I have a project about controlling stepper motor. I know the basics but confused about the DAC connection with unipolar stepper motor. Do i need 4 DAC for unipolar stepper motor 4 pin. I thought about one DAC and switching. I have no clear idea about that. kindly can anyone provide me a circuit drawing for DAC connection with unipolar stepper motor?

 

Stepping motors are usually controlled with digital pulses. No DAC is required.

However, there is a technique called "micro-step" which allows the controller to position the rotor in between digital steps by applying sine and cosine analog voltages to each stator coil. In order to accomplish this you will need a DAC and a current driver for each coil.

 

Stepping motors are usually controlled with digital pulses. No DAC is required.

However, there is a technique called "micro-step" which allows the controller to position the rotor in between digital steps by applying sine and cosine analog voltages to each stator coil. In order to accomplish this you will need a DAC and a current driver for each coil.

Yes, I am trying to rotate stepper motor with micro stepping. However i am confused as DAC i familiar with has 8 binary pin to 1 output pin for digital to analog conversion and if so my code for atmega32 will be complex too as i have to deal with four coil of a stepper motor. . and if you sat dac and current driver how can i connect them both?.

 

The 8-bit DAC you describe converts an 8-bit value (0 to 255) or (-128 to +127) to an analog voltage. This voltage is sent to a current driver chip which drives one coil.

For four coils, you will need four of the above circuitry.

 

The 8-bit DAC you describe converts an 8-bit value (0 to 255) or (-128 to +127) to an analog voltage. This voltage is sent to a current driver chip which drives one coil.

For four coils, you will need four of the above circuitry.

Then how can i connect them to atmega32????

 

You either need four 8-bit output ports or a single 8-bit output port and DACs with chip select inputs.

 

You either need four 8-bit output ports or a single 8-bit output port and DACs with chip select inputs.

is there dac chip available that can give 4 out ? (proteus library)

 

There is a micro-step controller chip which I will dig up for you.

Edit: Of course, you can google microstep controller.

Also you don't need DACs. You can still send PWM to each coil to get the same effect as DAC analog outputs.

 

Many years ago I used Ericsson PBM3960 Microstep Controller and PBL3771 Stepper Motor Driver.
These are most likely obsolete now.

There are modern controllers such as ST L6470.

 

Stepper motors only have 2 coils not 4. A unipolar motor has center connectors to each of these giving 6 wires out.
The center connections are connected directly to the power supply. 5 wire motors have the center connectors attached inside the motor.
On any one step one end of each coil is held open and the other end is shorted to ground.
Motors are current controlled not voltage controlled.
A chopper motor with microstepping would normally have FET on each of the 4 ends with a current sense resistor to ground.
The voltage on the current sense resistor is fed to a comparator.
If you want to use DACs then it is fed to the comparator to shut off current when max current required is met.
Since the other end of coil is left open you would only need 2 DACs.

 

Stepper motors only have 2 coils not 4. A unipolar motor has center connectors to each of these giving 6 wires out.
The center connections are connected directly to the power supply. 5 wire motors have the center connectors attached inside the motor.
On any one step one end of each coil is held open and the other end is shorted to ground.
Motors are current controlled not voltage controlled.
A chopper motor with microstepping would normally have FET on each of the 4 ends with a current sense resistor to ground.
The voltage on the current sense resistor is fed to a comparator.
If you want to use DACs then it is fed to the comparator to shut off current when max current required is met.
Since the other end of coil is left open you would only need 2 DACs.

Thank you george4657.But can you draw me the circuit. from 2 dac to stepper motor..

 

If you don't know much about how the stepping motor works then you can see the circuit below, when you got the idea then you can use uC to drive it.
Stepper Motor Forward And Reverse Testing circuit.