Minimost

We live Next to Ringkøbing Fjord, a shallow watered large nearly closed fjord. So it’s obvious that we should have some kind of toy for those summer days where the Water is magically calm. Begging for something that moves fast.

Which Means: We would have to build a speed boat! A quick Google leads you inevitably to the Minimost site. I have never build a boat before so it seems like a resonable place to start. It can’t be a standard boat, that much is sure so it has to have some Kühlmeier signature. What about a part carbon fiber version of the racer!? Yep. That will do. So part of the load carrying stressed skin structure of the boat will be build using unidirectional high modulus carbon fiber as reinforcement. Mostly for additional stiffness purpose. Where do you get that stuff? Well if you work within the wind turbine blade design business and have your contacts… Otherwise it is not easy and surely not cheap.

I added some Pictures on the build process. below. In short I made use of 6 mm plywood for the deck and sides. 22 mm plywood for the transom, frame and keelson. The keel and stringers were 45×45 mm and 95×45 mm stock wood.

The assembly was made with all Wood screws and all connections were glued with Hempels Epoxy adhesive only the carbon fiber UD was fitted to the lower and upper deck with Araldite 2011. A super stong multipurpose two component epoxy system.

Overall a nice build process. And the result is pretty nice. We look forward to getting it on the water…. So More to come shortly.

First test run will be with our 6 HP engine. We know it’s not enough so we already borrowed a 15 HP to test it out… Let’s see 🙂

 

 

DIY sous vide cooker

So, I got hold of this heating pot from a Bonamat bulk coffee brewer. Since some time I have been wanting to build a sous vide cooker, but not really been able to find out how to do it cheaply and with the capacity I wanted. Obviously this beast is the answer. Dobble walled insulated, stainless steel 20l pot with build in heating elements and even a tap for easy disposing of the hot Water after use.

This is a quick and easy DIY project but the result is so great that I just have to share it with the world. 🙂

The additional parts needed for this to become a high capacity sous vide coocker are:

  1. 6x100w PTC ceramic heating elements (Since the Bonamat pot defult comes with only 200W of heating installed).
  2. PID temperature controller including SSD relay.
  3. A small submersible aquarium pump to provide some Water circulation for a nice even temperature distribution.
  4. A stainless steel immersion pipe with a PT100 temperature probe.

This is how the assembly looks line inside the coffee pot. Note the extra heating elements installed in a row on the bottom of the pot. Also the PT100 immersion pipe installation is visible in the bottom right corner. PID controller is just above the PT100 immersion pipe.  It is not the prettiest wiring, but it Works and the Whole thing is properly grounded in case any 220V should come in contact with the metal casing!

Wiring inside the cofee pot
Inside the cofee pot

And in the pot itself I have installed the aquarium pump and a stainless steel stand to place the food on so it is not in direct contact with the heated surface.

IMAG0448

Lego RC car with Raspberry Pi

A Saturday hack

Saturday morning we found an old Lego RC car. Actually Duplo car to be precise. The relevant thing is that it had two internal DC motors and we had two IRF520 boards from Keys.
These boards are essentially driver boards for a MOSFET transistor. In short they allow the Raspberry Pi to switch the motors on and off. And also to control the motor speed py PWM (but unfortunately not direction).  Freely shipped from China the IRF520 is less than two Euros pr. piece. Versatile and fun. So make sure to buy a few more than you actually need :o)

The idea was to be able to control the Lego RC car from Scratch using some sort of GPIO control. We quickly discovered ScratchGPIO5 which very quickly became or new favourite tool! It has lots of support for add-on boards for the Raspberry Pi and the possibilities seem endless. Imagine it works with the Adafruit 16-Channel 12-bit PWM/Servo Driver! So that we have to try out at some point.

ScratchGPIO only works with Scratch 1.4 but not 2.0 since the Scratch people for some reason have removed the “remote sensor” option from Scratch 2.0(???).

Next we quickly set up our Raspberry Pi as a Scratch Interface Device following the instructions on the ScratchGPIO5 site.

First step was to slaughter the RC car. Carefully since we wanted it all to work when we put it together again.

Slaughtering Lego RC car

Slaughtering Lego RC car

Then we soldered some longer red/black wires on to the DC motor terminals so we could put them where we wanted them later. Also wires from the battery pack + and – were soldered with wires in appropriate colours.

When this was done it was time for a test run before assembling the car again.

Test runWhen we were happy with the result we could put it nicely together and this was more or less it. Done! :o)

Time for programming the basic features in Scratch to allow keyboard control over left/right/forward and speed.

ScreenShot155

ScreenShot163

Here is the final result. A nice little car which is easily controlled from Scratch. And there are still plenty of GPIO’s available on the Pi so we may just expand the world of the car some other Saturday.

ScreenShot157

Sunday hack: Now also with head lights which we can dim from 0 to 100%. Using the last MOSFET in the box, 2×12 V bulbs we had lying somewhere and a battery pack from a broken softgun.

We will NOT try and bring this throgh an airport security anywhere! :o)

Screen Shot 10-05-14 at 07.43 PM

Latest update: Now mounted with an ultrasonic sensor. This module is supported in ScratchGPIO5 and only takes up one GPIO pin. It is fairly precise and accurate. It gives a new dimension to the robot car since it can now “see” what is in front of it and react on it.

For the fun of it we are also streaming the data to plotly since we had an idea about monitoring and streaming the operational states of the robot car. But we are not exactly sure why. At least for no other reason than because it’s cool to do some IoT stuff and streaming of data to a graphing service on the internet. Could come handy at some other point.

Have a look see here. Perhaps it is on-line streaming right now 🙂

Plotly plot

Ultrasonic sensor mounted

The Pyhton script for doing this involves both connecting to Plotly and also connecting to Scratch from Python to poll some sensor data and stream these to Plotly. So others may find this interesting since this is how you get Scratch to plot whatever in Plotly. It does not need to be streaming data. So I uploaded the script here.

 

The sniper rifle

“Dad?”

“Mhm”

“You know I think sniper rifles are really cool right?”

“Mhm”

“You think we could build one down in you workshop?”

“…Mhmmmm!”

Sniper

… So searching pictures on the internet and printing profiles in 1:1. We glued the prints on to plywood and used a jigsaw to cut the shapes.

A football pump is used as silencer and some used 30.06 shells from my old rifle are mounted in the clip… Well and then some paint and 16mm steel tube for tripod and barrel. Plus an old second-hand Bushnell sight… Here we go :o)

Power meter pulse counter

Another smaller Raspberry Pi project. This is in addition to the Growatt inverter read-out project where I keep track of energy production from my PV array. The next obvious thing to ask is how the energy consumption compares to the production. I.e. I need some way of measuring the energy consumed in my house hold. Looking at my power meter it is a sealed box and I am not interested/legally entitled/brave enough/smart enough to do any measuremets on the high voltage side of the system. But I was inspired by a colleague to utilize the small blinking LED on the power meter to keep track of energy consumption. The idea is quite simple since the LED blinks 10.000 times pr. consumed kWh… Yes you get the idea. The blink speed is a measure of power and the total number of blinks is a measure of energy. Making a few Google searches quickly revealed that the idea is not novel. There are several applications like this out there. Even  commercial systems are available which are not that expensive and also offers some cool features. But hey! There is no need to go to the extremes and buy something reliable, ready made, cost effective and installation friendly when you can have some hours of fun making it your self.

I found this easy to understand and built circuit found at Adafruit. This circuit is actually not that well suited for the application since it will only give you an instantaneous reading of the light intensity (or an indication hereof anyways), which is a little tricky to translate to blink or no blink situation. This is a first version of the blink counter and if it does not work reliably I will upgrade it to a transistor type circuit as e.g.: http://electronics.stackexchange.com/questions/38258/plugging-a-ldr-into-gpio-pins-of-a-raspberry-pi

But let’s see how it goes. I have installed a 0.1 µF capacitor to be able to get some fast readings. Back-of-an-envelope calculations says that the blink rate at extreme consumption will be 20 kW*10.000 blink/kWh = 56 blinks pr. second which the circuit should be capable of following. That is one blink pr. 18 millisecond. The circuit at it’s present form looks to be fast enough at least up to 10 kW which was what I was able to test turning on all the rings on the stove and the teaboiler too :o) Much more than consumption than that is probably not going to occur I hope. The python script which I wrote for this is under ways. I’ll just debug a bit on it before I publish it here so it will be fairly well tested and stable when it hits the site .

Pictures of the installation:

Pyhton code for running the blink counter and upload to pvoutput-org is available here.  The script will count blinks for 5 min. Then recalculate the blinks counted to an average power over the time period and he total energy. Subsequently both are uploaded to www.pvoutput.org. (Production from my PV array and the household power consumption can bee see here)

In its current state the script is run 5 min past midnight each day. The script then runs over a while-loop the entire day and writes data to a text file each min and uploads data to pvoutput.org each 5 min. Then when the date changes the while loop in the script ends and a new text file is created for the next day… Hmm. I just need the text files for a detailed look into if the counter counts correctly under all consumption situations. It seems to be running ok, but it’s a little hard to get a solid validation of since the power meter only reports consumption in kWh, which is a coarse resolution.

To set up the cron job use:
sudo crontab -e
and edit the file to this

crontab - run python script 05 past midnight each day

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