Let's Make Robots!

Question about this Transistor!

Well, I was surfing eBay a few days ago.. and came across an exciting deal..100 S9013 NPN transistors for $4 with free shipping..

Of course, before looking into the specifications too much, just scammed over and seen that it can handle up to 30v at 500ma..

But I seen that the "Absolute Maximum Emitter Current"  is -500 ma.


Parallax Board of Education board + extras

This is a collection of items to make up a complete Parallax Board of Education training kit. The Basic stamp is a new BS2P processor which is faster, more memory and comands then the original Basic Stamp2. It retails for $79.99. The board is in mint condition (only used a few times) and tested before listing. Everything else is new except the USB cable I used with my camera a few times. Parallax retail value of over $190, not counting the cable and un-opened bag of electronic parts that go with the book.

problem with IR remote upgrade

i was trying to see if i could make sounds, LDR-test and ir remote test.

upgrade stuff here: http://www.rev-ed.co.uk/docs/axe040.pdf

but there is a syntax error :(



please help!


real time servo & motor control

Hi there

Sorry for this post as I`m sure there are many like this....

I need to be able to control upto around 70 servos and motors from a pc or networked pc`s 

I want to start with one servo and one motor for now.

the thing is tho, I know there is MANY products to set up a sequence of movements on software -> download to controller then run the sequence. or something like that

NiCd discharge question

i have any questions about the topic


when a nicd cell have to be recharged? i am taking about voltage... 1,15v? 1,10v? 1,05v? 1,00v?  per cell

i have a 3xcell batt pack in a bot , the system self recharge when the voltage reach 3,4v, so 1,13v  per cell

is it an insufficient discharge? which can bring to lazy effect?


assuming that X is the ideal voltage per cell  to decide to recharge..... have i to read X  when the battery is under load or when it isunder no load.

Motor Driver question


i'm trying to build 'start here' robot using  arduino as the brain 2 gear motor as the driving force.one of the forumer has point out to me that i need a motor driver to control the motor for forward and reverse movement,

my question is(sorry if sound stupid) do i need 2 motor driver for the 2 gear motor or 1 motor driver is enough.and how to use this motor driver.

thanks for the help.truly preciated



How to use two analogue devices with only one analoque input?

For now it's theory, it's for a future evolution of a future project (yeah i know that's two "future")
Ok actually i'll need 3 analogue inputs (one SRF05 ultrasonic rangefinder and one 2-axis accelerometer), but the 18x picaxe chip has only two. So basically, i need to find a way to share one of the inputs. As i won't need to read the all inputs at the same time, maybe it's doable.

So two ideas came to my mind, each one with its pros and cons.

First idea : a SPDT relay.

With that, two solutions :

Where to find Timing belts and pullies?

    Well for the next iteration of my sumo- "bot" I will need some timing belts and pulleys. The pulleys need a 6mm bore though, I've been searching Google with minimal success, anything I find is either really expensive or needs to be ordered in bulk, can anyone help out?


More info than you'll ever want to know about current LED technology

This is a great read if you like knowing about the current technologies going into the components we use to build our bots or other gadgets. It's heavy on the technical info just as an fyi. 

While reading it I was also surprised to find the company that makes those luxeon LED's have some damn cool tech.



Power Grid (boardgame)

Hello guys,

just wanted to introduce to lmr this cool boardgame i've played a few weeks ago. It's called Power Grid and the whole point of this game is to buy power plants and give power to cities to increase you profits. I really like it because there are no dice to be rolled, opposed to the majority of boardgames.

ROV submarine

I playing with the idea of building a ROV.

A ROV is a Remotely Operated underwater Vehicle.

I plan to start simple, with a webcam connected to a computer, and 3 motors with propellers controlled by switches, all of it strapped to a frame of sealed plastic tubes. Something close to this instructable

But the robot geek in me wont stop there! I want to build:

A moisture sensor (to warn if the electronics compartment has sprung a leak) 

Great quick reference tool for LEDs!

This little sliding tool may soon have a spot on my wallet right next to my CAT5 wiring guide card. I can do lots of electronics stuff, but figuring resistance for LEDs always makes my brain work too much.


Servo problem Picaxe


I have some Tower Pro 9 gram micro servo, I tried to control this servo using Picaxe servo command but it does not work. I have standard size Futaba servo those work fine with Picaxe. If anyone has any experience with this problem please let me know what is the problem here why is the micro servo not responding to Picaxe servo command.


It soon is time to have another LMR skype social weekend!

Yes, yes.

Will you get drunk, and join in? Theme will be telling people long tales about what you do when you are not making robots.

No one sticks to the theme anyway.

However, the word "Hello" is prohibited, anyone saying it will be kicked off the line.

Do you have a fast connection, can you host?

Is it possible to walk with only one servo?



i will make my start here robot, but while i wait for the weels/ ir sensor and motors, i only have a servo, the picaxe board and chip, and a few pieces of wire and metal.


do you think it is possible to make a servo walk/crawl with just this?




In the first video i made it walk, but it only works on top of paper... it has some "claw" shaped ends in the metal legs so it kind of works... :p


Help with XBee Explorer Regulated

Just received a couple of XBee & boards from SparkFun but I'm unsure how many pins are needed.


According to the schematic, http://www.sparkfun.com/datasheets/Wireless/Zigbee/XBee-Regulated-v10.pdf, there's a DIO3 pin.


What is it used for?