DC Motor Driver - L298

Thread Starter

trimbitassorin

Joined Jan 19, 2014
4
Hello,

I want to build a small robot with 4 motors (Key specs at 6 V: 75 RPM and 80 mA free-run, 85 oz-in (6.1 kg-cm) and 2.2 A stall.) and build 2 motor drivers like the one attached (one motor driver will control the motors from a side).

I have created the schematic based on the L298 data sheet and just added the 2 LEDs for visual feedback of the rotation of the motors.

Will it be ok?

Thanks

Sorin
 

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SgtWookie

Joined Jul 17, 2007
22,210
Do you realize that the L298 will drop in excess of 3.8v across itself when under a 2A load? This leaves only 2.2v at best for your motors. The rest of the power will be dissipated as heat in the L298. Is that acceptable to you?
 

GopherT

Joined Nov 23, 2012
8,012
Look for a modern MOSFET bridge, by the time you add a heat sink, that big chip for each motor and the extra battery voltage to overcome the drop-out (as mentioned by Sarge above), your robot will be huge, heavy and dead slow.
 

Thread Starter

trimbitassorin

Joined Jan 19, 2014
4
Do you realize that the L298 will drop in excess of 3.8v across itself when under a 2A load? This leaves only 2.2v at best for your motors. The rest of the power will be dissipated as heat in the L298. Is that acceptable to you?
No, I didn't know it is so bad and the motors will be probably a lot of time under 2A load. Thank you for pointing this out!
 

Thread Starter

trimbitassorin

Joined Jan 19, 2014
4
Look for a modern MOSFET bridge, by the time you add a heat sink, that big chip for each motor and the extra battery voltage to overcome the drop-out (as mentioned by Sarge above), your robot will be huge, heavy and dead slow.
Can you please suggest one that doesn't require a lot of external components and it is suitable for my motors?

Thank you!
 

Alec_t

Joined Sep 17, 2013
11,504
If you don't have a second voltage available (say 12V, able to supply 10mA or so on average) for the switching control of a FET bridge you would need 'logic-level' type FETs.
 

Thread Starter

trimbitassorin

Joined Jan 19, 2014
4
If you don't have a second voltage available (say 12V, able to supply 10mA or so on average) for the switching control of a FET bridge you would need 'logic-level' type FETs.
I will have only the Arduino Mega (with a 7.2V supply going through a 5V regulator) and supply for motors (probably another 7.2V Li/ion battery pack).
 

tubeguy

Joined Nov 3, 2012
1,157
If you can live with relays to switch direction, a circuit using a single logic-level Mosfet to drive the motor is also possible. :)
Or can you possibly use a higher voltage battery for the motors?
 
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