no more center negative DC-plugs! - Page 1
Forum section: electronics / general

author: fusionimage
author_rank: Contributor
timestamp: October 13, 2015, 01:57:03 am
content: just started this fanpagehttps://www.facebook.com/No-more-center-negative-DC-plugs-108361362856194/just for fun and not for commecial use, of course

author: crispy_tofu
author_rank: Super Contributor
timestamp: October 13, 2015, 02:02:09 am
content: Sorry I'm a noob, but what's wrong with centre negative DC plugs?

author: fusionimage
author_rank: Contributor
timestamp: October 13, 2015, 02:02:59 am
content: nothing; i simply don't like them, as a lot of othersthey work well, but most of the dc-plugs are center +

author: Stonent
author_rank: Super Contributor
timestamp: October 13, 2015, 02:04:55 am
content: I just like knowing that the outside is negative so that it is less likely to short out when being pulled out with some shielding nearby.

author: fusionimage
author_rank: Contributor
timestamp: October 13, 2015, 02:06:49 am
content: yep, usually you connect the outer side to gnd

author: IanB
author_rank: Super Contributor
timestamp: October 13, 2015, 02:19:15 am
content: Quote from: Stonent on October 13, 2015, 02:04:55 amQuote from: fusionimage on October 13, 2015, 02:06:49 amWell, suppose positive is ground? Then the outside should be positive.

author: DimitriP
author_rank: Super Contributor
timestamp: October 13, 2015, 02:21:57 am
content: Quote from: crispy_tofu on October 13, 2015, 02:02:09 ama) Yesb) makes sense to those that express a preference.b.1) (Plus witha center positive tucked away, you can't very easily short a +3 and a +20 together by the two outer contact touching each other accidentally (or on purpose).

author: DimitriP
author_rank: Super Contributor
timestamp: October 13, 2015, 02:26:21 am
content: Quote from: IanB on October 13, 2015, 02:19:15 amsounds sparky.... bzzt

author: crispy_tofu
author_rank: Super Contributor
timestamp: October 13, 2015, 02:41:25 am
content: Quote from: DimitriP on October 13, 2015, 02:21:57 amBut it's nice to see why people have preferences for things...

author: jwm_
author_rank: Frequent Contributor
timestamp: October 13, 2015, 03:12:49 am
content: I had two experiences with polarity reversal recently.One is a (cheap. beyond cheap) laser cutter I decided to tear down and see why the fan wasn't working. I was probing around and things sure looked odd... turns out, the "ground" pour was the positive voltage and strapped to the chasis. The connector for the fan had the polarity reversed. it is clear the board was designed for negative ground and somehow bodged to be a positive ground from the weird wires on it and the silkscreen having caps polarity reversed from how they were installed... why or how that was a good idea and cost effective I have no idea. they had a lot of extra PNP power transistors to use up?Another was more dangerous jumping my friends car battery. I open it up, nice big red terminal and black terminal on the battery, I start hooking up the jumpers and get this uneasy feeling, that red terminal sure looks sort of like it connects to the chasis and the black one sure looks like it feeds into a fuse box... pulled out my fluke 101 (pure coincidence I had it with me. the thing is so tiny I forget i have it) and wouldn't you know it, red terminal was negative, black was positive. That could have been a disaster and them some.now in my best J walter weatherman voice:"And that's why we don't have center negative dc plugs."

author: Galenbo
author_rank: Super Contributor
timestamp: October 13, 2015, 08:11:35 am
content: Quote from: fusionimage on October 13, 2015, 01:57:03 amI think making DC plugs with negative center is a crime, too.I have a box with all kinds of adapters, I cut all connectors off from the inverted ones.

author: tautech
author_rank: Super Contributor
timestamp: October 13, 2015, 08:42:55 am
content: Quote from: Galenbo on October 13, 2015, 08:11:35 am+1Except when a reverse polarity protection diode worth a few cents is installed.

author: Jeroen3
author_rank: Super Contributor
timestamp: October 13, 2015, 08:43:52 am
content: There is a special place in hell for people who chose center negative dc plugs.That place also exists for those adapters that are sized in a way they take up 3 sockets of the strip. Or that they cover the socket above by hanging over a few mm.

author: Gribo
author_rank: Frequent Contributor
timestamp: October 13, 2015, 01:31:29 pm
content: So what about all those Fluke scope meters? Can I have few of them?

author: G7PSK
author_rank: Super Contributor
timestamp: October 13, 2015, 01:50:00 pm
content: Quote from: jwm_ on October 13, 2015, 03:12:49 amI had a Vauxhall combo van like that the ground terminal was brown and the live was black. The vehicle was of course negative chassis, I never really noticed the colours were reversed until my father borrowed the van to jump start his car, the next thing I heard was a loud bang as the battery blew up.

author: bitslice
author_rank: Frequent Contributor
timestamp: October 13, 2015, 02:58:48 pm
content: Quote from: G7PSK on October 13, 2015, 01:50:00 pmI had a Vauxhall Corsa and I was trying the same thing, except I noticed the hissing sound before anything melted.In fact the whole wiring loom was the same combination of weird colours (and labelled in French)I'm never buying another one

author: BradC
author_rank: Super Contributor
timestamp: October 13, 2015, 03:13:55 pm
content: Center negative DC plugs are used because that way the switched element is +ve not gnd. Don't want to be switching ground references when you are using audio or music gear, so they make the center pin negative.I always thought it made perfect sense.

author: Mashpriborintorg
author_rank: Regular Contributor
timestamp: October 13, 2015, 06:32:25 pm
content: The worst I have seen: two modems from the same brand, one in 28.8, the other in 33.6. Same case design, same power supply design and voltage... but one with center negative. Magic smoke was released when I mismatched the power supplies...

author: karoru
author_rank: Regular Contributor
timestamp: October 13, 2015, 07:15:02 pm
content: I love the way Nintendo manufactured their NES console (at least American version, don't know about European). Adapter with just transformer inside (same thing was in my old Zoltrix modem from what I remember), rectifier was in the console itself. You could connect anything to it, AC, DC, negative everywhere you wanted, and if the voltage is high enough to power the 7805 and low enough to not melt it it works a treat. Sadly that's not longer a viable options since all that switched mode power supply rubbish;)

author: rx8pilot
author_rank: Super Contributor
timestamp: October 13, 2015, 08:02:36 pm
content: DC into a transformer is not a treat.Sent from my SAMSUNG-SM-G890A using Tapatalk

author: karoru
author_rank: Regular Contributor
timestamp: October 13, 2015, 08:08:03 pm
content: Transformer was in the wall wart? In the unit there is your usual barrel input, followed by bridge rectifier.

author: rx8pilot
author_rank: Super Contributor
timestamp: October 13, 2015, 08:18:15 pm
content: Oh of course. ...yes. SMPS has made things far smaller, lighter, and more efficient. All that at the expense of complexity. Shade tree mechanics step aside......Sent from my SAMSUNG-SM-G890A using Tapatalk

author: John Coloccia
author_rank: Super Contributor
timestamp: October 13, 2015, 08:18:29 pm
content: Quote from: BradC on October 13, 2015, 03:13:55 pmThat and some other reasons specifically having to do with how effects pedals with batteries and DC jacks are made.I really don't see the big deal. Transformer output is isolated, so what's the difference where that voltage is sitting? It can't do anything unless it find a path back to the transformer.

author: karoru
author_rank: Regular Contributor
timestamp: October 13, 2015, 08:32:46 pm
content: Quote from: rx8pilot on October 13, 2015, 08:18:15 pmCome on, we're in a topic about reverse polarity on wall wart plugs, and I've pointed out that some old day design has its merits, that's all, I should probably change "SMPS rubbish" to "SMPS black magic" to be more tongue-in-cheek:)

author: rx8pilot
author_rank: Super Contributor
timestamp: October 13, 2015, 09:19:41 pm
content: Quote from: karoru on October 13, 2015, 08:32:46 pmI think you took my post in the wrong way. The intention was to agree with you and point out the down side of the advancement of SMPS.On the topic, I can't stand center negative DC plugs. In fact, I think the barrel DC plugs are a design past it's day. I only use them when forced and never put them in my designs.

author: VK3DRB
author_rank: Super Contributor
timestamp: October 14, 2015, 01:52:45 am
content: A classic example where standards should have been introduced for DC connector polarity, such as IEC, AS or UL. The world stuffed up big time on DC connectors... it has been a free-for-all and it should not have been. I have a relative who blew up an expensive hand held game after he plugged a reverse polarity DC plug into the machine. It had no reverse polarity protection diode.Another stuff-up... English, EU and Australian mains plugs. We all use 220V-240, so whey the heck do we have different plugs?And another bigger stuff-up... Japan 100V, US 110V and Australia 240V. Lower voltage is safer form an electrocution perspective, but more dangerous with house fires (ie: higher current).And the biggest stuff-up of all... Driving on the left in the UK, HK, NZ and Australia; and other countries drive on the right.Standards might inhibit creativity, but they do make a lot of sense.

author: vk6zgo
author_rank: Super Contributor
timestamp: October 14, 2015, 01:55:28 am
content: Quote from: rx8pilot on October 13, 2015, 08:18:15 pmI think thatkaroruwas pointing out that the Nintendo box just had a bridge rectifier,followed by a linear regulator.Because of this, the actual box could run from low voltage acordc.SMPS supplies have been around for a long time--I fixed a lot of them back in the 1980s & '90s.A good Oscilloscope,a DMM,& most importantly,a schematic helps a "shade tree mechanic" quite a bit!The reason modern units are difficult to fix is lack of the schematic.

author: vk6zgo
author_rank: Super Contributor
timestamp: October 14, 2015, 02:46:01 am
content: Quote from: VK3DRB on October 14, 2015, 01:52:45 amOz & UK think their styles of plug are better designed than others---with some justification.230/240v allows the use of higher power appliances with thinner conductors.100v/110v exists for complex historical reasons.Driving on the left?---try India,Pakistan,Bangladesh,Malaysia,Thailand,Indonesia,Singapore,South Africa,Kenya,Japan,& many others.

author: BradC
author_rank: Super Contributor
timestamp: October 14, 2015, 04:32:01 am
content: Quote from: vk6zgo on October 14, 2015, 02:46:01 amLower transmission losses allowing fewer but bigger pole top transformers.. there are a few advantages to higher mains voltages.The strangest thing I've ever had to get used to was the frequency. I played a couple of gigs in the US years ago and I could not adjust to the 60Hz hum from the guitar amp. It just sounded wrong!

author: jwm_
author_rank: Frequent Contributor
timestamp: October 14, 2015, 04:50:37 am
content: Quote from: VK3DRB on October 14, 2015, 01:52:45 amThere is a barrel jack standard, somewhat belatedly, all the plugs you see with the yellow tips (supossedly) follow the EIAJ standard.https://en.wikipedia.org/wiki/EIAJ_connectorThere was also an attempt at a standardized international 220V plug. It has not exactly taken off.https://en.wikipedia.org/wiki/IEC_60906-1

author: iampoor
author_rank: Frequent Contributor
timestamp: October 14, 2015, 06:35:17 am
content: In Audio gear (guitar pedals etc...) Center Negative is a (pretty well) accepted standard.

author: JoeB83
author_rank: Regular Contributor
timestamp: October 14, 2015, 06:48:32 am
content: Quote from: iampoor on October 14, 2015, 06:35:17 am+1I'm a bass player. All of my effects pedals have center negative barrels.P.S. I know a lot of guitar players will say 'bass players don't need effects', but I like having an overdrive and an octave pedal, and a few others available.

author: bingo600
author_rank: Super Contributor
timestamp: October 14, 2015, 04:53:01 pm
content: A new 15v/3A switcher i bought , and me not testing , costed me a FEI-5680A Rubidium.People making Center negative psu's should be put away for a loooonnng timeOr maybe i shouldn't assume , but it was my first encounter with such a devlish device./Bingo

author: Galenbo
author_rank: Super Contributor
timestamp: October 14, 2015, 05:06:18 pm
content: Quote from: BradC on October 13, 2015, 03:13:55 pmWhat's the relation between where a wire is sitting, and a wire that is switched?

author: John Coloccia
author_rank: Super Contributor
timestamp: October 14, 2015, 05:21:00 pm
content: Quote from: Galenbo on October 14, 2015, 05:06:18 pmAll of the commonly available DC jacks switch the barrel, not the center pin, and we use that switch to disconnect battery +. Also, in effects pedals anyway, the way the battery is switched on is a stereo jack is used, and battery ground goes to the inner tip of the stereo jack. When you plug in a mono 1/4" plug, it connects the inner tip to the sleeve and makes the ground. So all of this adds up to generally having center negative plugs. That's how Boss started doing it decades ago, and now it's pretty much THE standard everyone uses unless you absolutely have to do something else.Like I said before, though, in practice, it's a non issue. The transformer isolates the plug, so it's actually quite difficult to cause a problem unless you're really trying. Even power supplies with multiple outputs are generally isolated these days, all but the cheapest solutions, but even if you short to the case with non-isolated multiple outputs, even the cheap power supplies generally have some sort of crowbar protection and just shut off.Anyhow, that's the history of why it's the way it is. 30 years ago, someone came up with a solution that worked very well with commonly available parts, and everyone quickly standardized on that solution. There was actually a little fight for a while. I still have a couple of old effects here that are expecting something like 1/8" phono plug for power. Now THAT was easy to short out if it was just laying around, and it disappeared right quick.

author: jwm_
author_rank: Frequent Contributor
timestamp: October 15, 2015, 01:48:36 am
content: Quote from: John Coloccia on October 14, 2015, 05:21:00 pmI have seen a fair number of effects that take 9V AC and some DC ones with bridge rectifiers, presumably for backwards compatibility with the AC ones. I wonder if it is common to just have a bridge rectifier in them in general. Who has a collection of 9V effects they want to take a poll of.

author: John Coloccia
author_rank: Super Contributor
timestamp: October 15, 2015, 02:57:20 am
content: Quote from: jwm_ on October 15, 2015, 01:48:36 amThere's no need to take a poll. I can tell you that there are many, many, many thousands of different effects pedals out there, and the VAST majority take a standard Boss 9V adapter. Some Line6 effects take 9V AC. There were a handful that used a rectifier and take anything pretty much anything. 9VDC, however, is nearly universal otherwise.

author: JoeB83
author_rank: Regular Contributor
timestamp: October 15, 2015, 05:09:20 am
content: Quote from: John Coloccia on October 15, 2015, 02:57:20 amI don't have a lot of effects, but:All 12 of my Boss pedals are center-negative. (Duh)Line 6 Bass Pod: 9VACA couple "boutique" pedals: all center-negative.

author: Galenbo
author_rank: Super Contributor
timestamp: October 15, 2015, 08:00:53 am
content: Quote from: John Coloccia on October 14, 2015, 05:21:00 pmSorry, I still don't understand why jacks are related to switch.Do you mean the center makes contact before the outside does, when plugging in?

author: John Coloccia
author_rank: Super Contributor
timestamp: October 15, 2015, 10:46:19 am
content: Quote from: Galenbo on October 15, 2015, 08:00:53 amThe DC jacks have 3 terminals....call them 1, 2 and 3. 1 goes to the pin. 2 goes to the barrel. 3 goes to 2. When you plug in a DC jack, the connection between 3 and 2 is open.So it's setup that 1 is ground, 2 is power, and 3 goes to battery +. With no plug installed, the battery powers the device. When the plug is installed, the battery is disconnected. Someone over at Boss got it in their head that this was the right way to do it, and everyone copied them. I guess the idea was that they really wanted to switch the battery +. Of course, they could have just switched battery -. Who knows. Maybe the idea was to do it in a screwy way so that you'd HAVE to use their adapter, and they figured that everyone else would do it differently.Switching battery + makes sense, I guess, because you'd really rather not switch ground if the device is on. You can get some massive pops if you do that. It's worth noting Boss has always used a buffered bypass, so even when the device is switched "off", it's still on and buffering your signal, so it makes sense that they wouldn't want the pedal to be poorly behaved when plugging in a DC jack.

author: madires
author_rank: Super Contributor
timestamp: October 15, 2015, 11:48:19 am
content: Quote from: bingo600 on October 14, 2015, 04:53:01 pmThe latterWe know of the issue and got at least one DMM nearby.You shall measure voltages!Hint: Label wall warts (which device is powered by that PSU?).Business idea: do a kickstarter for a PSU polarity checker

author: JoeN
author_rank: Frequent Contributor
timestamp: October 15, 2015, 07:24:26 pm
content: I test every one with my multimeter. It's a very quick check.

author: wagon
author_rank: Frequent Contributor
timestamp: October 15, 2015, 08:57:52 pm
content: Yesterday I had a mother and her sons come into my workshop with a blown up radio that had the centre-negative experience. The radio was centre-positve, but not the plugpack the young bloke used. Magic smoke was released.

author: Galenbo
author_rank: Super Contributor
timestamp: October 16, 2015, 03:51:30 am
content: Quote from: John Coloccia on October 15, 2015, 10:46:19 amThanks for the info. I never saw a DC jack with a switch, only saw this on PC's earphone jacks.I never had anything to do with battery powered devices, always assumed the dc goes to a charging circuitry.