From: Jim Meissner (jpmeissner_at_mindspring.com)
Date: 2002-01-13 20:20:04
Dear Joerg:
>> (BTW) I noticed the filter in front of the A/D converter. Do you
>> really mean a 20 K ohm and a 100 nf cap.
> It seemed like a pretty low frequency with a 100 nf.
f-3dB should be 1/(2*PI*R*C) = 79.6 Hz
>> the ADC-input pins in order to reject HF that might find its way
>> into the cable connecting the analog pcbs with the digital pcb.
>I agree that that is the correct location for the filter.
Thank you. I do not have your engineering know-how or simulation tools. My method over the years has been to build and test. My gut feeling was this capacitor was too large. Thanks for the correction.
+++++++++++++++++++++++++++++++++++++++++++++++
>> The schematics are in eagle CAD file-format.
>> If you download a freeware eagle CAD version
>> from www.cadsoft.de
>> you can view the files.
>Thank you I will try that. Is that what you draw your schematics with?
Have you had success with eagle-freeware ?
>> If you are interested I can alternatively convert the *.sch and
>> *.brd files to *.pdf or *.png
>After looking at your last pdf file my computer crashed. I could read it
>but not print it. After that nothing worked. I had to run scandisk from
>DOS to get it back.
Sorry to hear that.
Seems to me like you ran out of memory on win9x.
To avoid such problems in future I need some more infos:
1)Operating system used ? (win95, win98, win98se , WINME , NTxx, win2000, etc.)
2)RAM ?
3)Free space on HD (for swapping)
4)pdf viewer used ? (Acrobat reader Vx.x?)
Yes, I got the Eagle software to work. I have used Orcad in the past, but this is quite different.
I have a Compaq Presario Model 1250 Laptop.
Win98, 300 Mhz, 64 MB ram, 6 Gig hard drive, 2 Gig free, Acrobat 5.0,
I am looking forward to using the Eagle software for presenting better looking schematics. How do you convert the *.sch file to a *.gif?
BTW the link to your schematic came up with an error. I finally got into your website, but was confused as to which file you wanted me to look at. Please tell me which directory to look in and what the file is called.
Thanks for your patience.
Juergen P. (Jim) Meissner
Check out my Website at www.MeissnerResearch.com
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----- Original Message -----
From: Joerg Hansmann
To: buildcheapeeg_at_yahoogroups.com
Sent: Sunday, January 13, 2002 1:44 PM
Subject: Re: [buildcheapeeg]Patient Safety and Input protection
Dear Jim:
----- Original Message -----
From: Jim Meissner <jpmeissner_at_mindspring.com>
To: <buildcheapeeg_at_yahoogroups.com>
Sent: Saturday, January 12, 2002 12:25 AM
Subject: Re: [buildcheapeeg]Patient Safety and Input protection
> ...Normally the
> primary and secondary are wound on to of each other. The picture you
> sent shows that the design of your DC/DC transformer is very good.
So this could be a safe option ?
I have just emailed traco power products, the manufacturer
of the tmv-en DCDC converter series, if their TMV-EN DCDCs are
IEC601-1 compliant.
> It would take several layers of tape under each winding and vacuum
> impregnation make it really good.
>> The primary side of the DCDC (where the batteries would be) is
>> still connected via RS232 to the PC.
>No I had intended to separate the two. The PC side of the opto isolator
>should be powered by the PC or a separate power supply. The DC/DC
>converter would be completely separate when hooked up to a battery and
>insulated from ground. That should work safely.
Then I do not see the point for using the DCDC at all for battery operation.
A LDO regulator would perform better.
Perhaps the pcb layout could be done in a way, that alternatively
for battery operation a LDO could be used, and for DCDC powered
operation a TMV-EN DCDC.
So each user could decide what degree of safety he needs.
> Or if you trust the
> DC/DC then power it from a power supply rather than the battery. That
> should satisfy both?
Could be an option.
>> (BTW) I noticed the filter in front of the A/D converter. Do you
>> really mean a 20 K ohm and a 100 nf cap.
> It seemed like a pretty low frequency with a 100 nf.
f-3dB should be 1/(2*PI*R*C) = 79.6 Hz
>> the ADC-input pins in order to reject HF that might find its way
>> into the cable connecting the analog pcbs with the digital pcb.
>I agree that that is the correct location for the filter.
>> The schematics are in eagle CAD file-format.
>> If you download a freeware eagle CAD version
>> from www.cadsoft.de
>> you can view the files.
>Thank you I will try that. Is that what you draw your schematics with?
Have you had success with eagle-freeware ?
>> If you are interested I can alternatively convert the *.sch and
>> *.brd files to *.pdf or *.png
>After looking at your last pdf file my computer crashed. I could read it
>but not print it. After that nothing worked. I had to run scandisk from
>DOS to get it back.
Sorry to hear that.
Seems to me like you ran out of memory on win9x.
To avoid such problems in future I need some more infos:
1)Operating system used ? (win95, win98, win98se , WINME , NTxx, win2000,etc.)
2)RAM ?
3)Free space on HD (for swapping)
4)pdf viewer used ? (Acrobat reader Vx.x?)
> I hope that my comments are helpful. Sometimes another head and a new
> look at things helps.
Getting a design revised often will certainly improve the
quality. This is the same with GNU licensed open software
design.
Regards,
Joerg
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This archive was generated by hypermail 2.1.4 : 2002-07-27 12:28:36 BST