92Re: [buildcheapeeg] question about safety testing
- Jan 1, 2001Hi,
----- Original Message -----
Sent: Sunday, December 31, 2000 7:09 AM
Subject: [buildcheapeeg] question about safety testing
> --- In firstname.lastname@example.org, "Joerg Hansmann" <jhansmann@g...>
> hi jeorg
> if i understand correctly you have to test every unit that comes out
> of the factory with tests according to the iec601 ?
If IEC601-1 is applicable , I would say: Yes. In series production
probably random samples will be enough after an initial phase.
> one thing about irda versus cable -
> we can use a very simple not irda - infrared comm , that we'll
> specially design with full duplex
For full duplex the forward and the backward channel have
to be designed in a way that they will not interfere with each other.
This could be done with multiplexing (e.g. time-multiplex,
frequency-multiplex etc.) or physically isolated channels
(fibre optics, etc.)
IRDA transceivers simply suffer from scattered light that goes
from the IR-emitter to the IR-receiver in the same device.
IRDA transceivers block their input while transmitting in order
to not receive their own data and to keep the AGC of the
receiver adjusted to the remote device.
Scattered light could be avoided with tubes and lenses and
precise alignment of the two devices.
However the cost-benefit comparison seems unfavourable to me.
> , 115000 baud , and because we have
> to build reciever card - we can build it to connect to printer port
> throught long 5meter cable . this could be very simple little card ,
> that can be put near the device , and he'll get he's power from
> the printer port .
Why printer port ? What advantages do you see over com-port ?
The com-port seems better to me, because
it has windows driver support and is supported by
existing software like Rob's ElectricGuru.
> i think this interface design could be very simple one .
> it's seems o.k. with you ?
Hm, yes... as long as I am not the one, who has to build it ;-)
My current approach to solve the isolation problem
is two optocouplers _inside_ the RS232EEG that are
built of discrete IR-Emitters and Phototransistors and
have an isolation distance of 2cm (that will give protection
of about 20kV ).
For such short distances and fixed alignment there should
not be greater problems and the costs and development
time will be sufficiently low.
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