Power Supply: 12V in mutiple voltages out.

Dgswaner

I'm working on getting everything connected and powered on my bot. Adding the Propeller added the requirement of 6-9V I also need 5V for various sensors. and I figure while I'm at it I want to add 3.3V. I'm no electronics expert so I would like some advice before I start into this.

From what I've read I could just power the proto board from the 12v supply, but no one really know the long term effect of this. so it's not advisable. especially with out heat sinks.

also the greater the difference in the input voltage and the out put voltage, the more heat will be generated. so the lower the voltage the larger the heat sink will need to be and the less efficient it will be.

I could cascade voltage regulators 9V, 5v, 3.3v. but with 1A regulators, by time I get down to the 3.3v I will have used part if not most of the 1A in heat. at least as I understand what is going on. I don't need much more than 1A, in addition to the Proto board.

Can any one give me suggestions on the best approach to this.

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"A complex design is the sign of an inferior designer." - Jamie Hyneman, Myth Buster

DGSwaner

Post Edited (Dgswaner) : 11/27/2007 5:18:02 PM GMT

Franklin

You could use switching regulators and power them all off the 12v each supplying the parts they were for. This way the upstream regulators won't be passing current to the lower voltage units and you can size the regulator and heatsinks to the task at hand.

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- Stephen

Mike Green

There are some nice switching regulators available, like those from TI that have been mentioned before. They're designed to replace lm7800 style linear regulators. Why not get one with a 6V or 7V output and just feed that into the Protoboard? The switching regulator will drop the 12-14V supply to 6V and the linear regulators on the Protoboard can handle the small drop to 5V, then to 3.3V.

Dgswaner

well, that might normally be an option but I accidentally fried the 5v power supply on my proto board. had a short ;(. I could just get it fix (replaced) but I Have a lot of custom wiring on it which I don't really want to redo. I think I can fix it, perhaps thats going to be the best solution. If I needed more than the 1A from the proto board or I can't fix it, the thing to do is to add a 5V switching regulator?

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"A complex design is the sign of an inferior designer." - Jamie Hyneman, Myth Buster

DGSwaner

SailerMan

I built what you are looking for... mine is very basic and I am working on upgrading it. Here is the link.

http://forums.parallax.com/showthread.php?p=685484

Best Regards,
Eric

Mike Green

Sure. A 5V switching regulator would be fine. Be sure to remove or bypass the existing "fried" regulator.

Dgswaner

Sailorman.... I totally for got about your thread. I think I'll use your schematic. and it sounds like the switching regulators are a better solution than the 78xx series. at least in this application. Thanks guys... I'll let you know how it goes.

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"A complex design is the sign of an inferior designer." - Jamie Hyneman, Myth Buster

DGSwaner

SailerMan

In my new design I'm going to use Inductors rated at 150khz, the switching frequency of these regulators, the general Inductors are working but I want the circuit to be right.

Post Edited (SailerMan) : 11/27/2007 8:13:33 PM GMT

Dgswaner

ok, this is a little over my head. are you referring to L1 and L2 currently rated at 330uH, and if I was about to make this circuit I should get 150uH inductors?

like this one? beta.mouser.com/search/ProductDetail.aspx?R=18R154Cvirtualkey58010000virtualkey580-18R154C
I'm doing through hole.

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"A complex design is the sign of an inferior designer." - Jamie Hyneman, Myth Buster

DGSwaner

Post Edited (Dgswaner) : 11/27/2007 9:28:11 PM GMT

SailerMan

More like this, notice the heading that says 150khz.

dkc3.digikey.com/PDF/T073/P1329.pdf

This is one example... Search for 150khz Inductors.

I am referring to the switching frequency of the regulator not the inductance of the Inductor

I would select one rated at more that 1 Amp.

Post Edited (SailerMan) : 11/28/2007 1:30:58 PM GMT

Dgswaner

ok my head is spinning from all the new info. Here are my issues. I can't find a thorough hole inductor that meets the specs. I'm sure I can get one from some where tho. And also I need 6-9V which from what I can tell they don't make a switching regulator preset to anything in that range. so I'll have to use the adjustable version, Not a big deal. but keeping the KISS method in mind. Why not just use a LM7809? add a few caps. and I'm done. it seems like these switching Regulators are a little troublesome to work with in comparison. Do the benefits out way the issues? I liked the idea of the pre-made version in the 78xx format that Phli Phi mentioned but they are spendy!

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"A complex design is the sign of an inferior designer." - Jamie Hyneman, Myth Buster

DGSwaner

SailerMan

I'm kind of a do it myself sort. I like to reinvent the wheel ( [noparse]:)[/noparse] ) I was thinking along the lines of battery life and the LM78xx regulators Drop voltage in the form of Heat, I don't want to waste battery life so I started on a venture of building a dual power source from switching regulators which are much more efficient.

It's become a pretty neat project for me, but If you just looking for a simple regulator go with the 7809.

What are you powering that needs 6v-9v ?

Dgswaner

I'm all for saving battery life and this looks like a project I would use repeatedly, there for it's worth doing but I think I might opt for a lm7809. in the mean time because not having it is holding me up getting my bot running.

The 6-9v is for the Propeller Proto board. I need 5v for sensors and related hardware and 3.3 for a few things I would like to add later on.

I've looked on your other topic about measuring battery voltage, I'm trying to see if I can incorporate all of the ideas posted in that thread with your schematic.

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"A complex design is the sign of an inferior designer." - Jamie Hyneman, Myth Buster

DGSwaner

SailerMan

On my simple prototype it outputs 5v and 3.3 volts...

If you are using 9 volts on the proto board can't you just use a walwart? Or build your regualtor and bypass the one on the protoboard.

sam_sam_sam

SailerMan

Are you going to to make a switching regulatoring board

If you do PLEASE·let me know

Thank You for your help in this matter

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··Thanks for any··that you may have and all of your time finding them

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Sam

Dgswaner

he already has. check out his post at
http://forums.parallax.com/showthread.php?p=685484

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"A complex design is the sign of an inferior designer." - Jamie Hyneman, Myth Buster

DGSwaner

RDL2004

Building a switching power supply might be interesting. Maybe a suitable inductor can be found here:

Mouser search results


(Passive Components>Inductors>Power Inductors, select "Stocked" in the part#/keyword box, then select:
Inductance=330uH
Termination Style=all but smd
Maximum DC Current=all current ratings from 1 amp up)

I will have to research what effect the frequency rating has, none of the ones I looked at really had one other than like "nominal @1kHz"

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- Rick

Dgswaner

I don't know enough to know which one to pick. I'm going to work on a through hole board with 3 different outputs, Adj, 5 and 3.3. I'm also going to incorporate all of the suggestions by Mike green and everyone else about minimizing noise. I also want to have some sort of voltage meter built into it. So basically like what Sailerman is doing but 3 outputs and through hole.

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"A complex design is the sign of an inferior designer." - Jamie Hyneman, Myth Buster

DGSwaner