High power motor controller controlled by arduino - Page 1
Forum section: electronics / beginners

author: carbon dude oxide
author_rank: Frequent Contributor
timestamp: January 08, 2013, 11:38:11 pm
content: Hello everyoneHow would i go about controling 2 24V 25A motors using an arduino? It is part of a school project (all finished apart from the motor controller) and i have had several problems with previous pre built controllers and i would like to design and make my own. I need the motors to be able to turn both ways while also being able to control the speed. From my knowledge so far i know i will need 2 N channel MOSFETS and 2 P channel MOSFETS per motor along with some mosfet drivers so that the arduino can turn on the 24V p channel mosfet. Unfortunatly i dont know which MOSFET's to get or how to safley and correctly wire these up.i have already attempted this with a 2n3055 transistor as a test to see if i could control the speed little did i know about beta values and things like that as I am relatively new to transistors. any help on this would be great as i just want to get my project movingif you are interested in what the project is then its a wirelessly controlled platform with an arduino at its heart and remote

author: ConnorGames
author_rank: Regular Contributor
timestamp: January 09, 2013, 01:07:38 am
content: Sorry to say, but designing motor controllers, especially ones that big, is quite hard. This would not make a good starter project with transistors, at all. Sorry to disappoint, but prebuilt controllers are going to far outperform anything you can build, and when you factor in time and money to get spares for designing, they will be cheaper, too. I have designed a basic, bare-bones, low current 7.2v 3ish amp motor controller, and getting it right took weeks and cost more than a fully assembled controller. It sure was a fun build, but a fully-featured controller this size would be an absolute nightmare to design! If you want to build a basic, small motor controller for fun, you could always build this:http://www.mcmanis.com/chuck/robotics/tutorial/h-bridge/bjt-circuit.html, but it couldn't control motors anywhere near this big. With 24v at 50+amps(assuming you have 2 motors), safety issues are also a concern: hook up a MOSFET backwards and there will likely be shrapnel headed your way. Also, you will need a scope if you intend to design a motor controller for larger loads or PWM. Frankly, it is nice to have even with <12 volts at <1 amp. Sorryto disapoint, but I do recommend learning about transistors and building a small motor controller for fun -- nothing beats the satisfaction of knowing you did it yourself!

author: houdini
author_rank: Regular Contributor
timestamp: January 09, 2013, 05:42:55 am
content: so do you need to be able to vary the speed or just forwards backwards off?

author: Kremmen
author_rank: Super Contributor
timestamp: January 09, 2013, 08:22:37 am
content: The previous response was a bit pessi^H^H^H cautious and for a good reason. You need to make some effort to design a workable circuit for 25 amps, because there are certain elementary mistakes you can't afford any more at that level.If you can live with less than robotic agility in the drives, there is a simplification that will make your life radically easier: use an ordinary relay to change direction of rotation. That way you can get by with just a single N-channel power FET per motor. This works by using a DPDT relay where the contact midpoints go to the motor terminals and NO and NC contacts (crossed on each side respectively) to positive supply and to the FET drain. I attached a pdf that will illustrate the principle. Sorry you won't get too much from the text as it is all in Finnish. But you will get my point. One hint: the Finnish word "suunta" means "direction". (the circuit is for a reciprocating shooring target for rifle competitions).Do pay attentiuon to overcurrent and shor circuit protection though. That is not shown in the pic at all.

author: johnboxall
author_rank: Unknown
timestamp: January 09, 2013, 10:48:40 am
content: Consider two of these:http://www.pololu.com/catalog/product/2502