Forums

how to extract +12V from RS232

Started by Marcellus Pereira April 27, 2004
Dear ALL,

I'm trying to use the ADuM1301 to isolate my embedded system from the
PC.

How can I extract +12V from RS232 DB9? With two diodes? But in what
pins?

Thanx,

Marcellus
On Tue, 27 Apr 2004 17:08:35 -0300, Marcellus Pereira
<mpereira.nospam@myrealbox.com> wrote:

>Dear ALL, > >I'm trying to use the ADuM1301 to isolate my embedded system from the >PC. > >How can I extract +12V from RS232 DB9? With two diodes? But in what >pins? > >Thanx, > >Marcellus
Well, I found the solution ____ 1N4148 | | 4 )--------->|-----o------|7805|--------+------------ +5V | |____| | 1N4148 | | | 7 )--------->|-----o | | | | | | | ' --- | --- --- | --- | 100uF | |100uF | | | | | | 5 )----------------o--------o-----------o------------ GND RS232C created by Andy&#2013266100;s ASCII-Circuit v1.24.140803 Beta www.tech-chat.de Thanks a lot, Marcellus Pereira
In article <1s2u805c6mojpuoeofkj8euntlbufv0r22@4ax.com>, Marcellus Pereira wrote:

>>How can I extract +12V from RS232 DB9? With two diodes? But in what >>pins? > > Well, I found the solution > > > > ____ > 1N4148 | | > 4 )--------->|-----o------|7805|--------+------------ +5V > | |____| | > 1N4148 | | | > 7 )--------->|-----o | | > | | | > | | ' > --- | --- > --- | --- > | 100uF | |100uF > | | | > | | | > 5 )----------------o--------o-----------o------------ GND > > RS232C
You do realize that produces 5V rather than 12V? -- Grant Edwards grante Yow! The PINK SOCKS were at ORIGINALLY from 1952!! But visi.com they went to MARS around 1953!!
Grant Edwards wrote:

> In article <1s2u805c6mojpuoeofkj8euntlbufv0r22@4ax.com>, Marcellus Pereira wrote: > > >>>How can I extract +12V from RS232 DB9? With two diodes? But in what >>>pins? >> >>Well, I found the solution >> >> >> >> ____ >> 1N4148 | | >> 4 )--------->|-----o------|7805|--------+------------ +5V >> | |____| | >> 1N4148 | | | >> 7 )--------->|-----o | | >> | | | >> | | ' >> --- | --- >> --- | --- >> | 100uF | |100uF >> | | | >> | | | >> 5 )----------------o--------o-----------o------------ GND >> >> RS232C > > > You do realize that produces 5V rather than 12V? >
And even so, given the limited current available from the port, he'd be better off using say a TC55 that doesn't gobble so much in quiescent current. Paul Burke
"Paul Burke" <paul@scazon.com> wrote in message
news:c6nlif$d2j26$2@ID-128611.news.uni-berlin.de...
> Grant Edwards wrote: > > > In article <1s2u805c6mojpuoeofkj8euntlbufv0r22@4ax.com>, Marcellus
Pereira wrote:
> > > > > >>>How can I extract +12V from RS232 DB9? With two diodes? But in what > >>>pins? > >> > >>Well, I found the solution > >> > >> > >> > >> ____ > >> 1N4148 | | > >> 4 )--------->|-----o------|7805|--------+------------ +5V > >> | |____| | > >> 1N4148 | | | > >> 7 )--------->|-----o | | > >> | | | > >> | | ' > >> --- | --- > >> --- | --- > >> | 100uF | |100uF > >> | | | > >> | | | > >> 5 )----------------o--------o-----------o------------ GND > >> > >> RS232C > > > > > > You do realize that produces 5V rather than 12V? > > > > And even so, given the limited current available from the port, he'd be > better off using say a TC55 that doesn't gobble so much in quiescent > current. >
And further, if you are running this from a PC serial port, you are unlikely to be suppling the regulator with +12V - some PC serial ports only output +5V. Andrew
In article <c6nlif$d2j26$2@ID-128611.news.uni-berlin.de>, Paul Burke 
<paul@scazon.com> writes
>Grant Edwards wrote: > >> In article <1s2u805c6mojpuoeofkj8euntlbufv0r22@4ax.com>, Marcellus >>Pereira wrote: >> >>>>How can I extract +12V from RS232 DB9? With two diodes? But in what >>>>pins? >>> >>>Well, I found the solution >>> >>> >>> >>> ____ >>> 1N4148 | | >>> 4 )--------->|-----o------|7805|--------+------------ +5V >>> | |____| | >>> 1N4148 | | | >>> 7 )--------->|-----o | | >>> | | | >>> | | ' >>> --- | --- >>> --- | --- >>> | 100uF | |100uF >>> | | | >>> | | | >>> 5 )----------------o--------o-----------o------------ GND >>> >>> RS232C >> You do realize that produces 5V rather than 12V? >> > >And even so, given the limited current available from the port, he'd be >better off using say a TC55 that doesn't gobble so much in quiescent >current. >
I use a zener diode to regulate the voltage in a similar circuit we use, but in fact there is rarely much more than 5V available. When used with laptops it sometimes doesn't work at all. -- Tim Mitchell
"Paul Burke" <paul@scazon.com> wrote in message
news:c6nlif$d2j26$2@ID-128611.news.uni-berlin.de...
> > You do realize that produces 5V rather than 12V? > > And even so, given the limited current available from the port, he'd be > better off using say a TC55 that doesn't gobble so much in quiescent > current.
Schottky diodes are slightly better due to their lower forward voltage drop. As for regulator, I am using LM2931 - low dropout, low Iq at low Uin.
On Wed, 28 Apr 2004 09:03:10 +0100, "Andrew Jackson" <alj@nospam.com>
wrote:

> >"Paul Burke" <paul@scazon.com> wrote in message >news:c6nlif$d2j26$2@ID-128611.news.uni-berlin.de... >> Grant Edwards wrote: >> >> > In article <1s2u805c6mojpuoeofkj8euntlbufv0r22@4ax.com>, Marcellus >Pereira wrote: >> > >> > >> >>>How can I extract +12V from RS232 DB9? With two diodes? But in what >> >>>pins? >> >> >> >>Well, I found the solution >> >> >> >> >> >> >> >> ____ >> >> 1N4148 | | >> >> 4 )--------->|-----o------|7805|--------+------------ +5V >> >> | |____| | >> >> 1N4148 | | | >> >> 7 )--------->|-----o | | >> >> | | | >> >> | | ' >> >> --- | --- >> >> --- | --- >> >> | 100uF | |100uF >> >> | | | >> >> | | | >> >> 5 )----------------o--------o-----------o------------ GND >> >> >> >> RS232C >> > >> > >> > You do realize that produces 5V rather than 12V? >> > >> >> And even so, given the limited current available from the port, he'd be >> better off using say a TC55 that doesn't gobble so much in quiescent >> current. >> >And further, if you are running this from a PC serial port, you are unlikely >to be suppling the regulator with +12V - some PC serial ports only output >+5V. > > Andrew > >
Yes, I really need 5V... I dont know why I'd wrote 5V... too much coffe... you know. =) In my 5 computers, the serial port has +- 12V... I think that, in the near future, the max voltage will be +-5V, and I will need to change the circuit. I need this voltage to power an Analog Device ADuM1301, to get galvanic isolotion from my embedded circuit... it needs less than 2mA ( up to 1Mbaud ). []s Marcellus