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DC motor controling with L298

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Thread Starter

aGpLT

Joined Jan 21, 2010
128
Hello all :) So i have a little problem here. My DC motors are 2.4V ~1A and i used this scheme for controling it:

This circuit is working but when i send high to L1 or L2 motor dont start running i need to rotate rotor with hand when it starts. My input voltage is 5V and thinked that it may be the couse of this issue. And if its problem what kind of stabilizer you advise me ? i searched for one and i get my mind to this one: MLM350T LM350T V-reg 1.2 -33V 3A 4% Sorry for pure english but i think you get what i mean, i hope so :) Thank You for Your help in advance.
 
mik3

mik3

Joined Feb 4, 2008
4,843
Put a 100uF 16V electrlytic capacitor near the L298 driver between the 5V and GND. Also, the input voltage of the 7805 has to be greater than 7V.
 
A

Thread Starter

aGpLT

Joined Jan 21, 2010
128
mik3 said:
Put a 100uF 16V electrlytic capacitor near the L298 driver between the 5V and GND. Also, the input voltage of the 7805 has to be greater than 7V.
Click to expand...
Oh sure, i forgot to mention that i am not using 7805 i have power supply 5v directly. So i use same power supply for motor and L298. (Power supply is from computer 5V 15A)
 
mik3

mik3

Joined Feb 4, 2008
4,843
You need to put decoupling capacitors near the L298 between the Vs and GND.

Are you sure the motors are 2.4V ?
 
A

Thread Starter

aGpLT

Joined Jan 21, 2010
128
mik3 said:
You need to put decoupling capacitors near the L298 between the Vs and GND.

Are you sure the motors are 2.4V ?
Click to expand...
Yeah it's written on motor. Thank You mate it worked ! :) now i need to put big radiator on L298 becouse its hellish hot :) and now its only controling only one motor, it wont get burned of controling two motors ?
 
mik3

mik3

Joined Feb 4, 2008
4,843
If you attach the proper heat sink and do not exceed the maximum current rating stated in the datasheet then it will be fine.
 
A

Thread Starter

aGpLT

Joined Jan 21, 2010
128
I have one more question if You dont mind, what about power supply for motors ? i still think that i need use 2.4V for it. So what about that stabilizer is it good for it ? :)
 
mik3

mik3

Joined Feb 4, 2008
4,843
aGpLT said:
I have one more question if You dont mind, what about power supply for motors ? i still think that i need use 2.4V for it. So what about that stabilizer is it good for it ? :)
Click to expand...
Will you use PWM to control the motors or just an on/off signal?
 
A

Thread Starter

aGpLT

Joined Jan 21, 2010
128
mik3 said:
Will you use PWM to control the motors or just an on/off signal?
Click to expand...
I still thinking about it, becouse motors have quite big load on them and they are rotating slow of that. So i dont see need to use PWM, correct me if i am talking nonsenses ;)
 
A

Thread Starter

aGpLT

Joined Jan 21, 2010
128
They have reductors and are driving my robot arm axes. If i didnt answered your question, when i can take some pictures of it :)
 
A

Thread Starter

aGpLT

Joined Jan 21, 2010
128
mik3 said:
What capacitor did you put?
Click to expand...
100uF 16V, i tryed now 220uF 16V and it work better now :)

And its interesting why motor speed is much slower in circuit than i its connected directly to power supply. :/
 
Last edited:
mik3

mik3

Joined Feb 4, 2008
4,843
aGpLT said:
100uF 16V, i tryed now 220uF 16V and it work better now :)

And its interesting why motor speed is much slower in circuit than i its connected directly to power supply. :/
Click to expand...
Connect a 100nF ceramic capacitor in parallel with the 220uF one.

The speed is less because of voltage drops across the internal transistors of the L298.
 
A

Thread Starter

aGpLT

Joined Jan 21, 2010
128
mik3 said:
Connect a 100nF ceramic capacitor in parallel with the 220uF one.

The speed is less because of voltage drops across the internal transistors of the L298.
Click to expand...
Hmm, its no good, becouse i have only one power supply, also it have 5V and 12V outputs, but if i use 12V for motors i think they will burn :/ for L298 its not problem i will just use 7805 and its ok.
 
Last edited by a moderator:
mik3

mik3

Joined Feb 4, 2008
4,843
You can use 5V or 12V for the motor supply and use PWM to regulate the average voltage across the motor to 2.4V.
 
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