In search of a meter movement

Contrary to rumors to the contrary, Usenet is alive and well.

What distance?

I used to deal with theater applause meters in the 1960's. Something like this, but not quite so big (and ugly): They were huge meters, about 4x6ft large, with an indicator arm that probably weighted several pounds. The devices didn't use a standard meter movement. It used a geared motor fighting a spiral spring. The more power applied to the motor, the more it would compress the spring and move indicator. The motor would complain, sometimes get hot, but since the applause was not continuously present, it had time to cool down.

Most cheap automotive gauges are thermal gauges. That provides damping and vibration proofing. They're also dirt cheap. Tachometers that need to move rapidly use a taut band variation on the D'Arsonval meter. A jeweled bearing D'Arsonval movement wouldn't last a month in a vehicle.

In some places, but not all. D'Arsonval, taut band, thermal (bimetallic), electrodynamic, moving vane, thermocouple, piezo, etc.

50ua FS for the better meters. Moving mirror galvanometers will to maybe 5ua full scale.

Yep. I even got paid to play with them. Maybe if you supplied some numbers (i.e. distance, size, cost, etc), it might be possible to offer some sane suggestions?

Ok, enough nonsense. I have two suggestions:

1. Use a virtual meter. Yes, it requires a computah and LCD screen, but those are quite common and amazingly cheap. You can also do it with a SBC (single board computer). On the LCD screen is your meter. The audio goes into the sound card of the computah. If you need a monster meter, use a projection display. If an LCD screen is big enough, commandeer a hotel TV set.

1. Use a moving mirror. The deflection of the mirror will move a reflected light beam across the wall or ceiling. The amount of movement is proportional to the amplitude. The major problem will be damping the mirror so that it doesn't "ring" or move like sludge.

I doubt if you can find a large enough panel meter to be seen clearly across a room. I have several pieces of antique test equipment with maybe 12" meters. That's about as big as they get. The problem is that the indicator arm is rather thin and light by necessity, and therefore difficult to see.

--
Jeff Liebermann     jeffl@cruzio.com 
150 Felker St #D    http://www.LearnByDestroying.com 
Santa Cruz CA 95060 http://802.11junk.com 
Skype: JeffLiebermann     AE6KS    831-336-2558

I built an LED VU meter years ago. Like 5 green LED's, followed by 2 yellow LED's, followed by 3 red LED's, with them lighting sequentially with volume level, green to red, fluctuating with the level. Theoretically, one of these could be any size you want. I'm sure if you do some searching on LED VU meters, you'll find something.

Dan

That would be an LM3916 IC:

--
Jeff Liebermann     jeffl@cruzio.com 
150 Felker St #D    http://www.LearnByDestroying.com 
Santa Cruz CA 95060 http://802.11junk.com 
Skype: JeffLiebermann     AE6KS    831-336-2558

Dual LCD VU meters: The LCD meters are 4x5" and $50/ea. Probably not big enough to see across a room, but still interesting.

--
Jeff Liebermann     jeffl@cruzio.com 
150 Felker St #D    http://www.LearnByDestroying.com 
Santa Cruz CA 95060 http://802.11junk.com 
Skype: JeffLiebermann     AE6KS    831-336-2558

I hear you Jeff. I know the LM dot/bar chips too. All these things require another power supply to run them. I'm after something "self-propelled" .

The ideal situation is to take the 200 W, Step it up to 1,000,000 V and use the spearing arc to get the barman to turn things down a notch.

Reverting: Just looking at some E-diagrams for these car tacho's, some seem to have a double winding as a designate sine/cosine measurement from the chips. This implies we are still ultimately at an analog system.

Oh, as far as a deaf and blind barman can manage. About 10 ft max -) It would be within the bar area domain i.e. not for customer viewing.

Motorised is a slight overkill -) I'm thinking of using the Pwr-Amp output suitably rectified and damped.

Pretty much car dashboard size will be OK. Perhaps no more than 3" dia. They can occasionally wander over to inspect the audio level after being beaten by a whip (if they ever cared enough)

No, no, no. Its a pub not a disco. -)

Yep. There are kits out there and I could do the same. Two (three ?) things working against that.

1. Keeping a constant E/I supply to the displaying/sensing device which would probably be needed at low power levels. Easy to drain a watt or less at hi-levels (max 200 power amp)
2. Lights get 'missed' in a well lit area.
3. Cost. They won't come at things that cost money (gee. surprise).

A rechargeable with bridge rectifier and some kohmish droppers from the speaker line?

kohm values from some knowledge of what the pub's normal audio power throughput is

When the team hits on a device , my pub could do with one. Amp and controls in a sideroom with not even a monitor speaker in that room. Why is it beyond management to put stickers on the volume control scale with numbers of people in the bar comensurate with speaker audio levels and not the usual meaningless 0 to 10 numbers.

step up transformer of some kind?

Jamie

Make it big and easily visible and you have a way of keeping the noise level down in the bar. Calibrate it in SPL units and label it from whisper to threshold of pain. I just hate shouting over the music and the crowd.

You could also program in an upper limit threshold switch. When the bar noise level reaches the equivalent of a jet engine on takeoff, it automatically turns off the music and the house lights. Claim it's a power failure if anyone asks. The noise will subside as everyone looks around for what happened. A few seconds later, the power comes back on and life continues as before. Do it often enough, and the crowd will be trained not to yell so much.

--
Jeff Liebermann     jeffl@cruzio.com 
150 Felker St #D    http://www.LearnByDestroying.com 
Santa Cruz CA 95060 http://802.11junk.com 
Skype: JeffLiebermann     AE6KS    831-336-2558

That's an extremely BAD suggestion. First thing that's gonna happen is that the lawyers will descend on him with injury lawsuits and he'll be out of a bar.

Claim it's a

_highlighting FREE 831-336-2558

LOL

GM used to use balanced movements in gauges like that. DC on one coil, signal on the other. That allowed them to stay accurate, even with a low battery.

I am building a LCD level meter, and when the signal gets too high it will cause the monitor output to clip. The same circuit could be used to drive the main amp. Another approach would be to use the last two levels to reduce the amp output by 6 or 12 dB, so if it's dropping as they turn it up (or clipping if they are on the edge) they will back it off.

Already got that facility. It's called thermal overload protection system. It works too. Amazing the panic it causes when there's silence and they find they don't uderstand the problem and where it lies -)

No. Doubt it. This is the sort of thing I'm stumbling across.

Sort of implies a highly idiosyncratic measurement system and, at the least, a specialised meter movement.

Oh, you're no fun. If it turns into a litigatory exercise, just tell the judge that the music system blew the circuit breaker and that it took a few seconds/minutes to reset it. It's always best to have plausible denial prepared before doing anything risky.

However, it is possible that some patron in the noisy bar will complain from hearing damage. To prepare for that litigatory event, the bar should place signs indicating: "Yelling above 90dB (0.1Pa) prohibited" along with SPL bar chart and OSHA web site URL. If someone claims that their hearing was damaged, and that the bar did not take sufficient precautions to prevent hearing damage, then the sign should provide sufficient evidence of informed consent by the patrons to be bombarded with high noise levels. As an extra bonus, it might be useful too record the sound levels on a strip chart recorder for later use as evidence.

--
Jeff Liebermann     jeffl@cruzio.com 
150 Felker St #D    http://www.LearnByDestroying.com 
Santa Cruz CA 95060 http://802.11junk.com 
Skype: JeffLiebermann     AE6KS    831-336-2558

Here's a kit, ready to play:

You have heard of batteries? The problem is lighting up a mess of LED's is going to burn some power. If you must, point some solar cells at the room lighting and use that to charge the battery. Oh wait, it's a bar, where the lights are always dim.

Ok, all mechanical and no electronics. Take a large ring with a diaphragm stretched across the ring. Find a mechanical barometer and tear it apart. Remove the pressure chamber and connect the actuator arm to the center of the large drum. Add a bit of fluid damping by submerging the mechanism in thin oil (5-10wt). When the sound pressure in the room moves the drum slightly, the barometer mechanism will indicate the peaks. Patent pending...

--
Jeff Liebermann     jeffl@cruzio.com 
150 Felker St #D    http://www.LearnByDestroying.com 
Santa Cruz CA 95060 http://802.11junk.com 
Skype: JeffLiebermann     AE6KS    831-336-2558

. That's it. Sheer genius! A single 2" loudspeaker clamped to the back of a barometer. Speaker cone has a pressure valve fitted.