Saturday, August 9, 2014

Raspberry Pi cooling fan

Hi ! So, after quiet some time I've decided to post something here. Recently I've been working with Raspberry Pi more often, and I noticed that even with small load for longer periods of time it can get hot, and that lead me to decision to add a small fan to it.

You can check temperature of your Pi in Celsius via terminal by typing one of these two commands :
  /opt/vc/bin/vcgencmd measure_temp 
   cat /sys/class/thermal/thermal_zone0/temp (divide by 1000)
After one hour of pretty much idle sitting, Pi can get all the way up to 53.5 °C, which may not be critical but it's not ideal, taking in consideration fact that while performing demanding tasks temperature will grow higher. I went for 30x30 mm fan, that can sit directly above the processor. Screw in the mounting hole available at the Pi alongside with the s-video jack hold it in place. I wanted to keep 2x13 GPIO pin headers intact, so instead I've used P5 pins, that have all that is needed in order to make this work. I've then added simple header connector that has a 2n2222 transistor on it, base of which is controlled by GPIO pin number 30. By changing resistor value you can pretty much vary fan speed. One I've used is rated 5V and 72mA, but I decided to use 10k resitor on the base which together with beta of transistor (~ 100) gives around 45 mA to the fan, so that it runs smoothly and very quietly. At the bottom you can see simple bash script that is executed in rc.local to run as a background process everytime Pi is turned on. It's basically constantly checking whether temperature has crossed the threshold and when yes it activates the fan for 5 minutes. Of course you can go even further, use python for instance that will give you with help of RPi.GPIO library ability to use PWM to scale the speed to current temperature, but I wanted to keep it simple. 

Friday, December 27, 2013

STIGA table hockey custom scoreboard

Hi there ! First of all merry Christmas and happy new year. I am sorry that I wasn’t active for a long time, but things have changed lately. I had to overcome some things, I can’t tell you whether I’ll continue with this blog, but for right now I want to.

So, few weeks back my brother had called me, and he said that he would like to restore an old STIGA table hockey, that we used to play with, when we were younger. I thought it was a great idea, so he wanted me to create a scoreboard, since game itself had only mechanical one that was not very appealing. They also came up with new goals and nets for them and we’ve ordered original NHL teams. So when designing I went for the easier option, so I have found these I2C display modules, because multiplexing eight 7-segment displays with single atmega328 would be suicide. They came right before Christmas, and I brought home with me few tools to put it all together. It wasn’t as easy as though at the beginning since library provided by the seller wasn’t directly for the version of the displays we’ve ordered. That’s the reason why it took me some time to figure it all out. After that it was pretty straight forward. You can see the working scoreboard in the video, also Brandon Dubinsky scoring brilliant goal !


Saturday, June 1, 2013


Hi there ! Last week I had final exams at my secondary grammar school, so I want to apologize for inactivity, but there was no time for that. Good news is that I passed, and I've been accepted to the Brno University of Technology, so I'll be moving to Brno during summer. Thing is that I have almost 4 months of summer in front of me, so I will try to build as many cool things as possible, thanks for your support :).

Sunday, March 31, 2013

Portable Power Supply

Hi ! First of all happy Easter to everyone. If you haven’t seen it yet, go watch my reel, I hope you’ll like it.

Currently I’m working on a project that uses Raspberry Pi, but it requires Pi to be portable. This raises a question of power supply. Of course, I could just use 4 AA batteries or something temporary, but idea of portable power supply has been in my mind for some time. Once again I decided to use Nokia LiPo batteries, since they are great, and I have a lot of them. I used 3 x 1500 mAh ones so it gives me about 4.5 Ah to work with, which is not bad at all. At ebay I found these 3.7V to 5V booster converters, they’re great so I’ve already bought two of them. There was some problem with grounding, because circuit wasn’t working after resetting, so I had to connect battery and output ground with schottky diode, which solved the problem. I decided to put it all in an altoids tin. I still have lot of them from the times when I was building portable circuits. I have to say this thing is a beast, it has no problems with powering things like Arduino, Raspberry Pi or even charging my phone. Only problem is that circuit doesn’t have control of how much is being drawn from batteries, so when I’m charging my phone, circuit is giving out something like 1 ampere, and it gets really hot immediately. But that doesn’t matter since I will only be using it on my bench. Having handy 5V supply available every time is great.

Saturday, February 9, 2013

Observer Reboot [2.0]

Hi ! First of all I want to apologize for not being active for quiet some time. I was working on something big, but it was going slow so I had to make a break and I decided to reboot the observer !

Year ago I lost all of my data including code that was on observer, since that I'm storing all of my data on cloud, and a usb drive aswell. So when I was wondering what could I do with xbee modules, I thought that I could finally write some new code for observer, but at the same time I wanted to make some improvements. So I decided to use control glove, which has a lot of potential, even more now since I've added bend sensor to the index finger. So I've built small bracelet that has xbee inside and antenna. I etched new board for observer, which used a transistor to control whether servos are on or not, but that wasn't working quiet well because transistor wasn't able to provide enough current and to switch servos fast enough and it caused servos to jitter. Reason was that control glove sends data every 50 ms and observer refreshes itself every 45ms in order to make turning and speed control smooth enough. I am also using two power supplies now, because I like to separate logics from servos. It was quiet hard to synchronize data sending/receiving, and as you can see in the video it's far from being perfect.

This is the first time I've decided to make a proper narrated video, so please let me know what you think of it, because if it's bad I will return to the old way of doing short videos with music in background. So if you liked it please like it or let me now in the comments. As for my future plans, I'll get back to that big secret project and I hope, it won't take me lot of time to finish it.

Monday, December 31, 2012

PF 2013 !

I want to wish you all a great year full of joy and happiness !

From my perspective year 2012 was really good, I feel like I moved to a next level with my skills and everything. I build my best project yet - Bracerbot, which is still not finished, but I am really happy that I was able to bring my ideas to real world. Good news is that for Christmas I got tablet with the pen ! At first I thought I wouldn't be able to fully use it since I'm not an artist, but then I sketched some things and here you can see some things that come out. So I will maybe create new category called concepts for things that I have in mind, but I can't really realize them.

So what's next in 2013 ? Well I hope a lot more projects that you will like (I will probably start with that Biped on picture).

Sunday, December 23, 2012

Merry Christmas

I want to wish you all Merry Christmas !