Helmich de Lange - Standard measurement system developments

This is a summary of a presentation during the 3rd International Biomeiler Conference in Leipzig in 2018.
This presentation has been transcribed and summarised by Arie van Ziel, please contact me if you'd like to extend on the text or edit something.

Two years ago Helmich made his first biomeiler system focussed on measuring system development.

Continuous measurement with continuous water spray system. Depending on the temperature regulating the humidity and also the heat exchanger with an electronic T-valve. The biomeiler is still there, but most sensors are lost.

Last year he made a system for the minimeiler in NL.

This year he has been working on a better measurement system, useable for the whole community.

It is part of a standard IoT system, but with a local storage system, buffer for the uploading of data and UPS (backup power). For this he is using Raspberry pi to be able to configure everything of the system locally. With other devices this is not possible because there is not a full operating system on it. Also there are many easily useable extension parts like a driver pcb.

It uses the 1-wire cat5 system, easy to use, no need to calibrate and cheaply available from Ebay.

Helmich designed an extra pcb himself to make the connection of the sensors easier.

The whole system is in a watertight box with watertight connections on the bottom, very easy to install.

1 wire sensors actually have 3 wires, ground, 5v and communication (the 1-wire). It is sending and receiving messages at the same time. It is high frequency like radio and tv signals, so the chance of interference is very high from other machines around. By using cat5 cable the interference is less because it has twisted pairs of wires. It is now tested with 20 sensors and 50mtr cable, this should be more then enough for a biomeiler setup.

Inside the sensor is a little black transistor like device with the three wires. This works only with a so-called pull-up resistor to get the signal back up to 5v. It takes some time to use this system, so long cable lengths are a problem because you have to wait quite long.

The advantage is that each sensor has a unique id, so it automatically sends out it’s own address. This makes it very easy to identify which sensor is broken. Even though wire breaks and short circuits are a big risk in a biomeiler setup. The first systems are installed like this.

But with very long cables the pull-up takes to long, so it might lose the signal.

With the new drive pcb cables can be longer, because it doesn’t use a pull-up resistor, but a switching system.

To summarise: first it started with twisted wires in a cola bottle, then came sepperat connectors, now it’s developed into a shorter cable connection with cat5 cables. It’s also much easier to install. Only the first pcb has an extra connector.

With standard boxes with special rubber connectors it’s possible to make the whole system completely watertight. It’s important that the rubbers are combined with the right glands to make it correctly watertight. Each box can hold several sensors and with a cat5 cable it goes on to each next box, which can be extended very far.

For the software side to display all results nicely Helmich uses standard software. Open energy monitor.org in combination with emoncms and a little custom python code.

Now you can download the standard code from the internet to your raspberry pi and it can upload the data directly to the emoncms system. Also this gives the possibility to store it locally in emoncms and for 1 pound per sensor per year you can display it on a remote emoncms system. It’s open source, so you can also run it for free on your own webserver, but it’s easier online and not expensive.

Also it’s possible to send signals towards the system to switch pumps on or off, or similar things. And it’s possible to have the system send warning emails if you need it.

It’s smart to make a list with human readable hardware addresses before installing the sensors.

At the moment it holds 4 flow sensors and 16+ temperature sensors.

It can also calibrate the flow sensors and calculate the power itself.

The system is available for everybody to use freely.

One current weakness is mainly the SD card, which sometimes breaks after a power failure. With a better UPS it could be prevented.

Also, mind that after screwing the box to some backing to put the rubbers on top of the holes.