You have a power supply, say a 6 volt car battery. You connect a pair of headlights to it with two wires. All is well.
Now you start building cars. And you are going to wire up the headlights. Someone points out that you can save some money on wiring by using the car chassis instead if one of the wires. You decide to run the positive connection from the battery to the headlights with wire and return the current via the car’s chassis. Now you have turned a 6 volt electrical system into a +6 volt system. If you reverse the battery and connect the + side to the chassis and run the wire from the negative post to the headlights , it will still work fine. The headlights don’t care. Now you have a -6 volt electrical system. The headlights don’t care but the radio does. Most radios expect the chassis to be negative and their power wire to be positive. You can “float” the radio by mounting it on an insulator and connecting its power wire to the car’s chases and the chassis of the radio to the negative wire going to the battery. A bit dangerous but I have had to do this at times. Oh, and the car is an early VW. Sent from my iPhone > On Sep 20, 2020, at 2:19 PM, Steve Jones <thatoneguyst...@gmail.com> wrote: > > > I still cant comprehend any of this. I'm just dumb when it comes to it > >> On Sat, Sep 19, 2020, 2:51 PM <ch...@wbmfg.com> wrote: >> Yes. >> >> From: TJ Trout >> Sent: Saturday, September 19, 2020 1:48 PM >> To: AnimalFarm Microwave Users Group >> Subject: Re: [AFMUG] -48 noob questions (mikrotik) >> >> It's just a simple 48 to 12v converter to feed the mikrotik. I tested with a >> ict +48 supply and the 12v comes out fine, I'm 99% sure it will work on the >> wood bench, and about 90% sure it will work in a rack. >> >> If it was true -48 I would assume the + terminal would be bonded with >> chassis ground? >> >> On Sat, Sep 19, 2020, 12:45 PM TJ Trout <t...@voltbb.com> wrote: >>> I think some of my devices have the chassis ground bonded with the negative >>> input terminals, I discovered this >>> because I am running a telecom rectifier shelf designed for -48 on a +48 >>> system because it's floating, but this >>> causes the + output to not be fused, so I practiced arc welding once. >>> >>> Strange, didn't know the 1100 had dc input, but it looks floating though >>> (per specs -48, 12-57 V) >>> >>> >>> >>> >>>> On Sat, Sep 19, 2020 at 12:40 PM <ch...@wbmfg.com> wrote: >>>> I don’t think I have ever seen a true +48 load. >>>> >>>> From: Ken Hohhof >>>> Sent: Saturday, September 19, 2020 1:29 PM >>>> To: 'AnimalFarm Microwave Users Group' >>>> Subject: Re: [AFMUG] -48 noob questions (mikrotik) >>>> >>>> Different situation, but I have several sites with 1100ahx4 powered with >>>> +48, even though Mikrotik says they take -48. I suspect you will find the >>>> same to be true on the CCR. >>>> >>>> >>>> >>>> Connect the – terminal to ground and the + terminal to +48, obviously you >>>> don’t want to apply reverse polarity by trying to connect +48 to the -48 >>>> terminal. >>>> >>>> >>>> >>>> I have some ccr1009 and ccr1036 but they are all AC powered, and I have no >>>> ccr1072, so I can’t answer your exact question. >>>> >>>> >>>> >>>> >>>> >>>> From: AF <af-boun...@af.afmug.com> On Behalf Of TJ Trout >>>> Sent: Saturday, September 19, 2020 2:19 PM >>>> To: AnimalFarm Microwave Users Group <af@af.afmug.com> >>>> Subject: [AFMUG] -48 noob questions (mikrotik) >>>> >>>> >>>> >>>> So I have a handful of ccr1072's that I want to run on our +48v plant, >>>> mikrotik sells a '-48v telecom' power supply and they insist it's not >>>> compatible with +48v. I ordered one for testing and both +/- input >>>> terminals have no reference to chassis ground. I went ahead and applied >>>> +48v and the power supply fired up (no smoke) and when measuring from >>>> chassis ground to the input terminals I see no difference in potential. >>>> >>>> >>>> >>>> Before I shove this into a $3,000 router I wanted to see what I may be >>>> missing here? >>>> >>>> -- >>>> 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 > -- > AF mailing list > AF@af.afmug.com > http://af.afmug.com/mailman/listinfo/af_af.afmug.com
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