Hack a Day has great articles about hacks from all over the world. This time I want to write about a very interesting project about radio controlled lawnmower.

I wanted to build similar lawnmower with the difference that I would use Wiimote for controlling it. But interfering Wiimote directly to an AVR or other micro controller is a bit hard, so I thought of using the laptop to connect Wiimote to a mower. I already made some plans, but then I realized about the biggest problem - danger of using something like this without my direct control over it.

After all, I'm perfectly capable of hurting myself without additional help, so building this could end badly.

Anyway I'm happy that someone actually made something like this, and I have no problems about him using it as long as it's far away from me. :-D

More: http://hackaday.com/2009/11/14/rc-lawnmower/

I stumbled upon an interesting article about wireless transmission of power and thought of sharing it here.

It's really simple and cheap way to wirelessly transmit electricity on really short distance. It's made of big and small coil, a couple of capacitors and LED diode.

More info: http://www.instructables.com/id/Wireless-Power-Transmission-Over-Short-Distances-U/

I'm interested in omnidirectional wheels from when I watched Prototype This!, The Discovery Channel TV series. They used these wheels in episode Six-Legged All Terrain Vehicle.

I thought a few times about building a RC car with these omni wheels, but never got around to even buy needed materials. And of course there is also a lack of tutorials/articles about it on the Internet.

Well, I then forgot about it, but a few days ago I found a post about Omni-car on Hack a Day blog. http://hackaday.com/2009/11/17/omni-car/

Really interesting project, but sadly these wheels are a bit too expensive.

Direct link: http://didyoumakethat.webs.com/projects.htm

In the following files you can find code for AVR micro controllers to use this modules.

Source (.c) file: hopeTx

Source (.c) file: hopeRx

PDF file: RFM12B

RFM12B and AVR - quick start
I found this tutorial when I searched for connecting this module to AVR.
You can download the tutorial at: PDF file: zenburn.net

My Experience
My attempts to get this module working were all unsuccessful.

Presentation about why Linux sucks: http://www.hardocp.com/news.html?news=MzkzMjUsLCxoZW50aHVzaWFzdCwsLDE=

I mostly agree with him. But Linux is still cool and good operation system for using (excluding for electronics work, CAD, ...).

A few days ago a friend send me an old mobile phone for using in a project about weather information in a remote location.

On the internet I found which pins on telephone are TX, RX, GND. I simply connected them to USB -> RS232 cable, when I found out that I must destroyed it last time by shortcut between ground and 5V.

I remembered about a project in which author used V-USB firmware only implementation of USB fot AVR devices to create home made USB to RS232 converter. In a few minutes I had a working converter (Thanks toOsamu Tamura at Recursion Co., Ltd.)
I connected everything and result was ... garbage. On HyperTerminal I received only garbage. I remember about using MAX232 chip for converting TTL levels to computer levels and vice versa. Tried with this chip and the same thing, of course a little bit different garbage, but still garbage and nothing useful.
So I give up for today ... tomorrow is a new day and maybe I'll have more luck. I could try connecting AVR with code for serial communicating to see if there is a problem on converter/computer or somewhere else.

I haven't decided yet what wireless connection I am going to use to connect car to laptop.

I have a lot of options but every option have some advantages and disadvantages.


a) using old HP laptop - good options, i can connect webcam, additional hardware without a problem. Cons: battery has bad autonomy (about 20 minutes), weight, WLAN connection (as far as I know PCMCIA connector doesn't work, so I need to buy USB WLAN module
New battery is at least 100€ and USB WLAN module is 40€.

b) using RFM10 wireless transceiver - i have 2 transceivers at home but they are in SMD and they can be connected to microcontroller only by SPI interface which is really hard to write a firmware code for

c) using XBee - great range, a lot of resources for it but a little higher price (20€ a piece and I need two of them)

I'll probably use XBee modules but they are just too expensive. My goal is to build a car controlled by laptop for under 100€. Cost of these modules is a real set back for this project.

For a couple of days I was building a robot ... not really a robot, just a simple car, that I could controll by my laptop.

Today I got the wheels spinning, but only in one direction. I intended to use H-bridge but I didn't have both types of transistors (PNP and NPN) so I try to make a H-bridge with just 4 NPN transistor.

I learned, that you need to use electronic components as intended. You cannot use NPN transistors where you need PNP. Lesson learned for next time. ;-)

I'm back to start of the project ... Tomorrow I'll buy a cheap RC car and of course some NPN transistors or maybe MOSFETs.

I heard about DC motor driver (i think it's L293 or so) ... dunno what to buy.