Subject:
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Re: External motor power and expansion board combo problem?
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Newsgroups:
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lugnet.robotics.handyboard
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Date:
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Thu, 31 Jan 2002 04:17:03 GMT
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Viewed:
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6627 times
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Duncan,
You've done a good analysis of the potential impact of changing the motor
supply to an external source....when you are using the Expansion Board.
Undoubtedly there are several ways to accomplish what you want, but the way
I did it DOES require cutting one trace. Unfortunately, the trace is tough
to get to once J13 is installed on the HandyBoard. I ended up pulling J13
and reinstalling IT after the cut.
DON'T ATTEMPT THIS IF YOU'RE NOT ABSOLUTELY POSITIVE YOU KNOW WHAT YOU'RE
DOING.......MISTAKE(S) CAN DESTROY YOUR HANDYBOARD ----and the smoke makes
it hard to see !!!
Remove the Expansion Board and place the HB on the table with the component
side up and the red/green motor LEDs at the "top". This puts J13 to your left.
Look at a copy of the component side of the PCB and it will make this easier
to understand.
The "top" two J13 pins (+) are connected to the interal HB battery pack via
the HB power switch. On the component side of the PCB, there is a trace
from these top two (+) J13 pins over to pin 8 of Ull (L293D). This trace is
very short since pin 8 of U11 is right next to J13.....you need to cut this
trace BETWEEN J13 and U11 pin 8. Make a nice narrow cut and actually remove
a small amount of the copper foil so you definitley have isolated J13's
upper two (+) pins from U11 pin 8. A sharp pointed Exacto knife is perfect
for this job.
Once you've made the cut, you can go to the underside (solder side) of the
PCB and find the "V with wings" shaped trace that connects U11 pin 8 to U10
pin8. This is a nice fat trace and a good place to solder on a new wire
which will go to the external motor supply battery pack positive (+).... via
a switch and/or connector. I used both so I can easily remove the external
battery pack and also have an easy way to kill power to the motors. This is
handy for software troubleshooting and not having the motors run. Be
advised that you will get some "funny" motor LED indications when you have
the external motor supply turned off.
The heavy trace on the solder side at the top edge of the board above the
red/green motor LED connections is where you can solder the negative (-)
lead to your external motor supply battery.
!!!!!!!!!!! WARNING WARNING WARNING !!!!!!!!!!!
If you're not COMPLETELY sure of what to cut and where to connect, don't
touch the PCB.....you can easily destroy the HB.
I must also say that there is ZERO tolerance for connecting the external
battery up backwards.
!!!!!!!!!!! end of warning !!!!!!!!!!!!!!!!!
OK, there is it. Mine works. You're on your own. Drop me a line if you
have any questions.
Regards,
John
Duncan Lawrence writes:
> I wish to make the small mod to allow for external power to the motor
> outputs of the main board. However, this seems to cause several potential
> problems with the expansion board.
>
>
> Does it require some track cutting and re-wiring to solve problems 3 and 4?
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