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Low cost, low resolution optical absolute encoder?

I am designing a system, where I would like to add an absolute position encoder.  But, my idea does not need the high resolution, or cost of the encoders I am finding in the market so far. I prefer optical over a pot, for its reliability.

The object I am motorizing needs to spin slowly around an axis in continuous rotation, but will normally stop at 90 deg increments. It won't go faster than 3 RPM.

Mechanical CAM switches;

Phoenix code any 3DOF 18 servo hexapod.

Hi everybody,

After 8 long months, some trigonometry lessons and a lot of experimentation I finally was able to get my hexapod running and walking great. I tried using several different servo controllers. A torobot, one stamped with a decepticon and a pololu. The sequencer programs are pretty cool but theres lil documentation (except the pololu but no hexapod code) and most of it is too vague to get them going using a code or micro-controller and the sequencer just cant capture that creepy walk.

Phoenix hexapod femur motion reversed

Ive been trying to implement phoenix code to my small MG90 servo sized hexapod. Ive changed alot of the variables in the config_h. file including, the leg IK measurements, feet start positions, the min/max mechanical limits of each leg and so on.

The motion is correct for the coxa servos but the femur servos with out a doubt have thier motion reversed. The tibias might be right but i wont be able to for sure till i fix the femur servos direction. Also D-pad up lowers the bot while D-pad down raises it. So that should be a clue too.

Inaccurate readings of Distances (HC-SRO4)

Hi guys! This is my first time in this website. Just newly found out this community of robot enthusiasts, so I guess, and I hope you can help me with this problem, and by the way, I'm also a beginner of this one..


I just brought an ultrasonic sensor. Well it's working well after testing it with a code. But once I put some "if, else" statements, it's giving me inaccurate distances...

for instance... if I give the loop as ReadDist(); (// It is assumed that I've already put the right code for the Ultrasonic Sensor).

void loop()

ESP8266 Troubleshoot

Hello LMRians,

I recently bougt an esp8266 wifi module but when I enter any AT command (or gibrish) I get ERROR in return. What may be the problem?

I have tried all power modules, power is OK. The same thing happens with all modules i have.
Please HELP!!  URGENT!!!!!!!!!!!!!

MPU vs MCU - Which is more suited and what is the best one?

Hello all, brand new to the group.

Ultrasonic Collision Avoidance Arduino and Raspberry Pi


I am building and testing a telepresence wheeled rover bot that has two methods of control:

1. Web Interface (Manual Mode): This consists of a control panel on a web page served using WebIOPi on a Raspberry Pi which, when activated, sends commands to an Arduino Nano AT Mega328P via a two wire i2c interface (Forward, Back etc). 

Ideas Needed for how to open the back door for my dog... remotely?

I have a dog with health problems that needs to go outside a lot.  I'm just tired of getting up for him, and a doggy door is not an option.

I'd like to be able to hit a button from my couch, and have the door open up.  It only needs to open up about 9 inches.  I'm ok with taping down the latch, so I don't need anything that turns the handle.  Just needs to push it open and closed.

Serial vs I2C communication

Hi, please, can you tell me difference between I2C and Serial communication and which is the best for communication Raspberry Pi 2 with Arduino (T'Rex Controller). Thanks

Does this charger work well for Arduino?

Hello everyone! Recently I came across a Justin 5200 mah battery (https://www.youtube.com/watch?v=vNLnQ7RHDuk), and am wondering if anyone else has tried to use this to power an arduino. I've found that some people make use of usb portable chargers, and wonder if anyone has used that brand. It seems to get mixed reviews, but for it's size and even at half power, has more than I need for some of my projects. If you use portable chargers, what charger do you use? Or do you just stick to good ol' batteries?

Thoughts on the Hitec 33485?

I have been looking through higher powered servos for a while, and came across hitec 33485s. The Amazon page comments seem to praise them, but I wanted to hear more thoughts. Can these be relied on, or are there better servos for the price? Has anyone used them?

Controlling 12V stepper motor with L293D

I just got my first stepper motor. I just want to tinker around with it for now. Before I got it I saw many online guides that you can control it with an L293D motor driver. Since I have one of these I bought a stepper motor. My problem is that I forgot to watch for the operating voltage of the motor and I made the mistake of buying a 12V stepper motor. 

PWM switch - autonomous boat with Raspberry Pi

Hello everyone! This is my first post.

Need ideas on a robot arm.

I am looking to make a robot arm that is controlled via radio. 

The arm needs to be able to pick up wooden pieces that can range from 0.5lbs to 10lbs and carry them a fair distance. I already have a moving robot, but I am just stuck on what to do to pick up the pieces. 

I have parts readily available to me as long as if I don't have to buy a whole arm that's already pre made.

I have servos, arduinos, circuits, aluminium sheets - bars - rods - etc.

Servo powering problem

Hi guys, me and my friend have built an arduino controlled Quadruped "mantis" robot.

Seeking worm-drive gearmotor with encoder.

I origially started a thread at RobotShop, but they don't have anything that meets my needs in terms of torque. I am designing a mechanism that needs a Right-Angle gearbox with worm drive. 

I need the following;

Dagu ComMotion Confusion

I purchased a Dagu Scamper to enter the OddBot art contest. Mechanical assemply completed without problems. Trying to get started with the software. Found the ComMotion instruction manual and a package called "ComMotion_Redboard_Demo" which contains four .ino files which compile and load into a Sparkfun redboard.

Tips for having custom parts waterjet cut ⚙

If you have a sophisticated mechanical design for your robot, you may have considered having the parts made by CNC waterjet. But, as with any tool, there are some limitations to this approach. I created thse articles to explain the limitations of this technology and hopefully make it easier to get the custom parts you need from waterjet cutting

Affordable 3D printer? (For small robotics)

Lately I've been getting frustrated with cutting, sanding and drilling wood. It takes lots of time and the quality is low. Im thinking a 3D printer is exactly what I need. Anything from the $300 to $500 range? Cheaper the better? 

Where to start?

So, I'm pretty much a blank slate. I have no knowlege on anything, my question is...where do I start? Is there a how-to guide or something. What is the most basic knowledge I need to know to start? Any direction would be very much appreciated.


Thanks in advance! ^_^