Printing stuff causes lights to flicker
March 4, 2005 3:33 PM Subscribe
Why is it, when I print anything, that for minutes after the fact, the lights in my room continue to flicker?
Response by poster: Yeah, it's possible. It's a Samsung ML-1200. What would that feature do?
posted by Big Fat Tycoon at 3:53 PM on March 4, 2005
posted by Big Fat Tycoon at 3:53 PM on March 4, 2005
No, I know what he's talking about, as I've seen the same effect with my HP Laserjet 4+. The initial surge comes when the printer warms (which does brown-out the lights), and then every 30-40 seconds the lights will brown out for about a second, even while the printer is idle and not drawing any additional load.
I saw this effect at a rural house and in an apartment complex with this printer. I have not seen it in our suburban house. So I think this has something to do with some quirk in the step-down transformer (that goes from 440V to 110V) after reacting to the sudden load, but I have no idea what the mechanics of this are. I have noticed if you stick a voltmeter in the wall, you can see the power fluctuations... I saw the power varying from 110V to 95V during the brownouts. We need an electrical expert to figure this one out.
posted by rolypolyman at 3:54 PM on March 4, 2005
I saw this effect at a rural house and in an apartment complex with this printer. I have not seen it in our suburban house. So I think this has something to do with some quirk in the step-down transformer (that goes from 440V to 110V) after reacting to the sudden load, but I have no idea what the mechanics of this are. I have noticed if you stick a voltmeter in the wall, you can see the power fluctuations... I saw the power varying from 110V to 95V during the brownouts. We need an electrical expert to figure this one out.
posted by rolypolyman at 3:54 PM on March 4, 2005
It's the heating element in the fuser. The initial power drain is to get it up to operating temperature; then the occasional fluctuations after that are to keep it there. The increased current draw results in lower voltage on the circuit, which is running near the edges of its capability. It's just old wiring that was never intended to have a laser printer on it. It is probably not dangerous as long as it's not tripping any breakers. (If I have my laser printer turned on and try to use my hair dryer, I trip the breaker. So I try not to do that.)
posted by kindall at 4:24 PM on March 4, 2005
posted by kindall at 4:24 PM on March 4, 2005
Oh yeah, and the "power save" mode is where the printer stops heating the fuser after a period of time. The fluctuations will probably stop when the printer goes into "power save" mode. They are not being caused by "power save" mode.
posted by kindall at 4:25 PM on March 4, 2005
posted by kindall at 4:25 PM on March 4, 2005
I've actually developed software for digital copiers. Most of them use a technique called "cycle stealing", where the fuser element will get power from the AC line by turning on for a number cycles (a cycle is 1/60 sec in the US). The number of cycles it turns on, or "steals", in a given amount of time is dependent on how much heat needs to be applied. The more cycles it uses, the more obvious the flicker.
Obviously, initial warmup takes a lot of power, but as each piece of paper passes through heat is transferred to them and needs to be replaced. Fusers are designed to give up heat to the paper (a halogen lamp inside a metal tube is a common fuser design) so the flicker will continue as long as paper is moving. During quiet periods, very little power is needed so the flicker becomes unnoticeable. The amount of time until the lower power mode kicks in will vary but is seldom shorter than a minute or two, so if you have another print job right after, it won't have to wait for warmup again.
It's usually recommended that laser printers/digital copiers be on a dedicated circuit, but that's in commercial uses where running another line isn't difficult. When used at home, having a circuit that doesn't have anything else on it is more difficult to achieve. Any device that is subject to heavy current draw, either continuously or intermittently (fridges, air conditioners, heaters), will cause problems if on the same circuit. In particular, another laser printer is definitely not a good idea, as they're likely to try to steal cycles at the same time and one or both is likely to fault. Lamps aren't a problem, but they make the flicker noticeable.
There are ways to minimize the apparent flicker, using more sophisticated control algorithms, but you can't get around the fact that fusers need a lot of power.
posted by tommasz at 6:58 PM on March 4, 2005
Obviously, initial warmup takes a lot of power, but as each piece of paper passes through heat is transferred to them and needs to be replaced. Fusers are designed to give up heat to the paper (a halogen lamp inside a metal tube is a common fuser design) so the flicker will continue as long as paper is moving. During quiet periods, very little power is needed so the flicker becomes unnoticeable. The amount of time until the lower power mode kicks in will vary but is seldom shorter than a minute or two, so if you have another print job right after, it won't have to wait for warmup again.
It's usually recommended that laser printers/digital copiers be on a dedicated circuit, but that's in commercial uses where running another line isn't difficult. When used at home, having a circuit that doesn't have anything else on it is more difficult to achieve. Any device that is subject to heavy current draw, either continuously or intermittently (fridges, air conditioners, heaters), will cause problems if on the same circuit. In particular, another laser printer is definitely not a good idea, as they're likely to try to steal cycles at the same time and one or both is likely to fault. Lamps aren't a problem, but they make the flicker noticeable.
There are ways to minimize the apparent flicker, using more sophisticated control algorithms, but you can't get around the fact that fusers need a lot of power.
posted by tommasz at 6:58 PM on March 4, 2005
This thread is closed to new comments.
posted by pmbuko at 3:37 PM on March 4, 2005