H bridge IC!!!

[microzone]

I just bought L297 and L298n IC. I have read through this two IC datasheet.
But I still have some problem with L297 SYNC pin. Can anyone tell me how do I connect this pin? Thanks.

 

[dknguyen]

Do you mind giving a link for the datasheets?

 

[microzone]

Do you mind giving a link for the datasheets?

Sure, no problem. Below is the L297 and L298n data sheet.

L297 datasheet
**broken link removed**

L298n datasheet
**broken link removed**

Thanks.

 

[hjames]

Page 3, L297 PDF - Its an output, and can be used to connect multiple L297's together. So if you're only using 1 chip - don't connect it to anything.

 

[microzone]

Thanks for all the kind help, I have success to use L297 and L298n to drie my bipolar stepper motor. But I still have a problem that make me uneasy. When I stop my bipolar stepper motor by stop sending pulse to L297, my stepper motor will come out a small sound like "eeeee...". When I touch my bipolar stepper motor shaft, my motor shaft is blocking (hard to turn the shaft by hand). May I know how do I solve this problem? I connect L297, enable pin and reset pin to 5V and control pin to ground. Thanks.

 

[hjames]

I haven't used the chip, so I don't know what the chopper circuit sounds like, but that would be my first guess. In short, its a feature, not a bug.

Motors, and other inductors typically have maximum current limits. At some point electromagnets saturate(and get inefficient) and wires overheat(melt/short together), and in the case of motors, magnets get demagnetized(and it stops being a motor). For various performance reasons, steppers usually limit the current going into the motor - that's the purpose of the SENSE1, SENSE2 lines going between the two chips. The chip basically chops the current off when it hits a given threshold, and then turns it back on a bit later - hence the buzzing.

The reason why it does this is to hold the position of the motor so that it doesn't slip. If you want to disable this feature, use the enable line of the L297 chip to stop it when you want it to "let go"

 

[motion]

First of all, it is normal for ths shaft to remain stiff when the stepper motor is stopped. This is called the holding torque ot the motor. This is so for as long as the current continuously flows through the coils. This is how the motor and motor driver are designed to do. The motor may also heat-up because of resistance and magnetic core losses.

The high pitched is caused by the fluctuating current as the voltage is being chopped. I assume you followed the circuit sample from the datasheet. The frequency is chosen so that is supposed to be above the hearing frequency. However, probably because of poor layout of your prototype and/or interaction with the cable to the motor, the current flow may be modulated and so the frequency drops to hearing range.

 

[microzone]

First of all, it is normal for ths shaft to remain stiff when the stepper motor is stopped. This is called the holding torque ot the motor. This is so for as long as the current continuously flows through the coils. This is how the motor and motor driver are designed to do. The motor may also heat-up because of resistance and magnetic core losses.

The high pitched is caused by the fluctuating current as the voltage is being chopped. I assume you followed the circuit sample from the datasheet. The frequency is chosen so that is supposed to be above the hearing frequency. However, probably because of poor layout of your prototype and/or interaction with the cable to the motor, the current flow may be modulated and so the frequency drops to hearing range.

Thanks Motion. You are correct, I just follow the L297 and L298n datasheet to connect my IC. Do you have any method to reduce or eliminate the sound and I using full step operation to drive my motor? Do you have these connection diagram? Thanks.

 

[motion]

Do you have any method to reduce or eliminate the sound and I using full step operation to drive my motor?

As I said, you have to improve the layout of your prototype. The critical area is around the current sensing resistors. Place the resistors close to the GND line with minimal wire run. Put a high value filter capacitor across the supply and gnd lines near the resistors. Place the 4 freewheeling diodes as close to the capacitor as possible.

Raise the value of Vref to about 1V. Adjust the value of the sensing resistors accordingly. This will make it less prone to ground line noise.

Try experimenting with the control pin (pin 11) set to low. This might improve the current control for high inductance motors at the expense of higher power loss and heat due to core loss.

To reduce the noise when the motor is running, try selecting half steps (HALF pin high).

Use twisted pair cable for the motors, with each coil assigned to a pair. This will reduce the coils from interacting with each other.

That's probably all you can do with this simple circuit.