Chip with simple program for Toy

[John Fields]

On 4 Nov 2006 17:23:54 -0800, "Bill Bowden" <wrongaddress@att.net>
wrote:

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

---
Yes.

Matter of fact, I'd changed mine to exactly what you have, was
working on the 60-on 30-off circuit and was going to post them both
at once, but you beat me to the punch on both counts!
---

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>--------------+--------+

---
Yes. Very nice!



--
JF

 

[Jamie]

John Fields wrote:

On 4 Nov 2006 17:23:54 -0800, "Bill Bowden" <wrongaddress@att.net
wrote:



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


---
Yes.

Matter of fact, I'd changed mine to exactly what you have, was
working on the 60-on 30-off circuit and was going to post them both
at once, but you beat me to the punch on both counts!
---


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>--------------+--------+


---
Yes. Very nice!



it just amazes me, as old as the 555 is, it still a common base timer

to use! be it a cmos or monolithic type.


--
"I'm never wrong, once i thought i was, but was mistaken"
Real Programmers Do things like this.
http://webpages.charter.net/jamie_5

 

The sensor is a MEMS biaxial accelerometer I am using to measure tilt.
I am suppling 3V, the output voltage range is 1.25 V +/- 0.1 V and the
current is less than 0.01 mV (I calculated it to be aprox 0.005 mV).
Thanks

 

[redbelly]

gweedo225@yahoo.com wrote:

The sensor is a MEMS biaxial accelerometer I am using to measure tilt.
I am suppling 3V, the output voltage range is 1.25 V +/- 0.1 V and the
current is less than 0.01 mV (I calculated it to be aprox 0.005 mV).
Thanks

Current is measured in mA, not mV. Please clarify, are you talking
about the output voltage or current? Also, what resistance did you use
for the voltage divider?

Mark

 

Output voltage: 1.25 V
output current: .005 mA

I used a 150 and 220 kOhm resistors.

 

[redbelly]

gweedo225@yahoo.com wrote:

Output voltage: 1.25 V
output current: .005 mA

I used a 150 and 220 kOhm resistors.

From what little I have gleaned about MEMS accelerometers on the web,
their output is essentially a voltage source. The output current just

depends on what resistance is tied to the output.

I don't know what you're using to read the signal. If you're looking
at the output on an oscilloscope, that's typically a 1 M-ohm load and
that will alter the reading on a several-hundred kOhm divider. On the
other hand, a 10 M-ohm multimeter should have very little affect on the
reading.

I would try making a divider in the 10-20 kOhm range, and see if things
work better. Alternatively, if you're up to putting together an op-amp
circuit, that would work best of all.

Mark

 

[Ge0rge Marutz]

Thanks John

Fets are commonly used in this mode for things like reverse-voltage
protection between say a battery and a load. The s-d substrate diode
is used like a simple series protection diode, but then cranking in
gate voltage shunts current around the diode and reduces voltage drop,
getting closer to an ideal diode.

That is EXACTLY what I intend on doing.

Ge0rge

 

[Rich Grise]

On Sat, 04 Nov 2006 05:53:55 -0800, Bret Cahill wrote:
....

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.

Are Slinkys really made of recycled piston rings? ;-)

Cheers!
Rich

 

[Rich Grise]

On Fri, 03 Nov 2006 12:13:58 -0800, Bret Cahill wrote:

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 . . .

Most people ignore car alarms anyway. Did you ever see "South Park Bigger
Longer and Uncut"? A guy jumps out of a window and lands on some car,
which sets off the alarm. The car owner comes out, looks at the corpse
on top of his car, scowls, turns the alarm off, and goes back to whatever
he was doing before the alarm.

Cheers!
Rich

 

[Bret Cahill]

Lightening or anything sets them off so no one notices.

One guy in San Diego made millions off of auto alarms and financed the
recall of Grey Davis. When he realized he opened the door for Arnold
he pulled his funding but by then it was too late.

Unintended consequences seem to be the rule in crime and politics.


Bret Cahill


"The best laid plans o mice and men . . ."

-- Burns

 

[Larry]

budgie <me@privacy.net> wrote in news:t0v0l2to90k4lgncg3q3oork3hrt1o78io@
4ax.com:

The unwise practice is to leave a cell in an undervoltage condition, as
irreversible degradation occurs.

This is an excellent statement. Battery users got used to the Ni-Cd memory
problems and got used to the total-discharge-them-to-prevent-memory
scenario. When they migrated to Li-Ion, noone told them Li-Ions should be
immediately recharged, NO MATTER WHAT THEIR CHARGE STATE...just like lead-
acid float batteries.

So, the cellphone users sleeping right next to their chargers, don't plug
the phones in at night until they are nearly dead, causing premature
battery failures that could have easily been prevented by simply plugging
the phone in next to their beds. If you never discharge them below 80%,
easy to do in most cellphones, Li-Ion batteries will last for years, making
battery salesmen and manufacturers quite unhappy.

They all seem so proud of how long they can make them run before plugging
them in. How silly....

Larry
--
Halloween candy left over.....
Is there a downside?

 

[John]

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?

-Bill

A microcontroller with a built-in clock can probably provide better
than the 10% accuracy of the RC timer.

For the easiest programming (in a dialect of BASIC), the PICAXE 08
chips are under $3 (single quantities) and the needed external
components would be a 5 volt regulator (78L05 is more than adequate)
and some bypass capacitors. The 08 ouputs can provide 20ma, which is
more than enough to drive the transistors you plan to use to operate
the 24v relays. The various PICAXE chips (8 to 40 pins) offer ADC
inputs, PWM outputs, serial and I2C communications

The programming software is free. The primary site for the PICAXE is
here:
http://www.rev-ed.co.uk/picaxe/

Links to more info on the PICAXE chips:
http://www.picaxe.us/picaxe-links.html
http://www.picaxe.us/projects.html

John

 

Jonathan Kirwan wrote:

On 8 Nov 2006 15:07:16 -0800, mrdarrett@gmail.com wrote:

I was reading up on the theory behind the boost converter:

http://en.wikipedia.org/wiki/Boost_converter

and I thought, you know, there is a short circuit for a certain amount
of time. Actually, for a fairly long time, since Figure 5 of the above
link seems to show best performance for a duty cycle of 80% (please
correct me if I'm wrong).

Would having a resistor (even just one ohm) in the path of the
switching transistor improve efficiency at all...?

This is a sci.electronics.basics question, so I am setting followups
to there.

The inductor is not a short circuit in the sense you imagine. There
is an impedance to it, if not a lot of resistance. And you need to
imagine in a dynamic (time derivative) sense.

Let's say the inductor starts out with zero current when the switch is
closed. The switch closure would attempt to have the current suddenly
jump to some large value. But the inductor refuses to allow sudden
changes. Instead: dI = V/L * dt, or dt = L/V * dI

So for each fraction of time, only a small fraction of current change
is permitted. Since it starts at zero in this case, it cannot go
instantly to a large value. Assuming the voltage across the inductor
remains constant, and it does in this ideal case you cite, a fixed
change in current will require a fixed change in time. In other
words, it cannot happen right away. To achieve this, energy is
gathered up and stored in a magnetic field around the inductor.

If you wait short enough time, the current will never manage to rise
up too high. It will get to some point and then the switch opens.
When that happens, the inductor will alter the voltage between its
leads in any way required in order to maintain that current. Of
course, the current will then have to flow through the diode and into
the load. (Usually, there is a capacitor across the load at the other
end of that diode in models like this to absorb the energy and supply
current while the switch is closed.) This means that the energy
stored in the magnetic field, as it now collapses, will be consumed.

Again the law remains, dI = V/L * dt, or dt = L/V * dI. So it will
also take time to decline to zero current. However, in this case, the
V will not be the V of the battery, but instead the V that the
inductor creates as the field collapses, needed to ensure a gradual
decline in the current instead of a sudden decline.

Does that make sense?

Jon

Sure is. It's starting to remind me of V = - L di/dt...

Thanks...

Michael

 

[Genome]

"billcalley" <billcalley@yahoo.com> wrote in message
news:1163097056.753770.148150@m73g2000cwd.googlegroups.com...

Hi All,

I'm developing a 2.4GHz LC bandpass filter. In testing the
completed filter with a VNA, the filter's in-band response is perfect
both with and without an RF shield in place - but its stopband really
becomes poor with a RF shield over this circuit. In fact, the stopband
degrades by about 20dB all the way up to 6GHz (the top range of my
VNA). This effect seems too wide band (low Q) to be a waveguide box
mode. Any thoughts as too what causes this? (Maybe RF currents
"riding" the RF shield and bypassing the filter)?

Thanks!

-Bill

Ooooooo.... I don't know nothing about this stuff but I can fantasize, or
have a Glenda. It's all black magik anyway and you are having a Barbara
yourself so you don't really need the Tom.

If the ground stuff on your board is sorted then...... Ummmm. OK, to me it
sounds like what you might want to do is sort of separate the input and the
output grounds of your filter on the board.

Then your RF shield plate thing should have those pin bits that solder in
the board so it makes the ground connection between the two halves.....

And then you mill a slot across the top of the plate between the physical
location of the output of the input and the input of the output of the
filter

DNA

 

[billcalley]

Thanks for the pointers guys -- that really did the trick: better
soldering of the shield walls to the ground, and the shield walls to
the shield top!

-Bill

billcalley wrote:

Hi All,

I'm developing a 2.4GHz LC bandpass filter. In testing the
completed filter with a VNA, the filter's in-band response is perfect
both with and without an RF shield in place - but its stopband really
becomes poor with a RF shield over this circuit. In fact, the stopband
degrades by about 20dB all the way up to 6GHz (the top range of my
VNA). This effect seems too wide band (low Q) to be a waveguide box
mode. Any thoughts as too what causes this? (Maybe RF currents
"riding" the RF shield and bypassing the filter)?

Thanks!

-Bill

 

[Bill Bowden]

John 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?

-Bill

A microcontroller with a built-in clock can probably provide better
than the 10% accuracy of the RC timer.

For the easiest programming (in a dialect of BASIC), the PICAXE 08
chips are under $3 (single quantities) and the needed external
components would be a 5 volt regulator (78L05 is more than adequate)
and some bypass capacitors. The 08 ouputs can provide 20ma, which is
more than enough to drive the transistors you plan to use to operate
the 24v relays. The various PICAXE chips (8 to 40 pins) offer ADC
inputs, PWM outputs, serial and I2C communications

The programming software is free. The primary site for the PICAXE is
here:
http://www.rev-ed.co.uk/picaxe/

Links to more info on the PICAXE chips:
http://www.picaxe.us/picaxe-links.html
http://www.picaxe.us/projects.html

John

Yes, a microcontroller is a better approach that eliminates about 17
parts. I have the tools for the PIC16F628, which is an overkill, but I
don't want to invest too much in a hardware programmer to load the
smaller devices.

-Bill

 

[Costas Vlachos]

hybrid_snyper wrote:

Hi,

I'm looking for some advice, i am trying to control an Ericsson T28
mobile phone by using a PIC16F87X. I understand the how to talk to a
mobile phone by using my COM port on my PC. Is it as simple as
connecting the relevant TX/RX pins to the correct pins on the mobile
phone? Do i need any circuitry between. Ive seen something about MAX232
when using serial communications any tips would be appreciated.

yours

Wayne

The proper way is to use the MAX232. Another nice IC for this is the
SN75155 (8-pin DIL). Depending on the voltage levels recognised by the
T28, you may be able to do it using simple transistors for the signal
inversion.

--
Regards,
Costas
_________________________________________________
Costas Vlachos Email: c-X-vlachos@hot-X-mail.com
SPAM-TRAPPED: Please remove "-X-" before replying

 

[Charles Schuler]

"Gareth" <me@privacy.net> wrote in message
news:zsOdndIA_7tjxsvYnZ2dnUVZ8qWdnZ2d@brightview.com...

javithkhan@gmail.com wrote:
what is bluetooth


He was the King of Denmark from 940 to 985 AD and is most well known for
uniting Denmark and Norway.

He loved blueberries, by the way ... which turned his teeth blue!

 

[Tim Auton]

Costas Vlachos <c-X-vlachos@hot-x-mail.com> wrote:

hybrid_snyper wrote:
Hi,

I'm looking for some advice, i am trying to control an Ericsson T28
mobile phone by using a PIC16F87X. I understand the how to talk to a
mobile phone by using my COM port on my PC. Is it as simple as
connecting the relevant TX/RX pins to the correct pins on the mobile
phone? Do i need any circuitry between. Ive seen something about MAX232
when using serial communications any tips would be appreciated.

The proper way is to use the MAX232. Another nice IC for this is the
SN75155 (8-pin DIL). Depending on the voltage levels recognised by the
T28, you may be able to do it using simple transistors for the signal
inversion.

Have I read a different post to everyone else?

The guy asks how to connect a PIC to a mobile phone. Neither uses RS232
levels.

PIC <> PC RS232 = MAX232
T28 <> PC RS232 = MAX232
T28 <> PIC = NO MAX232

Find out what voltage levels the pins on the T28 are at. I suspect it'll
be 3.3V logic, but it might be 5V. The easiest thing to do is run the PIC
at the same voltage as the port on the T28, then you don't need a level
shifter and can connect them directly. Series resistors of a few hundred
ohms on the TX and RX lines won't affect the functioning but might save
your PIC or phone if you hook it up wrong.


Tim