I've recently written about some devices that we might consider in the class of integrated analog. Now let's take a more general look at integrated analog as it pertains to the design of factory automation equipment.
Why? Well ask anyone who runs a factory and they'll tell you their biggest expense will be power and one way to lower power is to increase the level of monitoring and control over factory equipment, to, for example, enable better control of motors and their loads to reduce annual power consumption. All this requires better sensing and control circuitry and the more you can get the core functions integrated, the better off you and your customer may be.
When we think of factory automation and motor control, we generally think of programmable logic controllers (PLCs) used on a automated production line. The line may be making automobile parts, wrapping up packages of cookies, or filling bottles with soda pop.
There is a lot to be monitored and controlled here by the PLC from various sensors, some simple and some not. Some of the sensors are simple limit switches. These can connect to a programmable controller with minimal interface -- typically a power source and some overvoltage or overcurrent protection. Other sensors may monitor voltage, current, temperature, pressure, sound levels, light levels, and magnetic fields for proximity sensing.
For monitoring anything but the simple sensors cited above, you'll want sophisticated monitoring circuitry. Here is an example of a bridge-type temperature sensor and the associated interface. Pressure transducers would have a very similar interface:
(Source: Maxim Integrated)
With just a quick glance, you can see why this calls out for an integrated approach. There is a lot of circuitry in each of those sections. Most of it would be classified as precision. That means it uses high performance parts (high bandwidth, low drift, accurate gain) and/or that there is a reliable, repeatable way to perform calibration, probably under an automated process.
Here's another example of a sensor interface, this time for a current monitor:
(Source: Maxim Integrated)
This could be used as a light-to-current converter where the current levels are nano-Amps to micro-Amps. Or the current source may be a current transformer monitoring the input power or an electromagnetic actuator's current draw.
These designs are so complex that if you can simplify them by any means, you should. Using an integrated analog approach will result in better performance, less use of expensive PC board real estate, and improved reliability. The integrated analog devices described will probably contain the ADC, so they will interface directly to the microcontroller at the center of the PLC. This helps to accomplish the simplification goal.
In future blogs, I will dive deeper into other parts of automation equipment designs. I'll take a closer look at the power and output sections of the PLC (for driving various actuators). I'll also discuss power issues. Here's a teaser: Automation and control equipment is becoming increasingly more complex and in general consumes large amounts of energy. Improvements in the designs such as detailed in this blog can help conserve power.
Also, with better automation control comes better motor control. This will result in more power savings which can decrease CAPEX cost for your customer's customer. A quick look at financial statements from companies will show that anything you can do to reduce CAPEX will help.