From: sleeper75se (sleeper75se_at_yahoo.se)
Date: 2002-03-06 02:48:49
Hi Joerg,
Thanks for your input, it is very valuable!
--- In buildcheapeeg_at_yahoogroups.com, "Joerg Hansmann" <info_at_jhansmann.de> wrote:
> What cables ? I thought your DCDC were pcb mounted ?
> (at least I had this impression from the pcb layout)
I wish I had a camera.... There are two dc/dc converters. Connected
to the mains is a medical power supply.
Data: IEC60601-1 compliant, 13.2V 3A output, 50mV ripple, 40kHz
switching frequency, switching noise energy in the 15-20MHz range.
Connected to the medical power supply is a PCB holding filters and a
dual output DC/DC converter given to me for free, by Scott Elofson.
Data: 500V isolation, +/-12V, +/-300mA, 20mV ripple with a 3uF
capacitor, 200kHz switching frequency.
I didn't put much effort in designing the filter. It was like "oh,
and by the way...", basically ignoring Jim's advice on capacitors
(sorry) and not following any common sense rules. So much for rushing
things... :-p
I'll get some EMC-parts tomorrow and backtrack a bit (new PCB). The
battery and the mains-powered solutions are worked on in parallel,
because they share 5V linear regulators and EMI filters.
> And don't get me wrong: I did not want you to break anything
> open...
Don't worry, I realized that. This medium (text only) is not very
suited for this kind of collaboration.
> BTW: The thing with putting the 10nF C close to the output (with X
> shaped traces) assumes that the DCDC has some output impedance
> (should be listed in the datasheet of the DCDC)
The medical power supply has a long cable. Shortening it to 10-15 cm,
and winding it a few turns on a ferrite toroid creates a 10-20uH
inductor that will be part of the filter.
> > Hmm, maybe I was unclear. The filter is not performing
> > well,
>
> In theory or in practical experiments ?
In theory, (I can hear someone on the list cringe... ;-) the
electrodes are not finished yet. I want decent offset handling,
because I don't think the electrodes will work as well as the ones
Jim use. Then again +/-15mV might be sufficient. We'll see...
> I would like to know, what DC offset the Abhayamudra unit
> can handle:
The designer is taking questions over at the Mind-L list. Considering
his openness on the specs, I think you will get answers to any
questions you may have (please share his answers if you ask him
anything).
Follow this link to get his e-mail address:
http://groups.yahoo.com/group/mind-l/message/19812
Regards,
Andreas
This archive was generated by hypermail 2.1.4 : 2002-07-27 12:28:39 BST