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'[EE] DC drive to aquarium diaphragm pump ideas?'
2005\09\29@182337 by Harold Hallikainen

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I have an application where I need to drive a diaphragm pump (like those
used in aquariums) from low voltage DC (battery). Here in the US, these
pumps are mechanically tuned to run directly off the 60 Hz line. A single
coil on a core moves an armature that has a couple magnets on it. The
armature moves back and forth at 60 Hz, vibrating the diaphragm.

So, in this application, I need to run the pump on DC. Ideas I'm
considering are:

1. Rewind the coil to have fewer turns and a center tap. Have a PIC drive
transistors that alternately ground one end of the coil or the other with
the center tap going to + supply.

2. Rewind the coil to have fewer turns without a center tap. Connect one
end to + supply, the other to a single transistor to ground that is
switched.

3. Electrically resonate the existing coil using a circuit similar to that
on page 4 of http://www.edn.com/contents/images/21705di.pdf ("Sine-wave
step-up converter uses Class E concept") where the inductor is the coil in
the pump.

Any ideas?

THANKS!

Harold


--
FCC Rules Updated Daily at http://www.hallikainen.com

2005\09\29@185913 by marcel

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...

> Any ideas?

a small DC motor that you run at 60*60 RPM that moves a piston rod back and
forth that physically toggles a switch between positive and negative voltage.

- Marcel



2005\09\29@185914 by marcel

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face
...

> Any ideas?

a small DC motor that you run at 60*60 RPM that moves a piston rod back and
forth that physically toggles a switch between positive and negative voltage.

- Marcel



2005\09\29@191029 by Harold Hallikainen

face picon face

> ....
>
>> Any ideas?
>
> a small DC motor that you run at 60*60 RPM that moves a piston rod back
> and
> forth that physically toggles a switch between positive and negative
> voltage.
>
> - Marcel


Pretty elegant! Actually, if I had the DC motor, a crank on it could run
the diaphragm directly. Turns out this pump is incredibly cheap (cheaper
than a motor), so I'm trying to figure out a cleaver way to drive it..

Thanks for the ideas... Any more?

THANKS!

Harold


--
FCC Rules Updated Daily at http://www.hallikainen.com

2005\09\29@202800 by Rob Robson
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I'd be inclined to hang the pump off a variac to see how little AC amplitude
you could get away with.  Also, the pump's coil might not be too thrilled
with square waves, so you might have to do what the cheaper commercial
12V-to-120VAC inverters do and simulate a sine wave with a two-step
staircase.  Just some thoughts.

RR


{Original Message removed}

2005\09\29@210124 by Richard Prosser

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Any idea on the power level / onductance / resistance of the coil?
RP

On 30/09/05, Rob Robson <spam_OUTrobTakeThisOuTspamsilk.net> wrote:
> I'd be inclined to hang the pump off a variac to see how little AC amplitude
> you could get away with.  Also, the pump's coil might not be too thrilled
> with square waves, so you might have to do what the cheaper commercial
> 12V-to-120VAC inverters do and simulate a sine wave with a two-step
> staircase.  Just some thoughts.
>
> RR
>
>
> {Original Message removed}

2005\09\29@224319 by Harold Hallikainen

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I'm waiting to get a sample. I understand it takes about 6W at 120VAC 60Hz.

Harold


{Quote hidden}

>> {Original Message removed}

2005\09\29@234228 by Richard Prosser

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OK.
I was looking at the ringing choke option & was trying to figure out
what size capacitor may be required for 60Hz resonance.
I think that it could be a reasonable option - and wouldn't require a
coil rewind which is another plus.
You may have to tune the capacitor value so that the resonant
frequency matches the mechanical resonance.

Other drive alternatives (using a rewound coil) could be a 1/2 or full bridge.

If you can find a centre tapped wall-wart or similar transformer a
simple push-pull  may be an option too.

RP

On 30/09/05, Harold Hallikainen <haroldspamKILLspamhallikainen.com> wrote:
{Quote hidden}

> >> {Original Message removed}

2005\09\30@153739 by Herbert Graf

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On Thu, 2005-09-29 at 15:23 -0700, Harold Hallikainen wrote:
> I have an application where I need to drive a diaphragm pump (like those
> used in aquariums) from low voltage DC (battery). Here in the US, these
> pumps are mechanically tuned to run directly off the 60 Hz line. A single
> coil on a core moves an armature that has a couple magnets on it. The
> armature moves back and forth at 60 Hz, vibrating the diaphragm.

This may be too simple, but why not just purchase an inverter? It sounds
like this device doesn't use that much power, and inverters of smaller
wattages are very cheap these days.

TTYL

-----------------------------
Herbert's PIC Stuff:
http://repatch.dyndns.org:8383/pic_stuff/

2005\09\30@161155 by Harold Hallikainen

face picon face

> On Thu, 2005-09-29 at 15:23 -0700, Harold Hallikainen wrote:
>> I have an application where I need to drive a diaphragm pump (like those
>> used in aquariums) from low voltage DC (battery). Here in the US, these
>> pumps are mechanically tuned to run directly off the 60 Hz line. A
>> single
>> coil on a core moves an armature that has a couple magnets on it. The
>> armature moves back and forth at 60 Hz, vibrating the diaphragm.
>
> This may be too simple, but why not just purchase an inverter? It sounds
> like this device doesn't use that much power, and inverters of smaller
> wattages are very cheap these days.
>


We're going to be shipping several thousand units a month. The pump is
about $5.00 I'm trying to keep costs down.

Thanks for the idea, though! Keep 'em coming!

Harold



--
FCC Rules Updated Daily at http://www.hallikainen.com

2005\09\30@165144 by marcel

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How about using a Wien bridge or something to generate the wave?
Alternatively, what about a PWM of some sort? Would just strobing a pulse
through the coil at regular intervals be enough to cause a vibration? In that
case you could just use a simple RC circuit or something.
- Marcel

"Harold Hallikainen" <EraseMEharoldspam_OUTspamTakeThisOuThallikainen.com> wrote:

{Quote hidden}

2005\09\30@170020 by Harold Hallikainen

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> How about using a Wien bridge or something to generate the wave?
> Alternatively, what about a PWM of some sort? Would just strobing a pulse
> through the coil at regular intervals be enough to cause a vibration? In
> that
> case you could just use a simple RC circuit or something.
> - Marcel
>


Thanks for the comments! Since there's going to be a PIC in the product to
handle other stuff, I'm planning on having it drive a transistor or two to
drive the pump. The trick is, should I:

1. Rewind the pump using a center tapped coil and pulse each end of the
coil to ground, or

2. Rewind the pump with a single ended coil and pulse just one end to
ground (mechanical resonance possibly would take it back the other way).

3. Don't rewind the pump, but make the coil resonant so I can get enough
current with low voltage drive (as mentioned in the article I posted
previously in this thread).

Again, THANKS for the comments!

Harold


--
FCC Rules Updated Daily at http://www.hallikainen.com

2005\09\30@194800 by William Chops Westfield

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On Sep 30, 2005, at 1:11 PM, Harold Hallikainen wrote:
>
> We're going to be shipping several thousand units a month. The pump is
> about $5.00 I'm trying to keep costs down.
>
If you have a cheap source that will do things like rewind the pump
magnet (!), perhaps you should just investigate what it would take
to implement a DC-based pump (either along the same lines as a DC
buzzer, or using a motor to drive a cylinder or diaphragm.  I have
such a motor driven pump surplus from Electronics Goldmine - it just
uses a rotating cam on the motor to drive a the diaphragm.)

BillW

2005\09\30@200313 by David Minkler

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Harold,

I'm curious why you don't just try your idea.  It looks reasonably sound
and a quick test with a 555 (or suitable substitute) where it's easy to
alter the frequency and duty cycle would get you a good answer in under
an hour.  It seems that if you can use the existing pumps "as is",
that's the way to go.  Go with plan 3 if there's any reasonable way to
make it work.

Dave

{Quote hidden}


'[EE] DC drive to aquarium diaphragm pump ideas?'
2005\10\01@131458 by Peter
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Must this be low voltage powered ? If you have mains available you can
pulse the coil with mains. Possibly with half waves to avoid kickback.
An opto and a mains rated transistor or thyristor switch will likely be
cheaper than rewinding the coil.

Since you are into light controls I am going to guess that this is for
some sort of light control (mechanical mirror drive etc). Then you could
sync your effect to the mains and use the solenoid as is.

In my limited experience the cheap aquarium solenoids have only 2-3 mm
stroke and they achieve that only at resonance. But the resonance point
is wide since they have a lot of damping (cheap thick rubber cap used as
membrane). Driving the device with unipolar pulses should not be a
problem because the moving armature is a permanent magnet (if it would
not be then the armature would have to vibrate at 2x mains frequency and
that is hard to do mechanically, plus the force would be lower). Just
pick the current direction that attracts the armature when the coil is
energised (has more force).

You might be able to achieve resonance using single-stroke drive if you
use a mains voltage doubler rectifier to provide the supply and a ~30%
duty cycle for the switch. But the kickback will be horrible. It could
be reduced using a RC damper of high value (say 3uF and 50 ohms if the
coil resistance is not enough).

'Some work' will likely be required.

Peter

2005\10\01@135756 by Harold Hallikainen

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Thanks for the comments! I'll probably do a little experimentation this
week. On using some sort of inverter to generate line voltage 60 Hz, it
doesn't seem cost effective. We already have a coil (in the pump), so why
add two more (a transformer). Just my opinion...

Again, THANKS for the comments. I'll experiment with one of the existing
pumps this week.

Harold

{Quote hidden}

> -

2005\10\01@140610 by Harold Hallikainen

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> On Sep 30, 2005, at 1:11 PM, Harold Hallikainen wrote:
>>
>> We're going to be shipping several thousand units a month. The pump is
>> about $5.00 I'm trying to keep costs down.
>>
> If you have a cheap source that will do things like rewind the pump
> magnet (!), perhaps you should just investigate what it would take
> to implement a DC-based pump (either along the same lines as a DC
> buzzer, or using a motor to drive a cylinder or diaphragm.  I have
> such a motor driven pump surplus from Electronics Goldmine - it just
> uses a rotating cam on the motor to drive a the diaphragm.)
>

I'm currently thinking mechanical design is the lowest cost. Since I'll
have a PIC in there anywhay to run other stuff, adding a transistor or two
to drive the coil seems simple enough. Just trying to get any other ideas
(and I'm getting them!).

Again, thanks for all the comments! Keep 'em coming!

Harold


--
FCC Rules Updated Daily at http://www.hallikainen.com

2005\10\01@143432 by Harold Hallikainen

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Thanks for the great comments! We do contract design work for several
companies, so this is not for the lighting industry. It is highly
desirable to have the thing operable on low voltage DC, both a wall wart
and secondary batteries. Driving the coil in only one direction and
relying on mechanical resonance for the travel in the other direction is
something I'm considering. I'll do some experimentation this week.

THANKS!

Harold

{Quote hidden}

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