Stepper motor controller with L6506 and L298

giamnac · ‎2012-10-01

Posted on October 01, 2012 at 11:52

Hi,

I'm new to this forum, because I really need some help designing a driver board for a stepper motor. The motor has to phases, 1A per phase, 8.6V and will be controlled over A+/- and B+/- (bipolar). The board will be powered via a 12V input.

I want to design this circuit: http://circuits.datasheetdir.com/391/L6506-circuits.jpg

The datasheets:

http://www.st.com/internet/com/TECHNICAL_RESOURCES/TECHNICAL_LITERATURE/DATASHEET/CD00000097.pdf

http://www.sparkfun.com/datasheets/Robotics/L298_H_Bridge.pdf

I have some question, I give them numbers to help understand.

1. Could you help me calculate Rsense? As I read, Ipeak is I per phase, so 1A in my case. Vref is 5V in this circuit, right? So in my case, I would need 5Ohms. This would leave me with 2 30W resistors. Is this correct? What about the maximum rating of Vsense? Or what voltage comes out of the L298 sensing pins?

2. Between pins 16, 17 of the L6506 and GND, there is another resistor. What for and what size?

3. In all, there are 3 enable inputs (1 on the L6506 and 2 on the L298), can I just give them 5V and it will work?

4. Will 1N4004 diodes do?

I would be really happy if you could help me here..

neophytou_m · ‎2013-03-10

Posted on March 10, 2013 at 18:11

Hi,

I have the same motor driver (

L298N) and the micro-controller which i have to used is the STM32F407VG.

I'm new on this kind of things, if you have the kindness to help me.

Regards

Marios

Enrico Poli · ‎2013-03-11

Posted on March 11, 2013 at 14:13

Hi,

1. The Vref in the circuit is ''not defined'' because the value of the resistor between the reference pins and the ground is not specified. A reference voltage of 5 V is not reasonable and leads to a number of serious operating issues (e.g. the extremely high power dissipation on the sense resistor).

In general a reference voltage of about 200 mV is a good compromise between sense resistor dissipation and current control performance.

In this case you can use a 0.2 Ohm resistor with a power rating of 0.3\0.5W (it is a good practice to take a 50% or 100% of margin on the power dissipation value) could be a good choice. Pay attention to the type of the sense resistor: the parasitic inductance is a critical parameter.

2. You need to set the value according to the reference voltage in point 1.

3. Yes, you can. I suggest you to pull-up them through an RC network in order to insert a short delay between the instant when the supply voltage is applied and the enable signal is asserted.

4. The diodes are needed for the current recirculation during the dead-time (L298 outputs in high impedance). The diodes must be able to sustain the motor supply voltage in reverse condition and the phase current in direct condition. The 1N4004 seems oversized, but it is ok.

Kind Regards

Enrico