Laser printer draws current in a spike, what for?

snipped-for-privacy@sacbeemail.com (~Dude17~) wrote in news: snipped-for-privacy@posting.google.com:

I suspect it may be the heating coils.

heater for the fuser assembly. On the first couple of generations of laser printers, they didn't even bother to use a zero-crossing switch, and that really made the lights flicker!

it's the heating element for the fuser, maybe a halogen lamp element inside the fuser cylinder. You're seeing a resistive current draw from the 60 Hz mains that tapers off as the element heats up and increases resistance. Your 26 amp initial draw is reasonable for a cold (relatively) element resistance of around 5 ohms.

The steady state value it's approaching is around 8 A, as you've described, as it reaches operating temperature. There's probably a bang-bang thermostat that pokes the heater when it has gotten too cold and runs the element until it reaches the other setpoint.

Absent reprogramming the temperature controls (probably do-able, esp if you could dig up the tech manual) the best bet is just to turn it off when not in use.

WRT the "drop out" cycles every 200 msec or so. Guessing but *maybe* they measure the temperature as a function of element resistance (saves the cost of a separate sensor) and are not triggering the heater during those half-cycles in order to measure the filament resistance (with an RC to a comparator and a timer?).

One 'easy' way might be to find an appropriate NTC thermistor, and put it in series with the lamp.

Maybe several small ones for their lower thermal mass.

Let me guess... it's a LaserJet 4 or 5. It's keeping itself warmed up, using heating coils.

We have moved to newer printers because the old ones were drawing so much current they would disturb computers on the same circuit.

I have a Brother HL-1470N, at home, which exhibits the same symptoms.

I too was thinking of posting about this. I am trying to figure out what to do about this. In my case, I simply moved it off of the UPS, but the lights flickering is still undesirable.

Is there anything I can actually do about this?

You definitely did the right thing in moving it off the UPS. There is no justification, normally, for running a printer off a UPS, and, as you see, it is a very stressful load which could adversely affect the UPS life or reliability.

A laser printer sold in Europe must conform to EN 61000-3-2 and -3. The former is concerned (indirectly) with limiting the peak pulse current, cycle by cycle, while the latter is concerned with limiting flicker. But you'd need to run it from 240 V - either directly or with 120:240 transformer. The frequency doesn't matter.

According to US sources, problems such as you report never occur, and they don't need to implement the IEC versions of those ENs as US standards. So you are actually just imagining the flicker. (;-)

Might be interesting if you told us what Brand/model printer you are complaining about.

Was a know fact in early laser printers.

I've got a Brother HL-1440 that also causes me to imagine the lights are flickering. ;-)

Bob Masta dqatechATdaqartaDOTcom D A Q A R T A Data AcQuisition And Real-Time Analysis

My NEC Superscript 860 has the same effect on my imagination!

Dave

What you're seeing, is the cycling of the heater for the fusing roller. This roller melts the toner into the paper. Without it, your print would simply blow away. It's integral to the operation of the printer.. Just don't put it behind your ups. There's really no need anyway, if the power goes out, then just restart the print later.

The irony is this is quite common in the US, but I've never seen it happening in a 240V country ;-)

| In article , | John Woodgate writes: |> According to US sources, problems such as you report never occur, and |> they don't need to implement the IEC versions of those ENs as US |> standards. So you are actually just imagining the flicker. (;-) | | The irony is this is quite common in the US, but I've never seen | it happening in a 240V country ;-)

We do have 240 volts. The problem is that we also have the NFPA that publishes the NEC which in 210.6(A)(2) restricts the voltage for cord and plug equipment to a maximum of 120 volts relative to ground, thus disallowing the use of the 240 volt connection for the typical laser printer. Of course one might get around this if they say it is a 26A load instead of a 8A (relative to 120 volts).

I guess I should put this in the "favorite beef with the NEC" thread.

I don't know that this would affect it all that much, but I've also heard that in UK, available fault current at homes tends to be higher than in the US (one transformer serving a whole block of homes instead of the typical 1 to 4 in the US). I'm not sure I'd really like having higher available fault current.

Well... obviously the current is halved, but...

A laser printer that dims the lights???? Jus how common is that, really?

I've seen it (NEC Silentwriter LC890). It's just a flicker- the problem is that the flicker is repetitive with the control of the fusion roller temperature and continued as long as the printer was switched on. My modern HP doesn't appear to do anything like that.

Best regards, Spehro Pefhany

X-No-Archive: Yes

hahahahahahahaha

me three. Mine's a BROTHER too. Brother DCP-1200 Scanner/Printer combo and it's not that old. Perhaps Brother's got an issue with their heater drive algorithm. It's ok if it's held on and caused a flicker every once in a while.

To the people who pointed out it's the heating element, I'm aware what the power is used for. My question was what the logical reason is for pulling current in the pattern my printer does.

I don't plug my laser printer into my UPS and only stupid users plugs one into an under the desk sized UPS. What I'm saying is Irise(dI/dT) is extremely fast. This in turn causes a line drop at high dV/dT. My UPS, which is on the same branch circuit transfers to battery every time the printer pulls a surge current.

UPS circuit transfers to battery in prediction of upcoming serious power problem not because the voltage drops too much, but rate of change of voltage (dV/dT) is excessive. When the cause of transfer information is extracted from UPS, it reports as "R", which means unacceptable rate of voltage change on APC UPS.

What did I do? I put the UPS on a different branch circuit with an extension cable and changed the ballast in light fixture to one equipped with an active PFC.

You might ask why active PFC ballast. The power factor controller IC is actively monitoring AC phase and DC bus voltage and it creates a near unity power factor as well as maintain a steady voltage on the DC bus. The controller samples the AC many times a cycle(In hundreds of KHz range) which is a must to correct power factor. The controller compensates for voltage dip and drives the MOSFET accordingly to maintain a steady DC bus voltage. Steady DC bus ensures flicker free lamp operation.

For us home users, "just put the printer on a dedicated circuit" isn't really an option.

I wonder how often 4 or 5 printers on one circuit might cause the fuse to pop, if "idle".

I read in sci.electronics.design that snipped-for-privacy@ipal.net wrote (in ) about 'Laser printer draws current in a spike, what for?', on Mon, 30 Aug 2004:

The transformer impedance is lower but the cables add impedance (mostly inductance unless they are buried coaxials). The typical fault currents in UK and US are not a lot different, i.e. in USA the impedance of a 120 V supply is about half that of a European 230 V supply. But note 'typical'. There is a lot of variation.

EU breakers have a magnetic tripping component to handle fault current interruption within half a mains cycle, in addition to the thermal tripping component for overload protection. Our residential breakers typically have a breaking capacity of

6kA, and this is sometimes increased to 10kA by use of specific suppliers cutout (main fuse type). Higher breaking capacity breakers are available (e.g. 10kA), but not normally required in residential situations.