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Bluetooth and Sensors

By: George Keremedjiev

Wednesday, February 01, 2012
 

As I look around my home, I spy numerous wireless devices communicating with one another using the Bluetooth standard—a Windows laptop, computer mouse, portable keyboard, etc. Bluetooth is prevalent everywhere in our daily lives, but why not in the pressroom within our dies and related sensors? Why not develop wireless systems that relay sensor status data to the die-protection control without the need for expensive cabling?

The primary limitation seems to be power, specifically: How do we supply power to the Bluetooth transmitter? One option is to connect the power cable to the die, and have it only provide power for the sensors and the Bluetooth transmitter. The die-protection sensors would connect to the Bluetooth transmitter within the die. Given the multiplicity of electronic devices that use Bluetooth technology, why not have a small Bluetooth transmitter buried within the die, with the appropriate nonmetallic areas in the mounting, to allow the radio signal to exit the die?

Think how much simpler the wiring would be to and from the die-protection control. A Bluetooth receiver would be connected to the sensor inputs of the control with the appropriate interface circuitry. On the die, I could see using a multiplexer of sorts that would send the appropriate sensor signals through the Bluetooth transmitter in a rapid, sequential manner, and monitor the sensors.

The cable to the die would have two conductors only, providing the positive and negative terminals for the DC voltage for the sensors and the Bluetooth transmitter. Such a system should be low in cost, judging by the enormous variety of Bluetooth-based devices available. The Bluetooth technology could perhaps be offered by the sensor manufacturers themselves, or maybe by the die-protection control suppliers. I can envision a module that would include a terminal strip on one side to accommodate scores of digital and analog sensors. The power for the sensors also would be supplied by this module. It would be small enough to mount within a small electrical box that would in turn mount on the lower die plate.

Many years ago I wrote about a similar desire, to have the die-protection and part-quality sensors communicate wirelessly with the die-protection control. Back then the wireless technologies were expensive, relatively large and notoriously noisy and unreliable. I think that a careful look into the Bluetooth standard could yield a fresh, new set of wireless technologies applicable to die protection and part-quality monitoring.

Perhaps this already has been tried and developed by one or more sensor companies. And perhaps a clever stamping company has invented such a wireless approach to its sensor program. If so, please let me know.

I also encourage sensor manufacturers to convene an industry-wide meeting to establish some standards covering the wireless transmission of sensor signals back to controllers, including PLC-based systems. Issues to address include signal-to-noise ratio, packaging, RF noise and FCC regulations. MF

 


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