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Chat Area => General Discussion Area => Topic started by: aaronjb on 19 July 2013, 11:12:28

Title: A question for those with good electronic engineering (or electrical eng.)..
Post by: aaronjb on 19 July 2013, 11:12:28
I bought a gizmo the other day that arrived with a European two-pin power supply.. Ok, ok, I bought a toy for the kittens that came with a two-pin Euro PSU :oops:

It's driving a little water pump (it's one of those cat fountain things) and it's a 12V DC ~0.4A transformer (too big & heavy to be a switched mode PSU so I think it's just a transformer in a case), anyway the supplied UK adapter is about as useful as a chocolate teapot so it's currently rammed straight in the UK socket. Fine for me but I'd rather nobody else tried unplugging it and gave themselves a belt on the exposed metal as it comes out ;)

Anyway.. given the driven load is a small motor (I'm guessing) is a switched mode PSU OK? I can pick one of those up with a 12V 0.5A output easily enough (e.g. http://www.maplin.co.uk/12vdc-0.5a-power-supply-with-2.1mm-tip-513515) - or does the nature of a switched mode PSU mean they can't drive motors for some reason..


Yes, the more time I spend writing this question the more it starts to sound like a stupid question...  :-[
Title: Re: A question for those with good electronic engineering (or electrical eng.)..
Post by: Kevin Wood on 19 July 2013, 11:19:21
Can't see why a switched mode PSU wouldn't work, except that if the motor takes quite a big surge on switch-on the supply might go into current limiting or even shut itself down. Worth getting one a bit oversized for that reason, perhaps? Or get a good old-fashioned linear one, as it's hardly a critical application.
Title: Re: A question for those with good electronic engineering (or electrical eng.)..
Post by: Field Marshal Dr. Opti on 19 July 2013, 11:20:07
I bought a gizmo the other day that arrived with a European two-pin power supply.. Ok, ok, I bought a toy for the kittens that came with a two-pin Euro PSU :oops:

It's driving a little water pump (it's one of those cat fountain things) and it's a 12V DC ~0.4A transformer (too big & heavy to be a switched mode PSU so I think it's just a transformer in a case), anyway the supplied UK adapter is about as useful as a chocolate teapot so it's currently rammed straight in the UK socket. Fine for me but I'd rather nobody else tried unplugging it and gave themselves a belt on the exposed metal as it comes out ;)

Anyway.. given the driven load is a small motor (I'm guessing) is a switched mode PSU OK? I can pick one of those up with a 12V 0.5A output easily enough (e.g. http://www.maplin.co.uk/12vdc-0.5a-power-supply-with-2.1mm-tip-513515) - or does the nature of a switched mode PSU mean they can't drive motors for some reason..


Yes, the more time I spend writing this question the more it starts to sound like a stupid question...  :-[


Ah.....You're a big softy at heart, Aaron.  ;D ;D ;D

I hope that Tiddles and co appreciate what you've done for them. ;)
Title: Re: A question for those with good electronic engineering (or electrical eng.)..
Post by: Kevin Wood on 19 July 2013, 11:23:16


Ah.....You're a big softy at heart, Aaron.  ;D ;D ;D

I hope that Tiddles and co appreciate what you've done for them. ;)

They'll probably appreciate it as much as ours did the scratching post that is now completely ignored. "But.. thanks for getting me into this scratching malarkey. It's fun! and.... yep.. Works just as well on the sofas you've just spent a fortune having re-covered, too." >:(

Title: Re: A question for those with good electronic engineering (or electrical eng.)..
Post by: Entwood on 19 July 2013, 11:49:27
??? cut the euro 2-pin plug off the cable and replace with UK 3 pin ??? seems simple to me ....  :)
Title: Re: A question for those with good electronic engineering (or electrical eng.)..
Post by: Andy B on 19 July 2013, 12:15:12
Nige. The 2 pin 'plug' is molded into the back of the transformer- like your phone charger. That's how I understand! ;)
Title: Re: A question for those with good electronic engineering (or electrical eng.)..
Post by: tigers_gonads on 19 July 2013, 12:34:51
Iphone / pods and various other bits and pieces come with a adapter that clips on.
Google and you might be lucky.

I have a old extension bank with a uk spec plug on the end of it which I keep for things like this  ;)

Might be able to pull one ebay if you look around.
Better then pishing around with power supplies imo  :)
Title: Re: A question for those with good electronic engineering (or electrical eng.)..
Post by: sdwall on 19 July 2013, 12:40:12
Both Kev and TG are spot on. Make sure the switched mode PSU will have enough overhead to cope with surge to start or just get a european schuco type extension and fit UK plug on the end.
Title: Re: A question for those with good electronic engineering (or electrical eng.)..
Post by: tigers_gonads on 19 July 2013, 12:50:13
One of these  :y

http://www.ebay.com/itm/New-Universal-US-AU-EU-to-UK-3-Pin-Travel-Power-Converter-Adapter-Plug-/281138249265?pt=Travel_Adapters_Converters&hash=item4175253e31
Title: Re: A question for those with good electronic engineering (or electrical eng.)..
Post by: Entwood on 19 July 2013, 13:01:46
Nige. The 2 pin 'plug' is molded into the back of the transformer- like your phone charger. That's how I understand! ;)

Makes sense now you say that .. :)

Easier ... and in £'s ..  :)

http://www.ebay.co.uk/itm/Schuko-Plug-Convertor-Euro-2-Pin-to-UK-3-Pin-Adapter-Ideal-Travel-Plug-Adaptor-/290690261204?pt=UK_Sound_Vision_Other&hash=item43ae7d60d4
Title: Re: A question for those with good electronic engineering (or electrical eng.)..
Post by: tigers_gonads on 19 July 2013, 13:05:54
Nige. The 2 pin 'plug' is molded into the back of the transformer- like your phone charger. That's how I understand! ;)

Makes sense now you say that .. :)

Easier ... and in £'s ..  :)

http://www.ebay.co.uk/itm/Schuko-Plug-Convertor-Euro-2-Pin-to-UK-3-Pin-Adapter-Ideal-Travel-Plug-Adaptor-/290690261204?pt=UK_Sound_Vision_Other&hash=item43ae7d60d4



 :P :P ;D
Title: Re: A question for those with good electronic engineering (or electrical eng.)..
Post by: aaronjb on 19 July 2013, 13:15:25
Or get a good old-fashioned linear one, as it's hardly a critical application.

They seem harder to find these days than switched mode supplies - although enough digging on the Maplin website did throw one up that doesn't say it's switched mode, so there is hope! ;D  Ta though - I have a bunch of PSUs lying around from various things now defunct (like monitors) and one of those will probably fit the bill for free so it's worth a stab  :y

Ah.....You're a big softy at heart, Aaron.  ;D ;D ;D

I hope that Tiddles and co appreciate what you've done for them. ;)

I'll do anything for furballs ;) They gained a whole bunch of new stuff yesterday - a ball constrained to a 'track' that flashes when they knock it around, a kind of face massage post thing, scratching post with beds, water fountain .. double sealed litter bin so the kitchen doesn't smell like cat crap anymore ;D ;D

Although they are still corralled into a makeshift 'room' we've built for them overnight - then again, we keep making the 'walls' higher and every morning they've either grown enough to jump over, or figured out what they need to push toward the wall to get a high enough vantage point to make it out ;D Oddly enough they only start doing that when we get up - overnight they're happy to be contained with their beds, food, etc etc.

Easier ... and in £'s ..  :)

http://www.ebay.co.uk/itm/Schuko-Plug-Convertor-Euro-2-Pin-to-UK-3-Pin-Adapter-Ideal-Travel-Plug-Adaptor-/290690261204?pt=UK_Sound_Vision_Other&hash=item43ae7d60d4

That's basically what it was supplied with ;) Only it's so appallingly badly manufactured that it only makes a good connection if you stand there holding it ;D

Annoyingly my folks used to have a whole bunch of old German extension leads with UK plugs on the end from our time stationed in Germany .. right up until they moved house on Tuesday and threw all that kind of stuff out  :-X :-X ;D
Title: Re: A question for those with good electronic engineering (or electrical eng.)..
Post by: Marks DTM Calib on 19 July 2013, 13:23:51
Its very dependent on the switchmode supply design.

Assuming the device being driven is a DC motor then at standstill the supply will see nothing other than the DC resistance of the stator and rotor. Its only when the thing starts to rotate and a back EMF is produced does the current drop and hence the start current can be very high and to the supply will appear as a very low ohmic load.

Many switchmodes wont like this high start current (some have crowbar current limit on the output), others will simply limit the current and be ok.

If going switchmode look to over rate it by a factor of 2 and all should be ok, I would actualy aim for one nearer to 1 amp.

Argos do one for about 13 quid:

http://www.argos.co.uk/static/Product/partNumber/9829701.htm
Title: Re: A question for those with good electronic engineering (or electrical eng.)..
Post by: aaronjb on 19 July 2013, 13:36:04
Cheers Mark - I'll pick something up at the weekend if I don't have something that'll work knocking about the garage somewhere  :y

Failing that it'll continue to work with the aid of a screwdriver in the earth pin and the German plug rammed into the other two  :-[ At least more reliably than using the cheap adapter they supplied with it!
Title: Re: A question for those with good electronic engineering (or electrical eng.)..
Post by: Marks DTM Calib on 19 July 2013, 13:55:29
No need to leave the screwdriver inserted in the earth pin (not that I have ever done that), its only needed to clear the shutters from the live plus neutral
Title: Re: A question for those with good electronic engineering (or electrical eng.)..
Post by: aaronjb on 19 July 2013, 14:03:54
Aye, I know ;) Actually as it's in an extension lead at the moment I just inserted the (plastic) earth pin on the schucko->UK adapter and then pulled it back out again. Fnarr..
Title: Re: A question for those with good electronic engineering (or electrical eng.)..
Post by: omega3000 on 19 July 2013, 14:04:09
Or get a good old-fashioned linear one, as it's hardly a critical application.

They seem harder to find these days than switched mode supplies - although enough digging on the Maplin website did throw one up that doesn't say it's switched mode, so there is hope! ;D  Ta though - I have a bunch of PSUs lying around from various things now defunct (like monitors) and one of those will probably fit the bill for free so it's worth a stab  :y

Ah.....You're a big softy at heart, Aaron.  ;D ;D ;D

I hope that Tiddles and co appreciate what you've done for them. ;)

I'll do anything for furballs ;) They gained a whole bunch of new stuff yesterday - a ball constrained to a 'track' that flashes when they knock it around, a kind of face massage post thing, scratching post with beds, water fountain .. double sealed litter bin so the kitchen doesn't smell like cat crap anymore ;D ;D

Although they are still corralled into a makeshift 'room' we've built for them overnight - then again, we keep making the 'walls' higher and every morning they've either grown enough to jump over, or figured out what they need to push toward the wall to get a high enough vantage point to make it out ;D Oddly enough they only start doing that when we get up - overnight they're happy to be contained with their beds, food, etc etc.

Easier ... and in £'s ..  :)

http://www.ebay.co.uk/itm/Schuko-Plug-Convertor-Euro-2-Pin-to-UK-3-Pin-Adapter-Ideal-Travel-Plug-Adaptor-/290690261204?pt=UK_Sound_Vision_Other&hash=item43ae7d60d4

That's basically what it was supplied with ;) Only it's so appallingly badly manufactured that it only makes a good connection if you stand there holding it ;D

Annoyingly my folks used to have a whole bunch of old German extension leads with UK plugs on the end from our time stationed in Germany .. right up until they moved house on Tuesday and threw all that kind of stuff out  :-X :-X ;D

Water fountain  ??? ???
Title: Re: A question for those with good electronic engineering (or electrical eng.)..
Post by: aaronjb on 19 July 2013, 14:20:03
You read it right ;) One of these: http://www.zooplus.co.uk/shop/cats/cat_bowls_feeders/cat_fountains/catit/277485
Title: Re: A question for those with good electronic engineering (or electrical eng.)..
Post by: Marks DTM Calib on 19 July 2013, 14:22:20
Ah so like electronic air fresheners its tech for the sake of it...  ;D ;D
Title: Re: A question for those with good electronic engineering (or electrical eng.)..
Post by: aaronjb on 19 July 2013, 14:59:41
Anything to keep them entertained ;)
Title: Re: A question for those with good electronic engineering (or electrical eng.)..
Post by: I_want_an_Omega on 19 July 2013, 16:04:15
A small word of caution - will almost certainly be ok anyway .....

Any item sold would only have it's type approval using the power supply provided by the manufacturer - so you probably need to be aware of that.

Insurers could get funny IF there was a problem as a consequence - so probably worth being a bit careful and unplugging if going out/at night etc.

I'm a bit of a Luddite regarding power supplies - I prefer a transformer at any time  ::)
Title: Re: A question for those with good electronic engineering (or electrical eng.)..
Post by: Kevin Wood on 19 July 2013, 17:02:23
A small word of caution - will almost certainly be ok anyway .....

Any item sold would only have it's type approval using the power supply provided by the manufacturer - so you probably need to be aware of that.

Insurers could get funny IF there was a problem as a consequence - so probably worth being a bit careful and unplugging if going out/at night etc.

I'm a bit of a Luddite regarding power supplies - I prefer a transformer at any time  ::)

Agreed about the approval, but, given that it wasn't even supplied with a proper UK mains plug, I'm guessing that's a dodgy area with this product to begin with. I'd rather have it powered by a properly compliant UK mains adaptor. Assuming that's what Maplin are selling. :-X

As to the type of supply - a cheap and nasty transformer is just as likely to burn the place down as a cheap and nasty SMPS. Granted, it won't create as much radio interference during its' short life, and, for that reason alone, I agree with you. ;)
Title: Re: A question for those with good electronic engineering (or electrical eng.)..
Post by: Marks DTM Calib on 19 July 2013, 17:07:02
A small word of caution - will almost certainly be ok anyway .....

Any item sold would only have it's type approval using the power supply provided by the manufacturer - so you probably need to be aware of that.

Insurers could get funny IF there was a problem as a consequence - so probably worth being a bit careful and unplugging if going out/at night etc.

I'm a bit of a Luddite regarding power supplies - I prefer a transformer at any time  ::)

Type approval relates to mains powered items only and hence only the adaptor would be considered part of it as the 'fountain' is a LV appliance.

Given the source and mains plug fitted, the alternative power source could be considered an upgrade.

This is exactly why in the telecoms kit design industry I used to be in, we never touched mains, we either bought in an approved closed frame supply or an external approved wall wart
Title: Re: A question for those with good electronic engineering (or electrical eng.)..
Post by: Bigron on 20 February 2014, 22:41:49
Poundland and 99p shops will supply 13A to yank 2-pin adaptors for £1 and 99p respectively.

Ron.
Title: Re: A question for those with good electronic engineering (or electrical eng.)..
Post by: AndyRoid on 21 February 2014, 20:26:42
Make a short extension lead using 3 core 1.5mm² flex, a rubberised trailing socket, and a standard 13A plug (preferably MK), job done!

If you decide to go the SMPSU route, allow for a 50% derating.