Fanless PCs based on mobile processors are exceptionally power efficient but the power that they do use is an issue for embedded system developers. It is dissipated as heat and, many systems need to run from batteries.
Fanless PCs draw between 4.5W and 17W depending on performance, and it is very hard to make the hardware more efficient. The way to use less power is actually to design efficient software that runs well on a lean hardware platform. This will allow you to specify a 4.5W platform which is also cheaper, rather than needing to go for the larger and costlier 17W units.
The processor and other hardware resources you will need are dictated by the application and operating system. Most of the things you can do in hardware to make the system run faster such as choosing a faster CPU, specifying more memory, and adding a GPU carry a penalty in terms of power consumption.
For example, Linux uses PC resources much more efficiently than Windows. It can run on a less powerful processor, and also requires less memory. One of our customers, EyeLynx, runs a graphics intensive CCTV application on a very lean platform with the Linux operating system. EyeLynx surveillance cameras need to operate reliably from a portable power source like a battery for days at a time capturing images and storing them for subsequent review and analysis.
EyeLynx Managing Director Jay Patel said, “SharpView is an efficient software solution that records HD video from multiple cameras and processes the images in real time. The challenge was to find a very low power PC, small enough to be hidden in the camera case and able to run for several days from a battery system. “
There are other things that you can do – for example, employing effective power management to turn the system or individual components off when they are not being used. The choice of storage is also important. Hard disks use almost no power when they spin down and are idle, but are slower so each disk access operation means that the disk is spinning for longer. Although SSDs can use more power when active, they are generally faster, so will get back to idle sooner than HDDs. The best storage from a power perspective depends on the frequency of read write operations and the volume of data being transferred by the application.
Start by writing efficient software and then think about power management. Using power management to make up for an inefficient design isn’t really a good approach.
Photo shows an Eyelynx security camera that incorporates a Tiny Green PC running from a lead-acid battery. The software was carefully written to make the best use of lean hardware resources.