Re: [Oap-discuss] TI Powertrends 78ST105HC Replacement

[Dafydd W. <daf...@gm...>]

Hi Scott,

When I drew the original prototype schematics, I wondered about separating
the power regulation, and running the regulated 5V around some of the
modules, but then I backed away from the idea, because I was concerned
about noise crosstalk between the modules (the sonar module is particularly
thirsty and "spikey" in power needs, and the pan-tilt module isn't much
better IIRC). I stuck with separate regulators in the end, so you could
wire up each module directly to the robot's main lead-acid battery with
little risk of introducing noise crosstalk.

If you decide to go down this central power regulation path, though, I
would strongly encourage you to add multiple 5V output connectors to the
power board, to encourage the power to be distributed in a "star"
configuration to each module, rather than in a "bus" configuration (the
latter is just asking for trouble).

I would also check to make sure that you don't break the bank in terms of
current capacity and make sure that the heat-sink is adequate to deal with
all the sonars firing at full-pelt at the same time as the pan and tilt
servos are moving (with a realistic head load mounted).

The thickness of the wiring between such a power module and the modules
must also be considered; the gauge has to be adequate to carry the current
for each module.

If you do this, it's probably a good idea to add a decent sized reservoir
cap (electrolytic, about 100uF) at the power input of each module to help
smooth the bumps too.

Regards,
Dafydd.






2013/11/29 Scott Crawford <rob...@gm...>

> Hi Dafydd,
>
> Thanks for the feedback on the schematic updates.
>
> I've added another i2c connector the HCM to support the TPA81.
> http://www.openautomaton.org/index.php/HCM
>
> I'm working on the TI Powetrends replacement schematic and PCB layout.
> Replacing these surface mounted components with through-hole equivalents
> will increase the PCB sizes, and drive up the component cost a few
> dollars.  While the LM2592HV costs less than the TI Powertrends, it means
> that the designer must supply a heatsink, inductor, and schottky diode.
>
> What do you think about reducing the number of DC-DC regulators in the
> design?  The TI powetrends is used on the PMM, HCM, and SAM.
>
> Could a single DC-DC PCB be used to power the PMM PIC, and supply the 5V
> LCD display, HCM, and SAM?
>
> Thanks,
> --scott c.
>
>
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