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Arduino FreeRTOS Mutex Examples

In this section, we will explain using an example to demonstrate mutexes in Arduino using freeRTOSThere are two freeRTOS Mutex examples in this tutorial, the first example demands some hardware (LCD) While the second does not need any hardware, you can try out both if you have the resources.

In the last tutorial, we considered in detail: semaphores and mutexes and we also established the difference between binary semaphores and mutexes.
Just for a review:Recall that a mutex is a locking mechanism that implements the take and gives functionality in itself, unlike a binary semaphore. See this tutorial if you have not before continuing.
Example 1: Protecting the LCD Resource Using Mutex in freeRTOS
Program Description

In this program, we Demonstrated the use a 16x2 LCD display to implement a mutex.

The LiquidCrystal library works with all LCD displays that are compatible with the Hitachi HD44780 driver. you can usually tell them by their 16-pin interface.


* LCD RS pin to digital…

Working Principle of a Gas Turbine Generator

How do Gas Turbine Generators work? If the steam turbine generator uses steam, do gas turbines use gas? In trying to understand the working principle of a gas turbine generator, these were the questions I asked during the course of my training. I was privileged to work with Korean engineers and experienced gas turbine specialists during my training, I have documented my experiences in this series be sure to see it.

In this post, I will be educating us on the fundamental principles of operation of a gas turbine generator or better still the basic working principle of a gas turbine power plant and then the comparison between a steam turbine and a gas turbine, the advantages and disadvantages.

The concept described below contains some specific information applicable to the generator I worked with. However, it can be applied to any other Gas Turbine generator except that values may be changed.

Working Principle of a Gas Turbine Generator

In an electricity generating plant, it is not unusual to find a gas turbine generator. In this scenario, it is not used as a generation source for commerce, rather it is integrated as part of the system to provide power during outages, system collapse or grid collapse. It forms an integral part of the black start.

The Gas turbine Generator works exactly like the steam turbine in its basic operation: the turbine rotates a shaft that contains the rotor windings and this relative motion leads to the generation of electricity, however, it is different in design. Which we would see shortly.

The gas turbine generator is taken to be self-starting as a unit, however,  in reality, it is not so, it is fitted with auxiliary starters that work in consonance with the control relays.  It can run on natural gas, fuel oil etc. The gas turbine (Prime mover) usually rotates at a higher speed say 5100rpm while the generator rotates at a lower speed 3000rpm. Thus, the Prime mover and the generator rotate at different speeds, unlike the steam power plant which is fitted with the same shaft, the gas turbine, and generator use a reduction gear to compensate for the speeds.

Speed of Prime Mover = 5100rpm

Speed of Generator = 3000rpm

Gear Ratio = 5100/3000 =  1.7

NOTE: This gear ratio is adjustable, thus unlike the steam turbine which is very sensitive to low frequencies, the gas turbine can accommodate lower frequencies without having many problems.

DC Source: The gas turbine generator is fitted with DC sources which could be a battery to introduce excitation.

Diesel Engine: The gas turbine is fitted with a diesel engine to drive the Prime mover. The diesel engine is not self-starting, it is run by a kick starter. When the start is initiated either on local or remote, the kick starter receives the signal and initiates the process by starting up the flywheel of the diesel engine. The diesel engine is fitted into the gas turbine.

The Gas turbine: The gas turbine shaft carries two sets of blades -  the turbine blades and the compressor blades which are opposite in operation. Whereas the turbine blade expands, the compressor blades compress air from the atmosphere.

Above 60% speed of the turbine, (60% of say 5100rpm), the diesel engine disengages. By this time, Gas (fuel) and sufficient air have been compressed and must have been introduced into the combustion chamber in a predetermined ratio, at the combustion chamber the mixture is heated and converted to high-pressure gas stream that enters and expands through the turbine section.

The gas turbine generator has to say 8 combustion chambers, thus increasing its potential to spin the turbine blades at a specified angle. The air sucked in from the atmosphere passes through some filters located usually on the top section of the gas turbine. Note all these operations are monitored by relays (eg, speed relays)

When the speed of the turbine approaches 5100rpm (full speed) excitation power is introduced into the generator winding to generate the magnetic flux. Once this is done, voltage is established at the output and taken back to sustain the electromagnetic field.

Comparison between the Gas Turbine and the Steam Turbine

Steam Turbine GeneratorGas Turbine Generator
Higher Power generation capacityLower Power generation capacity
Takes longer time to start upVery short time to power up
Usually a closed process cycleOpen process: Exhaust fumes are not used further except for other purposes like steam generation but not for power production.
Sensitive to low frequenciesSensitive to high frequencies
Superheated steam is the working fluidHigh-temperature fuel-air mixture is the working fluid


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