Extra PSU, non sequenced

bajaguy · 12-11-2003, 04:19 PM

I need to power the following:

7" LCD Power Supply: DC 12V, 1A
Garmin 18 GPS: DC 4.4 - 5.5 V, 53 mA

I already have the PW-70a and ITPS combo for the mobo and drives. What I want is to have the screen on sleep mode when the mobo is not on and have the gps on a fixed lock. Ideally I'd like to have a single regulated PSU with both 12V and 5V outputs. Also, I'm looking for a small unit that could be plugged directly into the cars "power grid". I'm installing my system behind my dashboard and I can't fit much or don't want to route anything to a lighter connection. Any thoughts are welcomed.

Ben

Ricky327 · 12-11-2003, 08:15 PM

You can build 2 regulators in one unit :

7812 for the 12V @ 1A max...go for a higher current output if you think you are pushing the 1A limit.
78L05 for the 5V @ 100mA max

The problem you may have is the 12V, since you need > 12 to get 12V out on a standard regulator.

But check if your device can take unregulated voltage, if it can and its within the car battery range then you are sorted...no need for anything.

bajaguy · 12-12-2003, 07:20 PM

Thanks Ricky327. But, I'm a total dweeb when it comes to circuitry boards. What you just told me is like Chinese to me. I sure wish there is a kind soul here who could put such a thing together. I want to keep both devices regulated through the same powering device. It seems like a little board, ITPS come to mind, would do. But I don't need the sequencing part (shutdown controller). Any soldering pros out there?

Ricky327 · 12-12-2003, 07:24 PM

I sure wish there is a kind soul here who could put such a thing together.

Infact I do need one myself as a power rails to my car PC.

Yes you can use the ITPS for this.

There is a permanent 5V @ 100mA in the ITPS as well as a 12V @ 5A

The 12V is of course sequenced, you need to do a little modification so you can have it permanently on.

bajaguy · 12-13-2003, 02:21 AM

Would it be cheaper to make one from scratch? And only with the functionality we need, meaning no sequencer?

Ben

Ricky327 · 12-13-2003, 01:39 PM

Yup,

It will cost you 5 USD or so. You just have to buy the components and solder them in. If you look around there should be a ready made one.

bajaguy · 12-15-2003, 10:50 AM

Ok, so I've learn Basic Fiberglassing 101... let's pick up Basic PSU Design 101. What parts do I need? And better yet... how do I go about putting this thing together?

BTW, if I haven't said yet, thanks for your guidance.

Ben

Ricky327 · 12-17-2003, 11:39 PM

Its not easy to describe here but look around the internet they are fairly standard

You will need :
7812 12V regulator 1A or 2A
78L05 5V regulator 100mA
4 small capacitors.

Check the exact values of the capacitors but the one used for these regulators are generally 0.22uF and 0.1uF

The 7812 regulator may not work properly as it need something like 14V or more so you may need to find a lower dropout voltage to subtitute.

If you dont have access to making PCB you can use a stripboard.

bajaguy · 12-22-2003, 11:08 PM

I’m completely doing away with this idea. Why? I figured out that my car has an extra cigarette lighter pretty close to where the screen is going to rest. So, I can plug that in there as the Lilliput came with a cigarette lighter psu. As far as the GPS unit, I’ll be using Garmin’s GPS 16 HVS. It can take unregulated power anywhere from 6V to 40V, and according to their documentation all you need is a 1A fuse. So, that solves two of my problems: constant power for always-on operation and power regulation. The only pain in the rear is that 1A fuse, I’ve been to 12 different shops and none of them had it. Luckily, through Google, I found a local company that can order it for me. Hopefully no one fell asleep while reading this.

Happy Holidays!

Ben