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Author Electronics Help - Resistors
Darren
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Registered: 21st Apr 02
Location: Hadleigh, Suffolk
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8th Feb 15 at 17:09   View User's Profile U2U Member Reply With Quote
Hi, got a bit of a random one if anyone can help...

Basically, I need to drop a 5v output down to 3.3v with a max of 500 milliamps - struggling to find out which size resistor I need? Everything on Google seems to relate to LEDs...

Thanks
Tiger
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Registered: 12th Jun 01
Location: Leicestershire Drives:Astra VXR
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8th Feb 15 at 17:46   View User's Profile U2U Member Reply With Quote
4 ohm
0.9w resister
Dom
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Registered: 13th Sep 03
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8th Feb 15 at 18:33   View User's Profile U2U Member Reply With Quote
Is the 5v regulated? If not, use a regulator like a LM2937 (3.3v variant); otherwise use a voltage divider (10k+20k divider should get you 3.3v IIRC; do a Google).
Rob_Corsa
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Registered: 4th Apr 02
Location: Derbyshire
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8th Feb 15 at 18:39   View User's Profile U2U Member Reply With Quote
As Dom said, you need a regulator rather than a divider network(a single resistor wont work as the Voltage output will vary depending on the current being drawn) if your looking at drawing a current like that.



[Edited on 08-02-2015 by Rob_Corsa]
Steve
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Registered: 30th Mar 02
Location: Worcestershire Drives: Defender
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8th Feb 15 at 19:35   View Garage View User's Profile U2U Member Reply With Quote
Regulator will be far more efficient too. Resistors are very inefficient
DaveyLC
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Registered: 8th Oct 08
Location: Berkshire
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9th Feb 15 at 17:15   View User's Profile U2U Member Reply With Quote
As above a switching regulator will be much more efficient! You can buy LM2596 based regulators on ebay for peanuts:

http://www.ebay.co.uk/itm/LM2596-Step-Down-Power-Supply-DC-DC-Adjustable-Voltage-Regulator-Arduino-LL12606-/161419156290?pt=LH_DefaultDomain_3&hash=item259554db42
Darren
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Registered: 21st Apr 02
Location: Hadleigh, Suffolk
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9th Feb 15 at 20:13   View User's Profile U2U Member Reply With Quote
Awesome, thanks guys

 
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