Chip with simple program for Toy

[Phil Allison]

"Avi Schwartz"


** Must be one of Freemont's fuckwit arse lickers.






....... Phil

 

[jasen]

On 2006-11-02, Ge0rge Marutz <gerbermultit00l@yahoo.com> wrote:

I need a reverse battery voltage scheme for a 60A max automotive
circuit design. Nominal current is 50A.

My first idea was just to throw a Schottky diode in series with the
battery feed like I do in every other circuit. However, 60A diodes in
a reasonably sized package are hard to come by.

I've seen 60A diodes in a package the size (and approximate shape)
of a LR44 button cell... try an automitive electrical place - they use them
in the recitifiers of the altenators.

Bye.
Jasen

 

[redbelly]

lerameur wrote:

I added a capacitor and a resistor in parallel at the output like you
said and it solved the problem. I already had a a resistor their. The
max current these chip can take is about 20ma for input anyway. I also
has some back ac lighting,weak but still affected the circuit, but when
in total darkness and just the white led, it works good.
thanks

ken

You're welcome ... and good luck.

Mark

 

[Bob Eld]

"Bret Cahill" <BretCahill@aol.com> wrote in message
news:1162498946.796294.160040@m7g2000cwm.googlegroups.com...

Would alternating a lot of capacitors and inductors in series
approximate a Slinky spring?


Bret Cahill

No...Placing a number of capacitors and inductors in series simply lumps
them as one capacitor and one inductor. The inductance adds: L1 + L2 +
L3.... and the reciprical of the capacitace adds: 1/C1 + 1/C2 + 1/C3....etc.
The result is a single capacitance, a single inductance and a single
resonant frequency. Apparently you are looking for a coupled group of
resonators each separate from yet dependent on the other. There are circuits
like this. Look up chaotic oscillators.

 

...... Phil

isn't this what we call inappropriate?

don't reply to him - you defeat filters.

 

[Bret Cahill]

On Nov 3, 9:47 am, "Bob Eld" <nsmontas...@yahoo.com> wrote:

"Bret Cahill" <BretCah...@aol.com> wrote in messagenews:1162498946.796294..160040@m7g2000cwm.googlegroups.com...

Would alternating a lot of capacitors and inductors in series
approximate a Slinky spring?

Bret CahillNo...Placing a number of capacitors and inductors in series simply lumps
them as one capacitor and one inductor. The inductance adds: L1 + L2 +
L3.... and the reciprical of the capacitace adds: 1/C1 + 1/C2 + 1/C3....etc.
The result is a single capacitance, a single inductance and a single
resonant frequency. Apparently you are looking for a coupled group of
resonators each separate from yet dependent on the other. There are circuits
like this. Look up chaotic oscillators.

As long as no new auto alarms come out of this . . .


Bret Cahill

 

[Baron]

Homer J Simpson wrote:

"Bret Cahill" <BretCahill@aol.com> wrote in message
news:1162498946.796294.160040@m7g2000cwm.googlegroups.com...

Would alternating a lot of capacitors and inductors in series
approximate a Slinky spring?

No: That would be more like a transmission line representation !



--
Baron:

 

[John Fields]

On Wed, 01 Nov 2006 03:38:07 GMT, "AJ" <itisme33@bigpond.net.au>
wrote:

Hi

I am currently driving a Piezo element (Part number KBS-27DB-3A) via a
transistor with a resistive load running on 5V but its not as loud as I was
hoping so I was thinking about changing the 1K resistor I have on the
collector of the of the transistor to an inductor/choke to try and get more
voltage across the element. I was just wondering what value inductor I
should use or how I might go about calculating one? Does anyone know of a
good web site that might help educate me a bit more in this area?

---

From your description, I assume this is your circuit configuration:

View in Courier.

+5V
|
[1000R]
|
+-----+
| |
C |
SQIN>---[R]---B [PIEZO]
E |
| |
+-----+
|
GND

The first problem I see is that while the piezo is rated to deliver
an SPL of 75dB minimum at a distance of 30cm with a 10VPP 3kHz
square wave across it, your circuit can only deliver a 5VPP signal
to drive the piezo. Also, the 1000 ohms will only allow, at best,
5mA of current into the transducer, so you won't get much of an
amplitude out of it while it's charging.

A second problem may be that you're not driving the transducer with
3kHz. If you're not, you won't be driving it at its resonant
frequency and its output level will not reach 75dB.

In order to get the 10VPP square wave across the transducer you
could drive it with a full bridge made from two 555 timers.

Each timer has a totem pole output which can source or sink 100mA,
which ought to be plenty for your piezo. Unfortunately there's no
mention of what its impedance is in the data sheet, but with 20nF of
capacitance that's a reactance of about 2600 ohms at 3kHz. Again,
unfortunately, that's with a sinusoidal drive, and you're going to
be driving it with a square wave, so there'll be some fairly high
peak currents at the edges.

If you wanted to you could but an inductor in series with the
transducer and tune out the capacitive and inductive reactances, and
that would leave only the real part of the impedance to drive, but
with a 3kHz and 2600 ohms that's a pretty good sized choke.

In any case, the LTSPCICE circuit file attached will show you a
driver that you can use to get the 10VPP square wave drive or, with
the inductor in there, whatever current the resistive part of the
transucer's impedance needs.


Version 4
SHEET 1 1144 788
WIRE -640 -288 -768 -288
WIRE -560 -288 -640 -288
WIRE -192 -288 -560 -288
WIRE -48 -288 -192 -288
WIRE 368 -288 -48 -288
WIRE 512 -288 368 -288
WIRE 976 -288 512 -288
WIRE 1056 -288 976 -288
WIRE -48 -256 -48 -288
WIRE 368 -256 368 -288
WIRE -192 -240 -192 -288
WIRE 512 -240 512 -288
WIRE -192 -128 -192 -176
WIRE -48 -128 -48 -176
WIRE -48 -128 -192 -128
WIRE 368 -128 368 -176
WIRE 512 -128 512 -176
WIRE 512 -128 368 -128
WIRE -640 -80 -640 -288
WIRE 1056 -80 1056 -288
WIRE -192 -16 -192 -128
WIRE 512 -16 512 -128
WIRE 976 48 976 -288
WIRE 976 48 640 48
WIRE -560 144 -560 -288
WIRE -512 144 -560 144
WIRE -144 144 -288 144
WIRE 704 144 464 144
WIRE 976 144 976 48
WIRE 976 144 928 144
WIRE -640 208 -640 0
WIRE -512 208 -640 208
WIRE -64 208 368 -128
WIRE -64 208 -288 208
WIRE 384 208 -48 -128
WIRE 704 208 384 208
WIRE 1056 208 1056 0
WIRE 1056 208 928 208
WIRE -640 272 -640 208
WIRE -512 272 -640 272
WIRE -240 272 -288 272
WIRE -192 272 -192 48
WIRE -192 272 -240 272
WIRE -48 272 -192 272
WIRE 96 272 16 272
WIRE 272 272 176 272
WIRE 512 272 512 48
WIRE 512 272 352 272
WIRE 544 272 512 272
WIRE 704 272 544 272
WIRE 1056 272 1056 208
WIRE 1056 272 928 272
WIRE -64 336 -288 336
WIRE 640 336 640 48
WIRE 704 336 640 336
WIRE -64 448 -64 336
WIRE -64 448 -944 448
WIRE 544 512 544 272
WIRE 1056 512 1056 272
WIRE -944 528 -944 448
WIRE -768 528 -768 -288
WIRE -640 528 -640 272
WIRE -240 528 -240 272
WIRE -944 672 -944 608
WIRE -768 672 -768 608
WIRE -768 672 -944 672
WIRE -640 672 -640 592
WIRE -640 672 -768 672
WIRE -240 672 -240 592
WIRE -240 672 -640 672
WIRE -144 672 -144 144
WIRE -144 672 -240 672
WIRE 464 672 464 144
WIRE 464 672 -144 672
WIRE 544 672 544 576
WIRE 544 672 464 672
WIRE 1056 672 1056 576
WIRE 1056 672 544 672
WIRE -944 768 -944 672
FLAG -944 768 0
SYMBOL Misc\\NE555 816 240 R0
SYMATTR InstName U1
SYMBOL Misc\\NE555 -400 240 M0
SYMATTR InstName U2
SYMBOL voltage -768 512 R0
WINDOW 123 0 0 Left 0
WINDOW 39 0 0 Left 0
WINDOW 3 24 104 Invisible 0
SYMATTR Value PULSE(0 5 0 1e-3)
SYMATTR InstName V1
SYMBOL res -656 -96 R0
SYMATTR InstName R7
SYMATTR Value 2.4k
SYMBOL cap -656 528 R0
SYMATTR InstName C1
SYMATTR Value .05e-6
SYMBOL res -64 -272 R0
SYMATTR InstName R1
SYMATTR Value 1k
SYMBOL res 352 -272 R0
SYMATTR InstName R2
SYMATTR Value 1k
SYMBOL cap -176 48 R180
WINDOW 0 24 64 Left 0
WINDOW 3 24 8 Left 0
SYMATTR InstName C2
SYMATTR Value 1e-8
SYMBOL cap 528 48 R180
WINDOW 0 24 64 Left 0
WINDOW 3 24 8 Left 0
SYMATTR InstName C4
SYMATTR Value 1e-8
SYMBOL diode -176 -176 R180
WINDOW 0 24 72 Left 0
WINDOW 3 24 0 Left 0
SYMATTR InstName D1
SYMATTR Value 1N4148
SYMBOL diode 528 -176 R180
WINDOW 0 24 72 Left 0
WINDOW 3 24 0 Left 0
SYMATTR InstName D2
SYMATTR Value 1N4148
SYMBOL cap 16 256 R90
WINDOW 0 0 32 VBottom 0
WINDOW 3 32 32 VTop 0
SYMATTR InstName C5
SYMATTR Value 20e-9
SYMBOL diode -224 592 R180
WINDOW 0 24 72 Left 0
WINDOW 3 24 0 Left 0
SYMATTR InstName D3
SYMATTR Value 1N4148
SYMBOL diode 560 576 R180
WINDOW 0 24 72 Left 0
WINDOW 3 24 0 Left 0
SYMATTR InstName D4
SYMATTR Value 1N4148
SYMBOL res 1040 -96 R0
SYMATTR InstName R3
SYMATTR Value 2.4k
SYMBOL ind 256 288 R270
WINDOW 0 32 56 VTop 0
WINDOW 3 5 56 VBottom 0
SYMATTR InstName L1
SYMATTR Value 110e-3
SYMBOL res 192 256 R90
WINDOW 0 0 56 VBottom 0
WINDOW 3 32 56 VTop 0
SYMATTR InstName R5
SYMATTR Value 100
SYMBOL voltage -944 512 R0
WINDOW 123 0 0 Left 0
WINDOW 39 0 0 Left 0
WINDOW 3 24 104 Invisible 0
SYMATTR Value PULSE(0 5 .005 1e-6 1e-6 .005 .01 2)
SYMATTR InstName V2
SYMBOL cap 1040 512 R0
SYMATTR InstName C3
SYMATTR Value .05e-6
TEXT -706 714 Left 0 !.tran 0 .02 0

--
John Fields

 

[Charles Schuler]

"Bret Cahill" <BretCahill@aol.com> wrote in message
news:1162522708.212184.55820@m73g2000cwd.googlegroups.com...

Would alternating a lot of capacitors and inductors in series
approximate a Slinky spring?

A simple model would be a parallel resonant circuit (RLC). L and C would
dictate the oscillation frequency and R the damping factor.

But, if you are talking about a slinky walking down a flight of stairs,
forget about simple models.

Ah HA! Finally a situation where mechanics is more sophisticated than
electronics!


The analogies between the two are mostly simple ones. I little direct
experience, but I'll guess that finite element analysis would do a great job
of modeling a slinky doing slinky-like tricks. Bad news is that those
software packages are REALLY expensive (might be some low cost versions ...
again, not my field). Ansys and Comsol are two FEA tools that I have played
with (demos only). Neat stuff!

 

[John Fields]

On 2 Nov 2006 13:16:23 -0800, "Bill Bowden" <wrongaddress@att.net>
wrote:

John Fields wrote:
On 1 Nov 2006 20:17:10 -0800, "Bill Bowden" <wrongaddress@att.net
wrote:

I need to close a relay 30 seconds after a signal is present, and open
the same relay 30 seconds after the signal drops out, (+/- 10%). I'm
considering using a RC network on the input of a comparator so that the
cap charges and closes the relay 30 seconds after the input is present,
and opens the relay 30 seconds after the input falls. There will be a
long period between on/off so the cap can fully charge and discharge.
There is also some feedback to avoid relay chatter. I need to use
fewest parts possible.

Is this about as simple as can be, or is there a better approach?

---
I think using a 7555 as a comparator would be simpler since the
switching points are already defined as 1/3 and 2/3 Vcc, the
reference divider's already in the chip, you've got an output you
won't have to fiddle with (it's not a couple of open-collector (or
totem-pole) comparator outputs), and you won't have to provide any
hysteresis since everything is internal to the chip except the
timing cap and resistor.

The internal reference divider will force the output high when Vt is
1/3 Vcc (Vth is a don't-care), and the output will go low when Vth
2/3Vcc and Vth is >1/3 Vcc.

So what you'd do would be to wire it like this:

View in Courier

+V>-------------------+-------+
|8 |
+---+---+ |
VIN--[POT]<--+ | Vcc | |
| | 2|_ _|4 |
+-----+---O|T R|---+
| | |
+----|TH OUT|--->OUT
| 6| |3
| | GND |
|+ +---+---+
[Ct] |1
| |
GND>---------+--------+

The 755 needs 500pA max for both the trigger and the threshold
currents, so you could easily use something like a 30ľF cap for CT,
with the timing being:

Vcc
T = RC ln ----------- = k (RC)
Vcc - Vth


k, then would be equal to:


Vcc 1
k = ln ------------ = ln ---------- = 1.0790
Vcc - 0.66 1 - 0.66


and, for a capacitance of 30ľF and a time constant of 30 seconds, R
would be:

t 30s
R = ---- = --------------- ~ 927000 ohms
kC 1.08 * 30E-6F

So, if you used (say) a 10% electrolytic for the cap and a
rheostat-wired 2 megohm pot you could easily get the timing down to
where you needed it with the wiper at about 50% of its travel.


--
JF

Yes, that's a good idea, but I forgot to mention the supply voltage
and relay are 24DC. I suppose a 12 volt zener in series with the 555
power line would help. I also have a second relay that requires 60
seconds delay on and only 30 off. I was figuring on setting the
comparator reference at 2/3 the supply so the cap takes twice as long
to ramp up as down. Maybe that can be done with a 555 using an extra
diode somewhere?

---
Thinking about it a little more, and being a little less grouchy, I
thought your 60 second ON / 30 second OFF delay could be done like
this: (Shift into present tense for a while)

+24V>---------------+-----+------+
| | |
[100k] | [10k]
| | |
Vin>----[Rt]---+----|----|+\ |
| | | >----+
| +----|-/U1A |
| | |
| [100k] |
| | |
+----|----|+\U1B |
| | | >----+--->OUT
| +----|-/
| | |LM393
| | |
[Ct] [100k] |
| | |
GND------------+----+-----+---------->GND


Initially, with Vin at 0V, the voltages on the - inputs of the
comparators will be more positive than the voltage on the + inputs,
and the outputs of both comparators will be low.

With RtCt chosen for a 60 second time constant and +24V step applied
to Vin, the voltage on the + inputs of the comparators will rise as
Ct charges, and when it goes more positive than the voltage on the -
input of U1B, U1B's output will go open collector. However, U1B's
output will still be low, keeping OUT low.

When Vin rises to >16V, (2/3 Vcc) U1A's + input will become more
positive than its - input, and U1A's output will go open collector.

Now, since both comparator outputs are no longer sinking current
through the 10k ohm resistor, OUT will go high.

If Vin is allowed to remain high until Ct is fully charged, then
when Vin is pulled low, to 0V, Ct will start to discharge, and when
the voltage on U1A+ becomes less positive than the voltage on U1A-,
OUT will go low.

But, the question is, how long will it take Ct to discharge to 2/3
Vcc from Vcc?

the answer is, not half as long as it took to charge up to 2/3 Vcc
from 0V.

Consider:

On the way up, when both comparators were open collector


T = kRC

where
Vcc 24V
k = ln ----------- = ln ----------- = 1.1
Vcc - Vth 24V - 16V


So, choosing the parts to get that time constant would involve
dividing their product by 1.1 and adjusting the value of either the
capacitor or the resistor to get there.


On the way down, though, we're starting with 24V since the capacitor
is fully charged and we want to know how long it'll take to get to
16V, since that's the switchpoint for the wired AND.

Since, in order to do that, we only have to traverse a potential
difference of 8 volts out of a total of 24, we can use the same
equation and write:

Vt 24V
K = ln --------- = ln --------- = 0.41
Vt - dV 24V - 8V

Unfortunately, 0.41 isn't half of 1.1...


--
JF

 

[BobG]

Radium wrote:

that your
super-tweeters can get?
=============================================

Sound has to do with air compression, and we all know air is
compressible, but evidently, the compressibility of air starts to add
distortion or something upwards of 150 dB or so. You want hi fi, or is
real loud good enough? Wonder if you can get the woofers louder than
the tweeters, transducrer power handling being equal? The JBL 2106
bullet tweeters were originally designed for ultrasonic traffic control
applications.

 

[Rich Grise]

On Thu, 02 Nov 2006 18:58:28 -0800, Bret Cahill wrote:

Would alternating a lot of capacitors and inductors in series
approximate a Slinky spring?

A simple model would be a parallel resonant circuit (RLC).  L and C would
dictate the oscillation frequency and R the damping factor.

But, if you are talking about a slinky walking down a flight of stairs,
forget about simple models.

Ah HA! Finally a situation where mechanics is more sophisticated than
electronics!

We have a Slinky that can walk down steps and you guys don't have
anything to compare..

Na na Na na NA NA.

It probably wouldn't be too difficult to make an electronic "slinky"
that could "walk" down a voltage.

It would make a really obnoxious car alarm.

Is it too late to cancel this post?

It is now. ;-)

So, write an equation for the motion of a slinky walking down the stairs,
and we'll simulate it. ;-)

Cheers!
Rich

 

[Rich Grise]

On Fri, 03 Nov 2006 16:51:13 -0500, Charles Schuler wrote:

"Bret Cahill" <BretCahill@aol.com> wrote in message

Would alternating a lot of capacitors and inductors in series
approximate a Slinky spring?

A simple model would be a parallel resonant circuit (RLC). L and C would
dictate the oscillation frequency and R the damping factor.

But, if you are talking about a slinky walking down a flight of stairs,
forget about simple models.

Ah HA! Finally a situation where mechanics is more sophisticated than
electronics!

The analogies between the two are mostly simple ones. I little direct
experience, but I'll guess that finite element analysis would do a great job
of modeling a slinky doing slinky-like tricks. Bad news is that those
software packages are REALLY expensive (might be some low cost versions ...
again, not my field). Ansys and Comsol are two FEA tools that I have played
with (demos only). Neat stuff!

But, that's not electronics, that's software. ;-)

Cheers!
Rich

 

[Radium]

BobG wrote:

Radium wrote:
Probably just one. What is the maximum loudness [in dB] that your
super-tweeters can get?
=============================================
Sound has to do with air compression, and we all know air is
compressible, but evidently, the compressibility of air starts to add
distortion or something upwards of 150 dB or so.

Clipping is something I certainly do not want.

You want hi fi, or is
real loud good enough?

As long as there is no loudness-caused distortion or distortion caused
by high-frequency crossing the threshold of the highest-frequency
allowed [the digital equivalent is the aliasing that would occur, for
example, if you attempted to encoded 5 khz tone in a format whose
sample-rate is 8 khz.]

Wonder if you can get the woofers louder than
the tweeters, transducrer power handling being equal?

Well, I'm not much of a bass fan.

The JBL 2106
bullet tweeters were originally designed for ultrasonic traffic control
applications.

Interesting.

 

[Blake]

"Ge0rge Marutz" <gerbermultit00l@yahoo.com> wrote in message
news:1162479756.328830.24810@i42g2000cwa.googlegroups.com...

I need a reverse battery voltage scheme for a 60A max automotive
circuit design. Nominal current is 50A.

. . .However, 60A diodes in
a reasonably sized package are hard to come by.

I found a single diode in a TO-220 package that can carry 30A.

A sixty amp diode shouldn't be any larger than two thirty amp ones. Consider
this 60 amp diode in a TO-220 package, for example.

http://www.irf.com/product-info/datasheets/data/62ctq030pbf.pdf

 

[Bret Cahill]

So, write an equation for the motion of a slinky walking down the stairs,
and we'll simulate it. ;-)

That's why I came here. To see if it was worth screwing around with
the math. All I have is a qualitative understanding:

From the angular momentum POV it isn't much different than a ball
rolling down a hill or down steps for that matter.

The torque from gravity in the y direction acting to accelerate one end
about the center of mass adds enough angular momentum to keep it going.

The difference is at the end of each "step" the angular momentum needs
to go somewhere and it goes to the flip. After each flip the angular
momentum goes back to rolling the coil.

Both the ball and spring both have translational as well as angular
momentum.

From the energy POV, since it doesn't accelerate from step to step we
know all the potential energy for each step ends up as heat as the

coils slap together.

It might not be that ugly a problem.


Bret Cahill

 

[Lionel]

On 2 Nov 2006 07:02:36 -0800, "Ge0rge Marutz"
<gerbermultit00l@yahoo.com> opined:

I found a single diode in a TO-220 package that can carry 30A. The
problem being I would need to place two diodes in parallel to carry a
maximum of 60A. My concern is whether or not the devices will share
current evenly.

They won't. The diode with the lower forward voltage rating will take
he whole load, release its magic-smoke, go open circuit, then the
second diode will do the same.

In theory, you could put resistors in series with each diode to
equalise the current, but it'd be cheaper, easier, tidier & more
reliable to simply use a single diode that's rated for the maximum
possible load (plus a safety factor!).
--
W
. | ,. w , "Some people are alive only because
\|/ \|/ it is illegal to kill them." Perna condita delenda est
---^----^---------------------------------------------------------------

 

[ehsjr]

Charles Schuler wrote:

"Charles Schuler" <charleschuler@comcast.net> wrote in message
news:X6adnRhmY-D2_dfYnZ2dnUVZ_oOdnZ2d@comcast.com...

"Bret Cahill" <BretCahill@aol.com> wrote in message
news:1162498946.796294.160040@m7g2000cwm.googlegroups.com...

Would alternating a lot of capacitors and inductors in series
approximate a Slinky spring?

A simple model would be a parallel resonant circuit (RLC). L and C would
dictate the oscillation frequency and R the damping factor.


But, if you are talking about a slinky walking down a flight of stairs,
forget about simple models.

I suppose it depends on what he means by
"approximate". You can make a simple stair
case with a counter driving voltage dividers.
Stuff the outputs through diodes into an RC
so that the steps take some time, start out
high and go to low. Heck, you can even make
the "electronic slinky" go *UP* the steps!

Ed

 

[Bill Bowden]

John Fields wrote:

On 2 Nov 2006 13:16:23 -0800, "Bill Bowden" <wrongaddress@att.net
wrote:


John Fields wrote:
On 1 Nov 2006 20:17:10 -0800, "Bill Bowden" <wrongaddress@att.net
wrote:

I need to close a relay 30 seconds after a signal is present, and open
the same relay 30 seconds after the signal drops out, (+/- 10%). I'm
considering using a RC network on the input of a comparator so that the
cap charges and closes the relay 30 seconds after the input is present,
and opens the relay 30 seconds after the input falls. There will be a
long period between on/off so the cap can fully charge and discharge.
There is also some feedback to avoid relay chatter. I need to use
fewest parts possible.

Is this about as simple as can be, or is there a better approach?

---
I think using a 7555 as a comparator would be simpler since the
switching points are already defined as 1/3 and 2/3 Vcc, the
reference divider's already in the chip, you've got an output you
won't have to fiddle with (it's not a couple of open-collector (or
totem-pole) comparator outputs), and you won't have to provide any
hysteresis since everything is internal to the chip except the
timing cap and resistor.

The internal reference divider will force the output high when Vt is
1/3 Vcc (Vth is a don't-care), and the output will go low when Vth
2/3Vcc and Vth is >1/3 Vcc.

So what you'd do would be to wire it like this:

View in Courier

+V>-------------------+-------+
|8 |
+---+---+ |
VIN--[POT]<--+ | Vcc | |
| | 2|_ _|4 |
+-----+---O|T R|---+
| | |
+----|TH OUT|--->OUT
| 6| |3
| | GND |
|+ +---+---+
[Ct] |1
| |
GND>---------+--------+

The 755 needs 500pA max for both the trigger and the threshold
currents, so you could easily use something like a 30ľF cap for CT,
with the timing being:

Vcc
T = RC ln ----------- = k (RC)
Vcc - Vth


k, then would be equal to:


Vcc 1
k = ln ------------ = ln ---------- = 1.0790
Vcc - 0.66 1 - 0.66


and, for a capacitance of 30ľF and a time constant of 30 seconds, R
would be:

t 30s
R = ---- = --------------- ~ 927000 ohms
kC 1.08 * 30E-6F

So, if you used (say) a 10% electrolytic for the cap and a
rheostat-wired 2 megohm pot you could easily get the timing down to
where you needed it with the wiper at about 50% of its travel.


--
JF

Yes, that's a good idea, but I forgot to mention the supply voltage
and relay are 24DC. I suppose a 12 volt zener in series with the 555
power line would help. I also have a second relay that requires 60
seconds delay on and only 30 off. I was figuring on setting the
comparator reference at 2/3 the supply so the cap takes twice as long
to ramp up as down. Maybe that can be done with a 555 using an extra
diode somewhere?

---
Thinking about it a little more, and being a little less grouchy, I
thought your 60 second ON / 30 second OFF delay could be done like
this: (Shift into present tense for a while)

+24V>---------------+-----+------+
| | |
[100k] | [10k]
| | |
Vin>----[Rt]---+----|----|+\ |
| | | >----+
| +----|-/U1A |
| | |
| [100k] |
| | |
+----|----|+\U1B |
| | | >----+--->OUT
| +----|-/
| | |LM393
| | |
[Ct] [100k] |
| | |
GND------------+----+-----+---------->GND


Initially, with Vin at 0V, the voltages on the - inputs of the
comparators will be more positive than the voltage on the + inputs,
and the outputs of both comparators will be low.

With RtCt chosen for a 60 second time constant and +24V step applied
to Vin, the voltage on the + inputs of the comparators will rise as
Ct charges, and when it goes more positive than the voltage on the -
input of U1B, U1B's output will go open collector. However, U1B's
output will still be low, keeping OUT low.

When Vin rises to >16V, (2/3 Vcc) U1A's + input will become more
positive than its - input, and U1A's output will go open collector.

Now, since both comparator outputs are no longer sinking current
through the 10k ohm resistor, OUT will go high.

If Vin is allowed to remain high until Ct is fully charged, then
when Vin is pulled low, to 0V, Ct will start to discharge, and when
the voltage on U1A+ becomes less positive than the voltage on U1A-,
OUT will go low.

But, the question is, how long will it take Ct to discharge to 2/3
Vcc from Vcc?

the answer is, not half as long as it took to charge up to 2/3 Vcc
from 0V.

Consider:

On the way up, when both comparators were open collector


T = kRC

where
Vcc 24V
k = ln ----------- = ln ----------- = 1.1
Vcc - Vth 24V - 16V


So, choosing the parts to get that time constant would involve
dividing their product by 1.1 and adjusting the value of either the
capacitor or the resistor to get there.


On the way down, though, we're starting with 24V since the capacitor
is fully charged and we want to know how long it'll take to get to
16V, since that's the switchpoint for the wired AND.

Since, in order to do that, we only have to traverse a potential
difference of 8 volts out of a total of 24, we can use the same
equation and write:

Vt 24V
K = ln --------- = ln --------- = 0.41
Vt - dV 24V - 8V

Unfortunately, 0.41 isn't half of 1.1...


--
JF

Yes, I follow that, but was expecting to use just one comparator.
Wouldn't you get the same result from something like this:

+24V>---------------+------------+
| |
[100k] [10k]
| |\ |
Vin>----[Rt]---+----|----|+\ |
| | | >----+----> OUT
| +----|-/U1A
| | |/
| [200k]
| |
[Ct] |
| |
| |
GND------------+----+------------------>GND


Anyway, I like your original idea of the 555 with the built in
references and feedback, but the output is inverted. That is, when pins
6 and 2 of the 555 move high, the output moves low, so inversion is
needed somewhere. I'm planning on using a NPN transistor on the input
with a pullup resistor so when the input goes high, the cap will
discharge through one 540K resistor and output moves high 60 seconds
later. When input moves low, the cap will charge through both 540K
resistors (diode conducting) and output will move low 30 seconds later.
I may have to adjust the resistors slightly to get it right. Something
like this without the front end transistor and pullup shown.

+V>-----------------------------+-------+
|8 |
+---+---+ |
| Vcc | |
2|_ _|4 |
VIN--+-------[540K]----+----|T R|---+
| | | | ___
+--[D]--[540K]----+----|TH OUT|--->OUT
| 6| |3
| | GND |
| +---+---+
[100uF] |1
| |
GND>--------------+--------+



-Bill

 

[AJ]

"John Fields" <jfields@austininstruments.com> wrote in message
newsu7nk21cuup8an3s6m81f8rbtjekuumctm@4ax.com...

On Wed, 01 Nov 2006 03:38:07 GMT, "AJ" <itisme33@bigpond.net.au
wrote:

Hi

I am currently driving a Piezo element (Part number KBS-27DB-3A) via a
transistor with a resistive load running on 5V but its not as loud as I
was
hoping so I was thinking about changing the 1K resistor I have on the
collector of the of the transistor to an inductor/choke to try and get
more
voltage across the element. I was just wondering what value inductor I
should use or how I might go about calculating one? Does anyone know of a
good web site that might help educate me a bit more in this area?

---

From your description, I assume this is your circuit configuration:

View in Courier.

+5V
|
[1000R]
|
+-----+
| |
C |
SQIN>---[R]---B [PIEZO]
E |
| |
+-----+
|
GND

The first problem I see is that while the piezo is rated to deliver
an SPL of 75dB minimum at a distance of 30cm with a 10VPP 3kHz
square wave across it, your circuit can only deliver a 5VPP signal
to drive the piezo. Also, the 1000 ohms will only allow, at best,
5mA of current into the transducer, so you won't get much of an
amplitude out of it while it's charging.

A second problem may be that you're not driving the transducer with
3kHz. If you're not, you won't be driving it at its resonant
frequency and its output level will not reach 75dB.

In order to get the 10VPP square wave across the transducer you
could drive it with a full bridge made from two 555 timers.

Each timer has a totem pole output which can source or sink 100mA,
which ought to be plenty for your piezo. Unfortunately there's no
mention of what its impedance is in the data sheet, but with 20nF of
capacitance that's a reactance of about 2600 ohms at 3kHz. Again,
unfortunately, that's with a sinusoidal drive, and you're going to
be driving it with a square wave, so there'll be some fairly high
peak currents at the edges.

If you wanted to you could but an inductor in series with the
transducer and tune out the capacitive and inductive reactances, and
that would leave only the real part of the impedance to drive, but
with a 3kHz and 2600 ohms that's a pretty good sized choke.

In any case, the LTSPCICE circuit file attached will show you a
driver that you can use to get the 10VPP square wave drive or, with
the inductor in there, whatever current the resistive part of the
transucer's impedance needs.


Version 4
SHEET 1 1144 788
WIRE -640 -288 -768 -288
WIRE -560 -288 -640 -288
WIRE -192 -288 -560 -288
WIRE -48 -288 -192 -288
WIRE 368 -288 -48 -288
WIRE 512 -288 368 -288
WIRE 976 -288 512 -288
WIRE 1056 -288 976 -288
WIRE -48 -256 -48 -288
WIRE 368 -256 368 -288
WIRE -192 -240 -192 -288
WIRE 512 -240 512 -288
WIRE -192 -128 -192 -176
WIRE -48 -128 -48 -176
WIRE -48 -128 -192 -128
WIRE 368 -128 368 -176
WIRE 512 -128 512 -176
WIRE 512 -128 368 -128
WIRE -640 -80 -640 -288
WIRE 1056 -80 1056 -288
WIRE -192 -16 -192 -128
WIRE 512 -16 512 -128
WIRE 976 48 976 -288
WIRE 976 48 640 48
WIRE -560 144 -560 -288
WIRE -512 144 -560 144
WIRE -144 144 -288 144
WIRE 704 144 464 144
WIRE 976 144 976 48
WIRE 976 144 928 144
WIRE -640 208 -640 0
WIRE -512 208 -640 208
WIRE -64 208 368 -128
WIRE -64 208 -288 208
WIRE 384 208 -48 -128
WIRE 704 208 384 208
WIRE 1056 208 1056 0
WIRE 1056 208 928 208
WIRE -640 272 -640 208
WIRE -512 272 -640 272
WIRE -240 272 -288 272
WIRE -192 272 -192 48
WIRE -192 272 -240 272
WIRE -48 272 -192 272
WIRE 96 272 16 272
WIRE 272 272 176 272
WIRE 512 272 512 48
WIRE 512 272 352 272
WIRE 544 272 512 272
WIRE 704 272 544 272
WIRE 1056 272 1056 208
WIRE 1056 272 928 272
WIRE -64 336 -288 336
WIRE 640 336 640 48
WIRE 704 336 640 336
WIRE -64 448 -64 336
WIRE -64 448 -944 448
WIRE 544 512 544 272
WIRE 1056 512 1056 272
WIRE -944 528 -944 448
WIRE -768 528 -768 -288
WIRE -640 528 -640 272
WIRE -240 528 -240 272
WIRE -944 672 -944 608
WIRE -768 672 -768 608
WIRE -768 672 -944 672
WIRE -640 672 -640 592
WIRE -640 672 -768 672
WIRE -240 672 -240 592
WIRE -240 672 -640 672
WIRE -144 672 -144 144
WIRE -144 672 -240 672
WIRE 464 672 464 144
WIRE 464 672 -144 672
WIRE 544 672 544 576
WIRE 544 672 464 672
WIRE 1056 672 1056 576
WIRE 1056 672 544 672
WIRE -944 768 -944 672
FLAG -944 768 0
SYMBOL Misc\\NE555 816 240 R0
SYMATTR InstName U1
SYMBOL Misc\\NE555 -400 240 M0
SYMATTR InstName U2
SYMBOL voltage -768 512 R0
WINDOW 123 0 0 Left 0
WINDOW 39 0 0 Left 0
WINDOW 3 24 104 Invisible 0
SYMATTR Value PULSE(0 5 0 1e-3)
SYMATTR InstName V1
SYMBOL res -656 -96 R0
SYMATTR InstName R7
SYMATTR Value 2.4k
SYMBOL cap -656 528 R0
SYMATTR InstName C1
SYMATTR Value .05e-6
SYMBOL res -64 -272 R0
SYMATTR InstName R1
SYMATTR Value 1k
SYMBOL res 352 -272 R0
SYMATTR InstName R2
SYMATTR Value 1k
SYMBOL cap -176 48 R180
WINDOW 0 24 64 Left 0
WINDOW 3 24 8 Left 0
SYMATTR InstName C2
SYMATTR Value 1e-8
SYMBOL cap 528 48 R180
WINDOW 0 24 64 Left 0
WINDOW 3 24 8 Left 0
SYMATTR InstName C4
SYMATTR Value 1e-8
SYMBOL diode -176 -176 R180
WINDOW 0 24 72 Left 0
WINDOW 3 24 0 Left 0
SYMATTR InstName D1
SYMATTR Value 1N4148
SYMBOL diode 528 -176 R180
WINDOW 0 24 72 Left 0
WINDOW 3 24 0 Left 0
SYMATTR InstName D2
SYMATTR Value 1N4148
SYMBOL cap 16 256 R90
WINDOW 0 0 32 VBottom 0
WINDOW 3 32 32 VTop 0
SYMATTR InstName C5
SYMATTR Value 20e-9
SYMBOL diode -224 592 R180
WINDOW 0 24 72 Left 0
WINDOW 3 24 0 Left 0
SYMATTR InstName D3
SYMATTR Value 1N4148
SYMBOL diode 560 576 R180
WINDOW 0 24 72 Left 0
WINDOW 3 24 0 Left 0
SYMATTR InstName D4
SYMATTR Value 1N4148
SYMBOL res 1040 -96 R0
SYMATTR InstName R3
SYMATTR Value 2.4k
SYMBOL ind 256 288 R270
WINDOW 0 32 56 VTop 0
WINDOW 3 5 56 VBottom 0
SYMATTR InstName L1
SYMATTR Value 110e-3
SYMBOL res 192 256 R90
WINDOW 0 0 56 VBottom 0
WINDOW 3 32 56 VTop 0
SYMATTR InstName R5
SYMATTR Value 100
SYMBOL voltage -944 512 R0
WINDOW 123 0 0 Left 0
WINDOW 39 0 0 Left 0
WINDOW 3 24 104 Invisible 0
SYMATTR Value PULSE(0 5 .005 1e-6 1e-6 .005 .01 2)
SYMATTR InstName V2
SYMBOL cap 1040 512 R0
SYMATTR InstName C3
SYMATTR Value .05e-6
TEXT -706 714 Left 0 !.tran 0 .02 0

--
John Fields

Thanks heaps John, I will give that a try over the next couple of days and
see how it goes, from what I could tell I would need a huge choke if I was
to use one instead of a resistor in my original circuit.

Best regards,


AJ