step up converter.

[TT_Man]

Can someone suggest a low cost solution....
3V lithium I/P, 9-12V O/P unreg is ok. 5mA min, 10 mA max, but must have
on/off control. Turn on time of up to 5mSec. is ok.
Problem is to drive a 12V self oscillating piezo from a 3.3V micro....
TIA

 

[linnix]

Can someone suggest a low cost solution....

Can be less than $1.

3V lithium I/P, 9-12V O/P unreg is ok. 5mA min, 10 mA max,

You would need 40mA to 50mA current from 3V.

but must have
on/off control. Turn on time of up to 5mSec. is ok.
Problem is to drive a 12V self oscillating piezo from a 3.3V micro....
TIA

Somewhere between the 7V @20mA:

http://linnix.com/larkin

and the 30V @ 1mA:

http://linnix.com/hyde

Try playing with R1 (Load resister) to get the right output power.

 

[Joerg]

Can be less than $1.




You would need 40mA to 50mA current from 3V.




Somewhere between the 7V @20mA:

http://linnix.com/larkin

Cool! How did you program that interactive user interface?

and the 30V @ 1mA:

http://linnix.com/hyde

That one times out but could be a traffic jam on the web.

 

[Joerg]

Can be less than $1.




You would need 40mA to 50mA current from 3V.




Somewhere between the 7V @20mA:

http://linnix.com/larkin

Cool! How did you program that interactive user interface?

and the 30V @ 1mA:

http://linnix.com/hyde

That one times out but could be a traffic jam on the web.

 

[John Larkin]

Can someone suggest a low cost solution....
3V lithium I/P, 9-12V O/P unreg is ok. 5mA min, 10 mA max, but must have
on/off control. Turn on time of up to 5mSec. is ok.
Problem is to drive a 12V self oscillating piezo from a 3.3V micro....
TIA

Do you have a pwm output available, or can you afford to make a
software pwm waveform? Figure 10-25% duty cycle at 20-500 KHz. Then a
very simple inductive boost circuit will work.

John

 

[TT_Man]

Do you have a pwm output available, or can you afford to make a
software pwm waveform? Figure 10-25% duty cycle at 20-500 KHz. Then a
very simple inductive boost circuit will work.

John

Yes I can get a pwm output,but even a simple inductive boost cct is beyond
my knowledge.
The larkin cct is ok but there's lots of components and I need to turn it on
and off. Easy with software pwm O/P... Easy with a boost chip as well but I
can only find expensive ones....

 

[linnix]

Cool! How did you program that interactive user interface?

Apache + Php + Spice3f5 + gnuplot

That one times out but could be a traffic jam on the web.

Yes, even with 3GHz quad xenon server with 8G memory. Every time I
post, people are hitting the server all at once. Try a little later,
it should be better.

 

[John Larkin]

Yes I can get a pwm output,but even a simple inductive boost cct is beyond
my knowledge.
The larkin cct is ok but there's lots of components and I need to turn it on
and off. Easy with software pwm O/P... Easy with a boost chip as well but I
can only find expensive ones....

+3.3
|
|
L
| diode
|
+-------ak-----+------out
| |
d |
pwm----------g fet cap
s |
| |
| gnd
gnd


Fet is a small logic-level n-channel mosfet.

L could be, say, a small 200-500 uH inductor.

Diode is almost anything, 1N914, whatever.

Cap is, say, 0.1 uF

Just futz with the pwm duty cycle and period until the output voltage
is right. Try maybe 25% on, 100 KHz to start.

The output can't go below 3, so it's possible the piezo may peep a
little down there. If so, you can use another fet or just a port pin
to open its low side.

Or you could do this, which does go to zero when you quit driving
it...


+3.3
|
|
L
| diodes
|
+----cap-----+----ak-----+------out
| | |
d | |
pwm----------g fet k cap
s a |
| | |
| | gnd
gnd gnd



or this, with a small transformer,


+3.3
|
| +--------ak------+-------out
| | |
x||x* |
x||x c
x||x |
*| | |
| gnd gnd
|
|
|
d
pwm----------g fet
s
|
|
gnd

John

 

[Joerg]

+3.3
|
|
L
| diode
|
+-------ak-----+------out
| |
d |
pwm----------g fet cap
s |
| |
| gnd
gnd


Fet is a small logic-level n-channel mosfet.

L could be, say, a small 200-500 uH inductor.

And never, ever, let L go into saturation by keeping the FET on for too
long. Else, phssstt ... POOF.

Diode is almost anything, 1N914, whatever.

Cap is, say, 0.1 uF

Just futz with the pwm duty cycle and period until the output voltage
is right. Try maybe 25% on, 100 KHz to start.

The output can't go below 3, so it's possible the piezo may peep a
little down there. If so, you can use another fet or just a port pin
to open its low side.

Or you could do this, which does go to zero when you quit driving
it...


+3.3
|
|
L
| diodes
|
+----cap-----+----ak-----+------out
| | |
d | |
pwm----------g fet k cap
s a |
| | |
| | gnd
gnd gnd



or this, with a small transformer,


+3.3
|
| +--------ak------+-------out
| | |
x||x* |
x||x c
x||x |
*| | |
| gnd gnd
|
|
|
d
pwm----------g fet
s
|
|
gnd

Might want to add here that the transformer needs to have an airgap when
used as a flyback like this.

 

[kevin93]

Can someone suggest a low cost solution....
3V lithium I/P, 9-12V O/P unreg is ok. 5mA min, 10 mA max, but must have
on/off control. Turn on time of up to 5mSec. is ok.
Problem is to drive a 12V self oscillating piezo from a 3.3V micro....
TIA

An RS232 level translator such as a MAX3232 (or equivalent from
another vendor) can be an easy solution to this. It has a charge pump
step up converter built in (just needs a few small caps) and you can
either use the enable signal where available or put a diode in series
with the output to drive a self-oscillating sounder by controlling the
input. You could even drive a piezo sounder (non-self oscillating)
directly and give it 40v p-p.

The MAX3232 is guaranteed to provide 10V between the outputs when
driving 5mA total. (2.5mA each).

kevin

 

[John Larkin]

And never, ever, let L go into saturation by keeping the FET on for too
long. Else, phssstt ... POOF.

It will drag down the 3.3 rail lithium battery, the low-voltage reset
will kick in, and everything will turn off!

A resistor from gate to ground might be prudent, I admit.


Hey, this is Digital Power, the wave of the future!

John

 

[TT_Man]

An RS232 level translator such as a MAX3232 (or equivalent from
another vendor) can be an easy solution to this. It has a charge pump
step up converter built in (just needs a few small caps) and you can
either use the enable signal where available or put a diode in series
with the output to drive a self-oscillating sounder by controlling the
input. You could even drive a piezo sounder (non-self oscillating)
directly and give it 40v p-p.

The MAX3232 is guaranteed to provide 10V between the outputs when
driving 5mA total. (2.5mA each).

kevin

Thanks for all the answers and help. I have enough to get a solution I
think. Not going to 0 is ok as the piezo is cpu controlled and puts out a
hi(3V3) for off and the pwm will be off.
neat idea on the 40Vp-p with a max chip too!!

 

[Traver]

Thanks for all the answers and help. I have enough to get a solution I
think. Not going to 0 is ok as the piezo is cpu controlled and puts out a
hi(3V3) for off and the pwm will be off.
neat idea on the 40Vp-p with a max chip too!!- Hide quoted text -

- Show quoted text -

One last thought: Zetex (and others) make tiny LED driver ICs that are
meant to do exactly what you want. They come in regulated and
unregulated versions and make up a boost supply as others have
mentioned. ZXSC310 is just one example.

 

[Joerg]

It will drag down the 3.3 rail lithium battery, the low-voltage reset
will kick in, and everything will turn off!

.... after which the LV reset lets go, the uC wakes up again and then the
whole thing starts pumping. Hey, a new oscillator!

Here's hoping that it's not an industrial grade cell that decides to go
"exotherm".

A resistor from gate to ground might be prudent, I admit.


Hey, this is Digital Power, the wave of the future!

A SW-engineer once proclaimed that since Max Planck everything can be
reduced to digital. And this is a guy who plays the guitar and likes
tube amps.

 

[John Larkin]

... after which the LV reset lets go, the uC wakes up again and then the
whole thing starts pumping. Hey, a new oscillator!

Who makes 56 Henry inductors in 0603?

John

 

[RST Engineering \(jw\)]

Who makes 56 henry inductors these days in anything smaller than laser
printer?

Jim

 

[John Popelish]

Who makes 56 henry inductors these days in anything smaller than laser
printer?

Hammond manufacturing:
http://www.hammondmfg.com/pdf/5c0032.pdf
Considerable smaller than a laser printer, but also
considerable larger than an 0603.

 

[Joerg]

Who makes 56 Henry inductors in 0603?

Should be possible some day soon, with nano-technology. Of course, then
it'll saturate at a few micro amps so the market would be a bit smallish.

 

[Fred Bartoli]

Le Sun, 12 Aug 2007 17:28:13 -0700, Joerg a écrit:

Should be possible some day soon, with nano-technology. Of course, then
it'll saturate at a few micro amps so the market would be a bit
smallish.

Hmmm, what can you do with 56H nano-inductors and nano-tubes?

 

[linnix]

Le Sun, 12 Aug 2007 17:28:13 -0700, Joerg a écrit:







Hmmm, what can you do with 56H nano-inductors and nano-tubes?

Unlimited dreams. Nano motors and nano generators, etc.