So, this is interesting thread, my question is why? What is better -48 or +48? Or any of those options. Why does telcom standardize on -48? There has to be a reason?
Dennis Burgess, Mikrotik Certified Trainer MTCNA, MTCRE, MTCWE, MTCTCE, MTCINE, MTCSE, HE IPv6 Sage, Cambium ePMP Certified Author of "Learn RouterOS- Second Edition” Link Technologies, Inc -- Mikrotik & WISP Support Services Office: 314-735-0270 Website: http://www.linktechs.net Create Wireless Coverage’s with www.towercoverage.com -----Original Message----- From: AF <af-boun...@af.afmug.com> On Behalf Of Chuck McCown via AF Sent: Monday, May 2, 2022 2:25 PM To: AnimalFarm Microwave Users Group <af@af.afmug.com> Cc: Chuck McCown <ch...@go-mtc.com> Subject: Re: [AFMUG] -48vdc site + goes to + - goes to - Always. Giving something -48 means you have grounded the + side of the power supply. Giving something + 48 means you have grounded the - side of the power supply. Giving something 48 might mean neither side is grounded and it is a floating power supply. Some devices use chassis ground in common with the power input. If a device grounds the negative side of the power input internally, then it will need a positive or floating supply. If a device grounds the + side of the power circuit internally then it needs a negative or floating supply. Lots of telecom gear is in this category. If you take a device and measure each side of the power input to ground, and find continuity from + or - to the chassis, you need to match that to the polarity. If you measure it and find no connection to the chassis, there is a chance it does not care. However powered off continuity measurements could change with power on. If you have it powered on on the bench and measure from the chassis to either side of the power input, and get a strong reading matching the input voltage on one of the leads, the the input of the device is definitely using the chassis as a ground. The ground can be positive or negative, whatever the designer decided it was. But you can still run -48 devices off of floating 48. And you can run them off of +48 under certain circumstances. 1) You have to insulate the chassis from ground. Best to put a warning sign on it that the chassis is hot. 2) It cannot have any external connections that contain a chassis connection like a coax with the shield connected to the chassis. A CAT5 cable drain wire would also short it out. As would most POE configurations. If it is a router, in a plastic box, without POE connections, you might get away with it. -----Original Message----- From: Christopher Tyler Sent: Monday, May 2, 2022 1:08 PM To: AnimalFarm Microwave Users Group Subject: Re: [AFMUG] -48vdc site So when I hook that up to -48vdc, do I just give it -48 or do the leads need to be reversed? -- Christopher Tyler Senior Network Engineer MTCRE/MTCNA/MTCTCE/MTCWE Total Highspeed Internet Solutions 1091 W. Kathryn Street Nixa, MO 65714 (417) 851-1107 x. 9002 https://imsva91-ctp.trendmicro.com:443/wis/clicktime/v1/query?url=www.totalhighspeed.com&umid=DA1B4682-DE0E-8C05-B4D1-EEC052AE5800&auth=079c058f437b7c6303d36c6513e5e8848d0c5ac4-1b5009a16c4202d4b572fc090c86aa255586d48f This institution is an equal opportunity provider and employer. Esta institución es un proveedor de servicios con igualdad de oportunidades. ----- Original Message ----- > From: "castarritt" <castarr...@gmail.com> > To: "AnimalFarm Microwave Users Group" <af@af.afmug.com> > Sent: Monday, May 2, 2022 1:58:47 PM > Subject: Re: [AFMUG] -48vdc site > I asked this list the same thing a while back and the answer was > Meanwell RSD-500C-48. You can probably get away with a lower power > rating than the > 500 > watt I chose if you are only powering a 'tik and not a pile of Cambium > radios like I was. > > On Mon, May 2, 2022 at 1:48 PM Christopher Tyler < [ > mailto:ch...@totalhighspeed.net | ch...@totalhighspeed.net ] > wrote: > > > Need some help from the smarter than me electrical engineers here on > the list... > > What is the best way to power a Mikrotik router that takes +18-56vdc > from -48vdc source? Providing part numbers or model numbers would be > greatly appreciated. > > We tried the redneck engineering approach of just reversing the > polarity and it popped the fuse, nice little light show, but > ultimately unproductive. > > -- > Christopher Tyler > Senior Network Engineer > MTCRE/MTCNA/MTCTCE/MTCWE > > Total Highspeed Internet Solutions > 1091 W. Kathryn Street > Nixa, MO 65714 > (417) 851-1107 x. 9002 > [ > https://imsva91-ctp.trendmicro.com:443/wis/clicktime/v1/query?url=http%3a%2f%2fwww.totalhighspeed.com&umid=DA1B4682-DE0E-8C05-B4D1-EEC052AE5800&auth=079c058f437b7c6303d36c6513e5e8848d0c5ac4-8afeff0d3de40be7cc2ad8e7616a489241467f52 > | > https://imsva91-ctp.trendmicro.com:443/wis/clicktime/v1/query?url=www.totalhighspeed.com&umid=DA1B4682-DE0E-8C05-B4D1-EEC052AE5800&auth=079c058f437b7c6303d36c6513e5e8848d0c5ac4-1b5009a16c4202d4b572fc090c86aa255586d48f > ] > > This institution is an equal opportunity provider and employer. > Esta institución es un proveedor de servicios con igualdad de > oportunidades. > > -- > AF mailing list > [ mailto:AF@af.afmug.com | AF@af.afmug.com ] [ > http://af.afmug.com/mailman/listinfo/af_af.afmug.com | > http://af.afmug.com/mailman/listinfo/af_af.afmug.com ] > > -- > AF mailing list > AF@af.afmug.com > http://af.afmug.com/mailman/listinfo/af_af.afmug.com -- AF mailing list AF@af.afmug.com http://af.afmug.com/mailman/listinfo/af_af.afmug.com -- AF mailing list AF@af.afmug.com http://af.afmug.com/mailman/listinfo/af_af.afmug.com -- AF mailing list AF@af.afmug.com http://af.afmug.com/mailman/listinfo/af_af.afmug.com
