controlling input voltage on the BS2

Archiver

I need to control the input voltage to a general-purpose pin on the
BS2. This voltage reflects the state of a remote device: When the
voltage is 1.7V, I want to ignore the [noparse][[/noparse]remote] device; however, when
the voltage drops to 1.5V (for a two-second period), I want to
trigger an event on the BS2.

My problem lies in the fact that 1.5V is still "HIGH" on the BS2.
What I need to do is somehow drop this input so that it's
consistently less than 1.5V. (However, given the .2V differential on
the remote device, I'm not sure how to go about this.)

Any tips or insight appreciate!

Thanks,
--Donn

Archiver

There may be a more simple solution, but how about this:

Use a serial ADC chip such as the Texas Instruments TLC548.

The routine to read the chip is very simple, eg the following will work:

ReadAD:
LOW ADenable
SHIFTIN ADdata, ADclock, MSBPRE, [noparse][[/noparse]datafromAD]
HIGH ADenable
if datafromAD < 77 then DOsomething
goto ReadAD

Then, all you have to do is tell the BS2 that if the data from the chip is
less than 77 (approx value representing 1.5V when +Vref is 5V), to do what
you want it to do...

Sample circuit, showing how easy it is to use this chip (and hence other
similar chips from T.I) is at my web site (url below, click on electronics,
follow the links...).


Cheers,


Ben, Wellington, New Zealand.

--
http://www.lennard.net.nz/
Ben Lennard, NCEE, Dip EE

Web Hosting and Electronics R&D

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> From: "donnmoidaho" <donnmo@l...>
> Reply-To: basicstamps@yahoogroups.com
> Date: Wed, 31 Jul 2002 04:46:31 -0000
> To: basicstamps@yahoogroups.com
> Subject: [noparse][[/noparse]basicstamps] controlling input voltage on the BS2
>
> I need to control the input voltage to a general-purpose pin on the
> BS2. This voltage reflects the state of a remote device: When the
> voltage is 1.7V, I want to ignore the [noparse][[/noparse]remote] device; however, when
> the voltage drops to 1.5V (for a two-second period), I want to
> trigger an event on the BS2.
>
> My problem lies in the fact that 1.5V is still "HIGH" on the BS2.
> What I need to do is somehow drop this input so that it's
> consistently less than 1.5V. (However, given the .2V differential on
> the remote device, I'm not sure how to go about this.)
>
> Any tips or insight appreciate!
>
> Thanks,
> --Donn
>
>
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