12 V regulator

[bcroe at juno.com]

On Sat, 1 Dec 2001 17:53:37 -0600 bcroe at juno.com writes:
> This may be a bit late, but trying to regulate 12V out 
> with 10V in is doing it the hard way.  I would use some
> CD4541 chips as adjustable timers, very happy at
> 5V and well under a $1.  No problem with heat either.  
> They could drive logic FETs which could drive regular 
> 12V relays unregulated.
> 
> Bruce Roe
> 
> On Thu, 29 Nov 2001 10:11:37 -0500 Steve.Flanagan
> @VerizonWireless.com writes:
> > I have a requirement for 12 V regulation (+/- 15% or 
> > a range of 10.2 to 13.8 volts).
> > 
> > My application is driving several 12V time delay relays 
> > (TDRs) and I am building it to work in a drag car that 
> > can be powered with 12v + Alternator or a 16V system.  
> > Keep in mind that with the 16V system, the battery 
> > charger can put over 18V's.
> > 
> > The TDRs pull as low as 1 ma each when in the off state, 
> > and as high as 200 ma each when the relay is triggered.   
> > So lets just say my requirements for a regulator are:
> > 
> > Input Voltage:  10v to 20v
> > Output Voltage: 12v (+/- 15%)
> > Output Current: 1mA to 500mA
> > 
> > I tried to use a 12V regulator purchased from Digikey just 
> > as a test and it seems to crap out at the lower current levels 
> > (I don't have the part number handy, its at home, and this 
> > was a project I was working on over a year ago, something 
> > just stirred up my memory that I never was able to resolve 
> > this.  Originally I was not aware of the lower current levels, 
> > so the regulator I purchased worked in the 100ma range, 
> > but not at lower (1ma) range.  
> > 
> > Could someone recommend a very reliable 12V regulator 
> > that I can use to meet my needs.  
> > 
> > As a work around I built my own regulator with a 12 V zener, 
> > resistor and 2n2222 transistor that seems to work, 
> > however, I am concerned about the reliability and heat 
> > issues with the 2n2222.
> 
> > 
> > Steve F
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