24 Volt DC to 5 Volt DC - need help constructing a simple circuit

Dec 09, 2005 9 Replies

It's been a few years since I had an electronics course, so I need help with a relatively easy question.



I need to reduce 24 volts DC to 5 volts DC. I think it's just a matter of a couple resistors but am unsure. The amperage is relatively low (not sure exactly).



Can anyone help? Details would be much appreciated.



Thanks,



-Dan



Look up a voltage divider circuit. It is made with a couple of resistors

+24V --------------------------- | < > R1 >

|-------------- +5V < > R2 >

| 0 -------------------------------------------- 0 i

On 09/12/2005 the venerable snipped-for-privacy@yahoo.com etched in runes:

7805L regulator. Costs about 50 cents and comes in TO92 package.
John B

But it might get hot fed with 24V

On 10/12/2005 the venerable Dope mcSmoke etched in runes:

Yes it might, that depends on the current consumption. But it won't get any hotter than the dropper resistor in a potential divider and the output will more stable.

If in doubt use a standard 7805 1A regulator bolted to Mr mcSmoke's dope tin.

John B

Yeah - details are what's needed- the "amperage" is all important so why don't you find out what it is before your ask your dumb question.

Ooohh such anger, now I know who the '40 Year Old Virgin' was based on.

If you're talking about more than 100 mA, consider a Simple Switcher from National Semiconductor. Check out LM2678-5.0. It won't need a heatsink for currents up to 2 amps or more. The website "web bench" will design the circuit for you, including giving you a parts list.

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Fred Bloggs contributes wonderful circuits here. You would be very hard pressed to get better help than he can provide - if that is possible. You mistake accuracy as anger.

Ed

Fred's response may be a bit blunt, but we do need to know the load you want to run from the 5 volts. If the current is very low and stable, a resistive divider may do, but if the load varies a lot, a regulator would be necessary.

Peter Bennett VE7CEI email: peterbb4 (at) interchange.ubc.ca GPS and NMEA info and programs: http://vancouver-webpages.com/peter/index.html Newsgroup new user info: http://vancouver-webpages.com/nnq

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