[hpsdr] Penny DB25 Pin 25 Open Collector Return

[Phil Harman]

Hi Raj,

Pin 9 of the ULN2003 is the common point for the back EMF suppression diodes 
of all the open collector outputs.  You can either use individual diodes on 
each external relay OR  connect pin 25 of the DB25 to the positive 
connection of your relay supply to use the diodes built into the ULN2003.

We did not connect this pin to V+ intentionally since that way you have the 
maximum flexibility as to external relay supplies.

You can use the Penny outputs with up to 7 transverters.  The limitation of 
2m is only a GUI| issue - you can change it yourself or be very nice to a 
programmer who can do it for you :)

73s es HNY Phil...VK6APH



----- Original Message ----- 
From: "Rajiv Dewan, N2RD" <n2rd at arrl.net>
To: <hpsdr at openhpsdr.org>
Sent: Friday, January 01, 2010 10:40 AM
Subject: [hpsdr] Penny DB25 Pin 25 Open Collector Return


> ***** High Performance Software Defined Radio Discussion List *****
>
> I am trying to interface the Elecraft XV series of transverters to the
> Penny.  I noticed that I am getting just 0.17v on pin 25 of the DB25
> connector on the Penny.  Looking at the schematic and the board, it
> appears that Pin 9 of the ULN2003 is only connected to pin 25 of the
> DB25 connector and not connected to V+ at all.   Is this correct?  Do I
> have to apply external power to pin 25 to use the open collector outputs?
>
> On the X2 connector of SDR1K, the collector reference was internally
> connected to V+.  It appears not be so for the Penny.
>
> Also, I want to use 4 transverters with 28MHz IF. Can these be mapped to
> the Penny outputs?  I notice that Penny setup only lists bands up to 2m.
>
> Raj, N2RD
>
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