How to step down 12vdc to 4.5vdc

These things...switching supplies are better since they don't heat up as much as linear supplies.

http://www.ebay.com/itm/Buck-S...6:g:tsEAAOSwzOxUXJAw

Chuck,

Thanks looks like a great solution.  Especially since I also have a need for a 9vdc tap.  Didn't know such a device existed.

Just when I think I have maxed out on all the things I don't know I find out about something else I don't know 

Thank you for the information.

Ed

i just searched for "12vdc to 5vdc converters" and many of these similar models showed up and if you need a bit more power, a few were rated up to 10amps.  seems to be a standard for boats, autos and other 12v systems.

cheers...gary

I'll second what Chuck said. Though I purchased some without the digital display which made them a little smaller.

I used mine to power my Manards buildings....

Bruce..

I got one in 3 weeks for $2.45 free shipping, ebay #262136734501.  Works exactly as described: one button turns the display on/off, other button toggles between displaying the input and output voltage (i.e., 12.0V and 4.5V).

banjoflyer posted:

Or these 5VDC regulators at 12 cents apiece:

 

 

Mark

These are good, small versions typically rated for up to 1.5 amp I believe, should have a heat sink added for full output. If you want to drop the voltage a bit more just add a suitable diode on the output lead.

You can even get the 7805 with connectors, heatsink, circuit board, and related parts in kit form or assembled for less than $1.50 free-shipping on eBay.

But for the applicaton at hand (12V to 4.5V), this approach is woefully inefficient.  For example, since the OP says he has a "number of" lighting accessories, let's just say he needs 1 Amp of current at 4.5V.  With the 7805 "linear" method, this draws 1 Amp from the 12V supply (12 Watts) to deliver 1 Amp at 4.5V (4.5 Watts).  That means 7.5 Watts is wasted as heat.  That heatsink will get mighty hot and even the one shown in the photo above looks a bit small to handle 7.5 Watts.

OTOH, with the "switching" method as in the modules shown earlier, the same 4.5 Watts of output would draw less than 1/2 Amp from the 12V supply (less than 6 Watts).   The net effect is the same 12V supply can power double the buildings and lit accessories.

The buck converters shown above, or the simpler versions that require a separate meter to set are probably the "best" solution to reuse a 12VDC supply.  the linear regulators like the 7805, or LM317 also do a great job, but they make a lot of heat if driving much current... For the cost of a good heat sink you can purchase the buck converters and not have the problem.  

My personal favorite 5VDC supply is to use a power supply salvaged from a computer.  Even a basic power supply will provide 5VDC at 25 amps or more.  You also get, even from basic models, over-voltage protection and in most newer ones a quick acting, self reseting, circuit breaker.  Add to that a 12Amp+ 12VDC line, and a 20 amp+ 3.3VDC line.  Hard to beat for the price of free (salvaged from an old computer) to $15 (brand new).

JGL

Thanks for the ebay listing number, Stan.  Although this vendor is currently out of stock, I found a vendor with an identical product and ordered a few.  Thanks, again.