CCTV TESTER MKII 002

INTRODUCTION

The MK II, in design, must overcome most of the problems of MK I, naturally. And so, the proposed features are, apart from the features of the MK I:

- Cable Short Test (MK I)

- Voltage Polarity Detector (MK I)

- Built-in CCTV Camera

- Voltage tester

- Built-in Video Monitor

- Automatic Power Selector

By having such features, the design must overcome some of the problems such as the requirement of a 12 volt power supply for the built-in camera. It must be light and still be compact enough. As they (could) use a lot of current, the battery must be able to supply them and not just the voltage alone. There is a thought of using rechargeable batteries but at the moment, until the design is ready for field testing, there is no indication how long the tester would last on its own power. Moreover, as the tester is not being used all the time, rechargeable betteries tend to lose their charge at a certain percentage a day. Still, as a matter of precaution, momentary switches would be utilised to activate any of the features when required to conserve power.

 

THE CASING

Like the MK I, the MK II must be portable and also easy to carry in a reasonable manner. So, the criteria at the moment are:-

- Able to house all switches, indicators and monitor

- Able to house eight 1.5volt batteries (which in this case would be AA types, due to weight and size)

- Must be handheld design and not normal rectangular project box

- Material must be robust enough to witshtand a reasonable amount of shock

 

After viewing many options available locally, I have chosen a design which met all the requirement above. Although it is a bit cumbersome, after going through the manufacturer's catalogue, this was the only choice. Moreover, carrying a large black clunky rectangular box at a customer's place is just so uncool. Its better to show up with a large white clunky handheld enclosure. Ha ha ha.

The design comes with two halves, has a window and a stand. Between the two halves, there is a rubber like string which acts like a seal. If you glue the transparent plastic window as well, the whole casing would be water proof. But once you start to drill some holes........

It is roughly about 9 inches long, 4 inches wide (at the grip area) and 2 inches thick. Although it is a bit large but it can still be held by (my) hand. For a field equipment, I guess the size is still acceptable. It (some of the time) will need two hands to operate anyway.

The metal receiver looks promising. Without them, if you drive the screws too often, they will wear the holes out. And I'll need to do that often because of the batteries inside. Here, you can see the trench for the rubber like material.

 

THE DESIGN

The main problem with the MK II is the batteries. It must be large enough to provide the current yet small enough to be housed inside. After much deliberation, the "C" type batteries are out (and they're very heavy too) in favour of the more common AA size due to the size of the switches and the casing. Just to build them up to the required 12 volts, you would need eight of them.

The bottom half would be used to house the batteries, the input/output connectors and the CCTV camera while the other half would be for the switches, monitor and panel meters.

There are two ways of making rectangular hole on this 4mm thick plastic. I could drill the holes and then use a blade to cut out the shape. Or I could just use a scriber and a can of Coke. As my hands are weak, I used the scriber instead as it is safer for me. My daughters Kristine and Kaelynn were curious about my project. But I have to keep them away as the scriber blade is very sharp and brittle. Luckily, I only need to make two holes. The rectangular hole for the meter is already done. I used a double-sided acrylic tape to stick the battery holders to the bottom half of the casing. So far, they have not failed me yet. But a potential problem here is, how to keep them in the holder if the case suffers sudden shock or was dropped?

 

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