From: Moritz von Buttlar (info_at_baltic-microsolutions.de)
Date: 2001-12-13 06:03:04
Hi !
The 6N139s are the cheapest option possible without making it
really dangerous. They are not good enough to pass medical norms.
>Does it need to be one of these expensive isolators?
>I don't think so. Joerg already has 6N139s in the
>design. Does the MAX232 need to be powered separately
>per the HAL specs for proper isolation?
The MAX232 has to be powered separately from the EEG. The easiest way would be
to use some of the RS232 handshaking lines as a power supply. Unfortunately
these don't deliver
enough power for a MAX232. What we could do is make a discrete transistor
design replacing the MAX232 and
powering it from the serial port. The disadvantage is maybe not 100%
compatibility to RS232.
This solution is also cheaper, because the MAX232 is quite expensive.
>Is the irDa
>idea better or is it really overkill?
It would allow our device to pass medical norms and it's not much more
expensive then RS232 with MAX232.
Moritz
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Moritz von Buttlar
Flash uC/DSP Development http://www.baltic-microsolutions.de
Free EEG Design http://openeeg.sf.net
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