A Dutch-designed pulse-width modulation (PWM) system for sprayers claims greater flexibility and application quality compared with other options on the market.
On traditional crop sprayers, the only way to change flow rate is by adjusting the system’s pressure – when the machine speeds up pressure is increased, and vice versa.
The major problem with this approach is that fixed-orifice nozzles are sensitive to any changes in pressure, so when it is too low, the spray pattern and coverage deteriorates, and if too high, droplets become too fine and dramatically increase spray drift risk.
A solution to this problem is PWM, which controls flow rate with electronic solenoid valves on each nozzle body, opening and shutting many times a second to create a pulsed spray.
The amount of time the valve is open, known as the pulse width or duty cycle, relates to the quantity of liquid flowing through the nozzle.
With the system at a constant pressure, most setups adjust the duty cycle to maintain a required rate as forward speed changes.
However, a relatively new system – the first one was retrofitted to a sprayer in the Netherlands in 2020 – comes at the PWM concept in a slightly different way.
Most work on a fixed frequency of anywhere between 10Hz and 50Hz and adjust the duty cycle by speeding up or slowing down the opening and closing time of the valve.
The LeapBox PWM system from BBLeap can work at up to 100Hz at each nozzle, so its valves are very fast and minimise opening and closing time.
The firm says this allows the LeapBox to maintain a large application rate range, without compromising spray quality or coverage at very high and very low forward speeds.
Range of options
BBLeap’s Martine Smeijers tells Farmers Weekly that the modular system also offers plenty of flexibility in configuration, with its control unit able to operate individual nozzle shut-off at up to 256 positions.
This makes it suitable for large sprayers with booms up to 50m at 50cm or 25cm nozzle spacings, but customers can also go as they want. The system can spray up to 100 times/sec, with variable-rate applications possible at 40 times/sec.
The ability to spray this accurately aligns with the company’s ambition to spray “at plant level”, but a lot of data processing is required during operation.
This means a sprayer’s existing GPS control terminal may need to be bypassed when installed, although its GPS signal will still be necessary.
Each modular Canbus control unit fitted out along the boom operates four nozzle positions and some sprayers will require an additional battery to cover electrical draw requirements when at peak usage.
Once up and running, the operator simply has to input the target rate (litres/ha) and desired droplet size for product and/or conditions. The sprayer will then maintain those targets, whatever the forward speed.
BBLeap has fitted the system on a range of mounted, trailed, self-propelled and specialist horticultural sprayers since 2020, with the oldest being a 2010 machine, right up to the latest models.
Its product has reached as far as Australia, but the pandemic has largely restricted its sales activity to within the Dutch market.
All brands can be catered for, and the firm has a neat configuration tool on its website that allows you to spec up your sprayer with a LeapBox system and offers a price.
The only downside at present is the absence of British sprayer brands such as Househam, Bateman and Sands, but these should be added to the drop-down menu soon.
As an example, it would cost about €43,150 (£36,000) to kit out a 24m Agrifac with 50cm nozzle spacing, but the price will vary widely depending on the sprayer and customer requirements on configuration.