Alt-BEAM Archive
Message #02038
To: Wilf Rigter Wilf.Rigter@powertech.bc.ca
From: Steven Bolt sbolt@xs4all.nl
Date: Mon, 5 Apr 1999 16:30:29 +0200 (CEST)
Subject: [alt-beam] Re: Better 74HC design
On Mon, 5 Apr 1999, Wilf Rigter wrote:
> Here are the results of testing a National 74HC14 CMOS oscillator of
> SunEater_IV type described earlier by Steven Bolt with and without the
> series input resistor (10M) at various supply voltages. The range of
> voltages tested was from 5.2V to 1.2V. Below 2.0V, the operating current
> drops almost to zero and there was no improvement using the 10M resistor.
> The 74HC14 oscillator actually worked down to 800mV at which point the
> current was less than 100nA.
Great fun, isn't it? I much enjoy micropower design, and 74HC logic
gives you *very* nice results.
> The same frequency and pulse/pause ratio was used for all tests
> although low duty cycle actually increased the current consumption of the
> oscillator itself, with or without the series resistor. The sampling
> threshold detector was not part of the test circuit since it is not directly
> affected by the series 10M resistor.
>
> Vcc w/o 10M (uA) with 10M (uA)
>
> 1.2 1.0 1.0
> 2.0 7.1 6.4
> 2.5 22.5 18.7
> 2.7 31.8 26.0
> 3.0 50.9 39.1
> 4.0 131 100
> 4.5 183 138
> 5.2 326 231
Nice work, and useful data.
> Interestingly, a 74C14 required only 10uA @ 3.0V and 1uA @ 2V
>
> After the experiment, I am convinced of the benefits of operating
> low-power HC BEAM type circuits at 2V or even 1.2V.
The 74HC-based SunEaters are intended to operate between about 1V
and 2.5V. The motor(s) are always switched off at a level which
allows any other 74HC logic in the circuit to retain state or even
continue operating, in the hope that some use for such `brain
activity' will occur to someone. Since the Icc of a good brain
design would drop to very low levels, brain state/activity could
easily survive a night, when a larger storage cap is used. The
SunEater_IV/V approach would still allow short motor bursts for
attractive photovore behaviour.
Best,
Steve
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# sbolt@xs4all.nl # Steven Bolt # popular science monthly KIJK #
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