MOSFET trsansistor and DC motor current limitation

Hi, I'm trying to control a DC motor using MOSFET transistor but something is always getting HOT.

Parts that i use in this project.

THE motor is actually a small model water pump like this: http://www.canton-electronics.com/rs360sh-dc612v-brushed-motor-micropump-micro-pump-water-motor-pumps-reversible-p-575.html Data sheet: http://www.mabuchi-motor.co.jp/ja_JP/cat_files/rs_360sh.pdf

Transistor that I use to control the motor: P60NF06 CZOLL 6 Data sheet: http://pdf.datasheetcatalog.com/datasheet/SGSThomsonMicroelectronics/mXyuyzw.pdf

How i connect my motor to transistor and arduino: I used this scheme as reference but added also a capacitor in place where diode is.

My power source is small universal power supply 3-12VDC 1200mA, 15W power

And now to the base of my problem, when I start motor it draws so much current that cables on my breadboard (Source one and +Volt one become hot like 50C degrees). And I noticed that my power source i very loaded so I started to read and found some info about starting DC motor in such way that it don't get full current just like that in one go. So i used e PWM of arduino to control this like that:

void loop() {
  analogWrite(motor, 64); 
  delay(2000);   
  analogWrite(motor, 96);   
  delay(2000);   
  analogWrite(motor, 127);  
  delay(2000);   
  analogWrite(motor, 159);  
  delay(2000);  
  analogWrite(motor, 191);  
  delay(1000);     
 analogWrite(motor, 255);  
  delay(10000); 
  analogWrite(motor, 0);  
  delay(10000); 
}

This helped a lot power source is not loaded instantly that much BUT transistor started do get HOT like 60C it's just unpleasant to touch it. Someone advised me to add a resistor like 1.2Ohm 3W on positive (+) output to the motor and yeah transistor is now slightly warm motor is spinning OK but resistor is hot it's not burning you can touch it but it's like 70C.

Well I could say OK it's working and leave it alone BUT even if it's working is such heat OK. How to properly control such motor using transistor. I watched many tutorials on motors and transistor stuff but no one said anything about heat and about what can get hot, and what should not. No I don't need motor shield just want to turn on and off this motor and maybe regulate it's speed with PWM if it's possible.

The problem you are seeing (transistor running hot) is because the MOSFET you selected is not a 'logic level' mosfet and will not turn fully on with minimum resistance using 5vdc gate voltage. Select a logic level mosfet with voltage and current ratings suitable for your motor. The Ron spec from the datasheet (if given) is another key parameter to analyze when selecting a device as the lower the Ron resistance the lower the amount of heat the mosfet will have to dissipate.

Lefty

What transistor would by good choice for this? I have BUZ11 also but probably this is bad one as well. I saw someone using TIP120 with bigger motors but I couldn't find one in local stores.

Peter_T: What transistor would by good choice for this? I have BUZ11 also but probably this is bad one as well. I saw someone using TIP120 with bigger motors but I couldn't find one in local stores.

Best to wait for someone from Poland to respond if local availability is an issue. Use E-bay and the world is your store. ;)

You may try this with your n-Mos transistor:
The polarity of your control signal is reversed with the Q2 there -

Arduino=1 - motor is OFF
Arduino=0 - motor is ON

You may use any junk box npn low power transistor as the Q2 there.
The resistors could be any values from 1k-10k (the faster switching you want the lower the values you have to choose).

nfetmotor.jpg

I used this scheme as reference but added also a capacitor in place where diode is.

So put the diode back or you could damage your components including the Arduino.

I said "also" diode is there all the time. I you can help than help, you don't have to point something that is obvious.

BTW. BUZ11 is 5V logic or not? http://www.fairchildsemi.com/ds/BU/BUZ11.pdf I'm a bit confused about this. I tried to compare those data sheets https://www.sparkfun.com/products/10213.

Peter_T: I said "also" diode is there all the time. I you can help than help, you don't have to point something that is obvious.

BTW. BUZ11 is 5V logic or not? http://www.fairchildsemi.com/ds/BU/BUZ11.pdf I'm a bit confused about this. I tried to compare those data sheets https://www.sparkfun.com/products/10213.

BUZ11 is not a logic level mosfet. The Sparkfun one is.

Lefty

On what parameters should I look to say if transistor is good for 5V logic?

Either the phrase "logic level" at the head of the datasheet or a value for Rds(on) quoted for "Vgs = 4.5V" or "Vgs = 5V". If it only shows Rds(on) for Vgs = 10V, its not logic level.

If Vth (threshold voltage) is quoted as 2--4V then its NOT LOGIC LEVEL. Threshold voltage is the OFF-THRESHOLD, nothing to do with being switched fully on. Vth will be more like 0.5V to 1V for a logic level device.

Thank you for informations now I know for what to search.

I said “also” diode is there all the time. I you can help than help, you don’t have to point something that is obvious.

When your grasp of English is as wobbly as that sentence it is hard to actually understand what you mean.
What is obvious to one person is not obvious to others.
So as you don’t appreciate help I will try and remember never to try and help you again.

Here's an example of a mosfet that would be suitable for your application: http://pl.farnell.com/international-rectifier/irlu8726pbf/mosfet-n-ch-30v-86a-ipak/dp/1698317?Ntt=irlu8726. The datasheet quotes Rds(on) = 8 milliohm max @ Vgs=4.5V, Id=20A.