Using a brushless DC motor to drive a coffee grinder

Transitioning from AC to Brushless DC

In this project we were tasked with working on a coffee grinder that had previously been setup with AC motors and delivering the same performance with brushless DC motors. The key motivation behind the switch to brushless DC was the energy savings but there were a number of potential issues with the feasibility of the project that were considered to be potential barriers for development.

Startup proves the trickiest part

As expected, starting the grinder was the most demanding element of this particular project. The way in which the beans enter the grinder means that they can often cause significant variation in the startup current required. Equally, different types of beans had varying physical properties which also impacted on the grinders ability to operate. Ultimately, it was simply a question of optimising the controller for this startup sequence by ensuring that the controller offered enough power at the startup stage of the duty cycle.

Using a stock controller to get started

Ultimately, for a high volume project such as this one it would be beneficial to design a custom controller. The reasons for this are fairly simple;

  1. The envelope can be reduced therefore making the final product more compact.
  2. There are almost always cost savings to be made.
  3. Reduction in components required reduces the overall environmental impact of the design.

However, there are also major benefits to being able to use stock controllers such as the ZDBL50DC to get the project started. These include being able to get a clear and accurate idea of the kind of power draw that will be needed for a certain application. This is especially useful for applications such as this where the startup current draw can be vastly different to the general running current as testing the application with a stock controller will help identify these issues quickly.

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