Let's Make Robots!

simple motor brake

hi all,

i need to control a simple DC motor (using Arduino and some H-bridge). 

what is the best/simplest way to implement a braking control? i don't mean to slow it down (by shortening its terminal) - i mean really braking it (against downhill slipping). 

will fast forward/backward alternation do the trick? or is there any more decent way of doing this?

thanks in advance !


Edge Detection

I've noticed a lot of robots with edge detection, to prevent them falling off edges (obviously).

I'm curious as to the type of sensor used for this. I'm assuming it's IR, but are people using an off the peg sensor, or making their own?


The Bromz.

Big choice of servos in Europe


I'm making a robot arm, and I need 1 shop to buy all my servos from (legal reasons).

Problem is, the shop has to have all the range from powerful and durable high-torque servos with full ball bearings (about 25 - 30 kg/cm), to lighter standard, to even some very lightweight mini servos.

So far the shop with the best choice is http://www.active-robots.com/products/motorsandwheels/servo-index.shtml, but I would be very happy if someone coined me some more or better options :)

Battery Backup 12v

Hello, I wanted to add a battery backup to a Picaxe circuit so when the AC main fails the power will switch from the AC-DC transformer to a 12v battery which is then lowered to 4.5v to power the PICAXE board.

after some research I found this circuit which seems pretty simple and I wanted to know if you people think its good or will I have fried PICAXE for dinner.

Thanks in advance!  :D

Advice for selecting a university course in robotics.

Heey guys,

I've just joined your community after going through your website. I loved it so decided to make an account!

I'm a 18 year old student currently living in Melbourne, Australia. I currently study an Advanced Diploma of Computer Science which I will be finishing in a couple months. To be honest just writing software (especially GUI's) for business, etc. doesn't interest me.

I've always had a passion for knowing how things work and designing things. But unfortunately I've never really finished any cool projects yet.

Now on to my questions:

Really small RF receiver

hey guys,

so i am building a really small robot( 25 X 25 X 10 mm) and i want it to be remote control. I wanted it to be controlled by IR initially but i found that IR cannot work in direct sunlight so i thought i need an RF unit. Do you guys know of any really small RF receivers. I was thinking of those used in real cars for door unlocking. What do you guys think??

LMR Member Discounts

Frits has negotiated discounts with a number of web shops. These discount deals are for LMR members only. Info on these deals is shown at the very bottom of the main page. I'm not going to list them here, as that is just duplication of effort.

However, a few shops have spontaneously started offering discounts for LMR members! You guys rock!

This post is my attempt to collect a list of them.

Panasonic's Evolta robot cycles to Le Mans 24hr world record

The little Panasonic robot manages to make it more than 5 times around the famous Le Mans track in France ......

....wait for it..........on just 2 AA batteries in 24 hours for a new Guiness World record.

HC-SR04 arduino codes

Hallo everyone 

I want to make a robot with the hc-sr04 ultrasonic sensor on a servo.

Can someone help me with some (example)  codes for the hc-sr04 utrasonic distance sensor?




I will upload some vids/pics/info about my first robot, that walks.

Edit: just neede to replace the numbers from the original ping sketch. it works now

Seeking knowledge to hack a cheap and small CMOS video camera

Has anyone happened to use something like the following cheap cameras with a microcontroller?  I'm interested in interfacing a camera with an STM32 ARM Cortex-M3 microcontroller to record pictures or video, or to stream to an embedded display or wireless link (for example via an RN-171 WiFi module).

Rover 5 Motor running backwards

I have gotten around to running all four motors on my Rover 5 at the same time.  One of them runs in the opposite direction to the rest :-/  (see my robot post)

While I guess I could negate the direction in the code, this seems fragile.  How do the motors work?  Is there a simple way to reverse it? (reverse the polarity of the power pins?)


Mini Makers Faire - ShenZhen, China - LMR will be there!!!

Much to my surprise and delight, DAGU will be attending the Mini Makers Faire in ShenZhen. We will also try and setup an LMR stand. I know this is short notice as the Faire is only 1 month away but I would like to invite LMR members to attend or at least send in one of their robots.

Links to photos and videos will also be welcome. I will get the photos printed and use them as a backdrop. I will have at least one large computer monitor playing LMR videos.

11 Servos on red back spider (ATmega1280), how to power?



I'm stuck! I am trying to connect 11 servos to the red back spider board, and as soon as I turn on the power (up to 12v) the servos all jerk and move like crazy and the board turns itself off again. 


I'm not quite sure what I am doing wrong or how I need to power 11 servos (9g micro servos) without the board crashing? 

Anyone can help me out?