You might also look into National's LM350 or LM1084 series. If your problem
is just more current than the 7805 can handle. The 350 is spec'd up to 3A
and the 1084 is up to 5A IIRC. Their both still a 3 terminal TO220 linerar
regulator, and if memory serves the 350 has the same pinout as the 7805
while the 1084 has a couple pins swapped. But don't take my word for it,
check the data sheet.

Good Luck
-Denny


----- Original Message -----
From: "cdb" <bodgy1@OPTUSNET.COM.AU>
To: <PICLIST@MITVMA.MIT.EDU>
Sent: Saturday, August 30, 2003 3:28 AM
Subject: Re: [EE:] Power Supply problem - short?


> On Fri, 29 Aug 2003 08:46:22 -0400, Olin Lathrop wrote:
> ::What it the 5V current draw before and after the VFD is attached?
>
> Well I removed the Pic and the sensor and the current draw from just
> the regulator was 7.7mA @ 5.06v.
>
> There was a larger difference between Vreg(in) on the development
> board to the prototype PCB than I had thought.
>
>         Dev board               Proto
> Vreg(in) 11.6v           13.2v DC
>
> I noticed that after a few moments the current draw on the proto went
> passed the 340mA increasing rapidly to 735mA when the VFD was
> inserted.
>
> I inserted a pre-regulator that produces 11.9v and I noticed that
> with nothing connected the unloaded current consumption was down to
> 6.37mA with Vreg(out) of 5.8v. I connected the VFD -no sensor, no pic
> and I could reset the VFD and run its inbuilt test routine.
>
> I still have a feeling that maybe this particular 7805 may not be as
> healthy as it could be, but at least i can solve the problem
> temporarily with either Jinx's suggestion two 8ohm 1W in series or
> another bolt on pre regulator or maybe try a LM317. A buck regulator
> will require a complete re-design of the PCB.
>
> My fault for deciding a VFD looked better than an LCD as an
> afterthought.
>
> Thanks for the advice.
>
> Colin
> --
> cdb, bodgy1@optusnet.com.au on 30.08.2003
>
> I have always been a few Dendrites short of an Axon and believe me it
> shows.
>
> Light travels faster than sound. That's why some people appear bright
> until they speak!
>
> --
> http://www.piclist.com hint: PICList Posts must start with ONE topic:
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>

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