Having trouble finding 15V AC 500mA Power Supply? (UK) - Page 1
Forum section: electronics / beginners

author: peps1
author_rank: Regular Contributor
timestamp: January 02, 2014, 08:02:44 am
content: Hello guys, I'm having some trouble finding a 15V AC 500mA Power Supply........only ones iv seen are on RS and an eye watering £30+ for a bloody wall wart!Anyone tell me where I should be looking?

author: strangelovemd12
author_rank: Regular Contributor
timestamp: January 02, 2014, 08:55:14 am
content: Are you looking for a one off supply or a source for x units? The voltage is a tad high, but this is in the range of a lot of cordless phone wallwarts, at least in the US. IIRC UK/US use roughly the same spectrum for this, so I'd imagine a lot of the phones are identical units with different transformers. (240v vs 120v mains)

author: Kjelt
author_rank: Super Contributor
timestamp: January 02, 2014, 11:33:48 am
content: Quote from: peps1 on January 02, 2014, 08:02:44 amUh yeah that would be a transformerI guess you mean 15V DC ? You have these universal supplies that have 9V/12V/13.5V/15V/18V/20V/24V selectable and 1Amp,for instance the Voltcraft SPS24-24W , available at Conrad for €20.- about £17 .-

author: peps1
author_rank: Regular Contributor
timestamp: January 02, 2014, 11:48:04 am
content: Nope, differently want 15V AC, not 15V DC.........So, my I should have called it a power adapter rather then PS?Want a 240VAC in with 15-18VAC 500mA+ out, and a type G plug.something likethese, but for UK mains

author: SeanB
author_rank: Super Contributor
timestamp: January 02, 2014, 11:52:20 am
content: How about taking a cheap adjustable one, unscrewing the 2/3 screws that hold it together and remove the bridge rectifier, switch and capacitor, and solder the leads to the 15VAC tap points on the transformer? If not then buy a plug in wall wart case from Maplin or RS, ( think Maplin may still have these in stock somewhere as a project box) and place a simple 15VAC 500mA wall wart inside the case.

author: peps1
author_rank: Regular Contributor
timestamp: January 02, 2014, 12:01:41 pm
content: Quote from: SeanB on January 02, 2014, 11:52:20 amWould love to make one, but mains scares the the bejesus out of me!Would it just be a case of Mains-> fuse-> transformer-> 2.1mm jack

author: SeanB
author_rank: Super Contributor
timestamp: January 02, 2014, 12:04:29 pm
content: Yes, just take care to use correct creepage distance, correct wiring and isolating barriers between mains wiring and low voltage side and you will be fine.

author: amyk
author_rank: Super Contributor
timestamp: January 02, 2014, 12:35:52 pm
content: Laptop PSUs are in that voltage range and can provide more than 500mA.

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: January 02, 2014, 12:55:40 pm
content: A 12v Halogen lighting transformer, under-run, may give close to what you want

author: Kjelt
author_rank: Super Contributor
timestamp: January 02, 2014, 01:00:15 pm
content: Quote from: peps1 on January 02, 2014, 11:48:04 amOk sorry, those are indeed much harder to findFarnell has only one: IDEAL POWER - 77DB-10-15M - POWER SUPPLY, AC/AC, 11.5W, 15V,0.67A,UKOrdercode: 2368009 €10.55 ex VATBut UK mains plugQuote from: amyk on January 02, 2014, 12:35:52 pmDC not AC and usually 19V

author: Rerouter
author_rank: Super Contributor
timestamp: January 02, 2014, 01:15:59 pm
content: just a small question what your actually powering? as if all it does it rectify it inside the device a 21V dc plug pack is the same thing

author: daveshah
author_rank: Unknown
timestamp: January 02, 2014, 01:16:22 pm
content: How abouthttp://cpc.farnell.com/1/1/113318-ac-ac-power-supply-15v-0-5a-universl-s2234st-stontronics.html

author: Zero999
author_rank: Super Contributor
timestamp: January 02, 2014, 01:36:44 pm
content: http://uk.rs-online.com/web/p/plug-in-power-supply/2813690/

author: peter.mitchell
author_rank: Super Contributor
timestamp: January 02, 2014, 10:48:03 pm
content: Oddly, in the security industry, they use a lot of AC wall warts (i think that in the past isolated smps weren't as common, so they use ac wall wart for isolation). Common voltage is something like 12-18vac at 500ma-1.5a. This may be a source.

author: peps1
author_rank: Regular Contributor
timestamp: January 02, 2014, 10:54:00 pm
content: Thanks guys,Found a 9v CT transformer in the bin, so think I'm going to hunt around the workshop for a 2.1mm jack and a 10mm fuse holder and try and build my own!Even though main voltage scare me still, advice welcome!

author: Unknown
author_rank: Unknown
timestamp: January 02, 2014, 10:59:59 pm
content: Quote from: peter.mitchell on January 02, 2014, 10:48:03 pmThey do? On what? Can't say I have much here that doesn't use 12VDC or more rarely 5VDC. Not really much in the way of AC apart from 24VAC for large loads like power domes etc...

author: SeanB
author_rank: Super Contributor
timestamp: January 02, 2014, 11:03:18 pm
content: Security system ones would work, 16VAC at 1A is common. Mostly used as the units have to last at least 10 years on 24/7/365, and at the price point of a transformer that is that reliable a SMPS will be more expensive. The transformer commonly supplies the alarm control box, and charges the back up battery inside it along with running the whole system all the time.

author: Unknown
author_rank: Unknown
timestamp: January 02, 2014, 11:12:36 pm
content: Quote from: SeanB on January 02, 2014, 11:03:18 pmHaha, that's a good one. lololol!!!!!Quote from: SeanB on January 02, 2014, 11:03:18 pmI think I may have found the confusion, that's not how we do security systems over here, we have power supplies screwed to the wall and secured in tamper proof boxes.

author: Monkeh
author_rank: Super Contributor
timestamp: January 03, 2014, 12:32:54 am
content: Quote from: peps1 on January 02, 2014, 10:54:00 pmI'll start by advising you not to be scared of mains voltages. They are not going to jump out and bite you like the neighbour's dog.

author: Rerouter
author_rank: Super Contributor
timestamp: January 03, 2014, 02:21:05 am
content: You dont have to fear it, just treat it with respect, even if it takes you 5 times as long, cover everything before you plug it in, if its for a smoke test cover it with some clear tuppawear, etc so that under no situations can you accidently brush up abuild in a AC side fuse, use heatshrink instead of tape, is these small things that can make it a bit more safe..if the box your using is metal, earth it.

author: peter.mitchell
author_rank: Super Contributor
timestamp: January 03, 2014, 11:01:41 am
content: Quote from: Lurch on January 02, 2014, 11:12:36 pmNo, it is true, SeanB is a very knowledgeable man of the industry in ZA (and probably elsewhere), and I also have a reasonable amount of knowledge relating to the Australian industry. I ahve seen Bosch, Pelco, GE and Inner Range units use AC supplies, even a lot of retrofits using existing powersupplies.

author: Unknown
author_rank: Unknown
timestamp: January 03, 2014, 03:01:04 pm
content: Quote from: peter.mitchell on January 03, 2014, 11:01:41 amI'm not saying it's not true where you are, I'm saying that isn't true in the UK.

author: Kjelt
author_rank: Super Contributor
timestamp: January 03, 2014, 04:46:27 pm
content: Quote from: Lurch on January 03, 2014, 03:01:04 pmSo what is the attack on an alarm systems power supply that it should be tamperproof protected? High voltage induction? Should have protection for that. Short? Alarm should have its own internal DC power supply (battery). Normally here the alarmsystems are 230VAC powered and the whole box is tamperproof as is the closet it is located (magnetic and contact switches). But don't see the problem with an unsecured AC power supply.

author: Unknown
author_rank: Unknown
timestamp: January 03, 2014, 05:24:58 pm
content: I have no idea what is going on. Think there's some language barrier issues.

author: SeanB
author_rank: Super Contributor
timestamp: January 03, 2014, 06:01:11 pm
content: A transformer that plugs in and has no other parts in it other than a fuse means the installer does not have to be a qualified electrician. An alarm system is considered as a fixed installation, and if it has a mains connection direct to the box then the whole installation would be classed as a fixed mains appliance, like a stove or water heater is, and would have to have mains insulation, earthing and creepage, along with needing a certificated installer.Having a plug in unit that is type approved and easy to replace for local mains voltage without needing any touching by an installer ( supply a box for the area be it 110VAC or 220VAC) means the equipment attached is classed as low voltage equipment that is touch safe. All isolation is in a non serviceable type rated box with only input and output, that can be installed into a plug point without needing a certificate.Alarm systems are designed for world wide use, so having a separate power unit is a good thing, as they are sold in the USA as a home owner installable unit. Many electric fences sold here have an integrated power supply, the same 16VAC transformer used in alarms, often being a hole in the housing where the complete mains module with attached leadset is placed so that you can install easily without touching or working on mains other than plugging in a prepared leadset to a wall socket. The ones with a separate mains supply are often used remotely with a long 16VAC power lead so that shorts do not trip the mains, the transformer being installed indoors. Same for most gate and door automation other than those that use 220VAC motors or 3 phase motors.

author: Unknown
author_rank: Unknown
timestamp: January 03, 2014, 06:45:16 pm
content: Quote from: SeanB on January 03, 2014, 06:01:11 pmNot entirely true, depending on where you are in the world. There are some limitations, but in the UK it's not really a major problem. All you need is a fixed point to take power from, the whole arm system doesn't become a fixed installation as you describe.Quote from: SeanB on January 03, 2014, 06:01:11 pmAs I say, it is obviously dependent on where in the world you are. The voltage is the same as what you would find from the AC side in a panel over here. You don't find any external supplies over here on alarm systems. Chances are the main boards are the same but we get a transformer in our panels, you don't, which is pretty much what I have said several times.

author: icon
author_rank: Regular Contributor
timestamp: January 03, 2014, 11:16:48 pm
content: 16v close enough -http://www.esr.co.uk/electronics/products/frame_powersupplies.htm?You need to click on 'Plug-in AC' - they're towards the bottom of the page. I bought one to power a Smiths electric clock that I modified to run off low voltage...John