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Converting 12VDC to 9VDC

electron

Administrator
Staff member
I use a 12VDC power distribution block to power all my accessories such as the Ocelot, camera etc, and would like to remove my remaining transformers as well. The problem is that these are 9V, is there an easy way of converting 12VDC to 9VDC (hoping maybe a few resistors here or so would do the trick)? Thanks!
 

electron

Administrator
Staff member
The problem is that I am trying to get rid of any transformers (space and asthetic reasons), so that would kind of defeat the purpose.
 

pkoslow

Active Member
If you're handy enough to build a small circuit, you can put something together with a voltage regulator. The problem is that these will produce heat and will require a good heat sink to produce much current.

If the devices you have require lots of current, you'd probably need several of these. Here are a couple links I found:

http://www.uoguelph.ca/~antoon/circ/ps-lm317.html
http://www.techlib.com/electronics/regulators.html

If you have numerous 9v devices you may consider just getting one larege 9v power supply and another distribution block to duplicate what you already have in place for your 12v devices?

Cheers,
Paul
 

electron

Administrator
Staff member
Interesting links, thanks! The first thing I wanted to convert is the W800RF32, it has a tiny 9V power supply, and I would just like to get it out of the way.
 

Spanky

Senior Member
I modify the ELK P624 for 9 volts DC. It uses an LM350 linear voltage regulator with adjustable voltages of 6.8, 13.8, or 27.6 to charge sealed lead acid batteries.

Change resistor R4 to 680 ohms from 1000 ohms and you should be able to adjust it to 9 volts from the 12 volt jumper setting.

Feed 12 - 13.8 volts DC into the transformer input terminals.
 

roussell

Active Member
How about a 7809 voltage regulator? Its a 3-terminal device with voltage in, ground, and +9 Volts out. With a small heatsink attached it can handle about 1 amp and is about the size of your thumbnail. You can find them at any electronic store, RatShack may even have them, I know they carry the 5 and 12 volt versions...

You'd have to size the resistors to your specific load, but how about chaining silicon diodes together, each diode will have a .7 Volt drop across the diode so chaining 4 of them together will cut down the voltage to 9.2 volts. Just be sure to size them for the amount of current passing through.

Terry
 

rocco

Active Member
Many of those 9 volt devices will run fine on 12 volts.

Most 9 volt devices are actually 5 volt devices. They typically contain a 7805 voltage regulator, which is good to an input voltage of 30 volts.

The problem is: The higher the input voltage, the more power is dissipated as heat from the regulator. It's only a 4 volt drop from 9 to 5, but a 7 volt drop from 12 to 5. Almost twice the heat.

My rule of thumb: If the regulator runs warm at 9 volts, it will run hot at 12 volts. If it is cool at 9, I would go ahead and run it at 12.

You could also cal the manufacturers to ask.
 

deranged

Active Member
I have used diodes for a really quick fix to drop 12 volts to 9.

in theory 4 or 5 should do it, and the amp rating of the diode needs to match your current for your device.

StevenE
 

Guy Lavoie

Active Member
By far the simplest way is with a 7809 regulator chip (as mentioned by Roussel). Assuming the 12 volts is well filtered, all you need aside from the regulator chip is a 100 uF and a 0.1 uF wired across the output. These regulators are of the TO-220 style case (like the triacs in X10 modules) and are easy to mount on a small board.
 

BraveSirRobbin

Moderator
Guy is correct on a simple way to convert 12v to 9v.

I also did this using LM317 adjustable voltage regulators (good for a little over an amp draw) as shown in THIS schematic for my Car Monitor How-To. Just look at the bottom part of that schematic. (I happened to already have a bunch of LM317's at the house). The Jameco links for the parts (including the heat sink and mounting kit) are even given in that How-To ;) .

FYI, the regulator with heat sink mount is shown in the lower right of THIS pic of the entire PC board. But, as Guy mentioned, you can use a breadboard to mount these components as shown HERE (left side of the upper bread board in that pic).
 

electron

Administrator
Staff member
Thanks guys, I need to process this information, and will give that circuit a shot once my stuff is up and running.
 

electron

Administrator
Staff member
For some reason, I didn't think of contacting the manufacture since some devices do support higher voltages, so per rocco's advise, I contacted WGL, and I got a response back already saying that the W800RF32 has a linear regulator, which can handle voltages up to 20 VDC. So it looks like I am set for now, until I have time to figure out the remaining transformers. Thanks again!
 

Digger

Senior Member
By putting the product in an "Over voltage" condition continously the temperature across the internal regulator will be much higher. I know some products that the company I work for manufacturer have a hard time when the input voltage is more than 110%. A 12 Vdc PS may actually put out 13 or more volts depending on the load if its not regulated.

As the temperature rises the life expectancy of the product can decrease. If the temperature rises to much the regulator can shut down at times (been there and done that).

While there may be plenty of room to play on some products you have to be careful is all I am saying. So if you notice the device running a lot hotter at the higher voltage you might want to keep an eye on it.

What about using zener diodes to drop the voltage? Cheap and easy?
 
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