Pulse Width Modulation Retrofit – Bateman RB35

The first of these installs was carried out at the beginning of 2021 on a used Bateman RB35. The customer was keen to upgrade from the 6 section manual control system supplied with the machine, to a setup that offered auto section control, guidance and Pulse Width Modulation. 

After contacting Chafer’s sales department to discuss the benefits offered by the Hawkeye PWM setup, initial pricing was provided. Further technical discussion was carried out by Chafer’s Precision Farming Manager – Ben Bryant – to ensure the system could meet and exceed the customers requirements. The Raven Hawkeye system was chosen with the HD unlock offering individual nozzle control on top of the systems standard features.

Being fully ISObus compatible, choosing Raven Hawkeye allowed an existing Topcon X30 terminal and receiver to be utilised. The terminal and AGI-4 receiver were fitted to the sprayer with both items receiving software updates as part of the process. Without the need for any additional terminals in the cab, the X30 looks after sprayer rate control, auto section control, guidance along with all the PWM functionality. 

Unlike other PWM systems available, Hawkeye has complete control over the sprayers regulation system along with the PWM valves on each nozzle. This ensures rates are maintained smoothly in all conditions, with these two functions working together rather than fighting against each other. 

Installation was carried out by Chafer, with fitting, setup and testing completed over two days. The Bateman’s air shut off system was completely removed and replaced by the Raven wiring looms, nozzle shut offs and ECU.

The ECU itself has built in gyroscopes to control the turn compensation functionality, which proportionally varies the output of each nozzle, preventing over/under application as the machine turns. Using a gyroscope ensures changes to output of each nozzle are based on real time information from the boom rather than being calculated based on GPS data. The advantages of this are two fold, not only is this more accurate in general use, but the system also accounts for any boom yaw occurring during spraying, cancelling out any missapplication resulting.

Turn compensation is a headline feature of PWM systems that attracts understandable attention, but PWM also has many other features beneficial to the spraying process.

On a standard pressure based sprayer, nozzles are chosen to provide the correct sized droplet for the spray target and conditions. However due to the nature of this system the droplet size will change as forward speed varies, with the pressure fluctuating to ensure the application rate remains correct. With PWM, operators are able to preselect their droplet size and have this maintained by the system regardless of forward speed. This means whether on the headland, managing tricky obstacles or spraying at normal speeds, the droplet size is always the same and always suitable for the conditions. Turn compensation ensures this is true across the whole boom, even as the machine steers, preventing missapplication and possible resistance issues.