Bloop Light....

[Michael P Clark]

Does anyone have a Bloop Light they would like to sell TODAY and ship to me overnight? Or a schematic in how to make one? Fast?

Thanks

[cmgoodin]

Bloop light for connection to What?

Most Bloop lights were made to interface to the Nagra IV or 4.2 .  Is that what you are looking for?

They triggered the internal bloop oscillator with a negative voltage (~ 10 V )on one of the pins of the sync connector (4 pin tuchel on the right side of the machine) Pin-outs are in the 4.2 manual and on some face-plates of the machine. you might try Location Sound Corp. and see if they have some old ones they want to let go.

To create one for other equipment means you have to also build the oscillator and a means of triggering it without it running continuously (can bleed into audio) and a method of feeding it into the mix buss of whatever you are hooking it up to without loading it down or interfering with the mix.  Building something like this from scratch overnight may be quite a challenge.

-----Courtney

[Philip Perkins]

I think you could make one with one of those Shure XLR plug oscillators (or the guts of it), a DPDT momentary on pushbutton, a 9v battery or two and an automotive tail light bulb or etc.. (Perhaps a brace of superbright LEDs.)  The button would connect the hot of the oscillator to an audio input at the same time that the lamp would be conencted to the batteries.  I cobbled something like this together on location MANY years ago and we got away with it (shooting 16mm film w/ audio to mag).  The main issue would be packaging this mess in some elegant way, and the fact that you are now working with an additional open input all the time.  CanaKit makes some good very small mic pres and the UK205 mini sine wave generator--if you had time that might be a better bet.  If you are looking for a old-fashioned film-era blooper, be sure you ask if the the unit has its own audio generator in it--most bloop lights had no sound making capability at all--they just triggered the oscillator in the Nagra--useless for other applications.  More sophisticated bloopers from the old days had big LED (or other numeric) displays that you could advance before each slate and perhaps even a slate mic in them as well. 

Good luck

Philip Perkins

[Fernando]

Hi Michael,

http://users.aol.com/fmgp/sync7.htm

I'm about to build myself a bloop, but don't hold your breath, I'm far from fast.

I'll look tonight for some oscillator schematic, etc

There's also the "tone plug" (Trew and Coffey have it I think) but it needs phantom...

There's also those cheap semi-pre-built electronic kits, you can find a function generator but those are usually more complex than needed for this application, but it may be OK since they usually need 9V. So you can add a high intensity LED, an on/off switch and a push switch for LED and tone. The box could be connected to a light weight wireless tx or be wired...

From here you can get a vey simple oscillator and then add the high bright LED and switches:

http://www.cgs.synth.net/modules/psycho_lfo.html

As you see it is a low freq osc for synth use.

Just isolate one of the cells (IC1 C already have a freq control) and change resistor (maybe the cap to -ve too) to get the freq you want (500 Hz is usual for bloop). Use IC2 but eliminate the glide circuit (pot, switch, 2u2 cap) The range pot can be a preset pcb pot and will determine the output amplitude. Read the text for details (CMOS is tied to -ve only, etc)

You can use an op amp that it's fine with + and gnd so you can use one battery.

You should add a cap at the output to eliminate DC offset, since this circuit is for generating control voltages.

This is just an example, a start, but it could work.

some more inspiration from the same source:

Oscillator built around 4046: http://www.cgs.synth.net/modules/cgs31_digital_noise.html (only the upper oscillator = clock) Add an output buffer. It looks like you'll control the base freq of this pll with the cap's value (10n there) and then tune it with the control voltage ("speed" on the schem. Ignore the jack, obv.)

* This one, out of three op amps, may be the right one: (see attached schematic)

Eliminate the LED and both switches. Use the pulse out. AC couple the output. Choose the "range" cap for the right freq (.001uF or smaller?) Symmetry and rate should be pcb trimmers, set and forget. Then add the bloop LED, switches, etc. This one looks good to me. IIRC I even tested it time ago (but on +-15V supply). Be shure to use an op amp that will work with positive supply only and within the voltage you will supply (9V or whatever) typical guitar pedal fx op amps for instance *

Synth circuits usually output 5 or 10 volts peak to peak, so you may have to scale the output...

I think you should buffer the LED to avoid a freq change due to the LED suddenly asking for current, but not too important here. A glissando bloop slate can be fun too =

p.s. this is just an in-a-hurry help out of my archive, check with someone with real electronics skills! If you build something, report back. And have fun

[Michael P Clark]

Wow! OK! That seems more complicated then I had originally imagined. I probably have the wrong idea here, also. I did notice that these were originally used for Nagras and went right into an input. I had a request to have an easy sync solution for a consumer DV camera, that was a "confession cam" with no audio inputs. So my "idea" was to create a "bloop slate" to give a sync option for the camera and a TRX900AA. Since the TRX records at turn on, searching for the actual pieces from the unit could be cumbersome, if the unit was on for some time before the camera rolled. So the tone would be a quick visual guide in the waveforms, and eventually assist in syncing, and the light of course for the camera.

After thinking more after the post I realized the timing is too short to build this in one day. Originally, I thought some light(from a maglight or LED light) that had a push button, that triggered the oscillator, and output the tone to a very small speaker, that could be picked up by the LAV connected to the TRX. Wishful thinking I think. I could've just handed them the sticks from one of those mini DV dumb slates, but thought this might be a smaller easier to handle apparatus. And that might be the best option on such short notice. Or phase syncing the audio with the camera scratch track is the way they will have to go. 

Thank you everyone for your responses. And thank you Fernando for your detailed schematic, I'll be saving that, and mull this over at another time.

Is my idea crazy?

[Philip Perkins]

The simplest thing to do is to tap the mic where the camera can see it--that becomes the clap.  We used bloopers mostly because there WAS no one to handle the slate on film docs, and because the boop was inaudible on the set (only the sound person heard it).  There are disadvantages--like the audio being interrupted by the beep.  On a Nagra one did NOT lose an audio input to use a blooper, since all that was happening was that the blooper triggered the Nagra's own test oscillator.  With any other scenario one has to find an audio input for the bloop.  You can build a simple beep/light flash blooper very easily w/ kit circuits.  The CanaKit stuff is very well made and very cheap.

Philip Perkins CAS