Hello,
I want to control 3 (12-24v) dc motors in both directions using pwm. I`ve tried the search function and found something about mosfets.
But i don`t understand it.
What do i need to controll 20amps?
Thanks in advance.
Collin
Hello,
I want to control 3 (12-24v) dc motors in both directions using pwm. I`ve tried the search function and found something about mosfets.
But i don`t understand it.
What do i need to controll 20amps?
Thanks in advance.
Collin
What do i need to controll 20amps?
You need a very chunky FET.
In fact you need to use 4 FETs in a H bridge circuit along with some FET drivers to change the Arduino output to be enough to drive the FETs. However this sort of current is not easy to control as it will need to be layed out and constructed properly. It's not a job for a beginner. Try and get someone local and experienced to help you.
20A! Thats massive!
I wouldn't recommend building one yourself, especially if your new to this. You'll have issues with everything from layout, to wiring, to PCB design.
Take a look at this: Pololu High-Power Motor Driver 18v15
Its rated for 15A or 21A with heat sinking. I'd spend more effort in buying something like this and trying to find a decent heat sink solution, rather than designing a H bridge.
Look around, you might find something that is rated for higher amperage. Or ask at pololu, they make a lot of motor drivers inhouse.
Thanks for the answers!
I found an H bridge with big mosfets:
http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1249661296/3#3
Can i use that, but with the following mosfets?
IRF1310N - N channel 100V 42A 160W 0,036 ohm
IRF5210PBF - P 100V 40A 200W 0,06 Ohm TO-220
These are easy to get for me.
Maybe i need less current for what i want, but im still researching
What i need to do is; pull (or hold/stop) a load of +/- max 80kg, shared by two dc motors.
Ill use a rotary encoder to make it servo
s.
So i think i have to calculate howmuch Newton every servo has to deal with.
Can someone make a guess about the motor power (N) i may need?
Thanks!
edit:
About the pololu driver, that looks very nice, but it`s more fun to make it myself (or at least try:P)
About the pcb design. I think that will work out. I could use thick wires connected directly to the mosfets.
IRF1310N - N channel 100V 42A 160W 0,036 ohm
This needs 10V to turn it fully on - to drive it from an Arduino, you need either a "logic" version, or another transistor to switch the 10V, otherwise it is going to get very hot, very fast.
A mass of 80kg exerts a force of about 800 newtons due to gravity (784N).
How powerful your motors need to be depends on how fast you need to counter this force; the faster you need to move it, the more powerful the motors need to be.
Ok, thanks that sounds very logical Ill look up something about acceleration forces.
Good to hear it will work.
If you are pulling horizontally, I don't think weight matters.
This should help you out: Torque - Wikipedia once you know the toque you need, you just need to find a motor, that gives you the torque and angular speed you want.
If you are pulling horizontally, I don't think weight matters.
You still have to overcome inertia, which like weight, is proportional to mass.
Ill search for Inertia.
I think i found a handy calculator:
If that`s correct ill need 2 +/- 8N motors for:
Mass: 100KG
Acceleration: 150cm/s
By the way i`m building a (race) motion simulator.
edit: maybe a stupid question, but where can i find the quote fuction?
where can i find the quote fuction
It's to the right of the "code" ("#") button on the top row of buttons when you edit a post.