Let's Make Robots!

serial port grayed out in Arduino IDE

I just purchased a Red Back Dagu Spider board and a hexapod kit.  But when I plug it into the USB, the serial port on the Arduino IDE is grayed out so I cannot upload any porgrams.  I've tried two different cables.  Any suggestions?

Thanks in advance for your insights.


Halloween bust Arduino sketch

Hi..New to code; I ask for advice on sketch shown below(attached txt also). This is another halloween bust that needs 2 motors+3 servo's all set to move randomly.

- Movement does not look so random..I do not know how to add Random seed which some say makes it better ?

- how to make entire movement triggered by 4-pin PIR sensor (ping & echo)? or even a shorter range IR reflection optocoupler ?

 #include <Servo.h> 

Servo servo1;         // Define servo1

Servo servo2;         // Define servo2

Arduino based butler


this concept as simple as it sounds; has some challenges.

The bulter is carring a tray where host palces drinks and cookies.

Butler looks for transceivers fixed on the furniture. It it progarmmed to reach and stop at 3 ft from each transceiver, greet the guest (welcome to my house; please take a drink) and after say 1 minute, move to next guest.

VADER Spider Controller Arduino Upload Issues

So it's been a while since I last got a chance to work on VADER (see http://letsmakerobots.com/node/39884) , but I recently was able to dust him off and finish up the wiring. VADER is a Service Droid mounted on a Rover 5 Base with a 4 channel motor controller and a Spider Controller.

GPS Guided Vehicles: Motor Quadrature Encoders vs ESC?


Hi all, I'm very new to electronics, R/C mechanics or anything related to robotics but I know programming.

I've read many good articles by people here regarding GPS guided vehicles and I noticed one of the most important thing is the precise control of motor speeds and steering servo.

If I understand correctly, both ESC and quadrature encoders can control motor speed with precision but I noticed all of the GPS guided vehicle articles uses ESCs and no encoders so my question is


desoldering technique/tools

I have been soldering kits and projects for years but have not learned to desolder.  I have bought numerous "tools" to help do this but have found nothing that works for me. (desoldering strips, suction devices, etc.)

Could I get some input on what LMR folks use.  Is it just a matter of practice or technique or is there a really good tool that I have yet to find?

A board or PCB with arduino, motor driver and bluetooth

My dream board or PCB would be a single piece with arduino, dual motor driver and bluetooth class 2 or 3, to embed with the lowest cost as possible.

I was thinking to solder arduino micro 5v, a motor driver chip and the bluetooth chip HC-05 on a perforated board, but i don't know what motor driver chip to solder.

The motor driver chip need to operate at max at 12v and move a small or medium robot with differential drive. If it works i'd like to replicate it by designing a PCB and making a dozen of that boards:)

Developing a small, arduino-like IoT product for monitoring and tracking

Hey guys!

Long story short, we're currently developing this small, water resistant IoT product which can be used for monitoring and tracking different things. The HW would be top-quality and the SW would let you come up with all kinds of neat uses for it. 

BoB from toy to tool

i think its time to take my BoB from a toy to a tool. and i would like ideas from you wonderful folk at LMR.

what improvements would you all make to make BoB more classroom friendly?

what ideas do you have to help in the aid of manufacturing?


my basic guidlines are:

4xAA powered (most likely ni-cad or nimh)

MG90 servos (metal gears and kids seem to sound likea  good idea)

Arduino for a brain (not sure what board)

so please throw your ideas in to the pot and ill try and incorporate them into the design

i'm new in this world i need some tips to follow

hi there everyone :)
i want to join the robots community but i have no idea about robots at all
i'm a .NET programmer c# , c...
i hope you give me some tips to follow in order to make a robot at least a beginners robot
and thank you so much  :)

chopsticks spider robot

hello everybody,

my graduation project is the chopsticks spider robot and i have a red back spider robot controller and its need a PCB but i don't have any idea about PCBs anyone can help me because we have 28 servos with 7 V  input battery and 4 IR sensors...

Thanks in advance..

serial between two picaxe

am having a strange issue  getting the 28x2 to communicate  with a 14m2

the 28x2 Tx code here http://pastebin.com/RtDvA4Sk and the 14m2 Rx code here http://pastebin.com/54KeXDaf

now the 28 Tx works as expected but the 14m2 Rx is not, it appears to go to the subroutine as it shows its recieved the data but in the terminal window no values are displaced. any and all ideas welcomed

Servo problems

I recently bought 4 Goteck micro metal gear servos with the intention of using them to move some joints in my 3d printed robot. I decided to test them onviously and ran some simple code on my Arduino (basicly cantering the servo, moving it to the left and then right). I had run this code before with some other servos which worked fine but these ones seemed to act weirdly. Instead of jumping straight to the right position they flapped around a bit before stopping at the right place.

Raspberry Pi Home Automation

I have begun work on a home (or rather room) automation system using a Raspberrry Pi as its hub. I am aiming for 3 primary functions:

     1. accept commands for interface device (ex: recieve instructions to turn lights on and off and do so using GPIO and servo)

     2. accept requests for sensor data (ex: recieve a request for temp. sensor data(GPIO) and respond by relaying data)

     3. collect and transmit large collections of data to be interpreted by interface device (ex: sleep datalogging)


Movable head without pulling wires

I'm working on a small form factor turret with a movable head.  The design has a camera (w/ raspberry pi) on a spherical mount that can rotate altitude and azimuth directions.  Unfortunately, since its a turret, it must be able to twist infinitely without getting its wires tangled.  Any ideas?  I've been thinking about a laser based system, but I seriously doubt that that is going to be able to transfer enough data to stream video.  Anyone have a simple suggestion that hopefully keeps everything hard-wired?  

T'Rex Controller Oops (Possibly Fixable)

Hello All,

I recently purchased a T'Rex Controller from Sparkfun that I think I probably blew a FET or two. I forgot to turn of the power while I was detaching the controller from my T'Rex Tank.  I'm looking to see if I just need to buy a new controller or if I can repair the one I have. So here's the symptoms:

How many sensor is needed for a line follower?

Line followers use 2-8 reflectance sesnsors for detecting the line.


This product has swift movement and turns, it uses 5 sensors 3 in middle and 2 on sides, but does the middle one is neccessary in any way? Or does it is just consuming one extra ADC pin?

I am looking for a perfect sensor array for line following robot.

LMR morès and web etiquette

tl:dr-If you violate our sense of order with (commercial) rudeness, you earn our rudeness in return.  Not saying it's right or wrong-just what to expect.

Fiberglass/Plywood panels

This might be in the wrong forum, if so, I apologize.

I'm doing a major re-design of RT, and trying to figure out a way of making more professional looking panels for the outside.

Mainly, the current method of laser-cut plywood shows off the grain after painting.  I want to get rid of that.  I've got a few options.

1 - Laser cut acrylic (expensive)

2 - CNC routed PVC sheet (moderately priced, will have to outsource to a friend)

Reverse commands

My problem is regarding the following link:

For movement, FRITSL use the following code:

low s.8
high s.9

high s.8
high s.9

low s.9

My results are: