Help with a sound-actived LED

[PerfectNeglect]

I apologize in advance for my ignorance concerning most electronics, but I suppose I have to start somewhere.

I do costume and prop fabrication and I have hit a snag with lighting. I need to install an LED in a helmet that will light when the wearer speaks, but the searches I've tried have only turned up results for larger-scale, music-activated lights. Because I need to fit this into a helmet, I need it to be smaller scale and only need to include one LED in the circuit.

If anyone would be willing to help point me in the right direction with this, it would be very much appreciated.

 

[ericgibbs]

hi PN.
Is the actor already wearing a microphone.?

Throat mic's are available that could be used for the drive to the LED circuitry within the helmet.
What colour LED and light output are you planning to use.?

E

https://www.google.co.uk/search?q=m...oTCIO0ldKZlMgCFYVuFAodbLIJ5w&biw=1434&bih=925

 

[PerfectNeglect]

Hello, E.

No, she isn't-- I suppose I should elaborate just a little more on the helmet. It's enclosed and the LED will be situated almost directly in front of her mouth, so it's likely (maybe) something sound-activated will work. I've considered just yanking the transistor/mic from a sound activated bracelet but I don't really trust it. I'm looking to use the smallest possible microphone (electretc?) since I'm working with limited space inside the helmet, and since I only need to power a single LED, I'm hoping it can be a fairly compact setup. Given the design of the helmet, the mic could be mounted an inch or so away from the wearer's mouth.

The LED will be purple or white, depending. I can tint the colour of the plastic that will be covering the LED, so it's not really imperative that I have any colour other than white.

(And thank you for your time!)

 

[ericgibbs]

hi P,
My!, that helmet is way out.
[reminds me of a girl I used to date]

With a White LED, it has a drive voltage of ~3.3V, so that means at least a 4.5V battery.
That could be achieved by using 3*1,5V AAA's, which would mean a battery holder.
A quick alternative would be a 9V PP3 battery, which could drive two White/Tinted LED's in series for a better light distribution.

The 9V battery could power a electret mic and amplifier, located inside a free space within the helmet.

Do you have a mic' link or type you could post.?

E

BTW: have you considered a possible problem for the 'girl', due to internal light reflection within the helmet visor?

 

[PerfectNeglect]

Haha-- well, it's one of the more interesting pieces I'm working on. It will also have a fan included, but that's something I've done before-- also powered by a 9B battery. Fortunately, the back is covered by the hood and there is space to attach batteries outside of the helmet if need be. The trick is fitting everything up in the front near her mouth. I will probably go with the 9V to power the mic and white LEDs, but I'm not really sure of the type. I haven't worked with them before, but was planning on something like this, unless you don't think it would work? (I believe that's for a phone, but the size is ideal.) I'm also unsure as to what I need to include with it, as far as an amplifier goes.

Fortunately, the light is located "outside" of the helmet. It's situated so the wires and setting will be in the helmet, but the LEDs will be outside of the visor. In the picture, the LEDs will be the small, purplish light in the centre near where a mouth would be. c:

 

[Mikebits]

I was surprised to learn, there is actually a Purple LED. Digi-Key carries them. https://www.digikey.com/product-detail/en/SSL-LX5093VC/67-2064-ND/1842141

 

[Colin]

Buy the sound activated LED kit for a helmet on eBay for $2.00 posted
**broken link removed**

 

[ericgibbs]

hi P,
These are 5mm diameter LED's
https://www.google.com/search?q=5mm...oTCP3am422mcgCFUJGFAod9-AJaQ&biw=1437&bih=925

These are 8mm dia LED's
https://www.google.com/search?q=8mm...oTCP3p4Ki2mcgCFcW3FAod-9UCqQ&biw=1437&bih=925

I would suggest a 'round' LED type as it will make mounting thru the helmet easier.

Choose a High light intensity White type as this will allow a lower operating current and longer battery life.
also if you tint it Violet it should still be bright.

The 'mic' link you posted looks good, the only point needing attention is the 2V at 2K load operation.

Are you able to manufacture the small circuit for the amplifier/LED driver circuit from a circuit design??
or do prefer to buy it ready made.?

E

 

[audioguru]

The cheap kit has nothing to limit the current in its LEDs except a cheap Chinese super heavy duty carbon zinc old battery that is weak. With a good modern 9V alkaline battery then some LEDs will burn out soon and others will look dim depending on the current gain and temperature of the transistors.

 

[PerfectNeglect]

I think I'll go with the 8mm round LED-- since I'm tinting the plastic that will cover the light, white will do fine.

What should I do to address the mic?

Provided I have a design/diagram telling me what goes where, I am capable of wiring and soldering. I've done some motherboard repairs where I replaced capacitors, so I can't imagine this is much different by way of attaching components. It's also something I need to learn how to do so I don't have to bug people for future projects, haha. Also, I'd like to avoid the aforementioned "cheap kits" that may affect the quality of the piece I'm making. I don't want the helmet light janking out halfway through her showcase.

 

[audioguru]

The circuit is that very cheap kit needs a resistor in series with the LED to limit the current so the LED does not burn out.
Since LEDs are available in many colors, I have never tried to tint one. A white LED does not have all the colors in a white light bulb or in white paint, instead it is actually a blue LED with a yellowish phosphor added and it produces very little red so violet will not work.

 

[PerfectNeglect]

Oh, I won't actually be tinting the LED itself, but a translucent plastic panel that will be covering it. It will be working as a gel/filter covering the light. Fortunately, I have access to my theatre's gels/filters and stage lighting has taught me that colouring LEDs can be tricky (so can tungsten light, tbh). As long as the LED is a cool white, we have a magenta tint that should end up quite purple once the light is shone through it. c:

 

[ericgibbs]

hi PN.
I would agree, the kit from eBay looks a poor design.

In order to suggest sources of components, what is you location.?

 

[PerfectNeglect]

Hey!

Ah, I've generally read poor reviews of most of the kits I've seen-- so I think I would feel more confident obtaining components and assembling them myself. I'm in St. Louis, Missouri (USA).

 

[audioguru]

A "cool white" LED has more blue and less of the yellowish phosphor (and hardly any red that is needed) so it would look like dim blue when you use a magenta light filter.
Why not use a purple (violet) LED or red plus blue LEDs?

 

[PerfectNeglect]

Looking at the link for the violet LED posted, I suppose something like that would work-- and remove the need for me to bother with trying to filter the light.

 

[audioguru]

That LED has a narrow viewing angle of only 20 degrees like a spotlight. It makes it appear brighter on axis.

 

[PerfectNeglect]

Ah, well I'm sure I'll find an LED that works.

 

[Mikebits]

If you want, I can put a circuit together for you, I have an idea of how I think I would do it. I was thinking your mic could be input to a comparator which would drive a PWM. The idea would be that the audio would modulate the led intensity so you would have flashing with changing brightness as someone spoke. Then again you might already have something in mind.

 

[audioguru]

I think a linear amplifier should be used with some automatic-gain-control (AGC) so that soft and loud speech controls the LED better than it being turned off or turned on for most of the time.