ACS-64 Headlights

[CSXfoamer1997]

How come at random times, or maybe on certain cameras, unlike on locos with standard halogen headlights, the LED headlights on the ACS-64's flicker like crazy? After a while, it can probably make you dizzy and ache your eyes terribly.

 

[CCC1007]

If the camera is operating at 60, 30, or 24 fps there will be a flicker as a result of the 50 hz electrical system.

 

[PVD]

I thought it was 60hz, but you're still "on the right track"

 

[niemi24s]

Because the D in LED stands for Diode and diodes only conduct current (and emit light) in one direction, a single LED will emit continuous light only when powered by a Direct Current source (of the proper polarity). When powered by a source of Alternating Current (AC) which undergoes a periodic polarity reversal, they will emit light only about half the time. That rapid on-off-on-off can be captured by the camera and is the source of flickering sometimes seen - especially when the frame rate of the camera is close to some sub-multiple (like ½) of the frequency of the AC voltage applied to the LED.

However, an LED can be made to emit light continuously when powered by an AC voltage provided that voltage is first converted to a non-pulsing DC voltage by a process called full wave rectification. But as far as locomotive headlights - I know nothing.

 

[CSXfoamer1997]

Hmm. Very interesting!

 

[PVD]

Most commercial LED light assemblies that connect to AC power would have that included in their drivers since they are, as you point out, DC devices. Not sure about the ones used on locomotives. Have done lots of stuff with LED lighting and lighting control in the world of electrical construction and renovation, since retiring, have been teaching energy conservation and lighting control, and when it comes to the ones on an ACS-64, I know nothing!

 

[CCC1007]

I thought it was 60hz, but you're still "on the right track"

I was referring to Amtrak using a nonstandard frequency to power their locomotives.

 

[Dutchrailnut]

they use 25 hz or 60 hz neither is non standard.

but headlights and markers are operated of battery which is DC.

 

[PVD]

which I should have thought of, the headlights can be on through phase breaks and pantograph down. When I was thinking power I was thinking trainline HEP which would be 480 60hz, not the supply. I wasn't thinking of utilization voltages in the loco itself, I probably also should have.

 

[west point]

The flickering might be because the battery for the lights is getting weak and rectifier for the battery is causing some voltage peaks. Such as battery supposed to be 72 volts but only has a 50 volt output and rectifier is putting out balance of voltage. Just speculation.

Also the rectifier might be only putting out a half wave DC instead of a full wave DC ?

 

[PVD]

I like the bad (half wave) rectifier over the bad battery. Are they rectifying and providing DC to a lighting assembly, or providing AC and the LED driver is handling the rectification (typical in commercial apps, but I don't know about loco construction)

If we knew the speed of the blinking it would help. We have new led streetlights, some of them are bad and exhibit this exact problem. they are on at each half cycle.

 

[railiner]

Say what?......All this techno-speak reminds me of the great scene in the film "Airport", when the character played by Dean Martin spoke some double-talk to a know-it-all kid to confuse his observation of the airliner turning around....

Due to a Cetcil wind, Dystor's vectored us into a 360-tarson of slow air traffic. Now we'll maintain this Borden hold until we get the Forta Magnus clearance from Melnics"