Anyone trying to get power from a RS232 port to power external devices is asking for trouble like being experienced here.
There is nothing in the RS232 spec that spec current capabilities other than providing voltages at driving impedances. One might take one port, make measurements and say this is what is needed or can be done. However, another port on a different device/computer will have different parameters and still meet spec. This is one of these issues where the designer just before he got fired says "well it works here". The next designer is left to clean up the mess. 73, ron, n9ee/r >From: "Bob M." <[EMAIL PROTECTED]> >Date: 2008/04/05 Sat PM 08:00:59 CDT >To: Repeater-Builder@yahoogroups.com >Subject: Re: [Repeater-Builder] RIB-less cable circuitry > >Thanks. That's what I was looking for. > >The reason I'm investigating this is that a friend >bought several RIBless cables to program GTX radios. >We used one on his Compaq laptop and it worked just >fine. We then tried to use one on two other computers >- both DELL - and the RIB seemed dead, as in no power. >The GTX thought the RIB was turned off and came up in >trunking test mode. We had to use a real RIB and cable >to finish the job. > >So I bought one of those LED testers for DB9 ports and >found low signals on DTR and RTS, as well as TXD >during idle periods. Starting RSS didn't change the >state of those lines, and as they're the ones that are >providing power, the RIBless cable is dead in the >water. > >Neither Radius, GTX, or Spectra programs activate any >of the serial port control lines to power the RIBless >cable. > >Strangely the MSF5000 program DOES turn both of those >lines on, and leaves them that way when it exits. A >subsequent program can thus use the RIBless cable. > >In a couple of weeks I'll be meeting the guy with the >Compaq laptop and the port tester will be plugged in >so I can see how it powers up. I don't know if a >serial port should activate the modem control lines >when it's initialized by the BIOS, but it certainly is >a problem with these particular RIBless cables. > >Bob M. >====== >--- Scott Zimmerman <[EMAIL PROTECTED]> >wrote: > >> Bob, >> >> Most of these cables use the DTR (pin 4 on a DB-9) >> and RTS (pin7 on a DB-9) >> lines (Data Terminal Ready and Ready To Send) on >> most com ports these are >> configured to be high (5-15v). There is not much >> current here, just a few >> mA. >> >> Here is a good article entitled "Get power out of a >> PC RS-232 Port: >> >http://www.tkk.fi/Misc/Electronics/circuits/rspower.html >> >> Here is a link to a good universal programmer that I >> use on occasion: >> http://www.cqham.ru/uniprog2_eng.html >> This works VERY well and like it's name implies VERY >> universal. The only >> addition I made was to add another diode to the >> input matrix from an >> external power supply. This was for those computers >> with poor serial ports >> and no power available from the radio being >> programmed. I simply used a >> 78L05 voltage regulator instead of the one listed. >> It's not low dropout, but >> it seems to wok fine. >> >> Good Luck, >> Scott >> >> Scott Zimmerman >> Amateur Radio Call N3XCC >> 474 Barnett Rd >> Boswell, PA 15531 >> >> ----- Original Message ----- >> From: "Bob M." <[EMAIL PROTECTED]> >> To: <repeater-builder@yahoogroups.com> >> Sent: Saturday, April 05, 2008 2:51 PM >> Subject: [Repeater-Builder] RIB-less cable circuitry >> >> >> > Does anybody know of schematics for RIB-less >> cables? >> > I'm trying to find out which pin(s) they use to >> get >> > power from the serial port to operate the >> circuitry >> > built into the DB9 connector body. >> > >> > I've got a couple that seem to be dead on two >> > computers but run fine on another one and I >> suspect >> > some very slight differences in the serial port >> > configurations when the machines are booted up. >> > >> > If you have links for such schematics, just post >> those >> > rather than the entire image which won't make it >> > through Yahoo's e-mail system. >> > >> > Thanks. >> > >> > Bob M. > >__________________________________________________________ >You rock. That's why Blockbuster's offering you one month of Blockbuster Total >Access, No Cost. >http://tc.deals.yahoo.com/tc/blockbuster/text5.com > > Ron Wright, N9EE 727-376-6575 MICRO COMPUTER CONCEPTS Owner 146.64 repeater Tampa Bay, FL No tone, all are welcome.
