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

[Scott C. <rob...@gm...>]

Hi Dafydd,

Would you mind taking a look at this design?  Is this what you had in mind?
http://www.openautomaton.org/index.php/PowerDistribution

Three TI Powertrends 78ST105HC replacement PCBs will cost about $50USD.
http://www.openautomaton.org/index.php/PowerConverter

This shows two of the OAP modules, modified to use +5V power:
http://www.openautomaton.org/index.php/PMM2
http://www.openautomaton.org/index.php/HCM2

Thanks,
--scott c.


On Sun, Dec 1, 2013 at 4:31 AM, Dafydd Walters <daf...@gm...>wrote:

> 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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>
>
> --
> LinkedIn: http://www.linkedin.com/in/dafyddwalters
>
>
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