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  • How PWM and Duty Cycle Works...

  • PWM is used throughout the automotive industry as a command signal. It is meant to make automotive

  • components work less, when the demands are not as heavy. And, we created the PWM Bi Directional

  • controller to help you test and diagnose all solenoids, motors and actuator components.

  • PWM, or pulse width modulation, is the ability to control a load or component, by pulsing

  • its electrical current. In this way, the load or component can be made to change its speed,

  • without any heat causing parts, like resistors. So, if PWM is using pulses to control a load,

  • then Duty Cycle is the measurement of these pulses.

  • The Duty Cycle of a PWM signal, tells us the amount of work this signal is supposed to

  • make the component perform. The duty cycle of the signal is always described in percentage.

  • So, a 10% duty cycle means, that the component is on 10% of the time. And a 90% duty cycle

  • means the component is on 90% or most of the time.

  • Now, there is a close relationship between duty cycle, and how the component is triggered

  • or turned on, which could be by applying power or ground. This relationship is very important,

  • so remember that thoroughly. Here is what we mean by that. Suppose a solenoid is activated

  • by ground. That means, that 12 volts or battery voltage is applied steadily on one side, mostly

  • through a relay, and the other side receives a PWM ground command signal. Now imagine that

  • a 10% duty cycle PWM signal is applied. What we then have is to measure is how long the

  • signal is grounded. And, how long as compared to the entire cycle. A 10% PWM duty cycle

  • means that the solenoid receives a ground only 10% of the time, and receives power 90%

  • of the time. Since we have already mentioned that this is a ground controlled solenoid,

  • the time the drive transistor provides power means that component is off. Why? because

  • you already have steady power on one side, so power on the other side equals no operation.

  • If, on the other hand, the component is turned on by power, meaning ground is steadily applied

  • on one wire, and power is pulsed, that same mentioned signal, will then become a 90% duty

  • cycle signal. Now with this power actuated component, the positive or 12 volt side is

  • what matters, and what is taken as the duty cycle. It is worth mentioning that most components

  • are triggered or actuated by ground. Why? It is because if that command signal is shorted

  • to chassis ground, the component will simply turn on all the time, like a 100% cycle. If

  • it were power triggered, then there would be a short, and the fuse would blow rendering

  • the system useless. But still, some components are power triggered, and be prepared to understand

  • the nature of PWM to Duty Cycle. Hopefully what you have learned here will give you some

  • insight on using the PWM Bi Directional Controller to perform your diagnostics.

How PWM and Duty Cycle Works...

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