Let's Make Robots!

Do H-bridge resistor values need to be calculated, or can they be played by "ear"?

Hi All,

I followed an H-bridgeschematic from a post by ignoblegnome and the resulting H-bridge worked perfectly.  I looked around online and saw some h-bridge schematics without resistors and also with resistors.  I wanted to know if resistors were necessary in h-bridges?  And I also came across a specific formula that is used to calculate the base resistor needed for a certain transistor.  Do these calculations need to be followed religiously? 

Decision tree for debugging robots

I want to make a web tool to help new people to debug bot related problem, based on decision trees.
it would be something like this:
"the bot doesn't move
    yes
        check the wires, it's all connected?
            yes
            no
    no
        it doesn't go straight?

problem with my code

hi i wrote a code to drive 2 motors but the weird thing when i run this on the arduino the arduino keeps going to setup each time it goes to read the serial recived but when i ran it on the aruino leonardo it kept writing a very weird error the io exception thing or idk

here is the code 

 

int motors[2][3]={3,5 ,                  //PWM PINs

                  4,6,                   // wire1

Robot Arm with Rotating Base, tangled wires

I'm stuck on a problem with my robot. Trying to add a rotating base to a robotic arm but Im not sure how I would keep the wires from the joints from spinning and eventually getting tangled. Anyone come across this problem? Base was orignally supposed to only rotate 180 degrees so I think I may have to start over on my design. Anyone have this problem with rotating bases?

PWM and motor torque

I'm building a robot using Pololu micro metal gearmotors, and I've noticed that the torque is very low using PWM (I'm using the Dagu Mini Driver). If I try running one of the motors directly off a battery pack with the same voltage as the PWM is generating, the torque is much higher. Is this normal? Thanks for your help--I'm very new to all this.

add a second WiFi antenna?

The USB on my raspberry pi has 1 x 5dBi antenna. I have a second one from an old router. Can I just connect the ground shielding and signal to the existing and and signal connections. Would it be beneficial? 2x 5dBi antennas, would that make it 10dBi or just 2 x 5dBi .

  I am trying to get a little more signal strength on a n300Mbps WiFi controlled vehicle. A little more range or stronger signal when it goes behind vehicles and block walls.

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The Parallella Board?

I was wondering what people think of this board and the supercomputer that this guy built with them.

The Board:

https://www.parallella.org/board/

This guy built his own supercomputer with 8 of them (each with 18 cores) wrapped around a gigabit switch and a couple of Intel I3 NUCs.

The Supercomputer:

https://www.parallella.org/2014/06/03/my-name-is-brian-and-i-build-supercomputers-in-my-spare-time/

Kirchoffs Voltage Law and Current Law - is there easier math for this?

I think I understand the simple examples for this law, thought the math (algebra) is a bit daunting as its been many many years since high school, and I wasn't very good at it then. The more complex examples make me dizzy.  I have to believe there is an easier way to understand and use this law in my robots circuits. Or is this something that I will rarely use? Is there an easy "rule of thumb"?

Here is an example from the class, not even terribly complex, but seems that way for me.

Personal assistant robot

Hi all,

I have plans for a robot for a college project: in short, this is a personal assistant robot. It should be able to use Wolfram Alpha (just like Anna) to get information on spoken search terms (I.E. voice recognition) and output them using text-to-speech. This is all for now, as I want to have a working base that I can develop of my own accord. 

Charging NIHM battery pack insitu help

**EDITED TO MAKE CLEARER*

Help LMR,

Im currently making good progress on my Rover 5 robot build and im at the point were i would like to stop taking the batteries out to recharge, and to prepare for autonamous recharging possibilities in the future.

im trying to get my head around what i have available component wise and my knowledge on batteries to make this work (both are limited).

**Batteries are 6x 1.2v nihm AA's

3D Printer VS CNC

if a robot builder on a budget to buy either this or that. which one ?

Help on motor selection for graduation project.

Hi, I'm calling out for help in selecting motors for a graduation project for my elecric mechanics course. I'm planning on building an R2D2 (Star Wars) robot, driven by 2 motors, controlled by motor drivers and picaxe controller using R/C controller/reciever). The dimensions i have in my head are about 35cm height(14"), 25cm width(10") including legs, leaving us with about a 20cm(8") can. I currently have in mind some geared motors(low amps) so weight should be around 2kg(4lb). I plan on add a few things in the future, like a spinning head, sound system, led's etc.

Additional information on robot page

I'm missing the form to enter additional informations (like CPU, operating system etc.). I could define these information for this project: http://letsmakerobots.com/node/38857, but not for my latest project (http://letsmakerobots.com/robot/project/pibot-a).

 

laser sensor in a old printer

hi everyone i recently bought a used printer for about 3 dollars

it is still functioning and working very good

i didnt buy it to print paper but to use the motors rails sensors etc

i found a very good and weird sensor idk how it  is working or how to disassemble it

Need a coupling for a 28BYJ48 stepper motor...

I'm building a device to pan a small camera. I'm using the uber cheap 28BYJ48 stepper motor. To mount the camera to the stepper motor I need a small coupling. One side should be bolted to the axle of the stepper motor, the other end should have 1/4"-20 thread (standard camera thread). Is there anyone here that could make me such a thing? I would like to build a decent, sturdy device so I don't want to resort to hotglue... I'm located in the EU (Belgium), any European people here that can machine such a coupling?

Drawing of the piece (dimensions are in mm):

search and rescue bot, first attempt, failure on mechanics/power !!SOLVED!! thanks

first robot

 

Building my first robot, want to make an autonomous "search and rescue" robot. I am using a raspberry pi b+, pirocon2 motor board and some sensors (distance sensor, bump switches and wheel decoders) to start with. First did the mechanical part using lego parts and lego motors in found in the attic, including tank tracks. No sensors installed yet and no logic programmed. Just testing with a python script and keyboard direction control.

Raspberry Pi offline Speech recognition?

I know a lot of the Speech controlled robots use the google api.

But I'd like a offline solution. It just has to listen for some key words like "time","temperature", ...

Would be great if someone could point me in the right direction....

Strange problem when saving data to SD card

I am using an Arduino Mega 2560 equivalent controller to read a G-code file received by an Xbee on serial port 2. The file needs to be saved onto an SD card until the machine is ready to process the data.

For this test I am using the Tera Term VT software to send and receive data over the Xbee modules on serial port 2 and the USB cable to upload code and debug. The code was written using Arduino 1.0.6 but i have also tested in Arduino 1.0.4 with the same results.