From: Joerg Hansmann (info_at_jhansmann.de)
Date: 2002-05-08 10:20:58
Hi Andreas,
----- Original Message -----
From: sleeper75se <sleeper75se_at_yahoo.se>
To: <buildcheapeeg_at_yahoogroups.com>
Sent: Wednesday, May 08, 2002 1:59 AM
Subject: [buildcheapeeg] Another update
> Hmm, this place has been very quiet for a long time now.
>
> Time for a small update - again:
> The serial port powered optocoupler works! It has been tested with a
> desktop PC serial port and an RS232-to-USB converter (Palm USB kit).
> I will test on a laptop as soon as I get my hands on one.
>
> The schematic is uploaded to
>
> http://groups.yahoo.com/group/buildcheapeeg/files
>
> under hardware design/RS232TX
I have just downloaded it and have a few questions:
What total current / power consumption does the circuit have ?
And what maximum baud rate ?
What happens at increased temperatures e.g. 60 degrees Celsius ?
Probly nothing, because you are using quite high photo currents
up to 30uA.
I am only asking because recently I have tried to build a POF
receiver based on your 2 transistor design (slightly modified,
9600baud and ca. 10m fiber length) and ran into some difficulties
at higher temperatures because the reverse current through
the photo-diode increased and got greater than the photocurrent.
(In the attachment is a schematic of a 1 op-amp solution with
thermal compensation, that should work with 500nA photocurrent
and up to 115200 baud. The simulation does not work as expected,
because the TL071 model file from TI is definitely wrong (10 times
supply current and 1/20 slew rate))
> (I suppose Joerg and Moritz and a few others is my entire audience
> here...? :-)
Difficult to tell. All subscribers could be listening ... ;-)
> Anyway, my projects chug along. The goals are a bit clearer and
> closer now, and I am looking forward to the end of the hardware-
> design phase and start of the software-design phase.
>
Regards,
Joerg
This archive was generated by hypermail 2.1.4 : 2002-07-27 12:28:43 BST