Alt-BEAM Archive

Message #05550



To: "'beam@sgiblab.sgi.com'" beam@sgiblab.sgi.com
From: Wilf Rigter Wilf.Rigter@powertech.bc.ca
Date: Sat, 7 Aug 1999 00:30:32 -0700
Subject: [alt-beam] Re: Low power oscillator



content-type: text/plain

Hi Ben,

I thought I would pass on this solution since it easily meets your
requirements and is very simple and compact. This micro power (uP) timer
uses a TI CMOS rail to rail dual opamp (TLC27L2) which cost less that $1
here in sunny Canada. Just add a 5.1M resistor, two 5M trimpots and a
tantalum 2.2uf capacitor to complete the circuit. The frequency and duty
cycle are stable from 5V to 15V and while current varies from 5uA to 10uA
over that voltage range with the 0.2 Hz/ 4% dutycycle waveform which you
specified. The output can drive a LED or equal load but of course this will
increase supply current. To set the output waveform, first adjust dutycycle
since it interacts with frequency and then adjust frequency which is
independent of dutycycle. Once the values of the pots are set they could be
measured and replaced with fixed resistors.

So let us know if the uP timer meets your needs or else it's back to the
drawing board.

regards

Wilf Rigter mailto:wilf.rigter@powertech.bc.ca
tel: (604)590-7493
fax: (604)590-3411


<>



> -----Original Message-----
> From: Sean Rigter [SMTP:rigter@cafe.net]
> Sent: Friday, August 06, 1999 3:19 PM
> To: beam@sgiblab.sgi.com
> Subject: Re: Low power oscillator
>
> Hi Ben,
>
> There are many solutions and you'll have to provide a bit more
> information to pick the most suitable one. One obvious solution is to
> lower the Vdd of the oscillator chip (only) by inserting a series ~7V
> zener diode. This dramatically reduces the curent consumption but the
> voltage swing is limited to Vbat-7V. A transistor with 1M base and
> collector resistors can restore the output voltage swing to 12V.
> Alternately, the previously posted 74HC4053 voltage doubler circuit can
> easily be adapted provide lowpower and full 12V swing. A micropower CMOS
> OPAMP can do the 12V oscillator with 100uA in an 8 pin package. Finally
> a universal "power smart" design solution could be designed (my
> preference) by adding one or two extra components. The latter may be the
> solution for reducing power in a variety of "high voltage" CMOS
> oscillator circuits.
>
> So we like to know a bit more about your application but at the very
> least: the "end of life" battery voltage, output voltage requirements,
> frequency stability, available space, and your access to purchasing new
> parts.
>
> enjoy
>
> wilf
>
> Ben Hitchcock wrote:
>
> > Although not strictly BEAM, I am putting this question to the list in
> the
> > hope that someone here can help me...
> >
> > I'm doing a project for university where I need a small, low power
> > oscillator. The oscillator must have an on-time of about 0.2 seconds,
> and
> > an off time of 5 seconds.
> >
> > I would like standby power consumption of less than say 0.1 mA.
> >
> > The voltage used is 12 volts (I can't change that). At the moment, I
> have
> > tried a couple of designs of oscillator, using a 74C14 chip but the best
> > power consumption I get is about 3 or 4 milliamps - way too high for the
> > poor little 12 volt battery.
> >
> > The whole circuit is going to fit inside one of those 'car alarm
> > transmitters' which use a 12 volt battery which is about half the size
> of a
> > AAA battery. The whole thing fits very easily into a pocket, or onto a
> > keychain.
> >
> > Any help would be greatly appreciated.
> >
> > Thanks,
> > Ben Hitchcock



Attachment: UPTIMER.gif

Home