Safe Speed Forums

Suspect this is in Roger/Smeggy's field.

Trying to find a 12v SMPSU capable of about .5 A --- I can easily design one working @ a few KHZ but can't find transformer or readily built one or smallish 50hz transformer. Problem is car kit has limits of 11-13v so 12v regulation is out due to diode losses. Any ideas .

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lets bring sanity back to speed limits.
Drivers are like donkeys -they respond best to a carrot, not a stick .Road safety experts are like Asses - best kept covered up ,or sat on

Not sure what you're asking.
Do you want to get a regulated 12V0 supply from a car 12V electrical system?
Have you considered a Low Drop Out regulator (series pass PNP/PchMOSFET - no diode drop) ?

I reckon what you want is RS stock number 478-4651

£5 plus the VAT. At that price, it's not even worth sketching a DIY alternative.

Nope, I can't figure it out either.

What's the input?
What's the output?

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Paul Smith
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looking for a 11-13 output from a nominal 12v car supply @ about 2 w. normally id look at a smpsu ic ,but they seemed to have dried up. Looking at Roger's reply - probably seems about right - though no contact with RS - now found maplin do a 2 w 5 -12 dc/dc converter( PITY, WOULD HAVE LIKED 12-12) .
Did look at the low drop out option , but best i could find was about .5v based on a 741 , so prefer to try the SMPSU idea in a chip.Power rating was the problem ---probably go with the Maplin IC - bit long dropping 12 to 5 , but can't find any other option easily -thanks all.

_________________
lets bring sanity back to speed limits.
Drivers are like donkeys -they respond best to a carrot, not a stick .Road safety experts are like Asses - best kept covered up ,or sat on

What about via ebay, such as item 200159584805 ?
At least there isn't any minimum order value or additional VAT.

Thanks Smeggy -but that looks like one of those convert 12 ciggie lighter socket to 9/6/4.5 ,whereas I need 11 -13 ,and only when the engine is off.
Rogers idea was more sort of idea i had in mind ---SMPSU in a chip -12 nominal in and regulated 12v out., all in an encapsulated lump.
Bounced the idea out to see what if anything new was around .
Last time I played with SMPSU stuff was with LM494 ,and getting a transformer for 10khz was the problem.(and all to fire a xenon tube for a timing strobe)
Used to be a hobby version of RS - postal only with an address in Corby - will try their catalogue (when i remember who they are ) or get a 2W one from Maplin ( 5v in only) and stick something like a 7805 in front.

_________________
lets bring sanity back to speed limits.
Drivers are like donkeys -they respond best to a carrot, not a stick .Road safety experts are like Asses - best kept covered up ,or sat on

One of us has misunderstood the other:

Saying that, these devices seem too cheap to be able to step up from <12 to 12V0 as well as step down. You might well be better off staying with your xV to 5V to 12V circuit.

Missed the last bit - looking at it and the pic thought it (and the price suggested it was ) one of the dropper types , starting usually at 9v.

Over all it seems from info from all ( thanks blokes) that the best solution is a 12v (nom) input to 12 v op @2w or failing that a 2w 5/12v type. Bit out of up to date ideas, so thought i'd ask around.

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lets bring sanity back to speed limits.
Drivers are like donkeys -they respond best to a carrot, not a stick .Road safety experts are like Asses - best kept covered up ,or sat on

Try RS - www.rswww.com - part no. 433-8242

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Malcolm W.
The views expressed in this post are personal opinions and do not represent the views of Safespeed.