The LEDs are flickering in a light tent (Puluz 60cm)

If I buy a new power supply it's either going to take an age or cost a
bucket in shipping.
Output 12V 2A 'constant current', dimmable.

So,
Why might it be flickering? Are these things servicable?

Does it matter if I replace it with something different that isn't
constant current but constant voltage?
Because I can't seem to find a 24W constant current driver operating at
12V, is that going to matter?

Any input.....

On 04/01/2021 15:41, R D S wrote:
The LEDs are flickering in a light tent (Puluz 60cm)

If I buy a new power supply it's either going to take an age or cost a
bucket in shipping.
Output 12V 2A 'constant current', dimmable.

So,
Why might it be flickering? Are these things servicable?

Does it matter if I replace it with something different that isn't
constant current but constant voltage?
Because I can't seem to find a 24W constant current driver operating at
12V, is that going to matter?

Any input.....

There's actually 2 strips with a Y splitter, so 12W would suffice (2 of)
and i'd keep some degree of dimmability.

In article ,
R D S wrote:
Does it matter if I replace it with something different that isn't
constant current but constant voltage?
Because I can't seem to find a 24W constant current driver operating at
12V, is that going to matter?

A plain LED is current driven. Voltage as such doesn't much matter. If you
have an adequate power supply of known voltage you use (in the simplest
form) series resistors to set the current. Multiple LEDs might be a
mixture of series and parallel connection, though. You'll find calculators
online to give you the correct series resistors for various combinations.
You'll need to know the supply voltage and the LED parameters.

If you can't find a suitable LED driver power supply.

--
*Happiness is seeing your mother-in-law on a milk carton

Dave Plowman London SW
To e-mail, change noise into sound.

Dave Plowman wrote:

Multiple LEDs might be a
mixture of series and parallel connection, though. You'll find calculators
online to give you the correct series resistors for various combinations.
You'll need to know the supply voltage and the LED parameters.

And each physical LED may internally be comprised of several actual
LEDs, so the voltage can be surprisingly high.

R D S wrote:

Does it matter if I replace it with something different that isn't
constant current but constant voltage?
Because I can't seem to find a 24W constant current driver operating at
12V, is that going to matter?

If it's a constant current LED driver, the it's odd for it to specify a
single voltage, rather than a range (e.g 25V to 70V) for a random one on
RS website

Also 2A sounds rather high.

Photo of existing driver?

On 04/01/2021 16:09, Andy Burns wrote:
R D S wrote:

Does it matter if I replace it with something different that isn't
constant current but constant voltage?
Because I can't seem to find a 24W constant current driver operating
at 12V, is that going to matter?

If it's a constant current LED driver, the it's odd for it to specify a
single voltage, rather than a range (e.g 25V to 70V) for a random one on
RS website

Also 2A sounds rather high.

Photo of existing driver?

https://drive.google.com/file/d/1JtQ...ew?usp=sharing

Reading the cautions, i'm thinking everything on that label should be
taken with a pinch of salt.

R D S wrote:

https://drive.google.com/file/d/1JtQ...ew?usp=sharing

Reading the cautions, i'm thinking everything on that label should be
taken with a pinch of salt.

I'd say not putting it in water or fire are good ideas.

It mentions batteries, I take it there aren't any?

On 04/01/2021 17:05, Andy Burns wrote:
R D S wrote:

https://drive.google.com/file/d/1JtQ...ew?usp=sharing

Reading the cautions, i'm thinking everything on that label should be
taken with a pinch of salt.

I'd say not putting it in water or fire are good ideas.

It mentions batteries, I take it there aren't any?


No batteries.
And I keep it away from the damp place anyway.

R D S wrote:

Andy Burns wrote:
R D S wrote:

https://drive.google.com/file/d/1JtQ...ew?usp=sharing

It mentions batteries, I take it there aren't any?

No batteries.

You mentioned a splitter inside the tent, can you measure the voltage there?

On 04/01/2021 15:41, R D S wrote:
The LEDs are flickering in a light tent (Puluz 60cm)

What's a light tent?

If I buy a new power supply it's either going to take an age or cost a
bucket in shipping.
Output 12V 2A 'constant current', dimmable.

So,
Why might it be flickering? Are these things servicable?

PSU doesn't like the load or a dry joint somewhere. I have noticed that
LED streetlamps seem to fail this way with monotonous regularity.

Does it matter if I replace it with something different that isn't
constant current but constant voltage?
Because I can't seem to find a 24W constant current driver operating at
12V, is that going to matter?

Any input.....

Constant voltage may well kill the LEDs or at the very least shorten
their lifetime. A series resistor with a constant voltage supply will
work OK but the resistor will get a bit warm try 1R 5W or 0.5R 2W.

--
Regards,
Martin Brown

On 04/01/2021 16:34, Martin Brown wrote:
On 04/01/2021 15:41, R D S wrote:
The LEDs are flickering in a light tent (Puluz 60cm)

What's a light tent?

Martin, just Google for Puluz 60cm.

I did.




--
Adam

R D S wrote:
The LEDs are flickering in a light tent (Puluz 60cm)

If I buy a new power supply it's either going to take an age or cost a
bucket in shipping.
Output 12V 2A 'constant current', dimmable.

So,
Why might it be flickering? Are these things servicable?

Does it matter if I replace it with something different that isn't
constant current but constant voltage?
Because I can't seem to find a 24W constant current driver operating at
12V, is that going to matter?

Any input.....

Here's another picture for context. This shows enough of the
product, so you can understand the application. "Well-lit
handbags at dawn."

https://flutter-shop.com/953249/prod...dc-12v-2a.html

*******

The supply is two 1A constant current sources.
The output voltage is the "compliance" voltage.

When the adapter runs no-load, the output voltage
on each barrel connector should be 12V. But maybe
not perfectly steady. A proper (theoretical) constant
current source, the voltage would rise to infinity if
such a thing existed and no load were applied. If
testing with your multimeter, you start on the 1000V DC
range first, and dial down as you develop some trust
it's a 12Vmax output.

Instead, when we make constant current sources, they're
non-ideal, and their ideality stops at the compliance
voltage. When the voltage gets to 12V, it can no longer
rise higher, and the "constant current" behavior stops
at that point.

The device can provide 1 ampere per lead-set. Even if
we short it out, 1 ampere flows through the short.

If we connect a 1 ohm resistor to a lead-set, the 1 ampere
flowing through 1 ohm, develops 1 volt. The power is
1 amp times 1 volt or 1 watt. The unit does not make
12V in that case. That's because it is a constant current
source. The output voltage happens to be 1 volt, because
we've placed such a heavy load on it.

You could run about four 2.5V white LEDs off a 12V compliance
source. When you connect the four LEDs, 10V drops across
the LEDs while 1 ampere flows. The load receives 10W total
power.

This blackbox is, in effect, a "dual buck puck". Two channels
running at 1 ampere each. We could connect a 10 ohm 25W
power resistor and verify that we're getting the voltage
and current expected from it. That would be a load test.

The danger with any constant current source, is they tell
a lie about the compliance voltage. And open circuit, it
rises to some absurdly high DC value. That's why, being
chinese, you'd be careful to not trust the ratings on it.
You can characterize the device by placing test loads on it
and see if it behaves as a constant current source.

In terms of internal stress, the max stress is when the
output is shorted. It doesn't stop running when shorted
(unlike a voltage-regulating wall wart). Since it's a
constant current source, it is designed to produce 1 ampere
of current per leadset, even if the voltage developed
across the load is zero volts. a second stressful condition
for a constant current source, is being operated open-circuit.
But the compliance voltage feature, says the voltage should
not be rising to infinity when no load is present.
(If a constant current source is made using vacuum tubes,
yes, you can get absurdly high voltages then :-) Nothing
says someone won't try to make a closer-to-ideal source.)

Since this is a photography light tent application, the
regulator should be a bit more precise than your average
"buck puck". You could use two separate buck pucks to replace
the defective item.

You could also use a laptop adapter, two LM317 regulators in
constant current mode, and make a solution that way. If
the output of the LM317 is shorted, it gets extremely hot
(which doesn't happen to the buck puck idea). But an LM317
or a circuit related to it, is something I have the parts
in the house, to put together right now.

I've lost my only electronics store, so I can't just drive
off and buy an NTE970 if I want any more. I have to get
crap shipped, which takes days. The NTE970 is an LM317,
but in a package that bolts nicely to various lines of
heat sinks.

My kitchen light runs off an LM317 inspired constant current
source, so I've already done one of these.

See, hobbyists are already out there doing this sort of thing.
Here, a person after my own heart, is using a laptop adapter
to power four LEDs. R3 sets the current flow level. R3 must
have sufficient power rating for the job.

https://static-resources.imageservic...hting-leds.png

Paul

On 04/01/2021 15:41, R D S wrote:
The LEDs are flickering in a light tent (Puluz 60cm)

If I buy a new power supply it's either going to take an age or cost a
bucket in shipping.
Output 12V 2A 'constant current', dimmable.

So,
Why might it be flickering? Are these things servicable?

What do you mean flickering. Is this to the eye or are you shooting
video at 60Hz?

On 04/01/2021 23:26, Fredxx wrote:

What do you mean flickering. Is this to the eye or are you shooting
video at 60Hz?

Visible to the eye.

Because it says constant current it sounds to me like there are no series
resistors or current limiting in the leds. If you bung on a supply, say
unregulated or regulated, you could end up with a lot of dead burned out
leds. As for serviceable, well that very much depends on your abilities and
whether you can get the psu apart. Flickering is odd, sounds like it might
be just a capacitor inside the unit to me, but beware, there are many
designs all of which are pretty lethal when uncased, especially if its
switch mode.
Brian

--

This newsgroup posting comes to you directly from...
The Sofa of Brian Gaff...

Blind user, so no pictures please
Note this Signature is meaningless.!
"R D S" wrote in message
...
The LEDs are flickering in a light tent (Puluz 60cm)

If I buy a new power supply it's either going to take an age or cost a
bucket in shipping.
Output 12V 2A 'constant current', dimmable.

So,
Why might it be flickering? Are these things servicable?

Does it matter if I replace it with something different that isn't
constant current but constant voltage?
Because I can't seem to find a 24W constant current driver operating at
12V, is that going to matter?

Any input.....