Let's Make Robots!


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Junkyard Challenge

Hi All,

I am new here. I have a following material

* Robot chassis
* 2 geared D.C. motors (6V D.C)
* 6 volt 4.5Ahr battery
* 4 ABS antiskid wheels
* 2 follower attachments
* 2 D.P.D.T. switches
* 1 castor wheel
* serial port programmer
* AVR Atmega8l development board
* L293d (2 x Channel H Bridge Motor Driver)
* 4 relay power driver



i2c new to me...

Allright Folks,

One of you all's gunna need to explain this whole i2c thing to me. I have done a wiki (which confused me even more) and a few google searches. What I have got so far is it is an extra little storage space that a pic can talk to. I guess there are "packets" of bits and addresses or something like that but really, I have no idea.

 Can someone explain this whole i2c thing and include some basic, pratical uses (and how to do it) when being used with a picaxe. --Explain it as if you would explain it to a 4-year-old.

Controlling belts

I set out to make an aggresive little tank and I got this far. It runs like a dream when I put a battery directly on the motors... in a straigt line. Any ideas on how to control it, so it can turn on a plate. All wireless.


Everything was made from old bits and pieces. I havent spend any money yet. 



Port problems on dsPIC33FJ128MC802

I have a problem that is driving me nuts. I am sure, that there is someting I just don't get, but can someone please tell me what?

 That setup is a dsPIC33FJ128MC802 which I try to program in C.

I have the following code (Let's assume that everything is setup and all ports are digital and outputs).

If I write this in my code:

PORTA = 3;

and take my measure thingy (danish for multimeter, I can see that Port a0 and a1 is high as expected. If I single step using the PIC simulator, I can see that PORTA is 0000011.

If I write this in my code:

Promising things on the horizon for LetsMakeRobots.com

Hey guys. I just wanted to give you an update on the upcoming changes we've got planned for the site. A month or two ago, after being frustrated at how limited our access to LMR's webserver was, I messaged Frits and offered to host the website on my own server. That way we would have the access to develop all the kinds of things we have in mind to continue improving the site and implementing all the great ideas we get.

What is Needed for a Circuit to Recharge Batteries

Has anyone made a circuit that recharges batteries without having to take them out of your bot and put them in a charger? I would like to be able to plug my bot into an ac/dc adapter and charge it without having to remove the batteries.

I am assuming you have to use caps to keep voltage in check as well as determine when the batteries are fully charged to keep them from being damaged.

Also I'm not sure what I don't know ;) Anyone have any suggestions or experiences with this?

courses in robotics and cs

Hey all,

I found this link this morning and figured I'd share it...it's pretty cool that they are offering these courses for free online! 


Dynamic measurement of robot's distance from fixed point


I am interested in wirelessly and dynamically/continuously measuring the distance between my slowly moving robot and a fixed point. The robot will act in a space which will never be more than 5ft from the fixed point. Is this possible??

 Thank you very much.


Robot shirt

I found this shirt today.  Kind of cool and only $10 USD, shipped in CONUS.

Robot shirt



Also on the site was a link to a PDF you can print and cutout to make paper toys of some the robots printed on the shirt.

Md23: the revenge

Hello :) I'm here again to annoy you with my md23 :)

So, a new board has arrived, but now the question is: how do i feed it without possibly burning it ?

I was planning to buy a 12V lead acid battery for the robots, are there some issue i should know? something like the fact that it gives 15V when you least espect it ? :)

Btw, if i would like to use the 12V unregulated adapter, how could i "regulate"  the output?

Also, could i use a PC power supply? It should be switched-mode, right ?

My SRF05 Wont work with my Picaxe!!

I soldered everything up correctly as Frits's tut said, and when I plug in the power to the picaxe, after 7-10 seconds, the SRF05 board and everything gets extremely hot... Did it burn out? How can I see if the SRF05 still works?

Arduino board

Well, frickin hell. I got my arduino in the mail and i was all excited to use it. Well.. I shoulda known it was gonna be hard to program it, but wow.... Anyway, my memory seems to be not working tonight (curse you television!!!) and so I can't seem to remeber how to open a line with the programming language. I am already learning German and Medical Terminology so learning something during the week is like trying to win an eating competition if you have no stomach. Any ideas on something simple i could program with just an arduino board? Or you know, some manual on the internet.

MCU for custom i2c motor driver

Ok supposing that i want to make my own motor controller, i'd like it to be controlled by i2c. What microcontroller could i use that can be used as i2c slave? Afaik, picaxe can only work as master, right ?

Possibly someone that doesn't need an hardware programmer :)

Decoding IR without INFRAIN

hi guys!

i need some help from you guys. I have found this page, and it has really helped me a lot: http://www.world-educational-services.net/PICAXE%20Infra-Red%20Interfacing.htm

 what i wanna talk about today is the "Decoding without INFRAIN or INFRAIN2", where the author of the page is trying to decode the IR signal coming from his sony remote. Above this is an explanation of how the Sony protocol works.

Arduino: How to make your first robot with..

When writing this, LMR only offers "Start here" - instructions on how to make your first robot, using Picaxe.

"Nebster" wrote to me, and asked if I could do a parallel, using Arduino, and I think that is actually a very good idea (now that Picaxe refuses to pay me commission, haha)

Focus should be on making first timers get a robot up and running at a low cost, and most importantly learn how to hook up motors, a servo, and a analogue input in "no time".

using single resonator with multiple ic's

hi all,

Does anyone know if it is possible to use 2 or more picaxe chips, linked to only one resonator, so they keep time together. I was thinking somthing along the lines of this:



belt track friction

I have bought the treads and wheels from MUTR,  the same ones as used in Fritsl's first robot. I have assembled a robot base using the treads and wheels, and two MFA multiratio gearboxes. the robot goes fine in a straight line, but the tracks have too much grip when it needs to turn. I have tried tape, but it makes the tracks too tight. coating the treads with correction fluid gives some improvement, but still not good enough to turn smoothly.

does anyone else have ideas that have/might work?

Flying bots

I'm working on making my own Robot controlled helicopter. Is there anyway to calcute the wing length of the blade in order to lift the helicopter?

My first robot

I want to build my first robot, and have planed it a little bit like

The Start Here Robot.

It will drag itself using its two front wheels, and a half-of-a-pingpongball.

i want to mount a distance senser on a servo so it can turn.

Should i use i picaxe 28?

Will this projekt even work?