Re: [Oap-discuss] Head Control Module (HCM) PCB

[Dafydd W. <dwa...@us...>]

Scott,

> http://www.mindspring.com/~scottcrawford/hcm.png
> http://www.mindspring.com/~scottcrawford/hcm.0.1.tgz

Not bad!

> I welcome your feedback.

I think you can apply most of my last comments (relating to the MCM) to
the HCM too.

There is one other significant change required, though, and that relates
to the voltage regulator.

As I intimated in an earlier posting
(http://sourceforge.net/mailarchive/forum.php?thread_id=3429165&forum_id=35189)
, the 7805 is unsuitable for this module (and the sonar and power
management modules too, for that matter), and needs to be replaced by a
switching voltage regulator such as the PT78ST105H. This part is available
from DigiKey for around $13. Although it has the same pin-out as a 7805,
it has to lie flat, and I think that two additional holes are needed on
the PCB to mount it.

Here's a PDF of the DigiKey catalog that shows the package (style EFA -
Fig 5).

 http://dkc3.digikey.com/pdf/T041/1170-1173.pdf

Unfortunatly, it's not a very good picture, and the best way to get a good
feel for the package footprint, as always, is just to get one and hold it
in your hand. I have a spare, so if you send me your mailing address
off-list, I'll be happy to send it to you.

There is also a vertically mounted version of this component, but
unfortunately, availability is not so good on that version, so it's better
to design the board for the horizontal version, because it's more likely
to be in stock.

Regards,
Dafydd.