Easily upgradeable PLC for bulk samplers

An Omron Electronics product story
Edited by the Engineeringtalk editorial team Oct 22, 2001

Distributor Control Components identified that the new CPM PLC range and associated products would suit Samplex's needs, when developing its next generation of bulk samplers

The health and safety risks associated with the manual sampling of grains, powders and pellets have been eliminated by Norfolk firm Samplex, which has built its business on developing automated bulk lorry samplers.

The company was founded by food scientist Sue Catchpole and agricultural engineer David Catchpole in 1988 on a £40 a week Enterprise Allowance and has constantly developed its products since that time, improving accuracy and enhancing productivity with ever more automation.

It now has clients across the world and is recognised for its ability to harness innovations and constantly push forward the boundaries of sampling technology.

For many years Samplex has enjoyed a close working relationship with nearby specialist industrial distributor Control Components Anglia which has recently been appointed Omron's official distributor for Norfolk.

Mark Abbot from Control Components identified that the new CPM PLC range and associated products would suit Samplex's needs, when developing its next generation of bulk samplers.

The basic principle of a Samplex machine is to probe a 'spear' deep into a grain lorry's load and suck out a sample for analysis.

Samplex built its reputation on the fact that it did not use vacuum extraction, which tends to collect smaller grains or pellets rather than larger, thus producing an unrepresentative sample.

Instead it uses a venturi technique in which air is blown across an orifice in the spear so that the sample it collects is truly indicative of the surrounding material, be it grain, oilseed, pulses, maize, pellets, or inorganic powers and particulates.

Sampling is not at a single point but is carried out constantly as the probe is inserted into the load.

Under instruction from the PLC it can also sample during withdrawal if required.

In practise lorries arriving at say a grain mill park on a weighbridge and the probing is done while the load is being weighed.

Several samples are taken from different points in each lorry, up to 15 points for a 32 tonne load, with the sample machine being drivable in X and Y axes to move from point to point.

A Z-axis is also provided for probe insertion.

Omron provided proximity sensors, contactors and limit switches and other automation equipment to control these movements.

The PLC, which has an I/O count of 30, holds in its memory a number of patterns of sample points and the operator selects the appropriate one for each truck.

Omron's CPM PLC was chosen in large part because it is easily upgradeable, which dovetails with Samplex philosophy of continuous development.

Next year, for instance, Samplex plans to add an Omron touchscreen controller to the sampler, replacing the current joystick so that user-friendliness is enhanced.

"The PLC we had been using previously had no flexibility for upgrading as the machine design developed," recalls Sue Catchpole.

"This was very frustrating because it meant not only a new PLC but a whole new control system every time we enhanced the sampler.

Part of our brief to Control Components was to get us out of this Catch 22 situation.

The market research identified Omron's CPM family of microcontrollers as never forcing machine builders to compromise on control system design because they are seamlessly scaleable to match individual system requirements, and programmes are 100 per cent transportable between the various sized units of the range.

They are also easily connectable to other control elements such as PCs and HMIs and there are options for temperature, motion and other control functions.

Omron's Paul Simpson says: "The CPM2A, as used by Samplex, is a compact yet high-function unit with features such as multiple counters, 10 kHz pulse output, programmable terminal connections through a built-in RS-232C port, positioning functions and analogue control.

"As we upgrade the Samplex machine, we will be able to either add I/O modules to the CPM2A or simply swap it out for a more powerful member of the CPM family.

All the CPM range use the same Windows based programming software which allows easy conversion from one range to another.

Find out more about this article. Request a brochure, download technical specifications and request samples here.

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