Let's Make Robots!

Swarm Robot build

Hey LMRians!

It's been quite a long time that I haven't been here (mostly due to being in the second last year of school and other projects). Recentlly I got interested in robotics again and I came up with the idea of building swarm robots (just a little group of maybe 10 bots, not 40+ that the universities use).

Here I want to describe my thought process a little and then ask some questions.

So my first goal is to make it relatively small, something of the size like the robots seen in this excellent video by the University of Sheffield (see embedded video below).

Open source 12 channel I2C servo controller anyone?

Hey guys!


I am thinking about this for a few weeks now but I'm still not sure ifI should do it. 

I have designed a 12 channel I2C servo controller and I had some proto boards manufactured by iTead studio. Of course the design will need some more refining but the main functionality is there.

Course correction with digital compass

Hello again LMRians!


I want to accomplish a course correction for my robot. I have written the code for the course correction and one for the object avoidance (without course correction). Now I need to somehow merge both loops so the robot detects the objects in it's way but also goes in a straight line.

The code can be found here: GitHub

I2C servo controller schematic and layout

Hello LMRians!


So after half a day of work I came up with this board design for an I2C servo controller (the schematic was done in 10 mins..). So could you please check if this design is going to work as it's the first board I've ever designed?


The schematic:


And the board layout without the GND planes:


With the GND planes:

Assembler question out of curiosity

I'm just curious if anybody of you uses assembler to program the µC on his robot.

I have had a look at AVR assembler and I know you can create super efficient programs (regarding code size and execution time) but I find it somewhat cumbersome to set a whole bunch of labels and comparisons up just for a simple for loop + delay.

Ok in the end everything ends up being an assembler listing and then a hex-file but I find it much easier to work with higher level languages like C because of ease of debugging (where ease is relative :P) and because it's simpler to read. 

Arduino not sending serial data

Hey guys!

I'm just trying to set up a wireless serial communication via IR. I generate a 38kHz signal on pin 9. The IR-LED is connected to pin 9 with it's anode and the kathode of the LED is connected to the TX pin of the Arduino.

Now the problem is that the Arduino doesn't seem to be sending data if I power it from batteries. It only sends serial data when I connect it to the computer and open up a terminal. I'm not quite sure why because I don't use something like this:



yada yada



PWM with the MP430G2231

Hey guys!

I was just messing around with PWM on the TI Launchpad and I want to make an LED simply fade in and out.

Now my problem is, that the LED fades in and out once and then it just jumps to full brightness. I don't know why this happens (on the AVRs I solved the problem by not counting down to 0 and everything was alright but that doesn't seem to do the trick for the MSP430)

Here is my code (the bit that fades the LED):

for(i = 1; i < 999; i += 10){ CCR1 = i; _delay_ms(10);}

Grounded Bicore

Hey guys!


I'm new to BEAM robotics and I want to build a simple grounded bicore. Now I want to use 100uF electrolytic caps and two 1k resistors (which should give me 1 pulse every second.

I'm using a 74HC14 inverting Schmitt Trigger. How are the caps connected to the inputs/outputs? Does the positive side of the cap go to the input or to the output?


Thanks in advance



Default Clock speed for MSP430G2231 supplied with LaunchPad

Does anybody know what the exact clock speed for the MSP430G2231 on the TI LaunchPad is? And is there any delay-function or header to use with CSSv4? 


 The user guide for the LaunchPad is not helpful at all at least in this respect, neither is the MSP430G2231's datasheet.



DFRobotics shipping

Hey guys!


I have some questions about DFRobotics. They seem to be pretty cheap, if I want to buy some XBee related stuff from them (buying them in Germany will cost me more, I don't care if they sell clones).


Now my question is, does anybody know how much shipping to Europe costs via DHL? I know they're shipping from China thats why it might be pretty expensive and I don't want to order and save about 50$ on parts and invest these 50 bucks into shipping cost.