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

danfman · #1 (**permalink**) 12-09-2005, 10:38 PM

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

#2 (**permalink**) 12-09-2005, 10:51 PM

On 9 Dec 2005 13:38:46 -0800, mulletteeth@yahoo.com <mulletteeth@yahoo.com> wrote:

Quote:

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.

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

+24V ---------------------------
|
<

Quote:

R1

|-------------- +5V

<

Quote:

R2

|

0 -------------------------------------------- 0

i

#3 (**permalink**) 12-09-2005, 11:17 PM

On 09/12/2005 the venerable mulletteeth@yahoo.com etched in runes:

Quote:

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

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

--
John B

#4 (**permalink**) 12-10-2005, 02:10 PM

John B wrote:

Quote:

On 09/12/2005 the venerable mulletteeth@yahoo.com etched in runes:

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

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

But it might get hot fed with 24V

#5 (**permalink**) 12-10-2005, 04:01 PM

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

Quote:

John B wrote:
On 09/12/2005 the venerable Dope mcSmoke etched in runes:

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

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

But it might get hot fed with 24V

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

#6 (**permalink**) 12-10-2005, 04:22 PM

Quote:

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.

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.

#7 (**permalink**) 12-11-2005, 01:03 AM

On 10 Dec 2005 15:01:16 GMT, "John B"
<spamj_baraclough@blockerzetnet.co.uk> wrote:

Quote:

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

John B wrote:
On 09/12/2005 the venerable Dope mcSmoke etched in runes:

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

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

But it might get hot fed with 24V

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.

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.

http://www.national.com/appinfo/power/webench/

danfman · #8 (**permalink**) 12-11-2005, 01:31 AM

Fred Bloggs wrote:

Quote:

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.

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.

siongboon · #9 (**permalink**) 03-09-2006, 01:49 PM

You can try this IC from National Semiconductor LM2576.
http://www.siongboon.com/projects/20...c-dc_converter

It will not generate as much heat as 7805 regulator.
LM2576 can power up to 3A, enough for most electronics.
Input can be from 7Vdc to 40Vdc, and output is regulated at 5Vdc.
Other version of LM2576 are available with 3V, Adjustable output voltage, and more...

Have fun.