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Topic: Controlling 2x 24 volts DC, 450 watts motors. Where do i start ? (Read 3378 times) previous topic - next topic

sync

I did search about it already and do i really need this stuff ?
http://www.robotshop.com/world/pololu-dual-motor-driver-shield-arduino-3.html
Pretty much expensive, any alternative ?

Thanks

retrolefty

Actually that is quite a reasonable price in my opinion considering you are wanting to control almost 1,000 watts of energy. If you have lots of knowledge and experience with electronics and high power semiconductors then it might be possible to come up with a DIY design for less, but probably not.

Lefty

sync

No, i do not have lots of knowledge and experience but i'm ok with programming Arduino. I have to get 50+ units, would it be smart to go DIY and be guided ?

CrossRoads

450W/24V = 18.75A.  Lot of current to mess with.
Can't believe those little screw terminals can handle that.

With that quantity, try talking to the pololu.com folks directly and see if they can help you out.
Or maybe you can use a less expensive single controller board:
http://www.pololu.com/catalog/product/706
Designing & building electrical circuits for over 25 years.  Screw Shield for Mega/Due/Uno,  Bobuino with ATMega1284P, & other '328P & '1284P creations & offerings at  my website.

sync

The VNH5019A-E itself cost $9.20 qty 1, from Digikey
Looks good. Heat sink will be needed
I'll buy one full board from polulu for testing.

retrolefty

#5
Sep 07, 2012, 09:34 pm Last Edit: Sep 07, 2012, 09:38 pm by retrolefty Reason: 1

The VNH5019A-E itself cost $9.20 qty 1, from Digikey
Looks good. Heat sink will be needed
I'll buy one full board from polulu for testing.


Well that one is rated for 24vdc, but the current seems to be limited to 12amps continuous full load, so too small for your motor? Plus it carries this notice:

Quote
While the overvoltage protection typically kicks in at 27 V, it can trigger at voltages as low as 24 V, so we do not recommend using this motor driver with 24 V batteries, which significantly exceed 24 V when fully charged.


It's never a good idea to use a motor driver that's rated right at or close to the limits you require, much better to select one that has some good 'headroom' for both voltage and current for the motor you will be using. 

Lefty

sync

For my amps requirement, i could use 2 VNH5019A to get 24 A (60 A peak) to a single motor connected to both channels but i still have the 24 volts overvoltage protection issue.

Documentation also says that it can survive input voltages up to 41 V.

retrolefty


For my amps requirement, i could use 2 VNH5019A to get 24 A (60 A peak) to a single motor connected to both channels but i still have the 24 volts overvoltage protection issue.

Documentation also says that it can survive input voltages up to 41 V.


Yes, survival from destruction. But it also seems to have an automatic 'overvoltage' protection feature that they state will trip when used with 24vdc rechargeable batteries, as such fully charged batteries exceed the 24vdc 'trip' value.

Lefty

zoomkat

The below might be worth looking at.

http://www.monsterscooterparts.com/otco.html
Google forum search: Use Google Advanced Search and use Http://forum.arduino.cc/index in the "site or domain:" box.

sync

Interesting stuff but it need to be Arduino controlled motor drivers.


The below might be worth looking at.

http://www.monsterscooterparts.com/otco.html




sync

Found this Home Built Dual 50A H-Bridge Circuit http://www.ianjohnston.com/content/index.php?option=com_content&view=article&id=63 wich is quite nice.

- Dual Channel (able to control each output independently).
- ~50A continous per channel @ 24vdc.
- Beefy design in terms of terminals, cooling etc.
- Output stage containing both N-type & P-type Mosfet for push/pull operation.
- PWM controlled with added logic for motor direction control input.
- Logic for protection against turning both left or right side push & pull mosfets on at the same time (a sure recipe for smoke!).

Design Specifications:
DC supply / Motor drive output = 10 - 30vdc.
PWM / Direction control logic = 5vdc TTL.
PWM frequency = Tested at 488Hz (standard Arduino PWM) & 1.95kHz (should also work a lot higher).
Main output max. load (Amps) = T.B.A. (theoretically = 50A).
+5vdc supply (onboard logic & external)= 0.5 Amp max (1.0A if you upgrade the inductor).

IMPORTANT NOTE: This design offers no real over-current or over-temperature protection. You will also need a suitable heatsink.


sync

Hi,
Everything going well about this project. I have one question... For test purpose, is there a problem running my 24 Volts DC 450 watts motors with only one 12 Volts battery ?

Far-seeker


Hi,
Everything going well about this project. I have one question... For test purpose, is there a problem running my 24 Volts DC 450 watts motors with only one 12 Volts battery ?


If the motors are intended for operation at 24 VDC they might not perfom as well, or depending on what you are trying to do with them, at all with only a nominally 12 VDC supply.  I think that this possibility would limit the usefulness of any results your testing yields.

Chiken

Why not design your own shield? I mean what do you need the motors to do? Do you need speed control? Do you need directional control? Whats the maximum current that runs through the motors?

I'm doing a similar project where I need to control 2 12V DC motors that need speed and directional control. All you need is Power transistors and H-Bridges that can handle your max current and you should be good to go. Maybe check some things like voltages drops, admittedly I kind of dropped the ball on that with my project, but like The maximum current on my motors are 4A, but that's only around stall, they typically run around 1-2A, so I have have a TIP120 and an L298 in series for each motor. The power transistor is used as a switch with a PWM value from the arduino on the base. The L298 is actually a dual H-bridge but you can tie em together to act like a single 4 A H-Bridge, and that gives me directional control with digital inputs from the arduino. In my case, the L298 was kind of a poor choice because of the voltage drops and how they propagate when you do what I'm doing with them, but it still works. Best part: You can get all the stuff from Jameco for like $.50-3.00 a part. You will have to make a board, either design a circuit board (Fritzing REALLY helps) or get some perf board with a million jumpers, but it WAY cheaper and not that hard. It does take some elbow grease though and design though. That's kind of what you pay for with those other motor controllers though; you're paying the guy who thought up and designed those break out boards, then you are paying the manufacturing costs. If you're doing a project on an arduino you probably aren't suppe worried about profession quality, time, or convenience, so why not make you're own board? Plus is super rewarding to build your stuff more from scratch than to just kind of buy things and stick them together.

jraskell

Quote
The maximum current on my motors are 4A, but that's only around stall, they typically run around 1-2A, so I have have a TIP120 and an L298 in series for each motor.


As retrolefty already said, it's never a good idea to operate electronics at or near their limits.  Doing so severely reduces the life expectancy and robustness of the circuit.  If it's a personal project, then it's a personal decision, so long as you understand the potential consequences down the road.  However, if you mix it with this...


No, i do not have lots of knowledge and experience but i'm ok with programming Arduino. I have to get 50+ units, would it be smart to go DIY and be guided ?


It's highly unlikely he needs 50+ units for his own personal use.  In those quantities, it's literally a necessity to use a robust, stable, and long lasting solution.  The consequences of not doing so are far more significant than when dealing with a one off setup.

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