Any truth to this power supply statement?

JohnMarcson

Administrator
May 7, 2010
10,971
Northwest Ohio
I got a comment on my youtube 120vac video. Any truth to the Reply or My Reply?
  • Comment-Interesting how the 120v lights seem to "keep time" better than their 12v counter parts.
  • Reply-This is because the nature of AC voltage acts like a built-in clock signal, so the lights are synchronized by the frequency of the AC voltage. DC doesn't have that advantage, so things tend to drift after awhile.
  • My reply- In the two I have opened (there are others I haven't looked at yet) the power supply converts the AC to DC before it hits the timing circuit so I'm not sure how the AC 60hz wave matters. The power supplies I have looked at are basically DC supplies with a converter. The speed and pattern are a lot more simple. They do drift, but not like a 120fpm quad flash. Also it is hard to notice the drift when it is one flash every 10 seconds. I notice the same thing with my DC 60fps aircraft supplies, they seem to drift less but it is an illusion of the pattern. Youtube user DrFrankenStrobe would know for sure, he rebuilds lots of supplies.



 
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RS485

Supporting Donor
Aug 5, 2019
369
Central MA
I got a comment on my youtube 120vac video. Any truth to the Reply or My Reply?
  • Comment-Interesting how the 120v lights seem to "keep time" better than their 12v counter parts.
  • Reply-This is because the nature of AC voltage acts like a built-in clock signal, so the lights are synchronized by the frequency of the AC voltage. DC doesn't have that advantage, so things tend to drift after awhile.
  • My reply- In the two I have opened (there are others I haven't looked at yet) the power supply converts the AC to DC before it hits the timing circuit so I'm not sure how the AC 60hz wave matters. The power supplies I have looked at are basically DC supplies with a converter. The speed and pattern are a lot more simple. They do drift, but not like a 120fpm quad flash. Also it is hard to notice the drift when it is one flash every 10 seconds. I notice the same thing with my DC 60fps aircraft supplies, they seem to drift less but it is an illusion of the pattern. Youtube user DrFrankenStrobe would know for sure, he rebuilds lots of supplies.


Are we talking about the revolving lights or strobes? The fedsig strobes at ~12:40 don't look sync'ed to me.
 

JohnMarcson

Administrator
May 7, 2010
10,971
Northwest Ohio
Are we talking about the revolving lights or strobes? The fedsig strobes at ~12:40 don't look sync'ed to me.
The strobes I thought. They aren't synched, but appear less "out of synch" than some other multiple flash style lights. I believe the closeness in flashing is being attributed incorrectly to 120 volts AC. Even though it's not really synchronized, I believe the slower flash rate makes it appear less unsynchronized.

That said, even AC rotators wouldn't synch based on being AC. There's always going to be differences in the motors such as winding length, etc and then small differences in the weight and balance of what they are rotating. Nothing really synchronizes 100% unless it is intentionally designed to do so via mechanical or digital means.

I think the "AC makes things more synchronous" statement is false all around.
 
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RS485

Supporting Donor
Aug 5, 2019
369
Central MA
Here's a vid of Whelen a couple of 120VAC 1500DLCs ca. 1983 that seem to start out, and stay perfectly sync'd.


The PCB doesn't remotely resemble any 12VDC PCBs and I don't know if Whelen even promised any kind of sync.
These 1500DLCs might appear to make the case that, "AC makes things more synchronous" but I won't buy it until I can understand how the design choices in the PCB made it so.
 
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JohnMarcson

Administrator
May 7, 2010
10,971
Northwest Ohio
That's interesting, I think it's also worth noting that the strobes that were being referred to have DC power supplies and AC inverters in them. I would be curious if actual AC power supplies do in fact stay more synchronous.
 

Sparky_911

Supporting Donor
May 15, 2013
2,648
Central Illinois
My comment was mainly was referring to the rotators and exl's.
 
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JohnMarcson

Administrator
May 7, 2010
10,971
Northwest Ohio
My comment was mainly was referring to the rotators and exl's.
The rotators are definitely a lot more on speed than standard 12 volt gear driven ones. The 120 volt direct drive motors are significantly nicer quality from what I can tell. I also believe that there is a more specific flash rate requirement for certain industrial signals, which is why the explosion proof whelen lights rotate at a very specific speed. Overall, the rotation is much smoother and I would agree it is much closer to the specified speed. Taking the gear and super cheap motor out of the equation using direct drive certainly makes a difference.
 
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