Subject:
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Re: Low battery detection
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Newsgroups:
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lugnet.robotics.handyboard
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Date:
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Wed, 18 Mar 1998 04:54:44 GMT
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Original-From:
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Patrick Cutts <patrick@surfari.net#stopspammers#>
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Reply-To:
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<patrick@surfari.netANTISPAM>
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Viewed:
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1429 times
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sure, it will drain the battery, but if it's a low enough drain, you don't
have to worry about it. for example if you have a 10 amp-hour battery,
drawing .5 mA would take something like 830 days to drain it. I wouldn't
worry too much.
to calculate the values, just assume a current drain and pick a max
(battery charged) voltage and insert your battery voltage into ohms law
(E=I/R) andout pops your resistor values:
(example) you have a 12 volt battery, you want to have a current drain of
.5 mA and you picked 4.5 volts as your 'fully charged' reading.
12-4.5=7.5
7.5/.0005=15000 so R1=15K
4.5/.0005=9000 so R2=9K
wiring:
connect one end of R1 to the positive term of the battery. connect the
other end of R1 to one end of R2. connect the other end of R2 to the
battery ground. connect the junction of R1 and R2 to an analog input of
the HB.
read the value at the analog input while you have your battery discharged
to the point at which you want some action to be taken.
program your robot to take the action when that analog input goes below the
value determined in the previous step.
----------
> From: Jaron Paludanus <j.paludanus@tip.nl>
> To: 'Brian Lavery' <blavery@acslink.aone.net.au>; • handyboard@media.mit.edu
> Subject: RE: Low battery detection
> Date: Tuesday, March 17, 1998 10:46 AM
>
> Can you translate this into "EE for dummies?".
> I slowly start to grasp some of the idea about
> voltage dividers but still don't understand.
> Won't this setup drain the battery? How does
> one calculate and wire such a thing - in this
> particular case?
>
> I ask this because I want to use a lead battery
> for my lego robot, not only do I have such a
> battery already :) but I understood that the
> characteristics of these things tend to be a
> more gentle curve towards the LOW battery
> situation and thus better measurable.
>
> (Opposed to NICADs steep curve from 1.2 to
> 0 point something very quickly)
>
> Help would be appreciated!
> jaron paludanus
> j.paludanus@tip.nl
>
>
> -----Original Message-----
> From: Brian Lavery [SMTP:blavery@acslink.aone.net.au]
> Sent: Wednesday, October 29, 1997 3:14 AM
> To: handyboard@media.mit.edu
> Subject: Re: Low battery detection
>
>
> > Is it possible for a handy-board program (either 'C' or assembler) to
> > detect a low battery condition?
>
>
> Sure:
> Solder a wire to the "BATTERY +", add 2 resistors to make a voltage • divider
> (to divide the battery ABSOLUTE MAX condition, say about 12V, down to • about
> 4 volts for the analog 0-5v range), and feed it into an ANALOG input • point.
> Put a multimeter on the battery to measure its volts in a LOW charge
> condition, and then in a HIGH charge condition. Read the HB analog input
> value for both those conditions, and assume a linear connection between • bat
> volts and analog reading.
> Pity it wasn't built in!
>
> Brian Lavery
> blavery@computer.org
>
> ============================= ===================================
> Brian Lavery BE MACS MIEEE Tel: +61 (2) 9906 3900
> Technical Manager Fax: +62 (2) 9906 3436
> Online International Pty Ltd Email: <blavery@reservhotel.com>
> 20/130 Pacific Highway Web: <http://www.reservhotel.com>
> St Leonards NSW 2065 and • <www.acslink.aone.net.au/reservhotel>
> Australia Personal: <blavery@computer.org>
> ============================= ===================================
>
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