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Saving power

New MessageSaving power (modified 0 times) newell
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I noticed on my webpals (Rev .01) the hottest chip is that Chrontel CH7001 VGA->Video converter. Power supply spec is 350mA! The CH7001 powerdown pin appears to be tied to one of the CL7500 I/O pins, controlled by bit 5 at 0x0320000c. Set the bit low to disable the s-video and composite output and save a lot of power.

Just sitting on the bench running gdb, I notice that the regulator runs much cooler now. This might be handy if you're running a hard drive off the internal regulator.

01-05-2003 22:34:33

New MessageRE:Saving power (modified 0 times) n1gp
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newell,

how can this be made into a utility that could be executed from a
command prompt. something like an app name "tvout" where you could
type "tvout off" and a "tvout on"?

not sure if one would have to write a kernel driver to support it or whether
one could simply write a small utility that did the memory write operation?

Rick

02-19-2003 21:30:05

New MessageRE:Saving power (modified 0 times) Vit_sfba
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Hi,

I have IBM harddrive hooked up Webpal, along with some ISA card, and Webpal's power supply just does not allow
it to boot, low power on drive. IBM Travelstar drives have 1A power consumption, unlike most Toshiba's drawing just 0.7A.

The solution was to use another power supply 8V/6.5A http://www.allelectronics.com/cgi-bin/category.cgi?category=480&item=PS-865&type=store

So far, works for about an hour, LM323 there is not even too hot :)

Now, I wanted to use the unit in the car, it turns out, that being fed with 12V, LM323 gets overheated very fast and switches off, so I want to try to replace it with a switching power supply and solve power worries once and for all :)
Maybe I'll have some results in couple of weeks :)

Vit.

05-02-2003 20:03:35

New MessageRE:Saving power (modified 0 times) Vit_sfba
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Hey n1gp,

I wrote that utility for you :) It was fun :)
Will post it today on my site http://luban.org/Webpal

Vit.

05-03-2003 06:25:32

New MessageRE:Saving power (modified 0 times) n1gp
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Tnx Vit, you rock!
05-22-2003 08:38:52

New MessageRE:Saving power (modified 0 times) m_bed
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Vit,

The spec sheet for the LM323 says it should get a minimum of 7.5V in, but that 8V supply should be reduced to 6.6V after it's gone through the bridge.

Are you sure you're getting good regulation out of the LM723?

Also, it looks like the ripple on the filtered DC could get pretty awful as you start to load down the supply with AC input, due to the relatively small size of the capacitor. The problem you saw running off the transformer might not have been "wimping out": it could well have been the LM723 dropping in and out of regulation because its input voltage was swinging too widely.

Iit's a rather nasty combination: as the current goes up, the average DC voltage goes down, and the swings get wider.

Feeding it regulated DC is a clever way to avoid that, but I wonder if it shouldn't be 9V, instead of 8V.

Ran

06-22-2003 16:51:56

New MessageRE:Saving power (modified 0 times) Vit_sfba
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Hi,

The second pover supply I'm using has the same voltage
rating as the original one, just the amperage is much higher :)

I've tried to use higher voltages, but, as power dissipation on
LM723 is proportional to the square of the voltage, the chip
shuts itself off on overheat protection rather soon. I'm
planning to replace it with a switching regulator in order
to be able to use the unit in a car with 12V power.

Thanks,
Vit.

07-01-2003 10:01:52

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