From: Joerg Hansmann (info_at_jhansmann.de)
Date: 2002-01-13 19:15:27
Hi Andreas ,
----- Original Message -----
From: Andreas Robinson <sleeper75se_at_yahoo.se>
To: <buildcheapeeg_at_yahoogroups.com>
Sent: Sunday, January 13, 2002 4:48 PM
Subject: [buildcheapeeg] Re: optical coupler
...
> Since the topic has been brought up, I'm attacing a
> new serial-port-powered fiber-optic receiver I'm
> considering for the TinyEEG. It is based on a
> micropower (0.47 mA) comparator that is very fast
> (60ns).
Nice circuit.
If the comparator could handle +-12V supply voltage,
it could drive the RxD line of the PC without DS275.
> The increased speed and reliability comes with
> increased cost. I've made some calculations below,
> going from high end to low end with various solutions:
>
> 1. Fiber LED & photodiode + comparator + DS275: $18.50
> 2. Regular LED & photodiode + comparator + DS275: $10
> 3. Regular LED & photodiode + comparator & 4053: $6
> 4. Regular LED & photodiode + transistor driver: $2
I have done some transient simulations for "4." and
found it to be too much at its limit for 112000 baud.
> No 1 is intended for fiber while no 2, 3 and 4 are
> useful for wide-spacing optocouplers. 2-4 can be used
> for fiber as well, but you would have to make your own
> connectors.
How much tolerance in current transfer ratio can the receiver
handle ? So how precisely must the IR emitter and the
receiver be aligned or how precisely must the fiber be mounted ...
and how difficult is the mounting of the optical fiber ?
> Option 1 relies on these parts (available at Digikey):
>
> FB134-ND - Plastic Fiber Optic IR-LED (7ns): $5.25
> FB128-ND - Plastic Fiber Optic Red LED (100ns): $4.88
> FB120-ND - Plastic Fiber Optic Photodiode (5ns):
> $4.18
>
> So, the question is now: Which option does the people
> of the group prefer?
1.) without DS275 (why a level converter if we have +-12V ? Or have I missed
something ?) it looks good to me.
Regards,
Joerg
BTW.:
Have you yet tried to use a third party opamp model in SWCAD ?
I have just downloaded a TLC272 macromodel from TI and now I
am trying to include it in the SWCAD library...
until now not very successfully.
This archive was generated by hypermail 2.1.4 : 2002-07-27 12:28:36 BST