Central heating timer inspection

Notable features…

This is another system I was very pleased with. It ran fast very efficiently and fulfilled the customers requirements.

All of the software was written in visual ‘C’ and used multi-threading for various sub sections of the application notably the PLC, image processing and user interface.

The company was Invensys.

We had an enquiry from a company that makes central heating timers. These were tested by hand and was a laborious job that relied on the concentration of the individual. Also, some of the tests were subjective, one person may pass some cosmetic damage, another would not.

vcl-inv-timer The requirements:-

What we came up with:-

How the system works…

vcl-inv-inputThe timers are loaded on to the input conveyor, make sure they are the correct way around (they will automatically be rejected if they are).

vcl-inv-int-illThe timers are then automatically feed in to the systems and the two inspection areas.

vcl-inv-camcosThe first inspection area check makes sure the timer have been loaded correctly and then proceeds to perform a cosmetic check.The cosmetic check makes sure we have the correct model by looking at the part number and the providers logo. It then check all of the surfaces for print quality and any blemishes. If any of these fail the functional check is skipped and the timer is placed into the rejection chute.

vcl-inv-camfuncAssuming the timer passes the cosmetic check the timer then passes to the functional check area.The meter is first held in place from above by the plunger plate that is lowered using a pneumatic cylinder.Once this is in place a second pneumatic cylinder below the timer raises a contact block on to the electrical contacts on the rear of the timer. This provides power for the timer and monitors the outputs from the heating and water relay contacts.


vcl-inv-scriptA script is loaded from the hard disk. This script is unique to each style of meter and contains a list of instructions to test the individual timers.

vcl-inv-plusideA set of pneumatically controlled plungers press the buttons on the timer in accordance with the script.

vcl-inv-blobAt each stage the display is read and the voltages and the voltages on the contacts measured, all controlled by the script.

vcl-inv-outputIf the timer passes all the tests it is placed on to the output conveyor.

vcl-inv-rejectIf the timer fails any of the tests it is placed into the output chute and a fail ticket is printed by a small printer in the side of the machine.If either the output of reject chute gets full the system automatically stops and a warning traffic light on the top of the system flashes.

Construction details


vcl-inv-dwg-topThe top down drawing of the system.

Note the four conveyor sections in the detail below.

vcl-inv-dwg-sideThe drawing of the system from the side.


vcl-inv-conThe base frame and conveyor.

vcl-inv-int-pnuThe pneumatic valve block.

vcl-inv-int-rearThe open rear.

vcl-inv-plungeThe functional test area.


The input and output conveyors

The tests

Finished system

vcl-inv-sfrontFront of system.

vcl-inv-srearRear of system (panel removed).

vcl-inv-sleftLeft (output) of system.

vcl-inv-srightRight (input) of system.

My part in the projectvcl-inv-sfront

This was one of my projects so I…