PLD (Part 6)

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The PLD features a multipurpose connector mainly dedicated to plugging sensors. This video shows how easy it is to configure a PLD an run an application for  monitoring temperatures.

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Do you want to know more about HL2, HL2 Panorama and HL2 PLD ? Check this video

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PLD (Part 5)

Part 123456

HL2 PLD may be used for safety applications too. In this configuration, the PLD is able to detect movements up to 7 m away within and almost 90° view angle. It features a PIR (Passive Infra Red) sensor from Panasonic.

This sensors is available in different sizes depending on the required range; the enclosures are available in white or black. On top of these specifications, various power consumptions are available, ranging from 1 µA to 6 µA. This criteria may be critical regarding the applications and the expected battery life time. More reading on this sensor > here <. Few extra component are required to convert the output signal from the sensor to the PLD: actually a N-channel MOSFET and a pair of resistors.

The sensor is encapsulated in a 3D housing which nicely fit the bottom gland from the PLD. In this way, the sensor can be oriented in any direction in the horizontal plane.

HL2 Panorama features all sorts of widgets: gauges, graphs, text, state buttons and tables. In this case, I used a gauge for the power reserve and a state button for the current state: RAS means “Nothing to declare” in French.

The principle of operation is rather simple and prevents sending useless information on the LPWAN networks. As soon as a movement is detected, the PLD sends a “NOK” status. Then, during a fixed period of time, the PLD will count the number of times it senses a movement. On completion of this fixed time, if no event is in progress, it releases a “OK” status along with the number of movements sensed. In this way you are aware about a presence right away, and on completion of the event you get an idea about how frequent where the movements. As the HL2 PLD is arduino ™ compatible, you can start from there and fine tune the code to your own taste !

Using no power line, no network cable and a small compact device will help you to monitor motions in a distance place for years.

Is this what you need ? Pay a visit to our Kickstarter campaign > here <

Would you like to get the STL file for the sensor housing ? > Here < it is and this is how it looks.

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3D Printing (Part 12)

Part 1234567891011, 12

3D printing can be tiring for the nerves… For a week or so, I was enable to print full size parts without enduring severe problems such as splitting layers, irregular faces and even gaps. Here is an illustration of the prints before the fix (on top) and after the fix.

The first layers where almost alright and the print was going worst and worst: awful ! I carefully and visually checked the printer and found nothing. It was obvious from the beginning that I faced a feeding problem. Usually, these problems come from clogged nozzle, clogged insulator, etc. So I checked and cleaned the whole filament path: no way. I ran a temperature measurement on the heater block: it was just fine. So what ?

I made the decision to install the printer on my desk and watch it working: “Watch out printer, big brother is watching you”. After few minutes, I heard little “klunks” next to the extrude stepper motor, once in a while. I squeezed the filament and felt that the filament was getting one step backward at each “klunk”. As the wheel was perfectly clean (I never had the least problem on this side) and the pressure mechanism free to move, my thoughts were that I was facing a torque problem. Firmly pressing the filament toward the feeder was helping quite a lot and resulted in a significant improvement of the printing quality. So that I decided to increase the current limit for the extruder driver (Check the procedure here) to 2.5 A which is the maximum rating for the stepper motor (Specifications here). In this way, the stepper motor can cope with the back-pressure from the filament being pushed toward the nozzle. Then I made sure that this increase had no dramatic effect on the motor and I checked it operating temperature using a PIR thermometer has shown here.

The stepper motor temperature stays below 60°C which is just fine. And… tadaaa, the problem has gone away !


PLD (Part 4)

Part 123456

Using the HL2 PLD (Place and Leave Device) is easy and usefull. We ran the earliest tests on… soil moisture. The reason why we chose this one is that I have always liked to have a green plant in my office and this one might last longer than the others. Because it is fitted with great soil moisture sensors connected to a PLD !

I am using a Capacitance-type WATERSCOUT SM100 sensor.

  • Range: 0% VWC to saturation
  • Power Requirements: 3 to 5V @ 6 to 10 mA
  • Output: Analog voltage 0.5 – 1.5V for a 3V excitation (ratiometric for other excitation voltages)
  • Resolution: 0.1% VWC
  • Cable Length: 6 ft (1.8 m) and 20 ft (6 m) standard, extendable up to 50 ft (15 m)
  • Accuracy: 3% VWC @ EC < 8 mS/cm
  • Sensing Area: 2.4 in (6 cm) x 0.8 in (2 cm)

It proved to be a very efficient, simple to use and pretty rugged sensor. The only advice that I may share here is related to the “installation” of the sensor. Water the ground, push the sensor down to the black ring and  tamped down to eliminate air gaps. This is critical regarding the reliability of the measurements.

Next is a picture of the oldest version of HL2 PLD (in grey) next to the PLD as proposed  by HL2 through the Kickstarter campaign.

Ultimately, this is a profile from the soil moisture as shown in HL2 Panorama where you can clearly see the decreasing moisture and the watering along the time.

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PLD (Part 3)

Part 123456

The name PLD stands for “Place and Leave Device”. The original design is big enough to encapsulate its power reserve, the radio module, an arduino ™ microcontroller which will run your own code, and connectors for programming, debugging or plugging sensors. The radio module features the HL2 stack which handles data in terms of optimization of the payload and protection of its content.

Here is an example of use: the PLD drives a DS28b20 temperature sensor that I put in my refrigerator.

Temperature mesurement

From my own experience, leaving the sensor on its own exposed to the “ambiant” air inside the fridge drives to unstable readings. A better practice is to immerse the sensor in a half-liter bottle filled with water. Water will damp the fast temperature changes which translates in smoother temperature profiles. This method is also more realistic as we are interested in monitoring the temperature of the food and goods inside the refrigerator.


The principle of IoT prevents you from uploading a googol of data bytes over the LPWAN networks. On the other hand, you do not want to miss critical events. The in between consists in using a relatively high sapling rate (e.g. one sample per minute) and a relatively slower upload rate (e.g. one upload per hour). This means that the device must be able to compute some statistics which will be chosen for their ability to describe to the user what happened between two uploads. After few experiments, we made our minds and decided to adopt the following statistics: median, quartiles and inter-quartiles. These statistics are much easier to understand than standard deviation and sigmas. The HL2 stack allows the upload of these 5 statistics and the battery level in only one frame thanks to the segmentation function !

Using the H2 PLD, it takes less than hour to configure, program and install a temperature monitoring device where ever you like and get the data from HL2 Panorama from any Internet navigator.

You cannot resist and deadly need a PLD ? Subscribe here

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PLD (Part 2)

Part 123456

Tadaaa ! This PL…D day

Simple and flexible is here! Check out our new campaign:

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PLD (Part 1)

Part 123456

Dear arduinoos followers,

You may wonder why the production line of arduinoos went to a stall along the last weeks…

Holidays ? Well it sounds reasonable and logical, however except for a few days of leave here and there (actually in Lyon, Annecy, Saint Martin des Baleines and Val-Andre) during summer time this is not the main reason.

BTW: look at the beauty of mother nature: rainbow over the sea near the Val-Andre

Health ? No trouble, as would say a very good friend of mine “my doctor is fine !” As he does not bother with my own health.

Laziness ? Actually no, definitely no as the world of science and technologies is such a fascinating and exiting one…

So what ? Work ? Yes indeed, and HL2 group, the company that I co-founded 5 years ago, is about to release an amazing product through a Kicktarter program.

Hang on ! I will keep you posted with fresh news very soon …

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Quote of the day

Summer time is often synonymous of getting back to the books and and enjoying good heavy reading sessions. Among the books my darling wife choose for me was a compilation of quotes from Dr. Albert EINSTEIN.

I love this particular one:

“You do not really understand something unless you can explain it to your grandmother.”

Albert Einstein

So, so true.

3D prints: USB housing

I had this cheap USB stick that I had to take apart in order to rework the connector soldering. Once the soldering works achieved, I had to think about a quick and dirty enclosure which resulted in this:

Two – almost – symmetrical parts. The top one has a bump and a small hole aligned with the LED, the bottom one has a carving which holds the PCB in place.

And here is the result

Link to the stl files

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3D prints: Coil

I have multiple projects in mind starting from a metal detector up to a NMR in field earth spectrometer which require one or more coils in various shapes and sizes. Here is the presentation of a double coil, 100 mm diameter, 5 mm thickness.

Here is a zoom on the back side of the coil showing the wire terminals. I used a adjustable female header

This is how it looks once wired to the driver

Next is the 3D view from FreeCad

And here is the link to the stl file

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