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Flashing Light Unit

Started by 12thdoctor, May 15, 2009, 09:49 pm

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Apr 14, 2014, 04:10 am #120 Last Edit: Apr 14, 2014, 04:31 am by galacticprobe
Quote from: wayne venomous on Apr 13, 2014, 08:44 am
There's no fading in the circuit as the effect is purely down to the light bulb I'm using!

It's the same with my buoy light flasher: no fader, just the "fading effect" of the bulb's filament warming up and them cooling down. But while it seems fine at night when the buoys are normally lit (unless something goes wrong with their photosensor and they're either always flashing, or never flashing), during daylight that bulb isn't so bright. It's just a 12VDC brake light bulb - bayonet socket - with an extra slotted flange soldered around it to help hold it in place. (Those ocean buoys do bounce around a bit.)

I could still use that flasher unit, though; I just need to throw a power amp together to handle a larger bulb - say something with an old-fashioned 2N3055 power transistor - that can easily handle a 55-60 watt bulb so my light is brighter. (Although, for the moment, that might be excessive for my living room!)

"What's wrong with being childish?! I like being childish." -3rd Doctor, "Terror of the Autons"

wayne venomous

When it's in the lamp housing 60 watts is pretty good and not too overpowering. There is a version using LEDs in a plastic lightbulb I made for a friend's TARDIS that looks ok in the dark but at an event during daylight it's impossible to see.

I know you mentioned you were concerned about the relay clicking in an earlier post - you tend not to hear the clicking when it's accompanied by the TARDIS take off noise!


I would have to check but I'm pretty sure the actual police box roof lamps were fitted with 100 watt.

As for relay clicking, I was in the Crich box doing some internal measurements (this was when the lamp flashed) and the unit which is used to make it flash made a very loud noise. You would definately know there was a call just from the noise it made

I have an exact same unit if you want pictures for interest value. It worked with a massive solenoid and a mega mercury position switch. All very primative compared with what you have there.


Per the 1937 GPO "P.A. 350 System Kiosk Equipt. Layout" plans the top light was a "60 WATT. VACUUM LAMP."

The central hanging interior light was specced as a "100 WATT GAS FILLED LAMP" and the pillar mounted internal flash indicator light was a "40 WATT BLUE LAMP IN PARALLEL WITH 60 WATT FLASHING LAMP."

As the top lamp was for a Fresnel, it looks like the specifications were to indicate a clear non-diffusion-coated bulb with as much a point source as possible - not your standard white incandescent.


Apr 15, 2014, 08:02 am #124 Last Edit: Apr 15, 2014, 08:02 am by galacticprobe
The top lamp bulb could have been a clear glass (white) incandescent bulb. The prisms on the Fresnel lens would have focused the light coming from the bulb making it appear much brighter than if it was inside a plain glass lens. (That's why a simple car brake light bulb can make a buoy light look so bright; the lens focuses the light so 90% of it goes into the "beam", making it more visible. Without those prisms most of the light is lost in all directions.)

"What's wrong with being childish?! I like being childish." -3rd Doctor, "Terror of the Autons"


Apr 15, 2014, 09:29 am #125 Last Edit: Apr 16, 2014, 03:25 am by hb88banzai
The vacuum bulb they specify would indeed have been an incandescent bulb, it's just that it's an older style one. Even the GPO plan's profile of the bulb is of the older type bulb shape. It would just be without all the coatings and extra gases to improve diffusion typical in a standard modern home type bulb (well, now obsolete), which is more the type they are specifying for the inside.

For anyone who's curious, here's a pic of the the Crich electrical board under the desk (photos courtesy of Mark)--


The white box at centre top with "DANGER 250V.A.C." and "G.P.O." on it is the relay mechanism for the top light.

Here it is with the cover open --


Up top is the mercury switch that activates the mains connection to the top bulb (and the parallel blue bulb and alarm bell (if switched on) inside) when it is actuated by the solenoid below when it's energized by an incoming ring.

wayne venomous

Ooh! I love old electro-mechanical stuff, keep it coming!

I'm curious about these GPO plans now.


Ah yes, I knew there was a 100watt somewhere in there, mis remembered.

You got there before me, was just going to put the exact same pictures up (mainly because the flasher unit I have is in the loft).

This would appear to be the later type of lamp flasher unit, the gpo plans show the earlier style which I am certain the Avoncroft Glasgow box still has inside. That version is huge.


Apr 15, 2014, 11:17 am #128 Last Edit: Apr 15, 2014, 11:37 am by hb88banzai
The GPO layout plans are in the Police Box Reference section here - http://tardisbuilders.com/index.php?topic=3280.0.

Here's a picture of Avoncroft's Glasgow Box electrical board (this time courtesy of Starcross) --


I assume it's the skinny (but deep) white box that's marked "Danger 240 Volts"?

For comparison, here's the board and relay as they appear in the GPO plans --


Top view --

Unless it's simply a matter of being mounted in a different way, I'm not sure it's the same as what we can see of the Avoncroft relay, that or I've misidentified it in the photo.


I would agree with you about the relay flasher being the long white thing, and I also agree that it looks nothing like the plans.

I gave definately seen something in the same place as on the plans and the same shape and size inside a police box. Perhaps it wasn't Avoncroft.

From memory (which isn't looking too reliable) the flasher relay was black.


Apr 16, 2014, 05:08 am #130 Last Edit: Apr 16, 2014, 05:16 am by galacticprobe
A mercury switch... Looks like real Met Boxes had an actual "fluid link" in their circuitry!


"What's wrong with being childish?! I like being childish." -3rd Doctor, "Terror of the Autons"


Apr 16, 2014, 09:16 am #131 Last Edit: Apr 16, 2014, 09:19 am by hb88banzai
Yep, they sure did!  ;D

BTW - Looked it up and non-Met boxes which used the P.A.1 lamps (eg, Glasgow) had 100 watt bulbs. Probably about the same output visually as they weren't Fresnels.

So, anybody having to use "fake" Fresnels without actual lens & prisms might have to up the wattage for a similar effect.


Apr 17, 2014, 05:08 am #132 Last Edit: Apr 17, 2014, 05:10 am by galacticprobe
Quote from: hb88banzai on Apr 16, 2014, 09:16 am
BTW - Looked it up and non-Met boxes which used the P.A.1 lamps (eg, Glasgow) had 100 watt bulbs. Probably about the same output visually as they weren't Fresnels.

So, anybody having to use "fake" Fresnels without actual lens & prisms might have to up the wattage for a similar effect.

I think it would depend on the intended use. For a TARDIS living outside (like Scott's and Volpone's, just to mention a couple), definitely; you are competing with the sun for brightness after all and a "pseudo-Fresnel" just won't focus the light without those prisms. In this case you might have to parallel batteries to handle the extra current that a 100 watt bulb draws, especially with the initial "on" surge. Paralleling batteries is easy - two (or more) batteries with all positives connected together and going to one of the bulb's wires, all of the batteries' negatives connected together and going to the bulb's other wire. You just need to worry about getting and wiring up multiple batteries.

But... if your build is a flat-pack one that you take with you to events such as conventions and fund-raisers, where it's always going to be on display inside, then the 60 watt would probably serve well, even without an actual Fresnel lens. Even in indoor lighting you can still see a regular lamp with a 60 watt bulb in it glowing on a table (depending on the lampshade); now put that 60 watt bulb - especially a frosted bulb - inside a pseudo-Fresnel on top of a TARDIS and make it flash. Oh yeah; it will be noticed, especially if it's flashing in concert with the sound of a 'wheezing' TARDIS. (People will home in on that in no time!)

"What's wrong with being childish?! I like being childish." -3rd Doctor, "Terror of the Autons"


Apr 17, 2014, 11:12 am #133 Last Edit: Apr 17, 2014, 11:21 am by hb88banzai

Sometimes even a 40 watt bulb can be quite bright enough for a stage TARDIS, especially if the pseudo-Fresnel is a little less "pseudo".

BTW - In looking at the GPO plans for the PA2 Pillars (which were prepared contemporaneously with those for the Kiosks) the lamp wattages were reversed, with a 100 watt "Vacuum" lamp for the top light and only a 60 watt "Gas Filled" lamp for the top signs and telephone cupboard/phone door sign illumination. The reason for the latter is obvious, because the lamp is so much closer to the signs than it is in a Box, but the top beacon light being higher wattage is interesting. Might be because it is lower to the ground and thus less prominent and/or because the Fresnel is smaller.


Mar 24, 2015, 12:03 am #134 Last Edit: Mar 24, 2015, 12:19 am by warmcanofcoke
Saw this cool video online while researching how to make a Flashing 12volt light.


I know of an Coast Guard Electrician that may be able to shed some light on weather we can make a Tardis Beacon with a system like this.

Ideally I'm hoping we can use one of those batteries that recharges your smart phone through a USB to power a Car Lamp.
why doesn't the Guide mention them? - Oh, it's not very accurate.
Oh? - I'm researching the new edition.