Wiring a motor to the RPi?

The RPi IO is pretty hopeless - the sodtware PWm is making the best of a bad job but it could well be OK for some things.

I will give software PWM a miss.  It looks like a messy job and probaby will not work with 12v motors that spin @160rpm.

as an example use pins 5 and 6 (pins 20 and 22 on J25) on the atmega328 and connect them to the motor_a and motor_b input (J5) on the gertboard.

Then the uart TXD (gpio pin22) of the raspberry to the RXD (pin 2 of the atmega, pin 1 of J64)

Then it is a simple mater to program the atmega328 to intercept the bytes sent from the raspbery and copy them to the 2 PWM ports.

http://arduino.cc/en/Reference/AnalogWrite

http://arduino.cc/en/Reference/Serial

Don't have a gertboard and won't get it for a while (Farnel issue).  But I am going to get an adruino eleven with ATMEGA328p which will help me do what I want.  I will look at your links though. 

The only problem I have with coding such a chip.  I have no experience and will require massive amount of help with the coding in python (I know some already) or C (which sounds easy to learn).

These Arduino are the easiest to program.

They made an IDE package that works on Windows, OS max and Linux 32 or 64 bits. These devices uses C

They have all the major function already available on their site "www.arduino.cc".

Plus they have "sheild" that can get you started then use the sheild schematics to build your permanent setup.

Ok, here is my idea:

Using some of the set-up features that @aonsquared used with his Robot/Rover thing.

Using a 5 volt supply to power the Raspberry Pi and the Powered hub.

The Raspberry Pi will send commands to the Ardunio Eleven (which I still have to get), which will control the Two Motors through a H-bridge and PWM.

That camera will be powered through the 10 port hub, along with the Ardunio and the W/LAN dongle.

The Motors will be powered though a 12 volt supply (8 AA batteries).

All the commands will be sent through an Ad-Hoc Network to a Laptop running Windows 7 Pro 64 bit.  I think that I will use by Joystick to move the Motors but I don't know how that is going to work as @aonsquared used a PS3 controller instead. (Saitek ST90 is the Joystick).

The LCD display will have the IP address so that I know exactly what it is whenever.

The Raspberry Pi will host a live webcam feed though an old Logitec Camera I have lying around.

One question is: Will PWM work on the motors through the Ardunio if I have the 12 volts going directly into the H-bridge Chip?   

What do you think?   

Yes it can be done.

Look at this chip the L298, it can accept input voltage for the motor up to 46 volts. The logic side is at 5 votls so it is safe for your Arduino.

You can drive up to 2 amps per output.

This chips can 2 motors or you can connect the outputs in parallel to double the current.

The datasheet even has some  circuits examples to try.

http://www.datasheetcatalog.org/datasheet2/2/052daje928cw7pc0uqs1ipyryppy.pdf

For the motor control via the joystick it is easy if you can convert the joystick position into values from 0 to 255.

for example:

move the stick forward, both PWM will increase simulatneously. this will increase your speed.

move the stick to the left or right, then deduct the values on one motor to make it turn.

Would you be able to help me code this?

Also, if the neutral position of the stick is (0,0) then that would mean the range would be from -255 to +255 on both the x- and y-axis.  Right?

Every position going up and down the x- / y-axis (+/- 255) will increase the motor speed by an incriment of

100/255 = 0.392157

Is this formula able to be included to decide on the speed of the motor?  I will improve it so that it works for all situations.

Yvan Turcot wrote:

 

For the motor control via the joystick it is easy if you can convert the joystick position into values from 0 to 255.

 

for example:

 

move the stick forward, both PWM will increase simulatneously. this will increase your speed.

move the stick to the left or right, then deduct the values on one motor to make it turn.

I just wiped up this python script.

# Converting Joystick Position to a Percentage that the PWM

# Channel can simluate on the motors

# By Wallarug

# Change the input value "i" to something that relates to the Joystick

 

 

f = float(100)/float(255)

i = input("Enter a number between -255 and +255: ")

 

 

while i!="":

    x = float(f)*int(i)

    print "PWM, " + str(x) + "%"

    i = input("Enter a number between -255 and +255: ")

 

 

# By Wallarug

Should work if it is converted to a different language and add in the motor commands and Joystick.