The Cyber-Spy.Com Usenet Archive Feeds Directly
From The Open And Publicly Available Newsgroup
This Group And Thousands Of Others Are Available
On Most IS NNTP News Servers On Port 119.
Cyber-Spy.Com Is NOT Responsible For Any Topic,
Opinions Or Content Posted To This Or Any Other
Newsgroup. This Web Archive Of The Newsgroup And
Posts Are For Informational Purposes Only.
From: Spehro Pefhany
Subject: Re: Linear voltage change over a 30 minute period?
X-Newsreader: Forte Agent 1.92/32.572
Date: Fri, 13 Dec 2002 19:54:59 GMT
NNTP-Posting-Date: Fri, 13 Dec 2002 14:54:59 EST
On 13 Dec 2002 11:26:33 -0800, the renowned firstname.lastname@example.org
>I have a basic electronics question (or I would think it's basic). I
>want to build a simple DC circuit that will supply a linearly
>increasing voltage from V=0 at t=0 to V=10 volts at t=30 minutes. The
>circuit would be powered by either a battery or an AC/DC adapter.
>If linear is too complex I would be okay with just getting the voltage
>to ramp up over a time period of about 30 minutes. Can anybody
30 minutes is a fairly long time for an analog circuit. You'd
either be dealing with very low currents and a film capacitor or
more reasonable currents and a potentially leaky and otherwise
troublesome special electrolytic cap. Resetting it accurately
could also be a problem (I've used reed relays in some cases).
I suggest you consider using an oscillator (a 555 will do), a
CD4040B 12 bit counter and a R-2R ladder to generate it digitally.
If you use up one output to halt the 555 at the end of the ramp,
you'll have 0.05% resolution (steps every 0.88 second), which
leads to quite reasonable timing components for the 555.
"it's the network..." "The Journey is the reward"
email@example.com Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog Info for designers: http://www.speff.com
Go Back To The Cyber-Spy.Com
Usenet Web Archive Index Of
The sci.electronics.design Newsgroup