Voltage tolerance of 12v pixels

Nightryder

John
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I'm thinking about getting into the hobby this year and would like to get a controller and some lights to play with. I have a couple of 12v supplies for ham radio (non adjustable) that output ~14VDC, in the interest of saving money I'm wondering if the 12v pixels will tolerate the higher voltage for testing purposes, I will obviously be getting a proper power supply when I decide I'm ready to put up my outdoor display.
 

algerdes

Al Gerdes
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Quite a few pixels have a hard time with over-voltage. With adjustable power supplies they need to be set at 11.9, or dead-on 12 vdc. Check out the pixels that you will be using. You could always try to use something like a buck-converter to bring the voltage down, but I'm not sure if they will work properly only dropping 2 volts.
 

Katekate

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yeah I wouldn't hook them up to 14v, you're gonna wreck something. I have a 12v 5a supply that I use for testing stuff, reasonably cheap on ebay but I already had it.
 

Nightryder

John
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Yeah, it's kind of strange because both say they are 12v power supplies but really output around 14. Do the falcon controllers tolerate 14v? I may just set it up with a pull down resistor to get closer to 12 for the lights, not expecting to be powering more than 100 pixels at once.
 

TerryK

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If they are Ham supplies they may be designed for 13.8 (automotive run voltage) to power a mobile radio on AC. As Katekate mentioned if they are sitting at approx 14 the regulation may not be very good either.
Using a resistor between the supply and its load is in my opinion never a good idea as the load voltage will obviously fluctuate as the load current changes. I cannot say never because I have done it but I carefully insured current fluctuation was minimal.
As to how the pixels will like the 14 volts, using as an example a WS2815 (a 12 volt chip), the manufacturer lists the absolute supply range as 9.5 to 13.5 volt. Operation under the 9.5 and correct IC operation is not guaranteed and anything over 13.5 runs the possibility of IC damage.
I do not see it mentioned here yet but the Mean Well supplies are rather well liked. If you are in the 'testing' mode a low current model can be had rather cheaply if you are not ready to invest in a high power unit.
 

David_AVD

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Some of the 13.8V (often marked "12V" on the outside) power supplies that are sold for Ham radio, etc use are actually adjustable internally via a small trim control.
 

Nightryder

John
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Some of the 13.8V (often marked "12V" on the outside) power supplies that are sold for Ham radio, etc use are actually adjustable internally via a small trim control.
I thought the same, one is a cheap radio shack unit. I cracked it open and didnt find any trim control. The other is a kenwood ps52, there is no external trim and i havent cracked it open to check yet. Its a very expensive unit so i trust the internal circuitry more. I may try cracking it open to see, that one outputs closer to 13.8.
 

Nightryder

John
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Cracked open the ps52 and found a trimming pot, looks like I have fine adjustment of voltage down to 8v :)

Thanks for the tips!
 

TerryK

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Checking this thread I noticed that no one has commented on your Falcon question. I looked at the F16V3 and F4V3 specs which do not clearly indicate what the Falcon controllers need. The F4 specs are 5 to 24 volt and the F16 is 5 to 36 volt with board voltage selection but not indicated is whether that is the logic or string or both supply. I recently asked David (of Falcon) about using the F4 on dual voltage and he indicated it was possible but did not go into detail as to how. Some one here may know better than I or you can drop David an email. David can be reached at pixelcontroller.com.
I too am new at this and should have in my hands a F4 within this week. I already have a string of 2811s and a strip of 2815s. I went with BTF Lighting (Amazon). I likely will swing into Microcenter and pick up a refurbished Intel i5 for xLights later this week. When you mentioned the Ham supplies I was also wondering if you are FCC licensed as it seems you are in the US. I'm currently 'grandfathered' as Advanced.
 

Nightryder

John
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Now that I know I can drop the voltage on the PS52 Im not too worried about it, actually seems pretty stable over time. My grandfather was into Ham radio. When he passed the family were going to throw out his equipment so I grabbed the power supplies, thought they might come in handy someday.
 

TerryK

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Hi John:

Sorry to hear about your grandfather.

I looked up the specs on the PS-52. It is indeed a supply intended to allow a mobile radio to be powered on AC. Kenwood specs that supply at 13.8 volt. Output regulation (at 13.8) is plus/minus 0.7 volt from 2 to 20 amp of load current. Output ripple is so low it is of no significance. The .7 volt of regulation concerns me somewhat without knowing exactly what it is driving. Kenwood makes good equipment so if they indicate a +/- 0.7 volt regulation it will probably stay in that range well.
 

Mark_M

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I've done a video on another thread about lowest voltage and what voltage regulator chip it uses.
According to most data sheets the highest voltage for this regulator part is 30v.
But with the resin coating it will likely over heat in no time. I'd say 20v should be fine.
In reality, I wouldn't want to.
I did in parts of my test accidentally ramp to 14v, it was only for a moment then back to 12v (Over throw on my power supply).

I haven't tested to confirm but plan on at some point. Knowing me, likely in a few months...


As to how the pixels will like the 14 volts, using as an example a WS2815 (a 12 volt chip), the manufacturer lists the absolute supply range as 9.5 to 13.5 volt.
Sneak in that video...... 4.9v is the lowest stable voltage from my findings.
Granted that is not the WS2815. I highly doubt that chip would take the 12v directly.
It will most definitely use a regulator. The voltage regulator will always output 5v to the chip, slightly below when input is below.
I'd expect the WS2815 to have the same arrangement.



This is not to say that results will be the same. Every batch and regulator part varies.
 

David_AVD

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The regulator may have a maximum operating voltage of say 30V, but that's only part of the story.

When the pixel is fed 12V, the regulator is dropping the remaining 7V (12V - 5V) across it. So this 7V multiplied but the pixel current (say 50mA or 0.05A) works out to 0.35W of heat generated by the regulator on full white.

Let's increase the input voltage to 24V. Now the regulator needs to drop 19V. That 19V multiplied by the same 50mA now works out to a whopping 0.95W of waste heat, just for one pixel.

With a thermal resistance of 180°C or more per Watt, our little regulator would be running at 63°C above ambient temperature even at the nominal 12V input voltage on full white.

Imagine what happens when you increase the input voltage. The regulator temperature can rise so high it soon hits the 150°C max and shuts down to protect itself. Mind you, by then the pixel casing has started to melt and we're past the max temperature rating for all the other parts inside.

Of course your pixels are unlikely to be running at 100% full white for long, so the average dissipation will be lower. It does show how much heat can be generated and why dropping the voltage in a linear way is not ideal.
 
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