I am building a robot with a 7V Motor. Since all pins of an Arduino cant output 7V i have to power the Motor with an external batterie. Now to controll when I turn the Motor on and of I either need to use Relays or Transistors. I wanted to know which type is better for an Arduino.
If you want to control motor speed you will want to use a transistor or MOSFET because they switch much faster than a relay.
If you just want ON/OFF control you can use a relay but if the relay coil requires more than 5V or more than 30 mA you will need a transistor to drive the relay.
If you want to control the direction as well as speed you will need an H-bridge motor controller.
If you want to control direction but not speed you can use two relays.
I only want to controll on/off and speed.So can you tell me which one and where I can buy a Tronsister or MOSFET.
Thx
How to use one:
http://itp.nyu.edu/physcomp/Tutorials/HighCurrentLoads
Good transistor to use: TIP120 (NPN 60V 5A)
Where to buy one:
http://www.google.com/search?q=TIP120+Transistor&tbm=shop
johnwasser:
If you want to control motor speed you will want to use a transistor or MOSFET because they switch much faster than a relay.If you just want ON/OFF control you can use a relay but if the relay coil requires more than 5V or more than 30 mA you will need a transistor to drive the relay.
If you want to control the direction as well as speed you will need an H-bridge motor controller.
If you want to control direction but not speed you can use two relays.
In theory you could do a hybrid system, using only two SPDT relays for the h-bridge part, and a high-current n-channel mosfet or NPN transistor on the low-side to PWM the motor; I've never seen it done, but I can't see why it wouldn't work.
There's also the possibility of using a dual-ended supply, and a half-bridge to control motor speed/direction (small ones were used on the Milton Bradley Big Trak back in the day, mainly because transistors were still fairly expensive, and they did everything they could to increase their profit margin on that toy).
7v DC motor? Grab a speed control for an electric RC car. Use the servo library to talk to it and your done.
-jim lee
Thanks allot. I´ll do it that way