When choosing the right driver for our system, we first need information about the motors we will be using. This is the main important information. We have to choose the driver according to the power stepper driver can deliver to the motor. For example, a bigger motor like NEMA 34 has a higher holding torque value than a smaller NEMA 17. That’s why NEMA 34 consume more current and we need a driver with higher amperage characteristic.
The next thing to consider is how and what would we like to control a driver. There is usually set up for maximum current and micro-stepping We can have an option to set up a driver with jumpers or more sophisticated with software that in most cases allows user to setup also other special options such as decay parameters, temperature protection limit, idle current and so on.
Some drivers we can use only with a controller that generates step and direction signals. On the other hand, we can drive over different communication protocols.
Types of drivers
In general, there are two types of drivers. The constant voltage drivers (L/R drivers) and constant current drivers (chopper drivers).
- constant voltage drivers (L/R drivers):
- they are cheaper than constant current drivers
- use voltage to produce torque
- usually not efficient
- worse performance than chopper drivers
- constant current drivers (chopper drivers):
- more expensive
- more complex circuits
- use constant current to produce torque
- much better performance than the L/R drivers
The constant current drivers are almost always used since there are many ICs available and offer much better performance. You can find integrated circuits which already have integrated FETs, these are usually meant for lower currents (up to a couple of A).
Since they are small a heat dissipation could be a problem. If we use external FETs, the maximum current is limited only to the characteristics of the selected FET and PCB design.