Subject:
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Re: Help with converting voltage on circuit board
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Newsgroups:
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lugnet.robotics, lugnet.technic
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Date:
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Sat, 8 Apr 2006 00:15:00 GMT
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Viewed:
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2806 times
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In lugnet.robotics, Dustin Jones wrote:
> I'd like to try to convert the output of the voltage on a 9750 from 4V to 12V
> (to control 12V trains :).
>
> I've taken a photo of the internal circuit board - my rudimentary EE knowledge
> leads me to be believe I need to swap out the transistors that are next to the
> output connections.
>
> Can anyone confirm or lead me in the right direction?
>
> http://homepage.mac.com/dustinmj/PhotoAlbum15.html
>
> Thanks!
>
> Dustin
Wow - I remember those, we used them at school. Now why is it that Peeron do not
have an entry for it under 9750?
Those are also some big old capacitors, I would be inclined to check out their
ESR (a rating of their health if you like) before anything else.
Now, is there any chance of an enhanced photo, where I may be able to see the
manufacturer codes on the IC's? Although I am inclined to beleive that at least
one of those is a voltage regulator (as Jonathan Said), they might not both be.
I note their is a DC cigar style adaptor on the top right - is that 9v or 12v
DC? you would be able to get a 12v supply from there maybe, but you wouldnt be
able to get it directly to the motors without your own set of H-Bridges, as
those ones around the ports might overheat very quickly at 9v. You could buy a
bunch of L298 series single chip dual bridges to do that job these days, and
give them a heatsink to handle the load.
However, this could be even simpler. I cannot remember if this device (the 9750
but I also cant remember the name of it) had speed control, or just forward,
stop and reverse. If it is that simple, you may want to just use relays,
attached to the existing ports to drive their coils, and connecting the motors
with the 12v supply on their switching contacts. I would be furthar inclined to
do this anyway, as trains tend to run for much longer periods in one direction
than most of the robots I build, and that could be enough to push many h-bridge
power transistors over their limits.
I just love the way they have positioned the motor h-bridge (at least I assume
they are) power transistors around the port. Any chance of a similar good photo
of the tracks on the underside too?
Cheers,
Danny
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