prafful
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For 1.9W a small clip-on heat finned heat-sink (with perhaps a 15-20W/C thermal resistance or better) to a TO-220 regulator package should be sufficient.you are right, that a small heat sink is necessary. I only want to show, that it is possible to make it without a switch mode circuit.
Please give me a advise, if I must tell, when heat sink or other accessories are necessery. You are an older Member then I. :
thanks to all of you...
but i m still afraid that 7805 can make 5A to 200mA???
is it ok if I give 12V and 5A supply directly to 7805..???
s it ok if I give 12V and 5A supply directly to 7805..???
Hello prafful,
the 7805 has intern current limiting to 1A. The 5Ah of your battery is their capacity. It means, that your battery can deliver 5 A for one hour or 1A for 5 hours. In your case, with 200 mA, you can use your battery for 25 hours before your must charge the battery.
Regards
Rainer
One more thing when switching voltage regulator is used, filtering should be carefully designed for ripple voltage, specially if uC is used in project.
Price of switching regulator can be almost like price of uC. :wink: But 7805 is very cheap and dissipate low power. 12V-5V=7V*0,2A=1,4W its :smile:
But its its needed to get some elementary knowledge or hire some friend with knowledge to do this for you.
Maybe they start to put arduino into cornflex boxes or detergent powder boxes.
Ha! I would eat a lot more corn flakes then. :grin: (Then again, I'm a programmer by trade, not an ee -- most of my "professional" hardware is a couple breadboards and terminal blocks nailed to a piece of plywood).
Prafful what bike you have ?
Do You trying to make RPM for bike ?
Whoa, folks - the question is about a battery as the source.
Using a Regulator to get his output is incredibly inefficient. Yes, it's the easiest to design and use, but his battery isn't going to last very long. (And for the record, the current draw by the regulator won't be '200mA'; yikes. That's his desired draw at the output. The draw isn't even a simple Power (VI) calculation, either.)
The suggestion of a DC-DC converter was the best. There are many on the market, and they are much more efficient than a regulator.
(Translated: Use a regulator, his battery won't last long. Use a DC-DC converter, it'll last much longer.)
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