CODE, bytes.getUint16(6, true)),
    transactionID : bytes.getUint32(8, true),
    payload : [],
  };

  for (let i = 12; i < length; i += 4) {
    fields.payload.push(bytes.getUint32(i, true));
  }

  return fields;
};

The getName() helper function looks like this:

const getName = (list, idx) => {
  for (let i in list) {
    if (list[i].value === idx) {
      return list[i].name;
    }
  }
  return 'unknown';
};

To get the object handles, we do the following:

  const getObjectHandles = {
    type: 1, // command block
    code: CODE.GET_OBJECT_HANDLES.value,
    payload: [0xFFFFFFFF, 0, 0xFFFFFFFF], // get all
  };
  data = buildContainerPacket(getObjectHandles, 4);
  result = await device.transferOut(0x01, data);
  console.log('result:', result);
  let { payload } = await receiveData();

Now we have an array of object handles. We can use the object handle to retrieve the filename, using the “Object File Name” object property code 0xDC07:

const getFilename = {
    type: 1,
    code: CODE.GET_OBJECT_PROP_VALUE.value,
    payload: [0x2B, 0xDC07], // object handle and object property code
  };
  result = await device.transferOut(0x01, buildContainerPacket(getFilename));
  console.log('result:', result);
  let { payload } = await receiveData();

The payload is a 16-bit unicode string containing the file name. Nice!

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#100DaysToOffload #day51 #mtp