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Neil Cherry | 8 May 19:14
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[EE] Hobbyist battery SMPS circuit

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 | 8 May 21:42

Re: [EE] Hobbyist battery SMPS circuit

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 <at> linuxha.com> 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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Neil Cherry | 9 May 18:32
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Re: [EE] Hobbyist battery SMPS circuit

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 | 9 May 18:44

Re: [EE] Hobbyist battery SMPS circuit

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 | 9 May 18:50

Re: [EE] Hobbyist battery SMPS circuit

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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Dwayne Reid | 8 May 23:32

Re: [EE] Hobbyist battery SMPS circuit

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
(Continue reading)

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Alan B. Pearce | 9 May 10:22

Re: [EE] Hobbyist battery SMPS circuit

>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 | 9 May 18:06
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Re: [EE] Hobbyist battery SMPS circuit

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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Jinx | 9 May 00:28

Re: [EE] Hobbyist battery SMPS circuit

> 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 | 9 May 06:13

Re: [EE] Hobbyist battery SMPS circuit

On 5/8/08, Neil Cherry <ncherry <at> linuxha.com> 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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Neil Cherry | 9 May 17:51
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Re: [EE] Hobbyist battery SMPS circuit

Vasile Surducan wrote:
> On 5/8/08, Neil Cherry <ncherry <at> linuxha.com> 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
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