From: Andreas Robinson (sleeper75se_at_yahoo.se)
Date: 2002-01-13 15:48:51
--- In buildcheapeeg_at_yahoogroups.com, michalchik_at_aol.com wrote:
> I was wondering if anyone has thought about using
> a simple electro-optical coupler to isolate the EEG
> from the computer. That seems simpler than try to
> go through an IR. port.
Hi,
if you are referring to an IC with a led and a
photo-diode, the answer is yes. But there are safety
issues, so other solutions are also interesting.
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).
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
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.
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?
/Andreas
PS. The PCB is coming along nicely. DS.
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This archive was generated by hypermail 2.1.4 : 2002-07-27 12:28:36 BST
