Help with a DC motor and board of education

jr072021

Hey, I wanted to try to put DC motors on my boe-bot instead of the standard servos because they are pretty slow, I don't know if i'm looking for the wrong things, but I can't find out how I would do that. If you could help me, I will be very thankful.

Mike Green

You need some sort of motor driver. If you want to reverse the motor, you need what's called an H-bridge. Look at the Wikipedia article and its links on "H-Bridge" for details. Parallax sells several DC motor controllers like those from Pololu. Have a look at those here: www.parallax.com/Store/Accessories/MotorServoControllers/tabid/160/CategoryID/35/List/0/Level/a/ProductID/491/Default.aspx?SortField=ProductName%2cProductName

Note that it's hard to control the speed of a DC motor using just an H-bridge and a Stamp. These normally use what's called PWM (pulse width modulation) to control speed and the PWM command in PBasic doesn't quite do what you need for this. The DC motor controllers like Pololu's do handle speed properly.

jr072021

Thank you very much for your help, I'll work on that and reply back If I have any questions.

DataJ

JR - -

You might try using an L298HN motor driver - - they are good for 3 amps and around 30 volts.
Check out Pyro-Electro web site, he shows how to wire one up.

I have one up on a breadboard operating the direction of an HO locomotive - the only thing I had
to change was instead of running a 10 ohm resistor to the current sensing line, just used a wire.· The
10 ohm resistance would not allow the motor to operate.

Hope this helps you.

Jim

Andy Lindsay (Parallax)

Like Mike Green, (see 3rd post above this one) I also prefer the Pololu Micro Dual Serial Motor Controller for DC motors that carry light loads like the Boe-Bot robot. The nice thing about having a coprocessor for motor control is that the Boe-Bot Robot's BASIC Stamp microcontroller can "set it and forget it". In contrast, servo control requires a pulse every 20 ms. Especially since your DC motors will go faster, your programs will need to pay closer attention to sensors so as not to collide with obstacles.

▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
Andy Lindsay

Education Department
Parallax, Inc.

ultimateremedy

Hi All

I also want to use 3 dc motors so do i need 3 Micro Dual Serial Motor Controller? can't i use something else like biStep 710 etc???

▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
An hour's contemplation is better than a year's adoration.

agfa

ultimateremedy said...
I also want to use 3 dc motors so do i need 3 Micro Dual Serial Motor Controller?

The Micro Dual Serial Motor Controller will drive two motors.

ultimateremedy

but with 1 amp what if i want to use around 1.5 amp per motor? this seems end up on 3 Controllers. [noparse]:([/noparse] any other option????

▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
An hour's contemplation is better than a year's adoration.

Mike Green

There are lots of DC motor controllers and H-bridge ICs on the market. Pololu (who makes one that Parallax sells) makes a whole line of devices with various capabilities. You'll just have to find something that fits your needs in terms of voltage, current, and # of motors. Parallax sells their own DC motor controller with a higher current and voltage capacity than the Pololu model they carry. You can also build your own. There are plenty of designs on the web that you can copy.

ultimateremedy

thank you mike for your prompt reply. I've already copied few designs from internet but in confusion which one i should use. can you suggest any article/design. I'm more interested in making my own PCB as it is really expensive to buy+ship from USA both in term of money and time.

▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
An hour's contemplation is better than a year's adoration.

agfa

ultimateremedy,

http://www.kronosrobotics.com/an101/DAN101.shtml

Take a look at this link.· It·mentions stacking sn754410s, a quad half-H driver IC, to increase its current handling capability.· Maybe a more economical·option to consider.