From: "milton_aupperle" <milton@outcastsoft.com>
Date: August 21, 2011 9:25:18 PM MDT
To: Astro_IIDC@yahoogroups.com
Subject: Re: Guiding HW Addition
Hi John;
Thanks for pointing that out. It should be NPN 3904, - I'll correct this in the version 3 schematics.
My initial understanding of the ST4 pins was that I needed to have the transistor "switch" closed by default so that the ST4 voltage was left high. So that's why I thought the the PNP 3906 was the correct choice.
After I got the first board built, I realized that this was incorrect and the switch needs to be left open by default or the motors will run all the time. So in the second board, I changed it to a NPN 3904 which by default are always open.
The other thing I missed in Version 2 was that I needed to have the Camera ground (pin 5) connected to the ground of the GPIO. Otherwise the GPIO control pins would not trigger.
I'll post Version 3 schema and an image of the cased board on the scope tomorrow.
TTYL..
Milton Aupperle
--- In Astro_IIDC@yahoogroups.com, "John" <jbuckley1@...> wrote:
Hi Milton,
I was looking at the V2 interface jpg and I had a question as to the 3904 transistor. Should the part list it as NPN instead of PNP?
Clear and steady skies,
John B.