Pro Audio Design Forum

I haven't messed with a strobe light since the 60's and that one used a gas filled (xenon?) flash lamp. As i recall a cap was charged to a higher voltage then discharged through the tube.

My present idea is to sync up a strobe light to my drum tuner so I can actually see the standing waves in the drumhead. I hooked up a red LED that was synchronized to the sine wave exciting the drumhead but it didn't make enough light to see anything.

I've got some white LEDs on order so I'll see if they get bright enough. I can pulse them momentarily with as much as 100mA which won't be good for battery life but may get bright enough to see something.

I don't know yet whether this will be useful or just another stupid electronic trick, we'll see. I don't expect the drumhead excursion to be very large so it may be hard to see even with a good strobe index. I'll probably provide the capability to vary the phase of the strobe so I can look for the changes.

JR

I would think that having visual feedback in that application could make a large difference in how easy it is (for some people) to get consistent results. Very interesting idea.

I already measure the phase of the standing wave using the audio return far more precisely than one could eyeball it, but this will make a cool show and tell if it works...

I'm not sure the amplitude of the vibrating drumhead is large enough to see easily.

Got my parts in today so I'll find out soon enough, If it works I'll make a video.

JR

What about a strobed laser pointer?

Some of the flash LEDs used in smartphones are really, really bright.

Not having ever tuned a set of drums I can't say how uesful it would be but I know it would look very cool.

I'm getting some decent light off a pair of LEDs... I just figured out why my strobe looked slow, because it was...

I was syncing the strobe to my synchronous detection but that actually under samples at a slower than real time rate, so my strobe was a sub fraction of the actual note pitch.

Time to sync the stobe to my sine wave generator.

That won't be as easy since I don't have a lot of processor time left over to crunch data during the sine wave generator interrupts.

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Thanks wayne that camera flash sounds like the perfect part for this... I looked at the lamp inside a small flashlight and it is running at 500mA continuous. The LEDs I have are spec'd 100mA peak... If this looks promising I will try to find that part.

I am not running my LEDs up to 100 mA yet... So still more light available, but first I need to get them running up to correct speed.

Almost time to go cut my grass...

I'll report back later.. thanx

JR

OK, easier than I thought to get it synchronized to actual sine.. but now it's not very bright because of short dwell... If I increase the dwell it smears the strobe effect, so time to amp up the LED current

more later...

I like the basic idea.

Well round one and my first pass has been found lacking. With the LEDs LEDs pushed up their published 100 mA peak, the very narrow pulse is insufficient to make enough light. If i leave it turned on longer I can get more light but the strobe effect will be imprecise.

Doing some more research there is a whole class of high power LEDs that are rated for more like 1 to 2A peak, not 100 mA and should make a lot more light.

http://www.philipslumileds.com/uploads/354/DS103-pdf

These puppies are serious, ceramic substrate, huge thermal pad, but can take 1.4A pulses...

oh well back to the drawing board...

I may need to draw up some lines on the drumhead to make it easier to see the patterns.

JR

John -

The lumileds may just be the ticket. What about a laser line generator like those used on power tools that is strobed? Do you need to illuminate the whole drum head?

The flash "assist light" on my Samsung Smartphone is very bright. I have to wonder if camera flash LEDs use lower persistence phosphors.

Go to Home Depot and buy one of the Malibu white outdoor LED uplights and use the engine out of it: http://www.homedepot.com/p/Malibu-Low-V ... 96538?N=yh

It's got two die mounted on a ~1" ceramic substrate.

mediatechnology wrote:John -

The lumileds may just be the ticket. What about a laser line generator like those used on power tools that is strobed? Do you need to illuminate the whole drum head?

A laser line would be cool if low and parallel to the drumhead so you could see the standing wave intercept the laser... Not sure how to use that effectively but another good idea to chew on.

The flash "assist light" on my Samsung Smartphone is very bright. I have to wonder if camera flash LEDs use lower persistence phosphors.

It appears the camera phones have two modes, a strobe at full peak current, and "torch" for shooting videos that run at lower but steady current. How much persistence can there be in the LED phosphor? It doesn't hurt the flash application but i don't want to stretch the light for strobes. I guess different colors require different tricks to make the perfect color.

Go to Home Depot and buy one of the Malibu white outdoor LED uplights and use the engine out of it: http://www.homedepot.com/p/Malibu-Low-V ... 96538?N=yh

It's got two die mounted on a ~1" ceramic substrate.

I'll check it out... I can buy the 1A LEDs for $4 and change.

I have a small LED flashlight running 500mA from 2xAA batteries. I might try switching that. To see how bright it remains. It is bright as hell on steady.

From my searches it looks like the flash LEDSs are on high temp substrates and heat sinking. There are also dedicated switching PS to boost 3V up to enough to make a flash.

In hindsight I don't have to have white LEDs, red leds would work if bright and fast enough.

I need to soak this in some beer and think about it.

THanx...

JR

After my ethyl assisted review, it looks like I would need to build up a PCB to use the $4 LED chips to properly heat sink them so I need to first prove or disprove the general concept before doing specific production type engineering.

Homedepot website didn't have any of those flood lights in stock and closest depot with stock is a couple hour drive round trip, but I found one on the web in CA so shipping will cost me more than the lamp, but we'll see if that gets bright enough, If I have to I can generate a 100V PS and strobe some big LED light bulbs. just to test the concept.

So project back on hold for now... waiting on parts

I may need to review my mosfet switch.. it's OK for low voltage (600mA continuous, 8A pulsed) but only 60v so no 120v lamps..

JR

[edit] I also ordered a cheap DJ strobe light, looks LED based. [/edit]

[edit2] I'm not sure what to make of this, but I found a restock cheap DJ strobe for like $10, so the DJ gear is a lot cheaper than yard lights. I'm guessing the fact that the are selling re-stock means they have lots of returns so we'll see what i get for $10... [/edit2]