Let's Make Robots!

Interfacing arduino with SIM900A GSM module

Hello guys, I'm new to GSM modules. I've a very little idea of there working. I bought my gsm module from here: http://www.ebay.in/itm/GSM-GPRS-SIM-900A-modem-with-Stub-Antenna-for-PIC-Atmel-Arduino-Raspberry-Pi-/291389483047?_trksid=p2054897.l5673

I'm trying to send sms from the module but it is not working. I found the following  code online but it is not working


Trex Robot Controller Battery voltage on Voutput does n't match the input

Recently I got a Trex Controller and was trying to understand the board not yet started with the motors. I connected a 11.1 V 6400 LiPo. At first I was able to see around 11.6 V on the input and the blue Voutput. I was trying out the sample codes and checking the voltage on motor outputs but never saw anything. It always show zero. Now I am seeing the D13 LEDs turned on along with the fault motor LEDs. I connected the battery properly but I no longer see the same voltage in the blue Voutput for the battery. I think it is reading voltage from the USB cable connected to PC.

Kickstarter 3D Printers

Hello bot brothers and sisters,

I strangly ran into some extra money not needed by our daily expenses.  I'm thinking of investing it in a second printer; a printer from Kickstarter.  I was curious of what some of our citizens thought of these two:

Can ED-209 be made to do PID balancing, like a MIP robot?

Hi All,

I'm having some trouble mentally figuring out how ED-209 could be combined with a two-wheeled PID balancing robot.  In a two-wheeled balancing bot, the gyroscope is ideally placed close to the axis of the two motors.  If ED-209 were to have "PID feet", would the gyroscopes go in his feet?  or would one gyroscope go in his torso to keep it balanced while his feet walked here and there?

First Arduino Obstacle Avoiding Robot

I am working on putting together my first Arduino robot. This is the set up I have come up with based on the parts I have on hand. Do note that the IR sensor is really a Parallax Ping sensor, but I couldn't find one of those in Fritzing. Does anyone see anything that stands out as a problem? I know that I should really be using a motor driver, but I don't have one yet, so I am hoping that this jury rigging will get me by till I can order one. Comments and suggestions are welcome!!

Speech Recognition

Hello everyone, I am a beginner and new to letsmakerobots.com. I love the site. I have a project in school that involves designing a speech recognition system,and am in dire need of help. Suggestions and resources would be a life-saver. feel free to drop a message,or better still,email me at: anijapan5@gmail.com. Thank you all. 


The new droid from Star Wars. Whoever makes one first wins at LMR this year.

Laser wood cutting

I'm working on outfitting a shop in an RV. I've been told that the noise from things like a table saw might be enough to get me kicked out of an RV camp so I'm looking at alternative ways to cut wood. Right now I'm looking at cutting up to 3/4 inch plywood and 1" of hardwood.

Would an affordable laser cutter (say under $10,000) be able to cut these types of wood?

I need to be able to cut up to a sheet of 8' by 4' plywood or maybe up to 8' of normal wood.

Is this a doable thing? Is it quiet?

GSM/GPRS module and arduino


I've just bought a gsm/gprs module named GTM900b and

this module has an option that when you give "A/" to it it'll repeat every command

you sent to it ...and when you want to get rid of it you shall need to reset settings 

for resetting the setting you've to use this command : "ATZ0"

I used it for the first time and it worked ...I became able to take "HUAWEI OK" and "GTM900B OK"

but just for one time ....I cannot use it anymore and I've no idea what the problem is :(

can anyone help me with that ?