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Flashing Lights Landing Pad - Part 2


Having done all the design work and testing in part 1, the next step is the most complicated of the lot. Moving from a breadboard to a piece of "Veroboard". Well, complicated if you want it to be as neat and compact as possible, easy if you don't mind wires running everywhere!

Most Printed Circuit Boards (PCBs) are specifically designed with tracks connecting the correct legs. Since this project is simple enough and a one off, we don't need to invest the time to make a PCB, which is a project in itself, but use Veroboard.

Veroboard is special board with copper tracks running in strips on the underside. Holes drilled through the board allow you to place the electronic parts on top, poke their legs through and solder them to the tracks underneath.

The trick is to lay out the components, in a similar way to their layout on the breadboard, to join up the correct legs with the minimum of connections. To stop the tracks connecting the wrong legs, the tracks can be broken by drilling through the thin copper layer of the track. For example, the IC legs are arranged opposite each other, so the tracks need to be drilled through to stop pin 1 connecting with pin 8.

Flashing Lights Landing Pad - Part 2The components, minus the ICs, on the veroboard. Always install ICs last, as they are the most sensitive to heat and static. Only one untidy wire, the white and orange wire on the right to connect pins 2 and 6 on the 555. Otherwise rather neat eh ? You can see the graph paper I used to map out the best way to site the components in the background. 1 hour of planning will save 6 hours of labour and the thing will actually work!

The underside of the veroboard, using a drill to break the copper tracks. I did this before soldering and used the legs of the components to help guide me. This is the most difficult part of the project, connecting up the right things underneath the veroboard, not helped by having to work back to front. The long drilled out strip is the centre of the 4022, while the smaller one where the drill bit is pointing in the centre of the 555.

Flashing Lights Landing Pad - Part 2Again, through a stroke of good luck and good management, my veroboard version worked first time, and hooking it up to the partly assembled model, I could see the lights flashing correctly. I still had 4 outputs left over on the 4022, so added a central green LED to the landing pad and left the other 3 unused. The 562 Ohm resistors for the output LEDs were placed on the model itself.

I soldered the ICs directly to the veroboard, but for a little extra expense, it would be wise to purchase IC holders. These are soldered as normal and the IC pushed into the holder. If something goes wrong, or if you need to replace the IC, you can simply lever out the IC and replace it.

Soldering the resistors onto the legs of the LEDs, underneath the main runway. My son was on tiptoes taking the photo over my right shoulder....kept bumping the soldering iron!

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The completed LEDs, current limiting resistors and wires running off to the Circuit Board. Note I saved time and space by taking the LED cathodes to a common ground through the resistors. The anodes wires are colour coded so that I could work out which to connect up to the circuit board. Red, then brown, then white, then blue, so that the LEDs chase in the right sequence for a landing. Wiring is quite messy.

The LEDs were inserted into holes drilled in the foamcore board and glued using PVA, then, since the PVA kept giving way, using dab of superglue. The LEDs have a polarity, it is important which leg is connected to the positive side ! Long is positive, and if you look carefully, or if someone has already been chopping the legs away, there is a notch or flat part on the LED rim, which designates the negative terminal. I always say: "notch is negative". I soldered in the current limiting resistors to the (cathode) negative side (by convention) of the LEDs and then to ground, while the output from the circuit board went straight to the anodes, or positive sides of the LEDs.

The circuit board was finally hot glue gunned inside the tower at the end of the building and the battery pack nestled in using a piece of foam. The top of the tower is removable so the batteries can be changed, but the circuit board is now buried in the model and is inaccessible. Tough luck if something goes wrong!

Finishing it all off

The rest of the construction was pure modelling. I was worried about it lacking the 40k 'feel', since the model looked fairly blocky, so a few 40K vehicle bits and the imperial eagles were added.

Flashing Lights Landing Pad - Part 2A few students had pulled apart some old hard drives at school and came up with some bits that looked suitable for a radar base. A search for a radar dish led me to the top of a roll on deodorant bottle. I had considered raiding my son's Lego or cutting up a ping pong ball for the dish, but being a bit fanatical about things wanted to get a parabolic looking dish rather than a spherical one. The radar feed was a left over transistor (I even hesitated about using that, I'm a miser at heart) and some guitar string for the waveguide, (okay, so I stopped short of using a rectangular guide).

The dish was mounted to the base using 40k vehicle bits from the HK missile box. The radar turns, but is not powered by a motor...maybe next time... The opportunity to put extra LEDs in was too hard to pass up, so a small array on the end wall and one inside the control tower were added.

Flashing Lights Landing Pad - Part 2Basing was simply expanded polystyrene, plaster to fill in the gaps, kitty litter rubble and painted using the dry brush technique from a dark brown to a light flesh/bleached bone. The sandbags were modelled using DAS putty, an air drying clay, by rolling out a sausage, chopping it up and squashing down the ends. People on <a href="http://www.wargamerau.com" target=_new>WargamerAU</a> recommend rolling the DAS out using a textured material, like denim or hessian, which gives the sandbags an even more realistic look.

I found some plastic disposable plates at a bargain shop that had a terrific 'chequer plate' pattern on them. They formed the floor of the roof and platform on the right of the landing pad. The platform supports are made from the handles of disposable razors.

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