From: Joerg Hansmann (info_at_jhansmann.de)
Date: 2001-12-22 18:09:12
Hi Doug ,
----- Original Message -----
From: Doug Sutherland <wearable_at_earthlink.net>
To: <buildcheapeeg_at_yahoogroups.com>
Sent: Tuesday, December 18, 2001 3:43 AM
Subject: Re: [buildcheapeeg] ModularEEG Parts Questions
...
> One more question: sometimes I run the embedded
> PC from a 12V 3A AC/DC adapter. This feeds into
> the PT6302A. I also sometimes use a vehicle
> cigarette lighter power cord feeding into this
> regulator. The 9-30VDC input range allows me to
> run off AC/DC or vehicle power or NiMH cells
> (12VDC). Are there any safety issues with using
> the AC/DC adapter or vehicle power (assuming I
> have the 6139Ns and TMA0505S installed)? Is it
> safe, or can I only use it on battery power?
Safety is a relative concept ;-)
Assurance companies (and safety norms) use risk-calculations
instead.
Just an example without real data:
If you get a probability of 1 severe accident leading
to injury or death in 1.46*10^8 users*hours
that would mean that 100000 users have used their EEG
4hrs per day each day of one year.
The probability for you as a single user to survive
1 year of EEG-usage would be 99.999%,
however if you are the unlucky one of the 100000 users
you are dead after this year (and the EEG manufacturer
will be sued ...).
If you want to be safer (whatever that means in exact values )
you should use the
HCNW139 Optoisolator (high-voltage 6N139 type, needs layout-change due to
wide-DIP -package )
"...
Safety Approval
UL Recognized - 2500 V rms
for 1 Minute and 5000 V rms*
for 1 Minute per UL 1577
CSA Approved
VDE 0884 Approved with VIORM = 1414 V peak for HCNW139 and HCNW138
BSI Certified (HCNW139 and HCNW138)
..."
and the
TMV-0505EN type with 3000Vrms isolation:
>From the TMV-EN datasheet (tmv-en.pdf):
"...
The TMV-EN series are DC/DC converters with supplementary high I/O-isolation,
which is requested by European safety standards EN 60950 and EN 41003.
They are designed for applications with particular safety requirements,
i.e. information technology equipment (PC-modems, Multimedia cards)
or medical equipment.
..."
[copy and paste from my posting from 16. December 2001 17:03]
<<<<<<<<<<<
...
One issue about the DCDC converter is isolation voltage:
The TMx-Series (http://www.tracopower.com/products/tma.htm)
comes in 3 isolation grades:
TMA: 1000 VDC
TMV: 3000 VDC
TMV-EN: 250Vrms working voltage, 3000Vrms, 6000Vpk
I assume the TMV0505EN should provide sufficient protection:
The brainmaster specifications say:
www.brainm.com/productinfo/bmr2emodule/systemspecs/systemspecs.html
...
Isolation: optically isolated to 130 volts (continuous) or 1500 V (1 sec)
...
The TMV-EN would provide twice of the BM isolation.
So I conclude that the BM is not IEC601-1 approved
(because that would require 5500V isolation)
On the other hand however the BM is FDA approved.
That means, there must be another norm that is
much simpler to comply to get the FDA approval.
...
>>>>>>>>>>
Regards,
Joerg
This archive was generated by hypermail 2.1.4 : 2002-07-27 12:28:36 BST