using pulse width modulation to control spray droplet size robert e. wolf extension specialist...
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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)
Droplet Spectrum (Range - big to small)
% Volume in droplets less than 200 microns in size
One micron (m) =1/25,000 inch
Drop Size:
1/2 of spray volume = larger droplets
VMDVMD
1/2 of spray volume = smaller droplets
Important Droplet Statistics
Operational Area
Example Reference Graph
Cumulative Volume Fraction
0.1 0.5 0.9
Drop S
ize (microns) 0
100
200
300
400
500
600
700
800
900
very fine/ fine fine/mediummedium/ coarsecoarse/ very coarsevery coarse/ extremely coarse
VF
F
M
CVC
XC
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
EPA Requested Changes Coming!?!?Example Reference Graph
Cumulative Volume Fraction
0.1 0.5 0.9
Dro
p S
ize
(mic
rons
)
0
100
200
300
400
500
600
700
800
900
very fine/ fine fine/mediummedium/ coarsecoarse/ very coarsevery coarse/ extremely coarse
VF
F
M
CVC
XC
Pulsed Emissions from Nozzles
Pulse Width Modulation - PWM
SYNCHRO® - Nozzle System
Capstan Ag SystemsTopeka, KS
Developed by thePrecision Spray Laboratory
U of CA - Davis
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 management
control
Synchro Controller Components:
How it Works
Uses high speed solenoid valves to regulate flow
Varies application rate with duty cycle: independently of pressure
Pulse compared to conventional:
What is Pulse Width? Type of control system Modulates a DC square wave signal
Synchro® Blended PulseEach 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.
11008 F la t Fan T ip, 5gpa, 15m ph, 50psiEVEN O D D EV EN O D D EV EN O D D EV EN O D D
G ood Pulse B lending
21"
110°20"
Spray pattern quality not sacrificed:
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?
Procedures:
Treatment 1• Conventional, 20 psi, 5 mph, tt11002, 8 GPA
Treatment 2• Conventional, 75 psi, 10 mph, tt11002, 8
GPATreatment 3
• PWM, 40 psi, 5 mph, tt11004, 8 GPATreatment 4
• PWM, 40 psi, 10 mph, tt11004, 8 GPA
Drift
Horizontal Drift Deposition
0.00
0.20
0.40
0.60
0.80
1.00
1.20
1.40
1.60
20 25 30 35 40 45 50
Card Position - Horizontal
% C
over
age Treatment 1
Treatment 2
Treatment 3
Treatment 4
Sharp Shooter/Synchro Controller:
Pulse generator• On/Off• Select volume %
Valve Driver• Power from battery
Nozzle valve• Creates spray pulse
For more information contact:
www.bae.ksu.edu/faculty/wolf
www.capstanag.com/
www.caseih.com/