Using Pulse Width Modulation to Control Spray Droplet

Using Pulse Width Modulation to Control Spray Droplet Size Robert E. Wolf Extension Specialist Application Technology Biological and Agricultural Engineering

Efficacy and Drift Potential is Influenced by: ü Size of the Spray Droplets Volume Median Diameter (VMD) ü Droplet Spectrum (Range - big to small) % Volume in droplets less than 200 microns in size

Drop Size: One micron ( m) =1/25, 000 inch

1/2 of spray volume = smaller droplets VMD 1/2 of spray volume = larger droplets

Important Droplet Statistics Operational Area

EPA Requested Changes Coming!? !? ü Guidance to Chemical Manufacturers ü Match the crop protection product to the target ü Adhere to label guidelines based on an industry standard ü Buffer Zones or No Spray Zones ü Maximize Efficacy ü Minimize Drift 900 800 very fine/medium/ coarse/ very coarse/ extremely coarse 700 600 XC 500 C VC 400 Drop Size (microns) • ASAE S-572 Example Reference Graph 300 M 200 F VF 100 0 0. 1 0. 5 Cumulative Volume Fraction 0. 9

Pulse Width Modulation - PWM Pulsed Emissions from Nozzles

SYNCHRO® - Nozzle System Capstan Ag Systems Topeka, KS Developed by the Precision Spray Laboratory U of CA - Davis

Synchro Nozzles ü ü Blended Pulse Technology Independent Flow Control (1 -8 X) Independent Drop Size Control Independent Band Width Control (Fan Nozzles) ü Separate boom section controls ü GPS - program management control

Synchro Controller Components:

How it Works ü Uses high speed solenoid valves to regulate flow ü Varies application rate with duty cycle: independently of pressure

Pulse compared to conventional:

What is Pulse Width? ü Type of control system ü Modulates a DC square wave signal

Synchro® Blended Pulse Each Synchro® nozzle emits 10 pulses per second, with adjacent nozzles having alternating timing. The alternating pulses, combined with overlapping spray patterns and the natural dispersion of droplets traveling in air, blend together to provide consistent coverage.

Spray pattern quality not sacrificed:

Electronics/Rate Controllers üHow does your system work when speed changes? üIs it pressure based? üWhat is the effect of going slower? üWhat is the effect of going faster?

Procedures: ü Treatment 1 • Conventional, 20 psi, 5 mph, tt 11002, 8 GPA ü Treatment 2 • Conventional, 75 psi, 10 mph, tt 11002, 8 GPA ü Treatment 3 • PWM, 40 psi, 5 mph, tt 11004, 8 GPA ü Treatment 4 • PWM, 40 psi, 10 mph, tt 11004, 8 GPA

Drift

Sharp Shooter/Synchro Controller: ü Pulse generator • On/Off • Select volume % ü Valve Driver • Power from battery ü Nozzle valve • Creates spray pulse

For more information contact: rewolf@ksu. edu www. capstanag. com/ www. caseih. com/ www. bae. ksu. edu/faculty/wolf