Thread: Casetronics Case & DC-DC PS

Originally Posted by jasonsp6

Does anyone in this group have experience using the CaseTronic mini cases with a built in DC-DC powersupply? It seems the DC-DC convertor accepts 12 volts from a wall adapter. I was looking at them and was pretty excited about using one for my new carputer project untill I looked further into the powersupply specs... and realised that the input range isn't wide enough for automotive use.


Thanks for your input,
~Jason

'Tis true. Mine did work in my vehicle for a while, but now the PSU will no longer accept a high voltage. It will run for at most about 90 seconds... which is enough time to post, boot into XP, and start winamp for about 15 seconds or so. From here you would have two choices: a) build a 12V regulator for input to the PSU, or b) build/buy a complete PSU replacement that has a wider input range.

The case is nice (I have the C134), but I find it to be a little small. I won't go into details unless you want them. I will likely buy a C137 and move to that.

Originally Posted by EBJUSTIN

The PW-60 power supply that comes with the Casetronix 2699R has two
limitations. First being the tight 12V input voltage tolerance (I think it is only 5%)
The other issue is the maximum current on the 12Vout. It is spec'd at 1A
which theoreticlly isn't enough to power most harddrives. I have had
no issues powering my 120GB IBM drive however if I try to power a cdrom
also the 12V supply will sag and the hard drive/cdrom will stop spinning.

My solution for tight 12V Input tolerance not suitable connected to car battery 12 - 14.5V.
First I tried using a low dropout linear 12V regulator however this proved to be a problem
when the car was off (12V- 1.2V dropout =10.8V out). I then decided to use four
TI PT5071 switching regulators in parallel. The beauty of the PT5071 is that they are boost/buck
with an input voltage range of 8V to 20V and a constant output of 12V. I used four
5071's in parallel (with a shottkey diode on each of the outputs) becuase the max rated
current output is 1.5A and I calculated that I would need about 5A max. The regulators
are rated at 84% efficency which isn't bad. The other nice thing about this setup is that the
engine can be started without resetting the computer since the regulators can tolerate an
input as low as 8V.

To resolve the current limitation (1A max) of the PW60 12V rail I used a USB2.0 external
enclosure for my DVD-ROM. I removed the AC power supply that came with it and made
my own DC-DC supply using one PT5071 for 12V rail and one PT6212 for 5V rail. This keeps
my 12V current draw within spec and now my entire system is not dependant on a tight
12V input tolerance.

Good call on the switching regulators. I would like to know about the schottkey diodes you used. It'd have to be a low drop diode (0.4V probably) and I was wondering what manufacturer (and part #) of diode you used for this setup you have (so I can order a few). I'm sure others would like to know as well.

Originally Posted by sq_geek

yeah, post up!!

Mase Casetronics DC-DC PSU says "12v/4.5A" input, so I guess that is the MAX.. What 12v regulator do I need to build to yield that (so I have all the power I can get) ??????

Why did you guys get the C-134?? That's a ripoff... My 2699 cost $70 and my M10000 (Nehemiah mind you) cost $161. The C-134 costs like $300 or something.. ouch! And all you get is a smaller case and 5watts more power.. *shrug*

<offtopic>
If you don't already get the smaller is better thing, then I'm not going to try to explain it. I would agree that the C134 is pretty expensive (and a bit too small), but it has no problems other than that. I've heard about problems with grounding in other cases. The only complaint I have about the thing is that it's so packed w/ a 40GB HDD and slimline DVD/CD-RW that wire routing is a pain. It tends to get wires next to the fans easily and make a whirring noise that is totally unacceptable. This is why as soon as the Lippert Pentium M board comes out, I'm getting the C137.
</offtopic>

As for the PSU/regulator thing, the schematic should not be that hard to come up with. From EBJUSTIN's description, it sounds like 4 reference designs of the PT5071 with 4 low drop diodes all wired together at the end like so (forgive my text art)

Code:

       +-----| PT5071 Ref |----|>|---+
       |                             |
       +-----| PT5071 Ref |----|>|---+
  +V --+                             +---- ~12 V @ 6 A
       +-----| PT5071 Ref |----|>|---+
       |                             |
       +-----| PT5071 Ref |----|>|---+

Notice that the output won't exactly be 12 V @ 6 A. It will be a little less than that.
EBJUSTIN: correct me if I'm wrong.

HTH Everyone.