I dunno. If I recall correctly, a DC signal should work just fine. You
just won't be using one of the quadrants that "every other Joe" usually uses
(the negative MT/negative gate). You'd be using the negative MT/POSITIVE
gate quadrant.

Curtis

Dazzle Mom this coming Mother's Day season with flowers!

On Tue, 13 Apr 2004 11:05:53 -0400, Roy J. Tellason <rtellason@...> wrote:

On Tuesday 13 April 2004 10:58 am, Stefan Trethan wrote:

I'm not entirely sure if the pulse can be both polarities or only the
one in which the current should flow, the datasheet can tell i hope.
(please answer if someone knows).
Tomi Engdahl has told me it can be both polarities, no matter which
polarity the main current has but i am not sure about this.

This is correct. However a triac _will_ have different sensitivity in
different "quadrants" (the term that the datasheet will used to refer to the
different combinations of gate polarity and other polarity).

that means if you apply a dc current to the gate (higher than trigger current in all quadrants)
the triac will be on all the time, throughout the full sine wave?


in which magnitude should one expect the difference between the quadrants?



I did forget to add you will need a RC network across the triac to protect it from possible high voltages.
you can find circuit examples and i think even a guide how to calculate the component values
at epanorama.

ST

On Tuesday 13 April 2004 10:58 am, Stefan Trethan wrote:

I'm not entirely sure if the pulse can be both polarities or only the
one in which the current should flow, the datasheet can tell i hope.
(please answer if someone knows).
Tomi Engdahl has told me it can be both polarities, no matter which
polarity the main current has but i am not sure about this.

This is correct. However a triac _will_ have different sensitivity in
different "quadrants" (the term that the datasheet will used to refer to the
different combinations of gate polarity and other polarity).

On Tue, 13 Apr 2004 14:11:30 -0000, ghidera2000 <ghidera2000@...> wrote:

I'm considering using triacs to switch 110VAC instead of relays.
Never used triacs before though and I want to double check my
understanding.

First thing is gate signal. This is AC, not DC correct? The AC
signal opens one SCR on the positive side of the sine wave and the
opposite SCR on the negative side?

it only needs to be a pulse, it is sayd the optimum is a pulse chain for
best triggering but it can be a continous signal too.

I'm not entirely sure if the pulse can be both polarities or only the
one in which the current should flow, the datasheet can tell i hope.
(please answer if someone knows).
Tomi Engdahl has told me it can be both polarities, no matter which polarity
the main current has but i am not sure about this.

A triac output optocoupler such as the MOC3022 would be used to turn
the triac on and off. Its triac side gets power from the AC line
directly. Is a simple triac opto good for a spindle motor or do I
need to get a zero-crossing opto like the MOC3040?

this is a good and widely used solution.

the zero crossing has the advantage you need no (or not much) choke inductance.
if you have no zero crossing you need enough inductance to prevent triac destruction
(max dcurrent/st from datasheet).
on the other hand you have no possibility to make phase angle control with zero crossing detector.
you also need to keep HF signals low, because of EMC, especially if you switch fast this can be a problem.
In this case the inductance of the motor might very well be enough and you will have no such problems at all.

(looking in the average electronically controlled power drill the inductance seems to be enough).

Last part - Do triacs generally fail open or closed? If they fail
closed, that could be a problem if used to switch motors on...

i think they fail closed more often but i'm not too sure...


sam's repair faq on microwave triacs:


7.20) Testing and replacing the triac

A triac may fail in a variety of ways:

* A shorted triac would result in the oven coming on as soon as the door is

closed or the power being stuck on high no matter what the touchpad setting.

* An open triac or one that didn't respond to the gate would result in no heat

and possibly other things like the fan and turntable not working as well.

* A triac that didn't turn off would result in the parts of the oven continuing

to run even after the timer counted to zero.

* A triac where one half was shorted would result in a blown fuse due to it

acting as a rectifier pumping DC through the HV transformer.

* A triac where one half doesn't properly turn off would result in the main

fuse blowing when the cook cycle completed.

Nearly all triac failures will be shorts. Thus, measuring across the
MT1 and MT2 terminals of the triac (the power connections) should read
as a high resistance with a multimeter. A few ohms means a bad triac.

As noted above, triacs can fail in other - possibly peculiar ways - so
substitution or bypassing may be necessary to rule out all possibilities.

Replacement is very straightforward - just don't get the wires mixed up.

i knew there was some text about it in there..

ST

Merci!

I'm considering using triacs to switch 110VAC instead of relays.
Never used triacs before though and I want to double check my
understanding.

First thing is gate signal. This is AC, not DC correct? The AC
signal opens one SCR on the positive side of the sine wave and the
opposite SCR on the negative side?

A triac output optocoupler such as the MOC3022 would be used to turn
the triac on and off. Its triac side gets power from the AC line
directly. Is a simple triac opto good for a spindle motor or do I
need to get a zero-crossing opto like the MOC3040?

Last part - Do triacs generally fail open or closed? If they fail
closed, that could be a problem if used to switch motors on...

Merci!

The quadrant thing refers to the gate sensitivity differences between the
"forward SCR with a positive trigger", the "forward SCR with a negative
trigger", the "reverse SCR with a positive trigger" and lastly the "reverse
SCR with a negative trigger". Some modes of operation are more sensitive
than others.

The RC network is to prevent, say a fast line spike ... from triggering the
triac "on" inadvertently. If I remember correctly, the triac has a small
internal capacitance between the gate and main terminal. And a fast rising
spike can be conducted through it ... to the gate

Curtis

Dazzle Mom this coming Mother's Day season with flowers!

On Monday 12 April 2004 04:31 pm, Alex Karasev wrote:

Hi,

I'd like to build a good quality portable/compact mic pre for field
recording, that would be powered by a small battery (9V or other
compact battery types), and provide phantom power for the balanced
condenser mics.

A 9V battery isn't going to have that much kick to it, compared to other
types...

Analog Devices SSM2019 may be a good chip to base this on:
,2121,SSM2
019,00.html

I would just use the simple datasheet diagram for the chip and
phantom power hookup.

What's left is the power supply that could turn a 6...9V battery
input voltage into a +/- voltage to power the SSM2019 chip, and
provide 15...48V phantom power to the mic. The Analog Devices
includes a passive component hookup diagram to make +/- 48V phantom
power available out of a +48V power supply.

That 48 volt requirement is typically what's supplied at the mixing console,
and then there are series resistors at both the console and mic ends, which
means that you can probably get by with a lot lower voltage.

So my voltage requirements are:

+15...+48V for phantom power
+ AND - (identical) 6...16V to power the SSM2019 chip.

Any suggestions on creating these voltages from a single +6V...+9V
battery? I do not want to have multiple batteries.

Do you mean you don't want multiple cells? I hope that's not what you're
saying here.

I have a DC/DC converter that, when fet +5VDC on input, can produce -
10 Vdc, -19 VDC, -26 VDC. I don't think I can just reverse the
battery supply input and turn the - outputs into +, as the outputs
are relative to ground common with input (plus there may be
polarized caps in there).

Phantom power shouldn't have any common connection with ground, anyhow, it's
that voltage between the two balanced lines. I don't know how you're going
to do this without multiple batteries, unless you get some sort of a small
switcher going that actually uses a transformer to get you away from that
ground connection.

I enthusiasticaly second Dave's recommendation. Advanced Circuits
does all of our boards and I couldn't be happier with them. Their
prices are low, their quality is excellent and they ship on time,
every time.

When they do screw up, (everyone does eventually) they make good on
it and they do it quickly at no charge. They do not argue to say it's
your fault or some other lame excuse. They have redone 1,000 4-layer
boards for us in 2 days.

Check out their $33 proto board deal (actually $100 because there is
a 3 board minimum).

Just a very satisfied customer.

Mariss
Geckodrive Inc.


--- In Electronics_101@..., James Liddle <jliddle31@y...>
wrote:

Hi Dave -

I have a friend who owns a mid-sized business - he uses and

recommends

Jim

Dave Mucha <dave_mucha@y...> wrote:
Hi all,

I have a small board with a couple 8 pin uSOC chips on it that I am
starting to sell.

I am looking for an assembly board house that can assemble these

for

me.

The boards are pretty small and the two chips are not too hard as

the

board is single sided.

I have been looking for a board house but cannot sort thru the huge
quantity of google hits.

Anyway, can anyone offer any ideas ?

Dave





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Just some info..

The two chips mentioned are available.. Cost around 13 Dollars.
I have received email back and they will ship my way so Iam half way
there..

Still need to TX it across but Iam sure with Serial signal I should be
able to find a way..

Thks
Gary

Hi,

I'd like to build a good quality portable/compact mic pre for field
recording, that would be powered by a small battery (9V or other
compact battery types), and provide phantom power for the balanced
condenser mics.

Analog Devices SSM2019 may be a good chip to base this on:
,2121,SSM2
019,00.html

I would just use the simple datasheet diagram for the chip and
phantom power hookup.

What's left is the power supply that could turn a 6...9V battery
input voltage into a +/- voltage to power the SSM2019 chip, and
provide 15...48V phantom power to the mic. The Analog Devices
includes a passive component hookup diagram to make +/- 48V phantom
power available out of a +48V power supply. So my voltage
requirements are:

+15...+48V for phantom power
+ AND - (identical) 6...16V to power the SSM2019 chip.

Any suggestions on creating these voltages from a single +6V...+9V
battery? I do not want to have multiple batteries.

I have a DC/DC converter that, when fet +5VDC on input, can produce -
10 Vdc, -19 VDC, -26 VDC. I don't think I can just reverse the
battery supply input and turn the - outputs into +, as the outputs
are relative to ground common with input (plus there may be
polarized caps in there).

Any suggestions would be greatly appreciated.

Alex

This came up a few months ago, it is against TI policy. Drat! But
I can email copies to potential customers (wink wink!)

I did find the direct link, it is at:



my stuff starts at page 45. If anybody is interested, I have a
newer and better 10 kHz heterodyne filter design that I can email -
it didn't make last quarter's journal "cut", though. I am on
temporary hiatus from the journal - focused on our new 14 bit data
converter, the ADS5500. Exciting stuff!

If anybody wants the audio parts 1 and 3, they are at:




I don't make the URL's, I just tell you what they are.

Some of this stuff is pretty old - I learn as I go, and pick up
ideas from readers. So post or email me before breaking out the
soldering iron - I may have some more insight. I build all this
stuff before publishing, but there may be even better ideas floating
around out there.




--- In Electronics_101@..., James Liddle
<jliddle31@y...> wrote:

Hi Bruce -

Would you consider uploading your article to our "files" area?

Thanks,

Jim

Bruce Carter <brucec@m...> wrote:

I've seen some of those little phono preamps around, switchable

for either

magnetic _or_ ceramic cartridges, and would like a schematic

for

such a

beast. The idea is to take it to "line level", whatever that

is. <g>

Anybody know where i can find one?

I've had very little luck searching the 'net for such stuff,

and

the few that

I've found seem to be only for magnetic cartridges. I'll be

damned if I'm

going to switch my turntable around just to get some stuff off

vinyl and into

my HD here, or spend the time/money/effort to do so.

I know this stuff has been "obsolete" for a while, but it's

gotta

be out

there somewhere! Anybody know?

RIAA is RIAA, regardless of whether it is picked up by magnetic or
ceramic cartridges. The difference is in the level. That is why
the magnetic stuff is a bad idea, it will clip with a ceramic
cartridge - unless you use a voltage divider to control the

level.

I also find that the little one op amp circuits do not do a very
good job - the poles and zeros are too close together to make for

a

close fit with the RIAA curve. It takes at least two or three
poles / zeros on each transition to get with a dB of the curve. I
wrote an article for TI's analog applications journal - I will be
happy to send you a copy if you want to email me, and can accept
large email attachments


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Hi all,

I have a small board with a couple 8 pin uSOC chips on it that I am
starting to sell.

I am looking for an assembly board house that can assemble these for
me.

The boards are pretty small and the two chips are not too hard as the
board is single sided.?

I have been looking for a board house but cannot sort thru the huge
quantity of google hits.

Anyway, can anyone offer any ideas ??

Dave

---

Do you Yahoo!?
- Enter today

--- In Electronics_101@..., "dangermouse"
<dangermouse1956@g...> wrote:

I realize that I'm jumping into a thread here, but I really want to

say one

thing.

An E-stop should be as fail-safe as physically possible. If there

is any

scenario in which the driver could fail in a way that would prevent

an

immediate (but controlled) stop, then the E-stop isn't

placed/designed

properly. That's the difference between the Stop button and the E-

stop.

You don't use the E-stop under normal circumstances, but under

ABnormal

ones, when the Stop control is either non-functional, or would be

too slow

to decelerate.

In other words, preventing someone from being injured by a runaway

machine

is worth the possible sacrifice of the driver, unless there is a

way to

GUARANTEE that the machine stops without damaging it. If the

operators of

the machine routinely use the E-stop to stop the machine, they

haven't been

properly trained.

<./rant>

-DM

This is fundamentally correct, however...

A true E-stop shuts off the machine power, spindle et-al.

The problem is that on a CNC machine, you lose all your home
posistions as you lose track of steps. and that means a laborous
recovery to get back to working again.

Since a part that is comming lose is already damaged, not a problem,
but a broken drill only needs to pick up from the next hole.

A machine stop in software is often NOT an immeadiate interupt, but a
once this hole/slice/cut is done, THEN stop. for a 6 inch long cut
that is going south in the first inch... that is a different
situation.


One additional word of advise, put the E-stop where you will be
standing when things are going horribly wrong. next to the exit is
one good place. Never near the part or the spindle as you will not
want to reach over to push it.

And multiple locations is also very wise.
within reach of your PC if you watch the progress on the screen for
instance.

Dave

I realize that I'm jumping into a thread here, but I really want to say one
thing.

An E-stop should be as fail-safe as physically possible. If there is any
scenario in which the driver could fail in a way that would prevent an
immediate (but controlled) stop, then the E-stop isn't placed/designed
properly. That's the difference between the Stop button and the E-stop.
You don't use the E-stop under normal circumstances, but under ABnormal
ones, when the Stop control is either non-functional, or would be too slow
to decelerate.

In other words, preventing someone from being injured by a runaway machine
is worth the possible sacrifice of the driver, unless there is a way to
GUARANTEE that the machine stops without damaging it. If the operators of
the machine routinely use the E-stop to stop the machine, they haven't been
properly trained.

<./rant>

-DM

> I've seen some of those little phono preamps around,? switchable
for either
> magnetic _or_ ceramic cartridges,? and would like a schematic for
such a
> beast.? The idea is to take it to "line level",? whatever that
is.? ??
> Anybody know where i can find one?
>
> I've had very little luck searching the 'net for such stuff,? and
the few that
> I've found seem to be only for magnetic cartridges.? I'll be
damned if I'm
> going to switch my turntable around just to get some stuff off
vinyl and into
> my HD here,? or spend the time/money/effort to do so.
>
> I know this stuff has been "obsolete" for a while,? but it's gotta
be out
> there somewhere!? Anybody know?

RIAA is RIAA, regardless of whether it is picked up by magnetic or
ceramic cartridges.? The difference is in the level.? That is why
the magnetic stuff is a bad idea, it will clip with a ceramic
cartridge - unless you use a voltage divider to control the level.?

I also find that the little one op amp circuits do not do a very
good job - the poles and zeros are too close together to make for a
close fit with the RIAA curve.? It takes at least two or three
poles / zeros on each transition to get with a dB of the curve.? I
wrote an article for TI's analog applications journal - I will be
happy to send you a copy if you want to email me, and can accept
large email attachments

---

Do you Yahoo!?
Yahoo! Tax Center -

Hi all,

I have a small board with a couple 8 pin uSOC chips on it that I am
starting to sell.

I am looking for an assembly board house that can assemble these for
me.

The boards are pretty small and the two chips are not too hard as the
board is single sided.

I have been looking for a board house but cannot sort thru the huge
quantity of google hits.

Anyway, can anyone offer any ideas ?

Dave

Actually, I just realized. Using E-Stop to cut ALL power to the
driver is probably a bad idea. The A3977 needs power to handle the
stepper motor deceleration (Back EMF). If I just cut all power I'll
likely force an overvoltage back to the A3977 and possibly damage
things.

I've seen some of those little phono preamps around, switchable

for either

magnetic _or_ ceramic cartridges, and would like a schematic for

such a

beast. The idea is to take it to "line level", whatever that

is. <g>

Anybody know where i can find one?

I've had very little luck searching the 'net for such stuff, and

the few that

I've found seem to be only for magnetic cartridges. I'll be

damned if I'm

going to switch my turntable around just to get some stuff off

vinyl and into

my HD here, or spend the time/money/effort to do so.

I know this stuff has been "obsolete" for a while, but it's gotta

be out

there somewhere! Anybody know?

RIAA is RIAA, regardless of whether it is picked up by magnetic or
ceramic cartridges. The difference is in the level. That is why
the magnetic stuff is a bad idea, it will clip with a ceramic
cartridge - unless you use a voltage divider to control the level.

I also find that the little one op amp circuits do not do a very
good job - the poles and zeros are too close together to make for a
close fit with the RIAA curve. It takes at least two or three
poles / zeros on each transition to get with a dB of the curve. I
wrote an article for TI's analog applications journal - I will be
happy to send you a copy if you want to email me, and can accept
large email attachments

Three hours? Giving up so soon? I did not find programming CPLDs to be
easy though it is rewarding in its own way.

no, never giving up, but getting frustrated.

An even better alternative is to build the counter as a BCD counter
rather than a binary counter and then converting. Do you have to have
a binary counter? Look at the logic diagrams for binay counters and
see how they work and then just implement that on the CPLD.

did just that, not complete yet but seems to work now.
great idea.

Generating the 7 segment display output should be easier if you
multiplex the display output. Meaning that you only drive one seven
segment display at a time and cycle through all eight. That way you
only have to create one set of logic that converts BCD to 7 seg
output. It also saves on precious I/O pins because you only need 1 pin
for each segment and 1 pin for each display.

i know 'bout multiplexing but i have decided once in my life i want to use
most of the i/o pins, so i try to use them 1:1 on the leds.
hope it works out thermally.
it is no good approach, you need loads of resistors too, scanning makes much more
sense but i sometimes do not want to make sense.

thanks for the suggestions.

ST