Maplin LED kits - can I run a wire from the board to the LED?

[Jram]

I need to make a prop which looks like a component part of a sophisticated computer system, and the script calls for all sorts of dials and switches, but also for flashing LEDs.

 

I don't know much about electronics, so my (hopefully straightforward) question is, if I buy the kit to make a metronome, a stroboscope, or an electronic die, can I use wires to extend the distance between the board and the LED?

 

I'm not talking by much, but if I was to solder six-inch long wires from the board to the LED would it still work? Because that would let me hide the board within the prop, and run the LED to a hole drilled in the casing.

 

I haven't done physics since 4th year, though I did some soldering (of these very kits) when I did my degree five years ago. Hence why I'd rather make a simple modification to a ready-to-assemble kit rather than try and follow any of Big Clive's various experiments, for example.

 

Advice appreciated, thanks :)

 

Wasn't sure if this should be in Effects & Pyro or Props & Wardrobe instead, sorry.

[gareth]

It'll be absolutely fine - but make sure you keep the polarity of the LED right otherwise they won't work.

[Jram]

Thanks, that much I did know. Thought it'd probably be fine, but since the budget is made entirely of money thrown in by friends I thought it best to check :)

[boatman]

To simulate a computer thingy you need something more random than any of those. There's a random LED flasher circuit on my website here. Go to the "WWRY Mind Control Helmets->Hardware" page. If you need any more info send me a PM.

[Jram]

Thanks for that, will bear it in mind - still waiting for the director to decide on the design, but the LEDs part is in the script.

[p.k.roberts]

An easier solution might be to just buy a bunch of flashing LEDs - available from CPC or loads on eBay.

[boswell]

An easier solution might be to just buy a bunch of flashing LEDs - available from CPC or loads on eBay.

That's the easiest, quickest & cheapest idea, true random. Wire all in parallel with individual limiting resisters off a couple of AA batts to give 3V.

Buy different colours.

[Jram]

Wire all in parallel with individual limiting resistors off a couple of AA batts to give 3V.

 

Bear with me here, like I said it's a while since I've done anything like this (I'm a carpenter/props dresser to trade)...

 

If I have 5 LEDs, say, I solder a resistor to each positive wire, then solder all five wires as one to the positive terminal of the battery holder, and solder five wires as one to the negative terminal, each one leading to the negative wire of an LED? That seems simple enough... I've watched a couple of youtube videos which link to resistance calculators based on the spec of the LEDs, so that should do the maths part for me...

 

Is there a limit to how many LEDs I can run from 2xAA batteries? Of course there is, but can I run ten, for example?

 

Will they all flash on/off at the same time? Or will some flash on while others are off?

 

I realise this is probably really basic stuff, but it's 13 years since I did my Standard Grade Physics, and I barely did any electrics during my degree apart from the required classes.

[musht]

Yup, resistor per LED for preference, wored as you describe.

 

Tin the leg of the LED and tin wire or resistor leg seperatly, then apply two tinned surfaces , apply heat, joint done, slip heatshrink on to taste.

 

2 AA batteries will limit you to red/amber/yellow LEDs, white, blue and bright green will need 3 off AAs for higher voltage.

 

Run time even for dozens of flashing LEDs on AA alakaline is probably measured in weeks, they don`t pull a lot and duty cycle is low.

 

They may start out flashing the same but will drift in and out of sequence, can get more flashing by wiring a normal LED in paralell to the flasher, it will light when the flasher is off.

[Junior8]

Cor this rakes me back. I had to do a similar thing in 1974 and used Uniselectors and ex GPO exchange relays (available in vast quantities for almost nothing back then) to arrays of miniature neons. It looked good but by heck didn't it make a row!

[boatman]

Yup, resistor per LED for preference, wored as you describe.

 

Tin the leg of the LED and tin wire or resistor leg seperatly, then apply two tinned surfaces , apply heat, joint done, slip heatshrink on to taste.

 

2 AA batteries will limit you to red/amber/yellow LEDs, white, blue and bright green will need 3 off AAs for higher voltage.

 

Run time even for dozens of flashing LEDs on AA alakaline is probably measured in weeks, they don`t pull a lot and duty cycle is low.

 

They may start out flashing the same but will drift in and out of sequence, can get more flashing by wiring a normal LED in paralell to the flasher, it will light when the flasher is off.

 

Sorry but that is wrong. Flashing LEDs will operate from any voltage between 3.5V and 14V and do not require a limiting resistor. However the optimum operating voltage is 5V so 4 off rechargeable AA cells will do the trick. Be aware that each one will draw around 25mA so you'll get about 10 hours from four 2000mAH cells with eight LEDs in parallel.

[timsabre]

I had a curious experience trying to do exactly this with flashing LEDs - they all flashed together. I would have expected them to gradually go out of time with each other but they didn't.

 

The only way I could get them to flash at different times was to use several different sets of batteries. I can only think the slight variation in the battery voltage as the leds came on and off was enough to trigger the flashing circuit to start.

[musht]

Flashing LEDs come from a variety of makers with some variety in operation.

 

Not all wont turn into a DED, Dark Emitting Diode, without a resistor.

 

Maplin`s `typical ` 5mm flasher

 

http://www.maplin.co.uk/Module.aspx?ModuleNo=220131

 

Operating voltage: DC 3-10V

 

They will go pop on 14V, or close to on a typical car battery voltrage without some resistance in line.

 

Guess the 5V optimum voltage is for the particular LED you used, it does pay to read the data sheet on the exact example being used.

 

>>will draw around 25mA so you'll get about 10 hours from four 2000mAH cells with eight LEDs in parallel.

 

If the duty cycle was 100% , which it isn`t , if they were dissipting 25mA when off, they would rapidly melt. On time is a specifiable variable on some flashers.

 

From some experience over several years , would expect several weeks from a handful of flashers on 4 2000+ mAh batteries.

[musht]

Teach myself to read some recent data sheets, apologies to Boatman , wider range of blinking LEDs nowadays:

 

Prettiest, available in green and blue, white typically for Rapid on backorder:

 

http://www.rapidonline.com/productinfo.asp...kw=flashing+led

 

Wired in paralell no resistor per LED but slight catch is rated at 5V, absolute max 6V, 4 fresh alkaline cells may exceed 6V, 3 may drop out below operating voltage.

 

Solution may be to use a 5V regulator, 3 additional components, regulator and 2 small capacitors between legs, will run a string of paralell connected LEDs,.

 

For few LEDs and long run time LP2950

 

http://www.rapidonline.com/Electronic-Comp...kw/5v+regulator

 

More LEDs , mebbe LM2940

 

http://www.rapidonline.com/Electronic-Comp...or-LM2940/29677

 

For car battery level voltage now a couple of 14V rated blinkers;

 

http://www.rapidonline.com/Electronic-Comp...kw/flashing+led

 

For the press button and lights come on effect, Rapid have this

 

http://www.rapidonline.com/Educational-Pro...kw/flashing+led

 

but it times out after 15 secs, the 6 LED module that keeps going....is on backorder.

[Jram]

Thanks very much for all your help and advice. I think we could all have safely predicted that the director would change his mind, so while this has all been very useful to read/learn about, I'm now instead looking for c.200mm battery-operated striplights to be encased in a mesh or clear perspex cylinder.

 

Might still incorporate some LEDs elsewhere, there are a couple other hero props to be built...

 

Thanks again :D