Voltage Regulators

DLMatthys · Post by **DLMatthys** » Fri Aug 11, 2006 11:46 am

I'm looking for schematics, components and or foil paths to make a practicle voltage dropper circuit that will bring down 9 and 12 volts dc down to 6 volts DC

Practicle and experainced advice is needed...as I want to construct a kit with PE boards and parts so folks can use several lighting subassemblies that work at different voltages.

Example: DLM Fed Flasher Board for blinks and strobes @6VDC....combined with... Autozone EL "pimp my ride" parts that work constant on at 12VDV.

I want to construct a device to drop 12 down to 6 VDC. And or 9 to 6 VDC.
A kit as such would give a lot of DIY light'em up folk a wide range of DIY lighting options.

Any bright ideas?

Umi_Ryuzuki · Post by **Umi_Ryuzuki** » Fri Aug 11, 2006 1:07 pm

I thought we had a simplified version posted somewhere, but I guess it's just here on my hard drive. I can't find where or who I posted it for.

Here is the mathematical version... Bottom of page.
http://groups.msn.com/QueensOwnAxisComm ... ation.msnw

These will need a heat sink, depending on what the amp draw required.

macfrank · Post by **macfrank** » Fri Aug 11, 2006 2:24 pm

The problem with any linear regulator (like the excellent LM317 family) is that going from 12V to 6V is going to generate a lot of heat; you'll need a heatsink - which'll grow as the current drawn by the circuit increases.

What would be ideal would be a 12V to 6V (or 5V) step-down regulator. They're typically switching devices and slightly more complicated 9and expensive) than the LM317, but they're more efficient, so they won't produce as much heat.
Maxim has a few nice switching regulators that'll do the job. Or just stick with the 317 - if it's not going to be inside a model, the heatsink shouldn't eb a big problem.

jwrjr · Post by **jwrjr** » Fri Aug 11, 2006 10:20 pm

Use an LM317 (available from many Radio Shack stores), a 220 ohm resistor (standard, common) and an 820 ohm resistor (standard, not common). That will give you 5.9 volts, depending on the tolerance of the resistors. There used to be a type 7806 fixed regulator wihch would give you 6 volts, but I don't know if it is still available. Even if it is, it will not be easy to find.

DLMatthys · Post by **DLMatthys** » Sun Aug 13, 2006 12:32 pm

I hsve tried the LM317 several times. If I recall I could not find the desired lower output voltage. I asume this circuit at http://groups.msn.com/QueensOwnAxisComm ... ation.msnw
has a comon or seperate goound?

macfrank · Post by **macfrank** » Sun Aug 13, 2006 2:58 pm

DLMatthys wrote:I hsve tried the LM317 several times. If I recall I could not find the desired lower output voltage.

Use the LM317 Calculator to get a ballpark figure for the resistor values, and compare them with the data sheet to make sure you're not coming up with out of spec values.

With the standard 240 Ohm R1, an R2 of 910 Ohms will give you an output voltage of 5.99 volts. The input voltage will have to be at least 7.5 volts for this output voltage. Since you want to feed it either 9V or 12V, that should do it.

The circuit diagram on that page (straight from the datasheet...) should do the job. Replace R2 with the 910 ohm resistor, add the bypass caps (make sure to use at least 25V rated caps!) and you're done.

Don't forget a nice heatsink for the 317!

Frank

jwrjr · Post by **jwrjr** » Sun Aug 13, 2006 11:14 pm

I checked. Digikey carries the type 7806 regulator, which is a 6 volt, 1 or 1.5 amp fixed voltage regulator.