Embedded Controller Technology

When coal analysis specialist Bretby Gammatech needed to turn the heat up on its new and existing product capabilities, it chose Micro-Robotics to provide the embedded system technology for the job.

Operating within a small niche market in the worldwide coal mining industry, primarily for open cast and deep mining, as well as coal-fired power stations, Bretby Gammatech designs and manufactures specialist monitoring equipment for measuring the ash content of coal. By calibration and then taking accurate readings of the stone content, the linear system interpolates data and determines the ash count. Two primary products from Bretby are an on-line NGCQM ash monitoring system for mounting on a conveyor system and the new, portable Ash Probe, which incorporates the Micro-Robotics controller.

The Ash Probe essentially comprises a hand held data logger linked to a 600 to 800mm long cylindrical tube housing a detector for monitoring gamma pulses from the test material. At the heart of the instrument is a Micro-Robotics' Scorpion K4S controller, keypad and a four-line LCD. The software is written in the company's Venom control language.

In operation, the probe is placed into a coal pile. The instrument then takes readings, counting for a preset or pre-arranged period of time, essentially until enough measurements have been taken. Several probings - up to 18 - are made to provide a good average ash count. The Micro- Robotics controller takes in pulses from the probe, operates the keypad display and provides all necessary processing functions and calculations.

Most importantly, the Micro-Robotics solution was chosen for its low power operation, which is essential in portable, battery-powered applications. For Bretby Gammatech the Ash Probe needed power for at least eight hours in operation. Bretby's Operations Director, Alan Cooke, said: "The majority of controller solutions we looked at were high on current usage and really there was only one that offered anything like the consumption we required. That was the Micro-Robotics Scorpion K4S which amazingly gives 2.5 days of battery life in operation."

Having had earlier, good experience with Micro-Robotics, Bretby Gammatech made the decision to design in Scorpion K4S and the Venom control language.

Plug and play controller

The Micro-Robotics Scorpion K4S embedded controller is a credit-card-sized, PCB mounted computer. It plugs into the main circuit board of any application and controls a range of user interfaces and I/Os, including alphanumeric and graphic LCDS. According to Sales Engineer, Clive Keeler: "Scorpion K4S is quick and easy to integrate, handling complex programs and control systems."

For specific applications such as the Bretby Gammatech Ash Probe, solutions comprising application boards and matching I/O cards can also be supplied. With its serial interface, any computer running terminal emulation can program the Scorpion K4S.

The Venom software is thought to be similar to C, Pascal and Visual Basic, providing a powerful, multitasking environment for developing control applications. Features include procedures and functions, as well as integer and floating-point arithmetic. A range of object-orientated drivers is also provided to simplify the user interface and I/O operations. Scorpion K4S controls and monitors up to 160 channels of I/O. Communications are via two serial ports for easy connection to peripherals and host alike. The controller comes with 128 K bytes of RAM and applications can be developed in RAM and securely stored in flash memory when complete.

Scorpion K4S systems are expendable via the industry standard 12C and Microwire buses, as well as by an expansion bus. On board features include watchdog timer, real time clock, as well as a calendar.

Alan Cooke said: "With the Micro-Robotics solution the programming language is specific but simple and the company itself provides excellent support and manuals. At our end we just designed it in and it ran-a very easy integration. And despite the fact that we are a low volume user, our relationship with Micro-Robotics is good, with help forthcoming from them when required, even beyond the call of duty. We have had no problems to speak of in integration or reliability and importantly, Scorpion and Venom provide a viable solution to our products for market."

Easy integration to bespoke solution

Initially, Bretby Gammatech used standard Micro-Robotics analogue and digital I/O boards with some additional components fitted to the prototyping areas, but with the easy integration of the Micro-Robotics system, a bespoke printed circuit board was quickly designed and used in the current production Ash Probes.

Alan Cooke continued: "Now the company is looking to develop its current on-line monitoring system to incorporate the Micro-Robotics controller at the sensor end. This would enable raw data to be gathered and packaged for transmission to the main computer using a simple serial link as opposed to using multi-core tables. In this way information can also be passed to, and displayed at, the sensor end of the system, which can be up to five kilometres from the main computer.

"We now have the total confidence to redesign the on-line conveyor mounted system to provide interaction between the main display computer and the Micro- Robotics controller at the sensor end, following our experience with the Ash Probe.

"This will give us an intelligent sensor at the far end of the system, which will be mains powered. The idea is then to use a standard computer for the main display computer, removing the need to add specific expansion cards to interface with the sensors."

For the future, a laboratory ash monitor, based on the Ash Probe system is being developed with a prototype system currently being successfully tested at a Yorkshire colliery.

Bretby Gammatech have since upgraded their instrument to use the newer VM-1 controller.