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Flashing Light Unit

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

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galacticprobe

Feb 23, 2010, 02:34 am #30 Last Edit: Feb 23, 2010, 03:46 am by galacticprobe
Darth,

  The fading in and out (presumably of the light - still working on getting the "blue box" to do that!) is a characteristic of the incandescent bulb (standard light bulb). It's caused by the filament heating up to emit the light, then cooling down when the light goes out. LEDs don't have this without some sort of RC (in this case, resistive-capacitive) circuit to build up, hold, and discharge the voltage used to light the LED. (My electronics background showing there.) Think of the difference in those road-side flashing yellow lights; ones that are clearly LEDs are just ON, and OFF, while the older models that still use bulbs have that bit of fade on and off.

  The original lamp was no doubt a standard bulb, and it was probably "flashed" by either someone inside the Tardis prop or someone working the sfx off camera; probably most incarnations of the Tardis used an ordinary bulb in the lamp. The fade on/off effect was also probably a factor of the medium used for the filming (film vs. video tape), plus whatever they call what happens in the [humanoid] eye as the light enters, hits the retina and builds up to what the brain recognizes and sees, then holds the image of the light for a second after it's gone. (OK... enough of the ocular guesswork.)

  That said, any bright bulb should provide the natural fading you're looking for. (Side note: The scanning lights on the original '82 Trans Am KITT from "Knight Rider" had a trailing effect that the usual replica scanners don't, and that's because the original scanner used 12 volt, 55 Watt halogens for its bulbs, which had a natural fading.) So maybe that would be one way to go if you're using a battery-type power source for the light: a 12V 55W halogen. Just make sure your flasher circuit has the power transister to drive it.

Just some thoughts... does any of this help?

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

DarthMoose74

Thanks for that info but I was asking more about the circuit that makes the bulb go on and off or the  circuit that makes the LEDs fade instead of blink in everyone's Tardis lamp. I am sure all the builders here have come up with a variety of ways they make their own do it and I was hoping a few would post their ideas here. (I did not see a thread about it anywhere.)

PS My friend has a KITT car :D

anotherwheeze

Jun 04, 2008, 02:22 pm #32 Last Edit: Feb 23, 2010, 09:13 am by scarfwearer
I went down the 12vdc route using a 10 amp bench transformer, 55w car headlight bulb and...

http://www.maplin.co.uk/Module.aspx?ModuleNo=25224&doy=4m6&C=SO&U=strat15

This is a self-build board, and only takes 10 mins to build. You can fully adjust the on/off frequency.

I have worked with bench transformers for years, and although you are not technically supposed to power a bulb with one, as long as the transformer can handle the load (one headlight bulb @ 3.8 amps @ 13.8v DC), you are working within very safe parameters.

Very happy with the result myself, as the high resistance of the bulb creates a fade on/off effect.

I decided to go down this route, although expensive, because my lamp housing is also a vent, so a very slim possibility of rain getting inside should I ever experience horizontal rain. I have incorporated a small drip rail to minimize the possibility, but you never know, do you?

As my TARDIS is used by my children, I wanted everything to be as safe as possible to include:

Consumer unit with 30ma RCD
4 x 30w 230v AC fluorescent tubes for the signs
2 x 10w 230v AC       "              "     for the pull to open sign
4 x 60 LED Blue strip lights - 230v AC
2 x 20w by four Halogen strip lights - 230v AC

Fully waterproof internal switches.

And finally, the now very poplar remote control activation/deactivation of the above items, together with demat sound effects.



chriskingbees

Jun 04, 2008, 08:43 pm #33 Last Edit: Feb 23, 2010, 09:13 am by scarfwearer
And a teriffic job it all does too! :)
KB

anotherwheeze

Jun 04, 2008, 09:01 pm #34 Last Edit: Feb 23, 2010, 09:13 am by scarfwearer
Quote from: chriskingbees board=manual thread=771 post=14195 time=1212612207And a teriffic job it all does too! :)
KB


Why thank you kind sir  :)

throgmorton

Jun 10, 2008, 04:34 pm #35 Last Edit: Feb 23, 2010, 09:14 am by scarfwearer
I have just been and bought me self one of these timers kits and have duly soldered it together.

I am going to be using it in my Rainy City 1/3 scale build.
Can anybody suggest what spec' bulb to get and what fitting?

Its going to have to be smallish to fit in my 'fresnel' and obiviously not to bright?

Thank you,
Chris E.

anotherwheeze

Jun 10, 2008, 07:19 pm #36 Last Edit: Feb 23, 2010, 09:14 am by scarfwearer
Do you have the dimensions of your lens? I'll figure something out from that (hopefully!!)

Sorry, I didn't realise you were working on a scaled down model.

throgmorton

Jun 13, 2008, 12:22 am #37 Last Edit: Feb 23, 2010, 09:15 am by scarfwearer
Quote from: anotherwheeze board=manual thread=771 post=14286 time=1213125574Do you have the dimensions of your lens? I'll figure something out from that (hopefully!!)

Sorry, I didn't realise you were working on a scaled down model.



Thanks for the help its really appreciated heres the Dim's for the light I'm using on the Rainy City TARDIS.

Approx 3.5 inches X 1.75 inches.

In that 'FUNNY MONEY' stuff  ;) 90cm x 45cm.

I may at a future date alter the fresnel to something more accurate but the light lense I have at the moment does look O. K.

Heres a pic of the old girl showing the light.
The sizes I have quoted above have taken in to account that I am going to chop off half an inch of its length to make it look more acceptable and of course it will be topped with a square piece of MDF to match the bottom of the light with 4 pieces of dowel too.

th_DSC00269.jpg

Chris E.

anotherwheeze

Jun 13, 2008, 08:08 pm #38 Last Edit: Feb 23, 2010, 09:15 am by scarfwearer
WOW!!  :D

What a fantastic model. I wish I had the patience to have a go at something like this.

I take my hat off to you and everyone else for making something so beautiful and intricate. I wish my sausage fingers would work on something as detailed at that - I can only do big stuff  :-[

Anyway, bulbs...

...try a 501 capless automotive bulb. This is 12vdc (very small) and rated at 5w.

There is a company called Durite that can provide the connectors for it - you are talking pence for the bulb and holder.

You can fashion a holder up yourself as the contacts are only small wire, just like on a Christmas tree  light.

I do believe that there is a 501 fitment LED, although with LED you will not have the fade on/off effect.

I assume you got the Maplin board like on the link above?

Rox

Aug 21, 2008, 07:10 pm #39 Last Edit: Feb 23, 2010, 09:15 am by scarfwearer
Quote from: anotherwheeze board=manual thread=771
And finally, the now very poplar remote control activation/deactivation of the above items, together with demat sound effects.


What would you recommend for mine?  I'm looking at the flashing on/off and sound effects.. any tips for the completely novice builder?

Lightwise, I'm just going to install a very bright bulb in there, and I have some outdoor gazebo lights for the lightboxes.
My pilot's license? That's out back in the Cessna. Or perhaps you're referring to my license to kill. Revoked. Trouble at the Kazakhstan border.

I could give you the details but then I'd have to kill you, which I can't do because my license to kill has been revoked.

zbigniev hamson

Aug 21, 2008, 09:40 pm #40 Last Edit: Feb 23, 2010, 09:16 am by scarfwearer
With my model I'm just going to be using a 3V bulb that has a bimetallic strip to make it flash automatically. If I don't like that then I will just build a circuit we were taught at school, amusingly called an "astable multivibrator", but I've also seen it called a flip-flop circuit.

I'm sure this is of no use to anyone here, I just thought I'd mention it :)

atomicgraph

Aug 22, 2008, 02:55 am #41 Last Edit: Feb 23, 2010, 09:16 am by scarfwearer
don't know if this is something that has been tried but maybe you can use an old strobe light. i have one somewhere and i was gonna use that to get the flashing the one i have has a knob that you can use to set the timing.... just have to find it  ::)

throgmorton

Oct 10, 2008, 12:48 am #42 Last Edit: Feb 23, 2010, 09:16 am by scarfwearer
well I have finally wired the circuit Maplins/Velleman circuit and guess what it dont work!!

The led flashes the relay clicks I can get the click and the flash of the LED to alter using the the two pot's. I get varying impedances at the output but no voltage. ???

I think my solderings  O. K. there doesnt seem to be any visible probs like dry joints etc.

Any clues anyone?
The other option I suppose is to buy one ready built but does anywhere do them like that?

Maplins only seem to do the kit.

Chris E.

Scarfwearer

Oct 10, 2008, 10:08 am #43 Last Edit: Feb 23, 2010, 09:16 am by scarfwearer
Quote from: throgmorton board=manual thread=771 post=17370 time=1223599730well I have finally wired the circuit Maplins/Velleman circuit and guess what it dont work!!

The led flashes the relay clicks I can get the click and the flash of the LED to alter using the the two pot's. I get varying impedances at the output but no voltage. ???

I think my solderings  O. K. there doesnt seem to be any visible probs like dry joints etc.

Any clues anyone?
The other option I suppose is to buy one ready built but does anywhere do them like that?

Maplins only seem to do the kit.

Chris E.

Most likely one of the components is connected the wrong way around e.g. a diode or one of the multi-pin components. It's happened to me before in other situations. Hopefully nothing's fried. I'd check orientations working back from where you want the voltage, as it's clearly partly working.
Having said this, I'm no electronics wiz - if this doesn't fix it I refer you to someone more knowledgeable than I.

Crispin

Rox

Oct 10, 2008, 03:22 pm #44 Last Edit: Feb 23, 2010, 09:17 am by scarfwearer
Now then, my friend who soldered mine said he thought the kit was very flimsy, and he had to resolder several parts because the tracks on the circuit board kept cracking and breaking [he replaced some tracks with wires instead].  You might need to check that none of the tracks have broken or lifted. 
My pilot's license? That's out back in the Cessna. Or perhaps you're referring to my license to kill. Revoked. Trouble at the Kazakhstan border.

I could give you the details but then I'd have to kill you, which I can't do because my license to kill has been revoked.