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Components and Circuits For discussions about component types, alternatives and availability, circuit configurations and modifications etc. Discussions here should be of a general nature and not about specific sets.

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Old 21st Oct 2017, 9:40 pm   #1
Biggles
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Default Barrel type power plugs and sockets.

Why oh why are there so many combinations of those DC power connectors commonly known as barrel plugs? Over the years I have grown accustomed to the general range of outside and inside diameters of these darned things but still always seem to have the wrong type of either plug or socket. For some bizarre reason the plug I am trying to plug in always has the different size internal "hole" to the pin on the socket. 2.1mm, 2.5mm, and now today I have a CCTV camera which requires 12VDC and is fitted with an in line socket on the cable supplied with it. I didn't buy the optional PSU, thinking that I would have a suitable one at home. I did. Or so I thought. The plug 2.5mm hole fitted to the psu would go in but was loose. Ah, I thought, it must be a 2.1mm type. Changed it. Still no power. So I tried a one I found with a smaller hole still. Too tight. On examining another camera PSU which was supplied with it as a kit, I discovered it cleverly had two flexible contacts in the centre hole, so making a good contact. Well I had nothing like that in my spares so tomorrow I will have to cut the plug and socket off and hard wire it. In fact I think I will make a 12V power distribution panel and power them all off a proper PSU. My dash cam has a similar problem, as the inner pin doesn't seem to mate properly with anything off the shelf. Bah humbug!
Alan.
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Old 21st Oct 2017, 9:50 pm   #2
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Default Re: Barrel type power plugs and sockets.

I too!
Never found the correct plug for Acer laptops. I use the next size up that fits with a bit of ally foil in the hole. Works for a while.
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Old 21st Oct 2017, 10:35 pm   #3
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Default Re: Barrel type power plugs and sockets.

Hi,
some of the new laptop power supplies have a 3 conductor plug, so it you use a standard dc plug the laptop works, but won't charge the battery...
but there are so many variations...
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Old 22nd Oct 2017, 12:50 am   #4
Dai Corner
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Default Re: Barrel type power plugs and sockets.

Wouldn't it be great if different sized plugs and sockets were used for different voltages in such a way that it was impossible to connect too high a voltage to a device?
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Old 22nd Oct 2017, 2:52 am   #5
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Default Re: Barrel type power plugs and sockets.

Is positive to the tip or the sleeve

YET another humbug

Joe
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Old 22nd Oct 2017, 8:45 am   #6
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Default Re: Barrel type power plugs and sockets.

Those 'barrel' plugs & sockets are yet another example of a so-called 'standard' with, IMHO, too many variations. Dai Corner, you are correct, but, of course that will never happen! Besides the different diameters of both barrel & Pin, there is also the fact that some makers use the centre pin as Positive, others have it Negative, then there is a variation of the Barrel plug in which the centre contact isn't a 'pin' as such, but an insulated tube. These are often used in Laptops and the like, but PURE also use them in their radios.
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Old 22nd Oct 2017, 9:00 am   #7
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Default Re: Barrel type power plugs and sockets.

And now I have found that there are different lengths too! Damnation on the design.
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Old 22nd Oct 2017, 10:23 am   #8
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Default Re: Barrel type power plugs and sockets.

Oh yes, I forgot about the "stretched" versions. The worst bit is that you think you have the right plug because it fits the hole perfectly, only to discover there is a 0.25mm air gap around the centre pin preventing connection.
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Old 22nd Oct 2017, 12:04 pm   #9
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Default Re: Barrel type power plugs and sockets.

The "stretched" ones I have seen appear to be designed to reach through a case to get to an ordinary socket inside the equipment.
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Old 22nd Oct 2017, 12:28 pm   #10
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Default Re: Barrel type power plugs and sockets.

Inner positive? Inner negative? AC on the connector? 3-pin to allow I2C/OneWire data-transmission to the PSU? Deep or shallow? Straight or right-angle? It gets kinda crazy after a while, even if you can find a combination that *physically* mates.

Maplin do a nice kit of polarity-reversable adapters and cable - I found this would handle something like 75% of things like non-smart-charge laptops, set-top-boxes, routers, scanners, WiFi modems, portable-radios... I even learned to superglue the reversible-bit of the plug together once the right orientation was determined, after someone yanked the cable, the reversible-bit came apart, and they replugged it the wrong way round.

https://www.maplin.co.uk/p/dc-output...tion-box-n98ap

https://www.maplin.co.uk/p/3a-dc-out...able-18m-aq81c
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Old 22nd Oct 2017, 12:36 pm   #11
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Default Re: Barrel type power plugs and sockets.

As with most useful (to us) things at Maplin, those adapter plugs and cable are being discontinued ('last few in store'). Does anyone know an alternaitve supplier?

I bought both years ago. I put 4mm plugs on the end of the cable so I could plug it into my bench supply. That lets me set any reasonable voltage. Obviously not practical for long term use (if only because I need the bench supply for other things) but it's saved me a lot of time (and swearing, since there are no croc-clips to fall off at the wrong moment) when powering things up for testing and repair.
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Old 22nd Oct 2017, 12:45 pm   #12
dseymo1
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Default Re: Barrel type power plugs and sockets.

I have several sets of those, mostly gleaned from auction-purchased customer returned 'universal' PSUs. Agreed that a couple of sets fitted with 4mm plugs save a lot of time and hassle.
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Old 22nd Oct 2017, 2:04 pm   #13
Refugee
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Default Re: Barrel type power plugs and sockets.

I have the bits of several of those kits.
Once I have established the polarity and wall wart for an item I solder the wires onto the pins and partly fill with hot melt glue before adding a heat shrink sleeve and a little more glue. The heat from the glue shrinks it on.
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Old 22nd Oct 2017, 2:37 pm   #14
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Default Re: Barrel type power plugs and sockets.

Those laptop ones have three connexions, +, - and a data pin. This uses the Dallas 'One Wire' protocol and is intended to make you buy a genuine replacement adaptor rather than overloading a generic type. I wouldn't mind so much if it was only the maximum current that was communicated, but, alas, it has to say "I am a genuine HP* supply" for example.
*other makes of laptops are available, mine is an HP.
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Old 22nd Oct 2017, 10:07 pm   #15
Richard_FM
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Default Re: Barrel type power plugs and sockets.

I have a couple of adaptors with switchable voltages & differing connectors.

One is an older "spider" & the newer one has a selection of bits.

I remember about 15 years ago my Dad complaining that mobile phones had so many different power connectors, as it seemed like every phone we had used different charger design.

These days almost every company other than Apple has a standardised connector.
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