Hobbyist battery SMPS circuit

[Neil Cherry-3]

I've been poking around and I've found a few good links (I can share
if you ask) but I'm a bit overloaded with information and could use
a little help.

What I'm looking for is a SMPS for use with batteries (AA). Does
anyone have any good sites for simple but efficient SMPS? Also
are there relays that can be activated by 3V?

Thanks

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[M. Adam Davis-2]

Spark fun has a few products that you can use as-is (no schematics):
http://www.sparkfun.com/commerce/categories.php?cPath=53_54

Usually I just go to national semiconductor and use their power designer:
http://www.national.com/appinfo/power/webench.html
You put in your input voltage range, output voltage and current, and
it spits out a design.  If it's a generic enough design you can even
order kits from them.

It gives you a good starting point, although all these places (linear,
maxim, etc) will have data sheets with good regulator designs using
their parts.

There have also been other cheap regulator designs posted to the
piclist - do a search.

-Adam

On 5/8/08, Neil Cherry <ncherry@...> wrote:

> I've been poking around and I've found a few good links (I can share
> if you ask) but I'm a bit overloaded with information and could use
> a little help.
>
> What I'm looking for is a SMPS for use with batteries (AA). Does
> anyone have any good sites for simple but efficient SMPS? Also
> are there relays that can be activated by 3V?
>
> Thanks
>
> --
> Linux Home Automation         Neil Cherry       ncherry@...
> http://www.linuxha.com/                         Main site
> http://linuxha.blogspot.com/                    My HA Blog
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[Dwayne Reid]

I'm using an oldy but goody in one of my current projects: National
Semiconductor LM2623.  Starts at 1.1V, runs from 0.8V through 14V,
internal switch is good for better than 2A, tiny 4.7uH inductor.  I'm
powering it with 2x 1650 mAH NiMh prismatic cells (in series) with
excellent results.

I spent a lot of time trying to find something better but cheaper and
gave up.  At the time the project was started (couple of years ago),
the MAX756 was hard to get hold of or I might have considered it.

And: Yes - there are many relays available with 3 Vdc coils.  Aromat
(NAIS) JS1 and DS2E / DS4E come to mind but there are plenty others.

dwayne


PS - Posting your list of links with info regarding low voltage SMPS
would be a great thing for you to do.  I'd sure appreciate it.

dwayne


At 11:15 AM 5/8/2008, Neil Cherry wrote:
>I've been poking around and I've found a few good links (I can share
>if you ask) but I'm a bit overloaded with information and could use
>a little help.
>
>What I'm looking for is a SMPS for use with batteries (AA). Does
>anyone have any good sites for simple but efficient SMPS? Also
>are there relays that can be activated by 3V?
>
>Thanks


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Trinity Electronics Systems Ltd    Edmonton, AB, CANADA
[phone] voice          [phone] fax
www.trinity-electronics.com
Custom Electronics Design and Manufacturing

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[Jinx-4]

> are there relays that can be activated by 3V?

Would you consider a voltage boost (capacitor dump) so you
could use a 5V relay

http://www.piclist.com/techref/io/relays.htm

or a temporary voltage doubler ?

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[Vasile Surducan-2]

On 5/8/08, Neil Cherry <ncherry@...> wrote:

> Also are there relays that can be activated by 3V?

Low voltage logic families (0.9V, 1V, 1.2V, 1.8V, 2.5V, 3.3V) have
been invented to minimise power dissipation. If you are using a
microcontroller supplied at one of these voltages and think to drive a
3V relay, I think something is wrong with your decision. As long you
didn't say wahy you need a 3V relay I can only guess.
Example of wrong decision: relay battery activated.

Vasile
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[Alan B. Pearce]

>I'm using an oldy but goody in one of my current projects: National
>Semiconductor LM2623.  Starts at 1.1V, runs from 0.8V through 14V,
>internal switch is good for better than 2A, tiny 4.7uH inductor.  I'm
>powering it with 2x 1650 mAH NiMh prismatic cells (in series) with
>excellent results.

Linear Technology also have a range of switcher chips designed for low
voltage input. Many are designed for use in cell phones and similar consumer
equipment, so come in horribly small packages, but there are also a number
that come in more manageable packages like SOT-23 and SO-8. They also are
happy to supply a couple of chips as samples for free, if you go through
their web page.

Another trick with Linear Technology is their Spice program which is
designed as a sales tool for their chips, so it has much of the range as
standard items that you can select. The program is totally free and you just
need to follow the download links from the home page.

For the required inductor, there are several companies can supply these.
Coilcraft is one I have used, and they also have a sampling program, but
there are others listed in the LT datasheets. It also pays to use the
capacitors recommended in the datasheet, as well as a PCB layout that is
very close to examples they give.

http://www.linear.com/index.jsp
http://www.coilcraft.com/

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[Neil Cherry-3]

Vasile Surducan wrote:

> On 5/8/08, Neil Cherry <ncherry@...> wrote:
>
>> Also are there relays that can be activated by 3V?
>
> Low voltage logic families (0.9V, 1V, 1.2V, 1.8V, 2.5V, 3.3V) have
> been invented to minimise power dissipation. If you are using a
> microcontroller supplied at one of these voltages and think to drive a
> 3V relay, I think something is wrong with your decision. As long you
> didn't say wahy you need a 3V relay I can only guess.
> Example of wrong decision: relay battery activated.

I'm not sure I follow, using the battery power supply is not a
choice, it's a requirement. It may be one to doom the project
but that is okay also. This project is 'driven' by my friend
and his needs for this odd-ball circuit. I initially wasn't
going to discuss what we're building but I will as it just
makes the discussion easier. My friend saw an article on a
'Cheese box' (a circuit that connects two POTS lines together)
and wants one for where he works. He wants to use it to connect
to old analog PBXs together POTS). I've looked at the circuit
and I don't like it. I'll be adding niceties to handle the
600V hot boxes they use to fix the copper and a few other
things. The reason behind the device is that they can't get
funding to properly connect the two circuits. This device
will make my friends life easier at work. This will not be
connect to the PSTN and it's not illegal. The use of batteries
and low power is to see if we can do it. I suspect we'll
eventually have to use local power (may be DC but not -48v)
but I'd like to see 'how low can we go'. I'll be using
an MSP430-2012 (I have 12) though I can use any number of
devices I already have.

Also if you're getting the impression that I don't know what
I'm doing you are correct, but I'm about to learn. The last
time I used a uC (micro-controller) to drive a relay I
needed a transistor and a diode external to the relay and I
had an AC-DC linear power source (plenty of power). This
is more of a challenge from my friend to see if it can be
done. He does to me a lot and he knows I won't turn it down
even if I think it will fail. Half the fun is in the learning.

The relay in question will drive another set of relays that will
get their power from the energized circuit (turning it off is a
question for later at this point ;-). The only decision made so
far is that a pin on the uC will drive the relay which will
energize the other relays. After n amount of time the relay in
question will be turned off as it's not needed to hold the circuit.

The reasoning behind the 3v relay is that the CPU can be run from
1.1v - 3.3v. I'd prefer not have to build two SMPS circuits for
different voltages. I'm know I can make the whole thing work off
AC.

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[Neil Cherry-3]

Dwayne Reid wrote:
> I'm using an oldy but goody in one of my current projects: National
> Semiconductor LM2623.  Starts at 1.1V, runs from 0.8V through 14V,
> internal switch is good for better than 2A, tiny 4.7uH inductor.  I'm
> powering it with 2x 1650 mAH NiMh prismatic cells (in series) with
> excellent results.

I had found a few LM26xx suggestions but I have to 'recover' the
sessions in my browser so I can bookmark them (I use Firefox and
have session saver).

> I spent a lot of time trying to find something better but cheaper and
> gave up.  At the time the project was started (couple of years ago),
> the MAX756 was hard to get hold of or I might have considered it.

I'll look into that, thanks.

> And: Yes - there are many relays available with 3 Vdc coils.  Aromat
> (NAIS) JS1 and DS2E / DS4E come to mind but there are plenty others.

Excellent

> PS - Posting your list of links with info regarding low voltage SMPS
> would be a great thing for you to do.  I'd sure appreciate it.

Dang, session saver didn't save them. I'll have to go looking for
them again. I had at least three that I liked.

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[Neil Cherry-3]

M. Adam Davis wrote:
> Spark fun has a few products that you can use as-is (no schematics):
> http://www.sparkfun.com/commerce/categories.php?cPath=53_54

That's not too bad, I may pick one up and see what we can do with it.
Thanks

> Usually I just go to national semiconductor and use their power designer:
> http://www.national.com/appinfo/power/webench.html
> You put in your input voltage range, output voltage and current, and
> it spits out a design.  If it's a generic enough design you can even
> order kits from them.

Thanks, I have their web page up now.

> There have also been other cheap regulator designs posted to the
> piclist - do a search.

Oh that's right, I remember now, there were these little contests
to see who could build the {simpliest,cheapest,efficientest,smallest}
power supply. I'll search for those.

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[Dave Schmidt-3]

I bought this 'toy' from SparkFun and was quite impressed given the
single AA power and the small size of the boost converter.

Schematic is there and in an email to them on what the part was here's
their reply.

We use a NCP1400 and here is the datasheet:
http://www.onsemi.com/pub/Collateral/NCP1400A-D.PDF

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[Dave Schmidt-3]

Sorry, forgot the link to the 'toy'.
http://www.sparkfun.com/commerce/product_info.php?products_id=7947

Dave Schmidt wrote:

> I bought this 'toy' from SparkFun and was quite impressed given the
> single AA power and the small size of the boost converter.
>
> Schematic is there and in an email to them on what the part was here's
> their reply.
>
> We use a NCP1400 and here is the datasheet:
> http://www.onsemi.com/pub/Collateral/NCP1400A-D.PDF
>
>  

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