Subject:
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Re: Battery Level Indicator
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Newsgroups:
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lugnet.robotics.handyboard
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Date:
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Wed, 20 Jan 1999 12:23:43 GMT
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Original-From:
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Fred G. Martin <fredm@media+NoSpam+.mit.edu>
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Viewed:
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844 times
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1. yes, you probably killed your analog 5. the analog inputs are
very sensitive to over voltage. if your ran more than +5v directly
into the input, you probably killed it.
next time you're playing with funky voltages, put a 5K resistor in
series with the funky voltage and the analog input. that should
protect it.
2. you can't tell if the robot is stuck by looking at the system
battery, because (as you discovered!) it doesn't drop by much when the
robot is stuck. one of the properties of nicads is that they can
supply tons of current w/o difficulty.
3. there is a method to measure the voltage drop across the motor
driver chips. this is a reasonable way to see if the motor is
stalled.
this was implemented on the MIT 6.270 board. see page 200 of the
appendix B document listed at
http://el.www.media.mit.edu/projects/handy-board/techdocs/
all you have to do is look at the voltage at the point between the
motor LEDs and their 1K drop resistor. use a 1K resistor between that
point and the analog input.
btw, this only works when you're running the motors at full speed. if
you are using speed control, the readings get messed up.
fred
In your message you said:
> I have been playing around with trying to make a battery indicator on
> my Handy Board. I did find the below diagram from a earlier posting in
> March of 98.
>
> BAT --------R1---------*--------- Analog5 Input
>
> +ve (10K) | (Active)
>
> R2 (4K7)
>
> |
>
> *--------- Gnd (at Analog5
>
> Connector)
>
> I tried this and it didn't seem to work, although if I changed the
> 10K and 47K resistor around I manage to get a reading from analog 5.
>
> I was trying to use the battery indicator to check if my robot had hit
> an object, although the analog reading only seems to drop 1 point
> between
> when the motor is running and when it is stalled. This then makes it
> difficult to determine if the voltage is dropping 'cos the battery is
> running out OR the robot has stalled.
> I guess my question is, is this a good/bad method to check if the robot
> is stuck?. I do like this method of testing if the robot is stuck 'cos
> I
> only have to check one sensor. Are there other better ways like this???
> Any help would be appreicated.......
> Cheers
>
> PS
> In my playing around I think I have zapped analog(5) as it now reads '0'
> when there is no input (OOoouups). Is it truely dead or can I bring it
> back??.
>
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Message has 1 Reply:
 | | Re: Battery Level Indicator
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| (...) When I first got my HC11EVB I ran 12V straight into the E port (one of the pins), and was sure I ruined the chip. I called the tech support person at motorola, and he said 12V on a A/D port should be no problem. Sure enough it all still (...) (26 years ago, 20-Jan-99, to lugnet.robotics.handyboard)
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Message is in Reply To:
| | Battery Level Indicator
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| I have been playing around with trying to make a battery indicator on my Handy Board. I did find the below diagram from a earlier posting in March of 98. BAT --------R1---...---*---...--- Analog5 Input +ve (10K) | (Active) R2 (4K7) | *---...--- Gnd (...) (26 years ago, 20-Jan-99, to lugnet.robotics.handyboard)
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