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Using Pulse Width Modulation to Control Spray Droplet Size

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:. Size of the Spray Droplets - Volume Median Diameter (VMD)

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Using Pulse Width Modulation to Control Spray Droplet Size

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

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

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

  4. 1/2 of spray volume = smaller droplets VMD 1/2 of spray volume = larger droplets

  5. Important Droplet Statistics VMD (50%) Operational Area VD0.1 (10%) VD0.9 (90%)

  6. Guidance to Chemical Manufacturers Match the crop protection product to the target Adhere to label guidelines based on an industry standard ASAE S-572 Buffer Zones or No Spray Zones Maximize Efficacy Minimize Drift Example Reference Graph 900 800 very fine/ fine fine/medium medium/ coarse coarse/ very coarse 700 very coarse/ extremely coarse 600 XC 500 C VC 400 M 300 F 200 Drop Size (microns) VF 100 0 0.1 0.5 0.9 Cumulative Volume Fraction EPA Requested Changes Coming!?!? VMD

  7. Pulse Width Modulation - PWM Pulsed Emissions from Nozzles

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

  9. Synchro Nozzles • Blended Pulse Technology • Independent Flow Control (1-8X) • Independent Drop Size Control • Independent Band Width Control (Fan Nozzles) • Separate boom section controls • GPS - program managementcontrol

  10. Synchro Controller Components:

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

  12. Pulse compared to conventional: PWM Conventional

  13. What is Pulse Width? • Type of control system • Modulates a DC square wave signal

  14. 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.

  15. Spray pattern quality not sacrificed:

  16. Electronics/Rate Controllers • How does your system work when speed changes? • Is it pressure based? • What is the effect of going slower? • What is the effect of going faster?

  17. Procedures: • Treatment 1 • Conventional, 20 psi, 5 mph, tt11002, 8 GPA • Treatment 2 • Conventional, 75 psi, 10 mph, tt11002, 8 GPA • Treatment 3 • PWM, 40 psi, 5 mph, tt11004, 8 GPA • Treatment 4 • PWM, 40 psi, 10 mph, tt11004, 8 GPA

  18. Drift

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

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

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