Conventional Fixtures LED Replacement bulb for our strip/par cans

[Bsancken]

Hi, our theater tried some led bulb replacements for out incandescent ones in our strip lights and they were great in color except for when they got down to about %20 and they all started flickering randomly.

The bulbs we tried were Polaroid 1600-Lumen 120-Watt equ.
PAR38 LED Bulb PLPAR38W-120.1600.23.7d
Dimmable

They got them returned, but were still wanting a replacement as long as it wasn't excessively expensive. (they paid about $26 a bulb, so in that ball park if possible)

Thanks

 

[robartsd]

One of the problems with switching to LED is that it is very difficult to get smooth dimming at the low end. In LED fixtures, the dimming curve is improved by the control electronics; but this is not easily accomplished (perhaps not possible) in an LED lamp intended as an incandescent replacement. The LED fixture has the advantage of clean power and a control signal; the replacement lamps only have chopped up input power to work with. With some dimmers, a ghost load helps and might be worth a try, but it would likely only improve the situation so that the flickering starts at a lower level - not eliminate the flickering altogether.

 

[Bsancken]

One of the problems with switching to LED is that it is very difficult to get smooth dimming at the low end. In LED fixtures, the dimming curve is improved by the control electronics; but this is not easily accomplished (perhaps not possible) in an LED lamp intended as an incandescent replacement. The LED fixture has the advantage of clean power and a control signal; the replacement lamps only have chopped up input power to work with. With some dimmers, a ghost load helps and might be worth a try, but it would likely only improve the situation so that the flickering starts at a lower level - not eliminate the flickering altogether.

Ok, thanks that makes sense, but would there possibly be anything that would help by the way of changing the dimming curves in the console?
Like getting the lowest possible level before they flicker then having the console take them out completely?
Thanks!

 

[dbaxter]

A "dimmable" replacement led is always going to drop out if you try to go below 10-15%. Inside the bulb is a small circuit power supply to provide the led with the 4 or so volts it wants to run. The "dimming" is either by limiting the current or chopping the voltage (% of On time). You will always get a snap-on or snap-off if you try to run them from your console. The good DMX controlled lights have a constant power supply and mitigate the low end snap by driving the led at a high frequency. Well, higher than 60Hz anyway. I beleive it's around 400Hz to fool the eye.

 

[JD]

Unless there is a second source of power, the supply and control inside the LED assembly will collapse once the voltage is low enough. There is no way around this. On a stand-alone DMX controlled lamp, the power supply and control circuits are always in operation, so a good fixture can chop the waveform at a high frequency all the way down to .5%, which is the limit for 8 bit DMX. (Note, I said "good fixture" as there are plenty that don't!) Technically, a 16 bit control could bring the lowest level down to 1/64,000th of the highest level.
These options are simply not available for a screw in replacement. The best I have personally seen are the TCP lamps, which get down to about 5% before winking out.

 

[derekleffew]

the supply and control inside the LED assembly will collapse once the voltage is low enough. There is no way around this.

Why hasn't any LED manufacturer figured out the minimum voltage for the power supply and then simply adjusted the output to be zero at that voltage? Thus 10VAC (let's say) is zero and 120VAC is full?

How does the Chauvet Ovation do it?

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[RickR]

I'm guessing there has to be a dead zone in the curve. 0-5%-ish gives no light then you ramp up in a smooth curve. After all incandescents take considerable voltage to get hot enough to glow.

Now imagine the wave form from a dimmer at 5%!

 

[BillConnerFASTC]

Why hasn't any LED manufacturer figured out the minimum voltage for the power supply and then simply adjusted the output to be zero at that voltage? Thus 10VAC (let's say) is zero and 120VAC is full?

How does the Chauvet Ovation do it?

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Market too small and that really only works logically when you have profiles in a console. If they could make money on it, they would. Plus seemed I saw something like that at LDI in a high wattage replacement lamp. Not sure it came to market.

 

[Bubby4j]

Unless there is a second source of power, the supply and control inside the LED assembly will collapse once the voltage is low enough. There is no way around this. On a stand-alone DMX controlled lamp, the power supply and control circuits are always in operation, so a good fixture can chop the waveform at a high frequency all the way down to .5%, which is the limit for 8 bit DMX. (Note, I said "good fixture" as there are plenty that don't!) Technically, a 16 bit control could bring the lowest level down to 1/64,000th of the highest level.
These options are simply not available for a screw in replacement. The best I have personally seen are the TCP lamps, which get down to about 5% before winking out.

1/65,535th. (2^16, 2 means bits, 16 means how many of them. Subtract 1 to start at 0 instead of 1.) Incidentally this is also the highest port that can be used on the internet, port 65535.

 

[robartsd]

Why hasn't any LED manufacturer figured out the minimum voltage for the power supply and then simply adjusted the output to be zero at that voltage? Thus 10VAC (let's say) is zero and 120VAC is full?

How does the Chauvet Ovation do it?

The Ovation must have a pretty special power supply. Not only is it not damaged by the choppy power (the reason not to put normal LEDs & Moving Lights on dimmer parked at full), it can function well on it. I imagine that there is a fair bit of capacitance in the power supply circuit to help smooth out the choppy voltage.

 

[Jay Ashworth]

1/65,535th. (2^16, 2 means bits, 16 means how many of them. Subtract 1 to start at 0 instead of 1.) Incidentally this is also the highest port that can be used on the internet, port 65535.

Don't tell screenwriters that...

# ssh 192.324.21.22

 

[robartsd]

Don't tell screenwriters that...

# ssh 192.324.21.22

I don't quite get your message. Perhaps you're confusing address and port. The highest address for a host (for IP v4) is 32 bits, the port is used to identify different services on the host (ie port 80 is typically used for HTTP). IP v6 (did they just skip 5?) addresses are 128 bits.

 

[Jay Ashworth]

Screenwriters (or production designers) are prone to specify 'impossible' addresses in various namespaces when producing films. Like TCP port numbers above 64k.

 

[Bubby4j]

Screenwriters (or production designers) are prone to specify 'impossible' addresses in various namespaces when producing films. Like TCP port numbers above 64k.

65,535

 

[Jay Ashworth]

yup, that's 64 x 1024 -1 alright.

 

[robartsd]

Screenwriters (or production designers) are prone to specify 'impossible' addresses in various namespaces when producing films. Like TCP port numbers above 64k.

Perhaps, but the example you gave is an IP address not a TCP port number. Port numbers are typically placed after the address as in 127.0.0.1:80 (loopback address to the http port of the current host).

 

[Bubby4j]

This is way off topic.

 

[Jay Ashworth]

Incidentally.

 

[JD]

Why hasn't any LED manufacturer figured out the minimum voltage for the power supply and then simply adjusted the output to be zero at that voltage? Thus 10VAC (let's say) is zero and 120VAC is full?

So anyhow, what you are saying is very viable!
In the Cree lamps, there is actually a circuit that looks for the chop point and drives the LED based on that. Of course, that falls apart when the supply voltage drops below what is needed to process the information.

I think the best answer to that question is the trouble getting all manufacturers to agree on the same voltage point! If they could, and for example, 10% was considered "black" then the lamps could be designed to have an excellent low end and a dimmer profile could be set up to convert 0-100% to 10-100% to drive it.

As for the Chauvet, don't know! Could be, on a unit that size and in that price range, there may be a Li battery in there to keep the logic alive.

 

[BillConnerFASTC]

So anyhow, what you are saying is very viable!
In the Cree lamps, there is actually a circuit that looks for the chop point and drives the LED based on that. Of course, that falls apart when the supply voltage drops below what is needed to process the information.

I think the best answer to that question is the trouble getting all manufacturers to agree on the same voltage point! If they could, and for example, 10% was considered "black" then the lamps could be designed to have an excellent low end and a dimmer profile could be set up to convert 0-100% to 10-100% to drive it.

As for the Chauvet, don't know! Could be, on a unit that size and in that price range, there may be a Li battery in there to keep the logic alive.

For console driven systems or where profiles are available, I would think it would be a simple matter for each lamp to just have indicated its bottom trim or threshold voltage. Would mean not mixing lamps, but seems easy. No doubt if successful there would eventually be a vhs vs beta stand off until one won, but so be it.

I still think the market is too small. At what factor - how many times current cost - would you not buy a retro LED lamp. I'd guess these would be at least three times current cost.