Let's Make Robots!


Biped Howto: Moving servos

+++ UPDATE (12-march-2014): Rename title as "Biped Howto".

Hi, I will try to explain, in a very simplistic manner, the way in which servo motors can be controlled.

Servo motors are controlled by a PWM signal, in which the active part of the signal (known as duty cycle) define the amount of degrees the servo will rotate.

Effect of timers on PWM

All the pwm-pins on my Uno are occupied and I would like to use timer 1 or 2 to set up a timer interrupt to resolve some timing issues. I have learned that using timers cause losing pwm-pins, since the timers are also used for generating pwm-signals by the analogWrite function.

How to handle more than 8 servos on a PWM with the same microcontroller?




As I see there are many boards for this solution, and I saw interest on this, I prepared a form to inform/check these solutions:

Form to inform about a Shield board to control several servos by PWM

I'll publish it here as I have enough information ;-)

Few questions about Spider Controller (DAGU)

Hello all!

I'm newbie and I have few questions about Spider Controller (from DAGU).

1) When USB is plugged and the battery is plugged too - which source of power controller will be use for servos?

2) As i understand, If i use analog servos I should plug it to PWM-outputs. And digitall servo can be plugged to any output. Am i right?

3) Can't understand what is the role of ON/OFF switcher. It is for battery only?


Many thanks in advance.

PWM and motors

Hey guys

I have built a robot using arduino UNO as controller and a L293D quad half H-bridge as motor driver. The motors are Pololu micro metal gear motor 100:1 HP hooked up to a 10,8V battery.

I am controlling the speed using arduinos pin 9 and 11 with PWM, but it seems difficult to get even a small amount for accuracy in speed, and the robot doesn't even move at duty cycles below 25%, and it is always quite noisy.

Raspberry Pi based, controlled remotely, exploring the environment, transmitting a webcam live stream
Using a
PiBot-B is a small mobile robot based on Raspberry Pi that moves on caterpillar tracks. A video live stream taken by a webcam is transmitted to an iPhone via WiFi. … Read more

hacked chassis' moves too fast or not at all

So I built three little bots so far. 

One with a raspberry-pi, (6V motors):  

One with an arduino (12V motors):  

And another with an arduino but a hacked remote car (7ish, volt motors):  

Three 08M2s and a Pi?

Hello! I'm a complete Picaxe n00b, but I have read quite a bit online, so hopefully my ideas here are not entirely inane.

I have been playing around with a Raspberry Pi as the brain for a small two-wheeled differential drive robot. It's very simple, but it more or less works.

L293D Motor Driver PWM Problems

I recently put together a L293D motor driver circuit (from Bajdi's very helpful website: http://www.bajdi.com/obstacle-avoiding-robot-made-from-cheap-parts/l293d-schematic/).

When I use PWM from a Teensy 2.0 (analogWrite) on the enable pins, the motors only make a soft high-pitched whining sound and don't move at all (but max duty cycle works of course). Using digitalWrite, the motors rotate fine. I would like to have speed control but am stumped about why the motors don't rotate. I've seen others use PWM on the enable pins fine so it might be my motors.

PWM through finger!

I can control a servo with my hands!

Create blocks of pleasing pulsating colors.
Intro: Sept. 23rd, 2012 - My buddy Mat Nix wanted a light display that would respond to people moving about a room. Something like a wall of little frosted windows … Read more

ESC + L293 + Brushless motor

So, i've been having some trouble lately and I can't seem to find a solution on the web. I've managed to controll a brushless motor through and ESC and arduino with PWM. Nothing too dificult. What I need now is a way to controll an inversion of the motor. Like you know, changing two of the wires from the motor makes it turn the other way around.

Pololu Plastic Gearmotors and PWM.

Does anyone know what's the best frequency to switch at when you're driving the 120:1 Pololu plastic gearmotors with PWM via a L293?

These motors : http://www.pololu.com/catalog/product/1125

A stepper motor driver where a dsPIC33 both monitors the current and controls the PWM via an L298N.
A few years ago I started building stepper motor drivers.  First it was a simple unipolar driver.  My motors wouldn't rotate faster than 1 to 2 rps.  So I … Read more

What happens if higher freq PWM is given as servo input

Has anyone tried giving a 5mS or 10mS (or lower freq - 40mS or 80mS) time period PWM signal to a hobby servo rated to work with a 20mS PWM siglan input...

What I am trying to ask.. Is there any way to give a higher (or lower like 25Hz) frequency PWM input signal to a servo...?

I dont have a servo with me right now or I would have tried it my self.. But Im guessing the servo jitters... If so why..?

Need to setup TIMER3 on Mega to higher frenquency PWM

I need to set TIMER3, controlling pins 2 and 3 on an Arduino Mega to either fast PWM mode (acceptable) or faster (higher frequency)(preferable).

I use this PWM to control an audio signal through a Silonex light sensitive resistor/LED unint and some audio contamination can be heard because of the speed at which the Silonex reacts. I used TIMER0 in tests with a prescaler of 1 and it works OK. But TIMER1 is "fast" PWM and TIMER3 is "phase correct".

Real-time enough? About PWMs and shaky servos

We are currently working on the next incarnation of our software and hardware platform for vehicles controlled over the Internet. Among others, we decide to investigate the way to control our robot without micro-controllers. In fact, BeagleBoard has a lot of GPIOs available. In addition, three hardware PWM generators and I2C bus should be enough at least to control the tank with camera, compass, GPS, and sonar.

How to use timer and interrupts on Arduino boards.
    Update 07/24/2013 04/24/2013 Example 3 has been updated to work with Arduino v1.x.Added ArduinoTimer101.zip examples source code for Arduino v1.x .    Read more

Rover 5 - 4 Channel Motor Controller: PWM Frequency

I just got hold of OddBot's Rover 5 platform and the 4-Channel Motor Controller.  I'm still fairly new to all this and I'm not sure what PWM frequency to use for the controller.  The datasheet that I have doesn't specify so I'd appreciate any advice you can give me.

Many thanks.

Electric braking

I'm working on an RC car and was thinking about the braking. The idea is: I'm driving at full speed and need to turn. Obviously, because my car is going to break the land speed limits ( ;) ), it cannot take the turn at full speed so I'll need to slow down. Now, just releasing the throttle won't be enough, so I'll have to brake extra somehow. I was thinking about giving slight reverse throttle, so that with PWM, I can handle the braking intensity. Now I don't know what this would mean current-wise.

How to use HPWM for picaxe chips.

This information is based on the chip that is used for the 20x2(PIC18F14K22) To get a better understanding of the modes, I suggest referencing this datasheet for further information on the chips features. IMages and info are referenced from both the picaxe 2 manual and the PIC datasheet for the above mentioned chip.

HPWM, what is it?

PWM IC simulation.....

please i need the library and model of sg3524, sg3525 sg2525


i need to simulate this IC...for motor driving, i cant jump directly on miCro controllinG...

Airship differential steering troubles

Hi all,

I'm faced with a problem - some friends and I are building a semi-autonomous airship (only a little one) and I've been given the electronics and programming to do, but I'm having trouble getting the pwm commands to work properly.

I'm using a little joystick with 2 pots to control it, the y-direction one controls the overall speed and direction of both motors and the x-direction one puts a left/right bias on them to turn the thing.

Here's the bit of test code I've got with just the one pot being used


symbol zero1 = b1

symbol zero2 = b2

High Current Motor Control with Arduino

Hi All,

Please excuse the commercial but I wanted to let you all know about our new motor control shield for Arduino.  It is called the MegaMoto and is designed for motors from 7V to 28V and up to 13A continuous current.  A peak of >30A for a short time has been demonstrated.  The unit is fully protected against thermal and current overloads.

I'm sure many users would like to be able to control something larger than the tiny motors you can drive with the L298 etc.

Navigate and avoids obstacles
Using a
A robotic platform far various experiments related to this field and to teach my kid some things about robotics. It's 16 years since I have build my first robot and … Read more

FLEXEL-1 PWM Question

Have any of you tried to enter a PWM value outside of the 500 to 2500 ms range for configuration 1 (RC Servo) on the FLEXEL-1 chip?  I would like to drive a couple of L298's with this and would like to have the full range of duty cycle.  Do values outside of the 500 to 2500ms throw an error?

Fades and flashes and keeps away the closet monster
Insired by Geir Andersen's RGB Nightlight, I thought I'd build one for my daughter. She's just started having nightmares (she's 3 years old) and wants the lights … Read more