Voltage & Current..

From: Jim Davis <jdavis_at_gorge.net>
Date: Mon Jan 26 08:52:30 2004

dvcorbin_at_optonline.net wrote:

>>Bwahahaha, I've written 10 replies, but canceled them all, because I can't
>>teach a house
>>plant calculus. You Win.
>>
>>
>>
>
>On the other hand, I do keep tring to teach some of my outdoor plants geometery...
>
>Seriously the TOTAL lack of regulation on "WallWarts" is quite common. I am currently (preofessionally) developing a product which normally operates off of AC power (via a wallwart), but needs to remort low AC conditions and fall back to battery.
>
>The load on this device is VERY dynamic ranging from under 10mA to over 850mA depending on what it is doing. The voltage fluctuations out of the wall wart (which is rated as 11.8V _at_ 1A) will rise as high as 17V when under a minimal load.
>
>Since the device is intended to have a very low production cost, they really cut some regulation requirements on the board as well, since the components WILL tolerate this range of voltages.
>
>Unfortunately, the side effect is that the voltage variation based on load is significantly greater than the voltage variation based on fluctuations in the AC (eg during a brown out). This has required the development of software that is constantly monitoriing the "active" state of many of the devices to "calculate" the current load, and then going through a transform to estimate the RAW AC that is providing power to the wart.
>
>DAvid.
>
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>
>
>
I re-read your message, but it's late and I need sleep, The questions I
have are?
1) Is the company too cheap to give you a large enough wallwart to power
the product under brownout conditions?
2) Why are you computing subsystem current usage if you have no
regulator to feed it back into?
3) I forget the third. Right, are you trying to control the voltage by
using the components on board as a crude
shunt regulator?
Ack! BINGO!

Jim Davis.
Received on Mon Jan 26 2004 - 08:52:30 GMT