So my newest project is a small tracked robot that is bluetooth controlled. The hardware is as follows:

  • Arduino Pro (5v, 16Mhz)
  • SN754410 – quadruple high-current half-H driver
  • HC-05 Bluetooth module.
  • Tamiya 70100 Track and Wheel Set
  • Tamiya 70097 Twin-Motor Gearbox Kit
  • RPM detection with 3144 Hall Sensors.
  • 4 AAA Batteries for power
  • Hacked on aluminum plate from a power supply
  • A few odds and ends (screws, tubing, nuts, bolts, etc.)



Watermelon Salad!

So thanks to the sample girl at Trader Joe’s we have a new summer favorite. It’s very simple and quick to make. So here goes.

watermelon salad with seeds
watermelon salad with sesame and poppy seeds
  • 1 small watermelon, diced (about 4cups)
  • 12 or so basil leaves, chopped
  • Juice of 2 limes
  • 2-3 spoons of chopped feta


  • Sesame and/or poppy seeds

Mix it all in a bowel and serve. Optionally sprinkle some poppy and and/or sesame seeds on top.


Temperature Update

At this point I am monitoring the temperature in my office, our bedroom and outside.

The outside sensor is in a north east window and gets some sun in the mornings. It is a black sensor in clear tape (a cheap-o water resisting, not water proofing). This causes it’s temperature to spike when the sun is on it.

An attempted fix. I took a little foil packet from an Emergen-C and turned it inside out. This gives it a little shade, and a touch of reflectivity. Tomorrow AM I hope to see a slight mediation of the sun’s warming effect.

The hardware setup has changed a bit for the second and third sensors.

The second sensor is a Arduino UNO with a DS18B20 One Wire temperature sensor and a nRF24L01+ radio attached. The whole mess is connected to a RaspberryPI via a USB cable. The rPI listens for temperature data from the Arduino via the serial interface. It then sends the data to the remote server for processing. The Arduino also listens on the nRF24L01+ radio for data from other sensors and relays the data to the rPI.

The third sensor is a home brew stand alone Arduino-ish thing. It also has a DS18B20 and a nRF24L01+ attached. It collects the temperature and sends it to the second sensor/relay for processing.

The nice thing about the second and third sensors is that the Arduino side of things is basically the same. Just the software on the two differ. I have created a circuit board layout using Fritzing. I sent the board layout off to and am awaiting my freshly minted circuit boards. Once these show up I will assemble one and test it.

Then I will attempt to take a few pictures of the whole setup. Both the different iterations as well as the current semi-final state. That is also when I’ll post the code and Fritzing files, but for now my lunch hour is almost up and I need to get back to wrangling servers.


I added some enclosures around the electronics last night. Even with the temperature sensor outside the case it added 20 degrees Fahrenheit to the reading. I’ve been tinkering with the design a lot today, one of the benefits of Lego enclosures, and have decided that I want the sensor out of any airflow coming from the Arduino. Since this requires hardware modifications it will have to wait a bit more.

Control those shoelaces!

So if your like me you hate it when your shoelaces tickle your ankles, especially when running. If so I have a quick fix for you, and a slightly quicker fix as well.

First the quick fix. Take a short piece of Velcro (hook and loop tape, whatever you want to call it) and poke a few holes in it and add two grommets to it.

Shoelace control!
Shoelace control!

Once it is laced onto your shoe it does a fine job.


And now the quicker method. Take a twist tie and use it to tie the flapping laces to the crossed laces. This works great, I used it for more then a year, until you need to take your shoe off in a hurry and you have stripped off all the plastic from the twisty. Sorry no pics.

Now I’m off to make a few more lace controllers for the motorcycle boots. The last thing I want is to get the laces caught in the chain or rear wheel. Yikes!

Temperature Graph Update

Today I added weekly, monthly and yearly graphs, as well as breaking the cron job into 3 different ones. One that runes every minute. An hourly and a monthly one.

I also learned that if you have a large dataset and you are using rrdtool to pull data from MySQL it can take a long time. This is completely understandable as rrdtool is optimized to use rrd (round robin data) files.

The last thing is that I had a few days where the temperature sensor could not reach the main server to insert data into the DB. This pointed out the need to cache the data locally then attempt to upload it, allowing for connection outages. This will be my next upgrade to the system.