Amps drawn by laptop & scope setup

[rogerg]

I found out some very interesting information yesterday. I bought myself a $18 amp metre (1 to 10A) from DSE and wired it inline in my astronomy setup between my 40 amp hr SLA battery and the first junction box.

Interesting notes:
- The losmandy draws around 300mA and spikes to at most 500mAh when slewing at full rate in both RA and DEC.
- The laptop in full power mode draws around 2.5A normally and will spike as high as 5.5A when processing and performing disk access.
- Turning the laptop screen down in brightness saves at most 0.5A
- Turning the laptop's processing speed to battery optimised saves negligable power, I couldn't distinguish much difference at all, but the speed reduction is a huge pain.
- Plugging in the QC Pro 4000 draws an extra 250mA.
- The biggest thing affecting power consumption of the laptop appears to be processing combined with disk access. Get it to load a program like photoshop and it'll spile to 5A almost continously but not quite, until the disk heads stop moving.

So, I've learned not to bother with stepping down the processor, to keep the screen at minimum but it doesn't make a huge difference, and to minimise what disk access and processor utilisation is done while on the battery, so I'd leave image processing until the next day when plugged in to mains.

Interestingly my laptop likes drawing about 2A and there ain't much I can do about it, for all the fanfair about powersaving technologies in it.

My laptop is a Toshiba TE2100 (a couple of years old now - 2gigHz/40gig/512mb/15").

So my setup could run for at most 20 hours with the laptop going and about 80 hours with just he telescope. I think I'll be only turning on the laptop once polar aligned etc to save a couple of hours.

Roger.

[Dennis]

Interesting measurements and information Roger - thanks for posting.

Cheers

Dennis

[h0ughy]

often wondered that. Bigger battery = longer time, add a few dew heaters in to the fry and hey - early night, no juice! Thank goodness for 240V

[Lee]

Surprising how much juice the laptop sucks in..... I did the same with my G-11 a while back, it was drawing about 300mA on RA tracking and 800mA with both motors slewing..... much less than I thought it would draw.....

[jase]

Have to agree with h0ughy - thank goodness for 240v:). I use to have a 65amp/hr duty cycle battery in the field to power all my kit. Heavy boat anchor it was. I also had the inverter for the laptop. Everything would easily run for two nights, but it became too much of a hassle (or more correctly - I became lazy :P)

Slightly off topic (but still talking power). For those Losmandy users with servos instead of steppers who have access to AC mains, I would highly recommend using 18v instead of 12v. Using 18v with servos really provides some extra torque if youre overloading your mount or want more slewing juice. Comes down to personal preference.

I'm not associated with this company, but I'll give them a plug for regulated DC power supplies: http://www.amalgen.com.au/

I purchased a 18v @ 5amp (2183-x-3) for the Losmandy Titan and 12v @ 10amp (2971-x-1) for auxilary kit such as Robofocus, dew heaters etc. They work a treat.:thumbsup: Have not experienced any stalls or servo overheating.
(http://www.amalgen.com.au/dc_power/linear_regulated_2183.asp)

[Lee]

I use a Jaycar 13.8V DC supply for my G-11 - works well, although I have noted some RA lagging with the 8" Newt on board if tighten the worm up a bit..... maybe 18V would push through..... Was having stalls on a 12V battery (70AH deep cycle)..... Now I think I'll need an inverter to run the 13.8V supply in the field! Will be a mess!

[bird]

Yes, I measured the current draw in the field once upon a time with my Dell inspiron 8500 laptop (2GHz p4-mobile), came to about 5A @ 12V, but then I was running that into a 240v inverter so maybe I was losing 10% efficiency or something.

Bird

[lost_in_space]

The constant high current draw on the laptop is probably the heater that keeps your knees warm.

Multi GB memory sticks are happening and mechanical disks will become redundant in portables. It won't be long before you can capture hours of hi res digital imaging in real time to solid state chips. Archaic power hungry mechanical storage will be relegated to the museums of the industrial revolution.

IMHO (not that I was ever humble) eventually solid state will replace everything that is round and stores data, but the cpu will stay cool as long as your knees need warming:).