Introduction: Blue Alert Prop (from Red Dwarf Series)

I really like Red Dwarf series. In episode "Legion" (S6E2) there is an excellent scene with "Alert situation". You can see whole scene on the internet (search for "Red Dwarf Blue Alert" on YouTube for example).

I have friends who also like Red Dwarf and we occasionally quote jokes from Red Dwarf for fun. I'm pretty sure, that they will appreciate this prop.

And I told myself it should be easy to make this prop. In general it is just a box with flashing light inside...


  • good quality cardboard. I used a type with thickness = 1.5 mm.
  • sheet of hard black paper.
  • sheet of tracing paper
  • aluminium foil (tin foil)
  • transparent office tape

elecronic components

  • 4 blue LEDs with good luminosity and wide beam angle.
  • 100 ohm resistor
  • module for flashing. I used a module with NE555.
  • switch
  • wires
  • clip for 9V battery (I-from)
  • 9V battery


  • printer
  • utility knifes
  • black color. I used a black spray.
  • glue stick (white glue)
  • hot glue gun
  • soldering tools
  • sandpaper

Step 1: Front Mask

Print attached PDF with "Alert" template to a paper in format A4 without scaling. (In the attachment there is also a source file for GIMP graphic editor.)

From the size of the "Alert" text I set size of the box (see in the next step).

Then prepare a hard black paper. It shouldn't be cardboard, but a thin paper. Glue the printed template on the black paper. Cut out the letters. Now take a tracing paper and glue it again on the black paper. Use a glue stick, don't use a liquid glue, because it would cause ugly curling of the mask after drying. (I found out in my first attempt.)

Put the mask between two books and let it dry.

Step 2: The Box

As I said, I took size of the box from size of the text. Specifically is size of the front mask:

  • width = text width + 2×12 mm
  • height = text height + 2×12 mm

Now take some good quality cardboard a cut these pieces:

  • 237×53 mm – two pieces,
  • 71×53 mm – two pieces,
  • and cut one piece 233×70 mm in advance for the next step. This piece should be a partition.

But you have to modify dimension of the pieces according the thickness of your cardboard. See sketch in the first picture.

Paint four pieces of the box to black. I used a black spray.

Cut the mask to size 237×74 mm. Cut off margins of the tracing paper (as you can see in one of the pictures).

Now you have prepared all parts of the box and you can glue the box. Use a hot glue.

Step 3: Partition

Make four holes for the LEDs in one horizontal line in the middle of the partition. See the pictures...

Add a layer of a waved tracing paper for making light from the LEDs more diffuse. See in the picture above, how I made it.

Step 4: Frame of the Front Mask

In the picture with screenshot from the scene you can see, that the front mask has a nice metal frame. But how to make it? I definitely didn't want to use real metal sheet. What about using a paper painted to silver?

I tried something else. It is a bit tricky.

Take a common aluminium foil and cut a few long strips. Place one strip to clearly flat surface. I used cover of my notebook. Then secure in place one side of the strip with a tape and smooth the strip with your nail. Go from secured side to second side, be careful. After smoothing secure in place the second side too. Now tape the transparent office tape on the strip. The tape will prevent crumpling of the foil. Cut this "crumpless" strip to wide 6 mm. Use a cutting mat and a very sharp utility knife. Repeat this process to get enough "crumpless" stripes.

Finally glue these stripes on the front mask as a frame. Use the glue stick.

Step 5: Electronic Components

Components list:

  • 4 blue LEDs with good luminosity and wide beam angle.
  • 100 ohm resistor
  • module for flashing. I used a module with NE555.
  • switch
  • wires
  • clip for 9V battery (I-from)
  • 9V battery

I had only LEDs with narrow beam angle at home, so I used sandpaper for flattening the tip of these LEDs. After this modification light beam angle became wider.

Module for flashing

Flashing period should be around one second.

I made my own module with classical NE555 chip. See sketch in the picture. I also created calculator for astable mode of the NE555 in LibreOffice Calc.

You can also make your own module or you can buy one on eBay or on AliExpress. For example:

Or you can use Arduino. Some people will instantly tell you, that using Arduino only for flashing is an overkill. But you can use Arduino – for whatever you want.

Step 6: Installation of the Partition

First, measure dimensions of a 9V battery. Thickness should be about 17 mm. So partition should be 17 mm deep inside the box, because the battery has the biggest thickness of all components.

Now create a holder for the 9V battery. Cut two cardboard pieces 48×17 mm to create sides of the holder. The back side should be created from a thin paper. The holder should be placed in the middle of the longer side of the box because of balance, because the battery is also the heaviest component. Glue one side to the boundary, then place the battery next to the glued side and glue the second side. Use a hot glue. See in the picture how I made it.

Cut a few pieces of small cardboard exactly 17 mm wide and glue them to the inner boundaries of the partition (see in the picture). This pieces will help you glue the partition into the box to the right deep. Now you can glue the partition to the box.

Make a hole for a switch in the box.

Step 7: Wiring

Do the wiring according to schematic in the picture above. It shouldn't be hard.

After soldering secure in place the components (LEDs, module for flashing, switch) using a hot glue.

Step 8: Finish

And now... Step up to red alert!

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