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Author Topic: Looking for transformer  (Read 221 times)

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Offline N Gauge Bob

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Looking for transformer
« on: October 11, 2018, 06:25:11 pm »
Can anyone advise where I can purchase a 240v 16v transformer which has positive and negative markings clearly shown on it?
I have spent 4 hours trawling the net and cannot find any manufacturer who offers a 16v transformer marked pos and neg. All I get is buy the tx and test it yourself, but I having nothing to test it with and pos and neg are critical for my application..
Cheers
Bob
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Amateurs..............built the Ark!
Professionals........built the Titanic!

Offline ntpntpntp

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Re: Looking for transformer
« Reply #1 on: October 11, 2018, 06:41:21 pm »
A transformer is an AC device, it won't have positive and negative markings.  You need to look for a DC power supply or power pack if you want it to include DC rectification. 

Alternatively buy a transformer and add your own bridge rectifier, smoothing capacitor and maybe a voltage regulator if the voltage needs to be accurate.

What sort of current draw does it need to handle?
« Last Edit: October 11, 2018, 06:44:24 pm by ntpntpntp »
Nick.   2016 celebrating the 20th anniversary of "Königshafen" exhibition layout!

Online Bealman

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Re: Looking for transformer
« Reply #2 on: October 11, 2018, 10:10:10 pm »
Bob,

Don't you have a multimeter? If you haven't, I don't know how you're getting by!

That is in no way having a go at you, mate, it's just an indispensable bit of test gear.

As stated in the post above, a transformer will only output AC. You require a DC supply for positive and negative.

A multimeter would quickly indicate the polarity.  :thumbsup:
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Online Bealman

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Re: Looking for transformer
« Reply #3 on: October 12, 2018, 08:56:03 am »
Here in Australia we have a plethora of what we call plugpacks, which can supply AC or DC at many voltages.

I believe they're called wallworts in the UK.

Could be an option?
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Offline ntpntpntp

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Re: Looking for transformer
« Reply #4 on: October 12, 2018, 09:00:06 am »
... plugpacks, which can supply AC or DC at many voltages.

I believe they're called wallworts in the UK.

I think that's very much an American thing, which some of us in the UK probably borrow from time to time as it's a handy shorthand.

In my original reply I asked what power output is required -until we know that it's difficult to narrow down options and recommendations.

I do very much agree that a multimeter is an essential bit of kit once you're working with layout electrics etc.  You can find a cheap but usable meter for less than £10 these days.   
« Last Edit: October 12, 2018, 09:03:41 am by ntpntpntp »
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Re: Looking for transformer
« Reply #5 on: October 12, 2018, 09:18:27 am »
Yes, even the full featured models are relatively cheap.
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Offline zopadooper

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Re: Looking for transformer
« Reply #6 on: October 12, 2018, 10:23:40 am »
Can anyone advise where I can purchase a 240v 16v transformer which has positive and negative markings clearly shown on it?
I have spent 4 hours trawling the net and cannot find any manufacturer who offers a 16v transformer marked pos and neg. All I get is buy the tx and test it yourself, but I having nothing to test it with and pos and neg are critical for my application..
Cheers
Bob

Clearly you have to select the right output - not all transformer / rectifiers are the same.  If you buy one with a dc plug moulded on the end then the label on the product should state whether the central pin is + or -.  Armed with this information you can either link it to a DC socket making sure you keep the same polarity or you can cut the plug off after identifying which is + and - by seeing which wire is connected to the centre pin.  I did this myself just last week with a transformer I bought off Ebay .

Offline Pjlons83

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Re: Looking for transformer
« Reply #7 on: October 13, 2018, 02:40:20 pm »
I’ve just bought a replacement laptop power lead;

https://rover.ebay.com/rover/0/0/0?mpre=https%3A%2F%2Fwww.ebay.co.uk%2Fulk%2Fitm%2F183426733255

And these sockets;

https://rover.ebay.com/rover/0/0/0?mpre=https%3A%2F%2Fwww.ebay.co.uk%2Fulk%2Fitm%2F321167655243

You have to look on the data printed on the transformer for the +/- ;



This particular one is pos on the inside and neg on the outside of the connector. When you look at the sockets closely you can follow the tabs to see which is which out of the 2 connector tabs. As others have said though; a multimeter is a must have for this kind of thing. Even the cheapest options at about £6 from amazon or home bargains, wilko’s etc will do the job for small dc stuff. Just make sure you’ve got the probes in the right way round and you’ll get a + or - 16v reading which will tell you whether your pos and beg are the right way around.

Hope this helps
Paul
Gold Hill - my rule 1, “just for fun” micro layout;

Clouds Hill - My first layout currently on hold;

 

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