Hardware To Software

Valve Hack

Buying from e-bay a common valve usually is not gravity feed.
Needs a lot of pressure in order to allow the water to flow when the coil is energized.
The tools that we are going to need in order to make this modification are :
A glue gun
A straw
A water bottle
Tape
A diode
A screw driver
A dremel with 1.7 mm drill bit
A 12V 1A AC to DC adapter / power supply

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In this short post we will see how to do a measurement of resistance when you have to test a grounding system and how to do a ground resistance measurement.

**Little theoretical summary**

One of the major causes of injuries and danger in the electrical systems are high failure voltages (rated value of the system plus the power surge), due to generally high failure current (look at this post) of systems. Those currents are usually drained to ground by grounding systems. It’s easy to understand why you want the lowest resistance possible in the grounding system, merely:

R_G = U_G / I_F            (1)

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IR-Receiver-Transmitter

An IR Led emitter combined with an IR receiver can make an opto-isolator.
By using an opto isolator we can transfer information between circuits without an electrical connection.
In opto isolators the emitter is always an IR LED.
The receiver can be a photo-diode or a photo-transistor.
Photo transistors are transistors using the base as “light” sensor. When light strikes the photo transistor’s base, it will conduct otherwise it will insulate.
Photo-diodes, on the other hand, are semiconductors that produce current flow when they absorb light.
There are two types of photo-diodes the photovoltaics and the photoconductors.
The photovoltaics when they absorb light create a voltage difference between the edges.
Photoconductors are reverse biased photo diodes. When they absorb light the reverse biased resistance will decrease.
Notice that a photo-transistor is nothing else than a reverse biased photo-diode + a normal transistor.

Photo diode and photo transistor

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Generics - GUI

When you face the matter of writing duplicated code, an idea generally rises about how to not waste time.

In strongly typed coding languages a simple mechanism exists, aiding the coder to solve the problem.
The so called Template.

They are designed so that classes and functions able to work with generic types, giving them the possibility to operate on different data types without the need of rewriting code for each of them.

Maybe you’ve just thought about the concept key: the abstraction.
Indeed we’re dealing with it in the sense described above: a template is a try to avoid useless repeating code writing, and to do this we’re forced to find a more general way than the direct and boring one.

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Interfaces2 – GUI

By reading the introduction of the interfaces, you obtained a mechanism that makes a class really and completely abstract.

From the article we highlighted their total abstraction.
We noticed that it’s contained methods must be overridden by the inherited class(es).
Furthermore a interface does not have any attributes.

Finally we wrote – just on the rush – that the Interfaces mechanism overpasses one compiler’s weak point, about the inability to support the multiple inheritance.

In brief: the multiple inheritance in FreePascal grants that an inheriting class can inherits from more than one more abstract class.
It so expands its possibility to enrich itself, always  by keeping the order and the hierarchy achieved with the interfaces.

And that’s very good… in theory.

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