Blog-PWM-1
8 June 2015
Wireless Trolling
Pro
PWM For Your Electric Trolling Motors
Why would you own one?
Aside from the cool
aspect of just having one, there is a very real, practical side for
owning one. The number one reason is the ability to vary the speed of
you boat. The second is the ability to save current from being
wasted, when varying the speed of you motor.
Most motors come
with 5 forward and 3 reverse speed settings. This method is very
inefficient and results in wasted battery current. So much so, as to
be as high as 5 times more current wasted at the low speed (1), then
when compared to the current required at the same speed when using a
PWM. That is a 5 to 1 ratio, you can fish for 1 hour or for 5 hours,
pick one.
OK, so how does my PWM work?
It is easier to
explain when
-
We pick a motor and battery combination. Lets say we purchased a 30lb thrust, trolling motor and 12Vdc 100 AH-Battery (100 amp hour battery). The electrical specifications are 12Vdc and the motor uses 30 amps, at the forward full speed position # (5).
-
The second thing is the PWM you purchased has a variable speed knob on/off, idle/run and a forward/reverse switch.
Here is the real beauty of the setup.
To operate
the system after installing the PWM, Battery, and Motor you
simply set the motor switch to full speed in the forward position #5,
where you get 0-100% speed control , On/Off, Idle/Run, Fwd and Rev,
all in a one hand held controller.
Speed Control
When you vary the
speed control from 0 to 100% , you are just dividing the batteries
12Vdc into small portions of the total 12 volts. The PWM output goes
from 0Vdc to 12Vdc, thus varying your motor speed from 0 to 100%.
So, just how do they
divide up the 12Vdc and how small are the steps from 0 to 100% speed.
How does the speed control work?
The electronics in
your PWM has the ability to convert the pot position setting by using
a device called an ADC (Analog to Digital Converter) to divide the
12Vdc into 128, 256 or 1024 different values.
WTP uses the 256
value. It is simply the % ratio of pot setting to the 256 value. Lets
say you turn the pot to 1/3 position. The PWM battery output is
85/256 = .333 x 12Vdc and that = 4Vdc applied to your motor. If you
set the pot to ½ position then the output is 128/256 = .5 x 12Vdc
and that is 6Vdc applied to your motor, if you set the pot to the
full on position then the output is 256/256 = 1x12Vdc and that is
12Vdc applied to your motor.
Now you know why
you should own one. It is this ability of the PWM to control your
motor speed 0 to 100%, that gives you the increase in motor running
time from 1 hour to 5 hours.
My
next blog will deal with the Amps to thrust having a 1 to 1 ratio in
performance.
How
the PWM can save you more current when operated correctly.
Misconceptions:
The concept of 1-lb
thrust = requires 1 amp of current or 1 amp current = 1 lb of thrust.
The power ratio of
voltage to current (E x I) does not translate to a 1 to 1 ratio of
prop rotation and current to thrust ratio.
Simply put the
power consumed by the motor does not translate to the prop rotation
on a 1 to 1 scale.
Thanks and happy
fishing, kayaking, or just casual boating, but do it with a WTP PWM.
No comments:
Post a Comment