HP Printer standby power consumption - Page 1
Forum section: electronics / beginners

author: TheAmmoniacal
author_rank: Unknown
timestamp: May 27, 2014, 07:01:59 pm
content: I own this small 4"x6" (10x15 cm) photo printer form HP, it's a Photosmart A516. From the time I bought it I've had in plugged in, which is some 2 years ago now, but just recently after moving and rearranging some stuff in my room I couldn't find the wall adapter for printer, which is a +32V (~900 mA) adapter, something I don't usually have around. So I wired it up to my variable DC power supply which also shows the current drawn - and I noticed something peculiar. The printer draws ~100 mA constantly, also when switched off. At 32V this is aorund 3W of power being consumed. Something I think is quite a lot, considering my reading lamp use about the same and I'm always conscious of not leaving that on.I'm just a beginner so I don't know much, is this normal? If so, is it because it's using an SMPS? That begs the question, how many other electrical appliances use power when shut off?

author: Stonent
author_rank: Super Contributor
timestamp: May 27, 2014, 09:31:37 pm
content: Quite a few. Any with a soft power switch will. Big clunking switches tend to remove all power.

author: xquercus
author_rank: Contributor
timestamp: May 27, 2014, 10:09:49 pm
content: That's normal and has nothing to do with the type of power supply. In their 'off' state, many consumer electronic devices are actually in a 'low power' state. One of the worst offenders I'm aware of are cable TV set top boxes. Even basic models without integrated DVRs often consume TENS of Watts when 'off'.Sometimes standby power is called a 'phantom load' or 'vampire load'. There have actually been calls for government to regulate standby power.

author: amyk
author_rank: Super Contributor
timestamp: May 28, 2014, 12:21:38 pm
content: Some of them implement "off" as meaning "don't react to external events except the power button", with everything else still powered up. Cheaper to design it that way, but much more expensive for the consumers.

author: SeanB
author_rank: Super Contributor
timestamp: May 28, 2014, 04:11:07 pm
content: Most set top boxes actually use the same power on or "off", only turning off the display and often still leaving the RF modulator powered with no video signal. The reason offered is that the LNB will be more stable with always being powered, and the heat dissipated in it will help keep it ice free.As to printers, any with a soft switch ( and many with a big click switch as well) will only turn off the fuser, disconnect the USB port by turning off the on chip drivers and keep the rest of it running. With a 32V supply ( meaning it is an inkjet with a thermal print head) you still have either a small SMPS to provide 5V to the internal logic or even some have a linear regulator to drop the excess 27V as heat.

author: Stonent
author_rank: Super Contributor
timestamp: May 28, 2014, 11:49:55 pm
content: I suppose with set top boxes, very few people want to wait 2 or 3 minutes for it to boot up, establish a link and start decoding.

author: saturation
author_rank: Super Contributor
timestamp: May 30, 2014, 01:52:35 pm
content: I concur with others. I plug any wall wart into an SPD/power strip and power off the switch to insure there is no phantom draw. While green wall warts draw under 1 W, collectively they adds up. I salvaged old power stations like that below that were once the rage in PCs, and use them to switch off banks of SPD and power strips for all my home appliances, wall warts or not. Many appliances [ e.g. bluray players, DVRs] are powered similarly and have a phantom draw and have "wall warts" 'built in'.The main advantage is these power stations are its sturdy enough to be on tables and not be unsightly. The only switch you need to kill is the main or you can do it selectively; naturally watch that you don't overload it.Often the main switch may be bad as its often heavily used and has a limited number of switch cycles before failure, however most of the banks switches are never used while it was in operation. I just switch the defective main switch with one of the 'aux' or 'monitor' switches [ they have the same rating] and permanently wire the salvaged port ON, and just plug the hole with the unwired former main switch to maintain the look.You can find these on eBay and refurbish them for about $5 delivered. The ones from the 1980s-1990s are made of heavy gauge steel and are preferred. They were built like tanks and made to hold the weight of the then huge heavy CRT monitors, so they will last a lifetime. Avoid those with all plastic bodies.