Chip with simple program for Toy

[Watson A.Name - \"Watt Su]

"Daniel Kelly (AKA Jack)" <d.kellyNOSPAM@NOSPAM.ucl.ac.uk> wrote in
message news:ckdkja$ica$1@uns-a.ucl.ac.uk...

Hi,

I have just built a PCB which holds a switched power supply and a
microphone
amplifier. The power supply runs a camera whilst the audio amp is
powered
directly from the 3.7v lithium polymer battery. The problem is that
the amp
picks up a lot of noise from the powersupply. So much noise that the
amp is
unusable at the moment. If I turn off the power supply then the amp
runs
perfectly. Please could I ask your advice as to how best to limit
this
noise? I've had a few ideas myself:

1) The PCB is doublesided and the back of the PCB is a ground plane.
This
ground plane is continuous across the entire PCB so the powersupply
and the
amp both share the same ground plane. If I separate the ground plane
by
cutting the copper with a knife at the boundary between the two
circuits,
will this limit some of the noise that's leaking from the power supply
to
the amp?

That's the first thing I would do. It might help a lot, but not totally
cure the problem.

2) Use better shielding on the PSU's inducer.

3) Build a separate PCB for the amp (something I don't really want to
do
because I'm quite short of time).

Well, if the circuit doesn't work, then it doesn't matter now little
time you have. Use a saw and cut the circuits apart.

Things I've tried already (but with no success):

1) Running separate power leads from the PSU and amp to the battery

2) Putting coupling capacitors all over the place.

Try adding some toroid chokes to the incoming power leads, both + amd -.

3) Shorting the length of the microphone cable to the absolute
minimum.

4) Shielding the entire PCB with grounded silver foil

5) Shielding only one circuit with grounded silver foil.

Welcome to the world of analog preamp meets switched power supply. ;-?

It will probably take a combination of isolation techniques to solve
your problem.

Thanks,
Jack

 

[Ban]

Daniel Kelly (AKA Jack) wrote:

Hi,

I have just built a PCB which holds a switched power supply and a
microphone amplifier. The power supply runs a camera whilst the
audio amp is powered directly from the 3.7v lithium polymer battery.
The problem is that the amp picks up a lot of noise from the
powersupply. So much noise that the amp is unusable at the moment.
If I turn off the power supply then the amp runs perfectly. Please
could I ask your advice as to how best to limit this noise? I've had
a few ideas myself:

1) The PCB is doublesided and the back of the PCB is a ground plane.
This ground plane is continuous across the entire PCB so the
powersupply and the amp both share the same ground plane. If I
separate the ground plane by cutting the copper with a knife at the
boundary between the two circuits, will this limit some of the noise
that's leaking from the power supply to the amp?

2) Use better shielding on the PSU's inducer.

3) Build a separate PCB for the amp (something I don't really want to
do because I'm quite short of time).

Things I've tried already (but with no success):

1) Running separate power leads from the PSU and amp to the battery

2) Putting coupling capacitors all over the place.

3) Shorting the length of the microphone cable to the absolute
minimum.

4) Shielding the entire PCB with grounded silver foil

5) Shielding only one circuit with grounded silver foil.

Thanks,
Jack

Did you by chance use the autorouter to make this board? And aren't you a
digital guy maybe?
I have done a mike preamp and a complete DSP with fast parallel flash
memory on a supertiny board for a cellphone with 2 switching supplies et al
on 2 sq. inch, and no crosstalk at all. I suspect your problem can come from
the voltage supply for the electret mike which must be heavily filtered and
a wrong reference point for the mike preamp, which should be the positive
supply. A ground plane is not always the reference, a complete understanding
of the function is needed, determining which way currents are flowing into
and out of the circuit.
You will probably need a redesign, this cannot be just updated like a
software, sorry for that.
--
ciao Ban
Bordighera, Italy

 

[Nico Coesel]

"Daniel Kelly \(AKA Jack\)" <d.kellyNOSPAM@NOSPAM.ucl.ac.uk> wrote:

Hi,

I have just built a PCB which holds a switched power supply and a microphone
amplifier. The power supply runs a camera whilst the audio amp is powered
directly from the 3.7v lithium polymer battery. The problem is that the amp
picks up a lot of noise from the powersupply. So much noise that the amp is
unusable at the moment. If I turn off the power supply then the amp runs
perfectly. Please could I ask your advice as to how best to limit this
noise? I've had a few ideas myself:

1) The PCB is doublesided and the back of the PCB is a ground plane. This
ground plane is continuous across the entire PCB so the powersupply and the
amp both share the same ground plane. If I separate the ground plane by
cutting the copper with a knife at the boundary between the two circuits,
will this limit some of the noise that's leaking from the power supply to
the amp?

2) Use better shielding on the PSU's inducer.

3) Build a separate PCB for the amp (something I don't really want to do
because I'm quite short of time).

Things I've tried already (but with no success):

1) Running separate power leads from the PSU and amp to the battery

2) Putting coupling capacitors all over the place.

3) Shorting the length of the microphone cable to the absolute minimum.

4) Shielding the entire PCB with grounded silver foil

5) Shielding only one circuit with grounded silver foil.

No, simply limit the bandwidth of all audio amplifying elements to
25kHz (or less if permissable) and you'll be fine.

--
Reply to nico@nctdevpuntnl (punt=.)
Bedrijven en winkels vindt U op www.adresboekje.nl

 

[Dirk Bruere at Neopax]

Rich Grise wrote:

[crossposted to sci.electronics.design,sci.electronics.basics, with
followups-to the same.]

On Monday 11 October 2004 08:38 am, Ian Stirling did deign to grace us with
the following:


REMUS <suk@itspambot.com> wrote:

Hi i'm new to the group, and i'm not really to awesome when it comes to
electronics, so I thought I would ask people who really know!

Heres the situation: I play bass in a thrash/rock-punk band and I want to
customise my bass a little. And my idea is to place red LED's under the
scratch plate which I will raise up with washers/nut(s) to give a glow
eminateing from underneath on dark gig's. Ideally I suppose 4 or 5 LED's
on a 9v battery would be about as much as I could fit under there.

I dont know how to make a circuit with a switch and LED's, or where to
buy them in the UK.

http://www.maplin.co.uk/

You may get a better response over on sci.electronics.basics.
Take the forward voltage of all the LEDs, say it's 2V * 3 = 6V.
Now, 6V/.02A (typical maxiumum current) = 300 ohms.
So, you need a 300 ohm resistor, and 3 LEDs in parallel connected up to
the 0V battery.


If you're going to answer the guy, at least give accurate answers.

In the first place, 6V LED voltage from 9V (the battery) leaves 3V
for the dropping resistor. 3V/.02A = 150 ohm. You put this, three
LEDs, the battery, and the switch all in series.

- + K K K
+-[9V Batt]--[sw]--[150R]--[led]--[led]--[led]--+
| |
+-----------------------------------------------+

where the - and + by the battery are the polarity, the +'s in the
wire just mean "bend here", and the K's are the LED cathodes.

FWIW, a 9V "transistor" battery in this app will last about one gig.

And check out the hyperbrights!
Make sure they are wide beam angle.
They tend to drop more voltage, so if necessary experiment by altering the
resistor (lower).

--
Dirk

The Consensus:-
The political party for the new millenium
http://www.theconsensus.org

 

[Daniel Kelly (AKA Jack)]

Hi everyone,

Thanks loads for all your feedback. You're all right - I've designed the
board badly.

I tried separating the ground planes, using a star configuration ground and
putting the mic on its own supply but none of this worked. So I went ahead
and cut the PCB in half! Which worked fine! It's a bit of a crappy
solution but it's worked! Now I can propperly sheild the two PCBs from
eachother.

Thanks,
Jack



"Nico Coesel" <nico@puntnl.niks> wrote in message
news:416aae2e.82401577@news.planet.nl...

"Daniel Kelly \(AKA Jack\)" <d.kellyNOSPAM@NOSPAM.ucl.ac.uk> wrote:

Hi,

I have just built a PCB which holds a switched power supply and a
microphone
amplifier. The power supply runs a camera whilst the audio amp is
powered
directly from the 3.7v lithium polymer battery. The problem is that the
amp
picks up a lot of noise from the powersupply. So much noise that the amp
is
unusable at the moment. If I turn off the power supply then the amp runs
perfectly. Please could I ask your advice as to how best to limit this
noise? I've had a few ideas myself:

1) The PCB is doublesided and the back of the PCB is a ground plane.
This
ground plane is continuous across the entire PCB so the powersupply and
the
amp both share the same ground plane. If I separate the ground plane by
cutting the copper with a knife at the boundary between the two circuits,
will this limit some of the noise that's leaking from the power supply to
the amp?

2) Use better shielding on the PSU's inducer.

3) Build a separate PCB for the amp (something I don't really want to do
because I'm quite short of time).

Things I've tried already (but with no success):

1) Running separate power leads from the PSU and amp to the battery

2) Putting coupling capacitors all over the place.

3) Shorting the length of the microphone cable to the absolute minimum.

4) Shielding the entire PCB with grounded silver foil

5) Shielding only one circuit with grounded silver foil.

No, simply limit the bandwidth of all audio amplifying elements to
25kHz (or less if permissable) and you'll be fine.

--
Reply to nico@nctdevpuntnl (punt=.)
Bedrijven en winkels vindt U op www.adresboekje.nl

 

[Tim Shoppa]

"Daniel Kelly \(AKA Jack\)" <d.kellyNOSPAM@NOSPAM.ucl.ac.uk> wrote in message news:<ckdkja$ica$1@uns-a.ucl.ac.uk>...

I have just built a PCB which holds a switched power supply and a microphone
amplifier. The power supply runs a camera whilst the audio amp is powered
directly from the 3.7v lithium polymer battery. The problem is that the amp
picks up a lot of noise from the powersupply. So much noise that the amp is
unusable at the moment. If I turn off the power supply then the amp runs
perfectly.

You note in idea 1) grounding, and good grounding is essential, but
I'm 99% sure that what you're seeing is magnetic coupling into a loop
in the microphone preamp. Making the preamp circuitry be small would be
a Good Thing. But with an inductor millimeters away I think this may
not be enough.

2) Use better shielding on the PSU's inducer.

Shielding the magnetic field from an inductor is rarely economically
possible. Yes, you can buy mu-metal, but that's a very expensive
and clunky afterthought. (I once worked with a mu-metal shielded
phototube that we nicknamed "the planet crusher" because of the
extreme weight of all the shielding!)

Toroidal inductors are preferred but not a cure-all (they still leak).

3) Build a separate PCB for the amp (something I don't really want to do
because I'm quite short of time).

Geographic separation, if you can be flexible about PCB shape, may help
you a lot since magnetic fields decrease like 1/(distance cubed). Simple
orientation of the inductor may help by a factor of ten or so.

4) Shielding the entire PCB with grounded silver foil

5) Shielding only one circuit with grounded silver foil.

Those would maybe help with electrostatic radiation, but you're
seeing magnetic radiation.

Tim.

 

[Daniel Kelly (AKA Jack)]

Great, thanks a lot for your really detailed reply.

Jack

"Tim Shoppa" <shoppa@trailing-edge.com> wrote in message
news:bec993c8.0410111707.11bde9b7@posting.google.com...

"Daniel Kelly \(AKA Jack\)" <d.kellyNOSPAM@NOSPAM.ucl.ac.uk> wrote in
message news:<ckdkja$ica$1@uns-a.ucl.ac.uk>...
I have just built a PCB which holds a switched power supply and a
microphone
amplifier. The power supply runs a camera whilst the audio amp is
powered
directly from the 3.7v lithium polymer battery. The problem is that the
amp
picks up a lot of noise from the powersupply. So much noise that the
amp is
unusable at the moment. If I turn off the power supply then the amp
runs
perfectly.

You note in idea 1) grounding, and good grounding is essential, but
I'm 99% sure that what you're seeing is magnetic coupling into a loop
in the microphone preamp. Making the preamp circuitry be small would be
a Good Thing. But with an inductor millimeters away I think this may
not be enough.

2) Use better shielding on the PSU's inducer.

Shielding the magnetic field from an inductor is rarely economically
possible. Yes, you can buy mu-metal, but that's a very expensive
and clunky afterthought. (I once worked with a mu-metal shielded
phototube that we nicknamed "the planet crusher" because of the
extreme weight of all the shielding!)

Toroidal inductors are preferred but not a cure-all (they still leak).

3) Build a separate PCB for the amp (something I don't really want to do
because I'm quite short of time).

Geographic separation, if you can be flexible about PCB shape, may help
you a lot since magnetic fields decrease like 1/(distance cubed). Simple
orientation of the inductor may help by a factor of ten or so.

4) Shielding the entire PCB with grounded silver foil

5) Shielding only one circuit with grounded silver foil.

Those would maybe help with electrostatic radiation, but you're
seeing magnetic radiation.

Tim.

 

[Winfield Hill]

Tim Shoppa wrote...

Daniel Kelly \(AKA Jack\) wrote ...
I have just built a PCB which holds a switched power supply and a microphone
amplifier. The power supply runs a camera whilst the audio amp is powered
directly from the 3.7v lithium polymer battery. The problem is that the amp
picks up a lot of noise from the powersupply. So much noise that the amp is
unusable at the moment. If I turn off the power supply then the amp runs
perfectly.

You note in idea 1) grounding, and good grounding is essential, but
I'm 99% sure that what you're seeing is magnetic coupling into a loop
in the microphone preamp. Making the preamp circuitry be small would be
a Good Thing. But with an inductor millimeters away I think this may
not be enough.

To the extent that Daniel / Jack is suffering from magnetic pickup,
we can point out this pickup is proportional to the cross-section
area (whose plane is at right angles to the magnetic vector), so
reducing this area (e.g. keeping signal paths immediately adjacent
to ground return paths, etc.) will help dramatically. Second, keep
in mind the effectiveness of twisted-wire pairs in rejecting magnetic
pickup; each half-turn's pickup is canceled the opposite polarity of
the next half turn. It's at least theoretically possible to cancel
all the pickup entirely in an analogous manner, with a loop of input
wiring arranged to add in its pickup with the opposite polarity. :&gt


--
Thanks,
- Win

(email: use hill_at_rowland-dotties-org for now)

 

[Rich Grise]

On Wednesday 13 October 2004 01:25 am, Squidster did deign to grace us with
the following:

Hello,
I'm trying to design a 230VAC/50Hz to 115VAC/60Hz converter. This is
specifically for applications that are frequency sensitive.

Specs:
Input: 220-240VAC/50Hz (plusminus 1Hz) @10A
Output1: 110-120VAC/50Hz (plusminus 1Hz) @20A \Combined is 20A
Output2: 110-120VAC/60Hz (plusminus 1Hz) @20A /

Here's the blocks:
1. 230VAC/50Hz input, offline rectified and filtered to 340VDC.
2. Chopped up (20-50Khz) either via a BJT or MOSFET power switch with PWM
controller (either 555 or PWM IC).
3. PWM wave fed into a high-frequency transformer (2:1)
4. Rectified secondary with schottky power diodes to recover DC.
5. This then is pass throught the 2nd. stage low-frequency choppers one
for 50Hz and one for 60Hz.
6. After going through the 50Hz and 60Hz choppers; we pass through a final
stage of low-pass-filter (LC, with fT=50 and fT=60 respectively)
7. Feedback from output fedback into the PWM controller.

Is there anything fundamentally wrong with the design?

Yes.

1. It's obviously homework. We don't do other people's homework for
free.

2. This is a terribly stupid approach to this problem, when you can
get a 50 HZ synchronous motor and couple it to a 115V 60 Hz generator,
for about one-tenth the time and money.

Have Fun!
Rich

 

[John Duffus]

"Mikal Hodvik" <damnspam@decadenet.com> wrote in message
news:416df8a2$0$797$2c56edd9@news.cablerocket.com...

I'm no expert on this, but I'm under the impression that it's primarily
LOW
INERTIA that distinguishes a servomotor from the ordinary.

Cheers,
Mikal Hodvik

Like you, my experience is that the name servomotor was reserved for one
specifically designed for the purpose, not just any motor that was used in a
servomechism. Aside from the inertia requirement I personally always
associated the name with a motor that was supplied with a constant armature
current and push-pull field controlled, but I don't know if that's general.
I think that the term servomotor came into use in the RC field because the
motor is often part of a servo package that contains the motor, transducer
and even electronic controller. Depending on how it is packaged the term
seems to apply variously to the motor, the motor-transducer combination, or
the motor-gearhead-transducer. I doubt whether the motors themselves have
any performance characteristics that particularly suit them to servo
applications.
Regards,
John Duffus

DCServoMotor> wrote in message
news:416cab1d$0$26323$afc38c87@news.optusnet.com.au...
What is the difference between a brush type "ordinary" DC motor and DC
"servo" motor?
Does adding a quadrature encoder to the ordinary DC motor convert it to
a
DC sevo motor?

 

[Daniel Kelly (AKA Jack)]

Hi,

Thanks loads for your ideas. Yes, I originally thought it was radiation.
But then I cut the PCB in half, separating the powersupply and the mic
pre-amp. This didn't solve the problem. Then I noticed that if I powered
the switchmode PSU from a separate battery then the intereference went away.
I've also done some tests with an oscilloscope and the PSU is DEFINITELY
injecting noise into the battery.

Here's a quick box diagram showing the circuits:


Battery---+---------+
| |
PSU Amp
|
Camera



"petrus bitbyter" <p.kralt@reducespamforchello.nl> wrote in message
news:HwNbd.32294$Ye1.12086@amsnews05.chello.com...

"Daniel Kelly (AKA Jack)" <d.kellyNOSPAM@NOSPAM.ucl.ac.uk> schreef in
bericht news:cko5qp$n34$1@uns-a.ucl.ac.uk...
Hi,

I have a switch-mode powersupply unit that's injecting a high-frequency
ringing onto the input power rails (which is from a battery). Does
anyone
have any ideas how to stop this? Would a simple diode and capacitor
work?
Or an inducer? In which case, how do I chose the value of the inducer?

The DC-to-DC converter is:

http://www.maxim-ic.com/quick_view2.cfm/qv_pk/1831

Thanks a lot,
Jack



Most likely the ringing comes from radiation. Too long powerlines that are
not properly decoupled or long and/or thin traces in the power circuit.
The
coil itself also may be a radiation source. You may have to redesign the
layout. Keep the traces around chip and coil thick and short. The same for
the other components. You may need some shielding or a ground plane. Keep
the input lines away from the powersupply.

I see no use for a diode in the power supply input. A decoupling capacitor
is absolutely necessary as shown in the example circuit. If that capacitor
is good there is no use for a coil. A good decoupling requires a low ESR
elco of some tens uF (or larger, depending on the current) parallel to a
ceramic capacitor of let's say 10nF.

Main rule: Prevent the disturbing "signal" to escape from the circuit.

petrus bitbyter


---
Outgoing mail is certified Virus Free.
Checked by AVG anti-virus system (http://www.grisoft.com).
Version: 6.0.771 / Virus Database: 518 - Release Date: 28-9-2004

 

[John Popelish]

"Daniel Kelly (AKA Jack)" wrote:

Hi,

I have a switch-mode powersupply unit that's injecting a high-frequency
ringing onto the input power rails (which is from a battery). Does anyone
have any ideas how to stop this? Would a simple diode and capacitor work?
Or an inducer? In which case, how do I chose the value of the inducer?

The DC-to-DC converter is:

http://www.maxim-ic.com/quick_view2.cfm/qv_pk/1831

Thanks a lot,
Jack

This circuit makes noise when the internal switch disconnects the
LXP,LXN terminal from ground. This allows the inductor to snap
positive, forward bias the output diode and dump the inductor current
into the output capacitor. So the ground terminal of the output
capacitor has fast rising current coming out of it. If this capacitor
is not connected very closely to the bottom of the input capacitor and
to the ground terminal of the chip (where the internal switch suddenly
turns off the current), this current path switch produces voltage drop
between these three points on the ground line. This voltage tends to
leak out into the rest of the system.

If you already have these three points closely connected, then you may
have to add another small inductance in series with the input supply
line. I would first try a bead on lead or other small inductance with
a low DC resistance. It has to be rated to not saturate at the
maximum current that will pass through it. Increasing the value or
paralleling a couple caps at the input side may help. also.
--
John Popelish

 

[N. Thornton]

Rich Grise <null@example.net> wrote in message news:<WCbbd.83$dI6.56@trnddc03>..

On Wednesday 13 October 2004 01:25 am, Squidster

Hello,
I'm trying to design a 230VAC/50Hz to 115VAC/60Hz converter. This is
specifically for applications that are frequency sensitive.

Specs:
Input: 220-240VAC/50Hz (plusminus 1Hz) @10A
Output1: 110-120VAC/50Hz (plusminus 1Hz) @20A \Combined is 20A
Output2: 110-120VAC/60Hz (plusminus 1Hz) @20A /

Here's the blocks:
1. 230VAC/50Hz input, offline rectified and filtered to 340VDC.
2. Chopped up (20-50Khz) either via a BJT or MOSFET power switch with PWM
controller (either 555 or PWM IC).
3. PWM wave fed into a high-frequency transformer (2:1)
4. Rectified secondary with schottky power diodes to recover DC.
5. This then is pass throught the 2nd. stage low-frequency choppers one
for 50Hz and one for 60Hz.
6. After going through the 50Hz and 60Hz choppers; we pass through a final
stage of low-pass-filter (LC, with fT=50 and fT=60 respectively)
7. Feedback from output fedback into the PWM controller.

Is there anything fundamentally wrong with the design?

2. This is a terribly stupid approach to this problem, when you can
get a 50 HZ synchronous motor and couple it to a 115V 60 Hz generator,
for about one-tenth the time and money.

True, but there are issues with rotary convertors.
Lack of voltage stability
Lack of frequency stability
weight
noise
non-instant start and stop
inductive source
and efficiency typ. in the region of 65%

It could be just the thing in some cases of course, it all depends on the app.

More app info would help, as there may be simpler app-specific options too.


NT

 

[George]

"Omega Red" <omega_red32@yahoo.spam.com> wrote in message news:<Jyibd.3668$NX5.2379@newsread3.news.atl.earthlink.net>...

Can anybody recommend a good, fairly readable textbook concerning
solid-state physics/electronic devices.

I have a good microelectronics book, but it doesn't include any theory about
how and why diodes, BPJs, etc. work the way they do.

Thanks,
Omega Red
"Remove the spam to e-mail me"

In my class on this at university, we use this book:
http://www.amazon.com/exec/obidos/tg/detail/-/0471333727/qid=1097898465/sr=1-3/ref=sr_1_3/102-1315967-2723345?v=glance&s=books

 

[J M Noeding]

On Sun, 17 Oct 2004 05:59:02 +0000 (UTC), "Reg Edwards"
<g4fgq.regp@ZZZbtinternet.com> wrote:

Some years back, after retirement, I bought out of curiosity a copy of
Electronics Work Bench. It was and still is the only such program I have
ever had my hands on. I think it arrived on a collection of floppies.

After a few days curiosity was satisfied. Then I junked it.
---
Reg

In 1970 I bought the latest issue RSGB Handbook, obviously a decade

before the transistors were being discovered in England, and several
decades before the spectrum analyser were applied over there. So after
a week I managed to find another person to keep the book, not sure if
he paid for the rubbish

73, Jan-Martin
---
J. M. Noeding, LA8AK, N-4623 Kristiansand
http://home.online.no/~la8ak/c.htm

 

[Franks]

try like this:

> PRINT #1, theChar$;

 

[tlbs101]

Geodanah@yahoo.com (George) wrote in message news:<7c28d4ba.0410151949.4d9747d7@posting.google.com>...

"Omega Red" <omega_red32@yahoo.spam.com> wrote in message news:<Jyibd.3668$NX5.2379@newsread3.news.atl.earthlink.net>...
Can anybody recommend a good, fairly readable textbook concerning
solid-state physics/electronic devices.

I have a good microelectronics book, but it doesn't include any theory about
how and why diodes, BPJs, etc. work the way they do.

Thanks,
Omega Red
"Remove the spam to e-mail me"


In my class on this at university, we use this book:
http://www.amazon.com/exec/obidos/tg/detail/-/0471333727/qid=1097898465/sr=1-3/ref=sr_1_3/102-1315967-2723345?v=glance&s=books

My favorite: "Analysis and Design of Analog Integrated Circuits", by
Gray and Meyer (in its 3rd edition, now), published by Wiley.

It starts out with alot of high level math to explain the basic PN
junction, but don't let that scare you -- they still do a great job of
explaining the basic operation of the diode junction, then BJT's, then
FETs, and MOSFETs. They have alot of practical examples, as well.

 

[peterken]

Try building a circuit generating a square wave of say 5V-50Hz and use a
small 1:1 transformer or a (big enough) coupling capacitor
For low energy I'd try the latter
For a simple 1:1 transformer you might use an 'off the shelf transformer'
having 2 identical 6V "outputs", use one as input and the other as output,
thus ignoring the 110/220V connections


"Sepp Spenlinhauer" <seppspenlinhauer@hotmail.com> wrote in message
news:Ifvdd.127$oI6.41@trndny03...
Hi - I am hoping someone can help me....

I have some small "Christmas light turners" (the kind you replace a light in
your Christmas light set with and it spins your ornaments on the tree)
I am trying to drive those motors from a DC power source (batteries) as part
of a mobile display.
I only need about 3 volts AC (not sure of the current - can't be much)

I have looked a LOTS of DC/AC inverter circuits but they are all designed
for 110volts.

ANY help here is really appreciated - I am getting down to the wire on
finishing this project.

Thanks SEPP!

 

[Nicholas O. Lindan]

"James Varga" <james@jamesvarga.com> wrote

This is as good as I've gotten it so far
http://www.jamesvarga.com/projects/beblu/pcbtest3.jpg

I take it the trace widths and pad sizes are the same on
both sides? Traces and pads are thicker on side 2.

Side 2 looks like it was one (or more) of:

o under etched
o under developed resist
o bad artwork
o under exposed resist

My guess: under etched.

You may want to lift the board and spin it 1/2 turn
at the midpoint of the etching time: that way both
sides should get etched the same amount (maybe).
Increasing etching time for 2 may result in over
etch on 1.

--
Nicholas O. Lindan, Cleveland, Ohio
Consulting Engineer: Electronics; Informatics; Photonics.
Remove spaces etc. to reply: n o lindan at net com dot com
psst.. want to buy an f-stop timer? nolindan.com/da/fstop/

 

[Roger Hamlett]

"Frank Bemelman" <f.bemelmanx@xs4all.invalid.nl> wrote in message
news:4178aec3$0$37789$e4fe514c@news.xs4all.nl...

"Matt Warnock" <warnockmREM@OVEcox.net> schreef in bericht
news:EZZdd.9081$6P5.8851@okepread02...
I'm working on a project to install a car computer in my car. The
next
step
is to put the LCD screen in the dash. I removed a double DIN spaced
CD
player and its going in there. To make it fit better I removed the
"guts"
of the lcd screen from its case and I want to attach this to the
original
CD
player bezel and just install the bezel w/ the LCD screen attached to
it.

I ran into a snag when I started figure out how to attach the screen
to
the
bezel. I purchased an extra one to play with so I don't mess up the
original, but I set the bezel face down, then I put the LCD screen
face
down
on the bezel, but I don't know how to attach it.

I thought about fiberglassing brackets by molding them to the back of
the
screen then epoxying them to the bezel and sliding the screen down.
Or
perhaps hot glue gunning it in some how.

I'm looking to see if anyone has any ideas on this part. I've
included a
link to a picture that shows where I am:

http://www.warnockinc.com/Projects/LCD3.jpg

Any suggestions would be greatly appreciated!

Silicone. The stuff you use to seal windows and bathroom edges.
Takes 24 hours to dry, but it works quite well as 'glue'.
Yes, but....

Beware that silicone RTV (room temperature vulcanising) rubbers, come in
two distinct varieties. The commonest, contain acetic acid as part of the
chemistry, and can cause damage to things like LCD screens, if applied to
the edges. Look for varieties used in electronics, and trades like
aerospace, that are sold as 'acid free'.

Best Wishes