25v to lower voltage

[Guy Paddock]

Is there a quick and easy way to drop the voltage in a circuit down from 25
volts, to, say, 9v? I'm assuming a transformer, but I was wondering if there
was a resistor that might handle it, or something of the sort...

Also, if a transformer is required, where would I get one to match those
specs?

--Guy

 

[JD Steffen]

Hi,

Might check into the LM7809 voltage regulator. I don't remeber what
the voltage limit is for it, so you'll have to check out the data sheet. Try
Motorola or Linear. This way you don't need a transformer. The
regulator will output a clean 9 volts.

JD

"Guy Paddock" <Guy@paddocklan.tzo.com> wrote in message
news:yiERb.11819$Mo5.6197@news01.roc.ny...

Is there a quick and easy way to drop the voltage in a circuit down from
25
volts, to, say, 9v? I'm assuming a transformer, but I was wondering if
there
was a resistor that might handle it, or something of the sort...

Also, if a transformer is required, where would I get one to match those
specs?

--Guy

 

[Robert C Monsen]

"Guy Paddock" <Guy@paddocklan.tzo.com> wrote in message
news:yiERb.11819$Mo5.6197@news01.roc.ny...

Is there a quick and easy way to drop the voltage in a circuit down from
25
volts, to, say, 9v? I'm assuming a transformer, but I was wondering if
there
was a resistor that might handle it, or something of the sort...

Also, if a transformer is required, where would I get one to match those
specs?

--Guy

Are you interested in 9V A/C? Transformers don't work with DC. For A/C,
it'll be hard to find a transformer that will take 25VAC -> 9VAC.

If its DC, using a 7809, like M. Steffen suggested, would work:


25V .-----. 9V
---------|7809 |------+--------
| | |
| | ---
| | --- 0.1uF
'-----' |
| |
| |
| |
-------------+---------+-------- GND
created by Andy´s ASCII-Circuit v1.24.140803 Beta www.tech-chat.de

However, the 7809 will consume 64% of the power through the circuit. Its
also limited to some small current, say 500mA.

There are more exotic chips used to drop DC voltage called 'switch mode
power supplies' that are more efficient, and thus will generate less heat
for larger power requirements. They are also more expensive.

Regards,
Bob Monsen

 

[Olaf]

On Wed, 28 Jan 2004 01:32:14 +0000, Guy Paddock wrote:

Is there a quick and easy way to drop the voltage in a circuit down from
25 volts, to, say, 9v? I'm assuming a transformer, but I was wondering
if there was a resistor that might handle it, or something of the
sort...


is the 25V AC or DC, do you need 9V AC or DC, what current do you need at

9V? Without this information it will be quite impossible to give some
advice

bye, Olaf

 

[Guy Paddock]

I need 9v to power an electromagnetic coil. The current 25v makes the coil
very powerful, but makes it heat up too much. I need it to run with less
heat.

--Guy

"Olaf" <olafdonk@wanadQQ.nl> wrote in message
newsan.2004.01.28.09.35.16.840623@wanadQQ.nl...

On Wed, 28 Jan 2004 01:32:14 +0000, Guy Paddock wrote:

Is there a quick and easy way to drop the voltage in a circuit down from
25 volts, to, say, 9v? I'm assuming a transformer, but I was wondering
if there was a resistor that might handle it, or something of the
sort...


is the 25V AC or DC, do you need 9V AC or DC, what current do you need at
9V? Without this information it will be quite impossible to give some
advice

bye, Olaf

 

[John Popelish]

Guy Paddock wrote:

I need 9v to power an electromagnetic coil. The current 25v makes the coil
very powerful, but makes it heat up too much. I need it to run with less
heat.

If you are not worried about loading the 25 volt supply the least
possible amount, then just connect a resistor in series with the coil
that will reduce its voltage drop to about 9 volts. If you measure
the coil resistance, I can help you spec the resistor.

--
John Popelish