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'[PIC] Connect 4 : Let me know what you think!'
2008\06\20@094546 by Tomás Ó hÉilidhe

picon face

I'm making an electronic portable Connect4 game that will run on
batteries. It started out as a project for college but now I'm just
doing it over the Summer for fun.

The game consists of a matrix of bi-colour LED's which represent the
chip places:

   x   x   x   x   x   x   x
   x   x   x   x   x   x   x
   x   x   x   x   x   x   x
   x   x   x   x   x   x   x
   x   x   x   x   x   x   x
   x   x   x   x   x   x   x

The display is multiplexed, only one column is ever lit at a time. In
each column, all the LED cathodes are common, and the common cathode
goes to a low-side driver which is controlled by a PIC pin.

Under each column there's a push button. You press the push button and a
chip falls into that column. Player 1 has green chips, Player 2 has red.

I've decided to use the three-pin LED's that are called "tri-colour",
but I'll only be using them as bi-colour (i.e. I won't ever have both
colours lit at the same time).

I'm using the PIC16F887 this time around (the 40-pin DIP kind) and I'm
using the Pickit2 to program it.

The 887 has 5 ports: A, B, C, D, E

Port B is the one that has internal pull-up's so I think it's the
natural choice for the push buttons. I'll have 7 push buttons but
unfortunately I can only use 5 pins on Port B because I need RB6 and RB7
for hooking up to the Pickit2 (my board is going to have a header for
hooking up the Pickit2). For the final push button, I use the RE3 pin in
conjunction with my own pull-up resistor.

For driving the rows, I opted for port D because it's pretty much just
an I/O port. I needed more pins for driving the rows so I used A0 thru
A5 also.

For driving the columns, I opted for port C.

Port E is the "save the day" port that just cleans up the mess of not
being able to use other pins such a RB6 and RB7.

Here's a link to the current schematic of my project, I'd appreciate if
you'd take a look and see what you think, give me advice! :-D

http://users.imagine.ie/toe/scoth.pdf




2008\06\20@104930 by Wouter van Ooijen

face picon face
> Here's a link to the current schematic of my project, I'd appreciate if
> you'd take a look and see what you think, give me advice! :-D

Nice project, do publish it somewhere on the web when you are finished.
(extra points for selecting the 887 instead of an older chip) If you
have no web space available call James.

You used a funny style for the schematic, which probably makes it more
readable for absolute beginners, but less for more experienced persons.
Some details are omitted (power decoupling, reset circuit values).

You are reserving RB6/7, that's required when you want to debug, not
when you just want to program.

Depending on the currents, I might have selected a HC595 for the low
side driver, saving some PIC pins.

What's that thingy on RE2, an SMD LED? Without series resistor?

--

Wouter van Ooijen

-- -------------------------------------------
Van Ooijen Technische Informatica: http://www.voti.nl
consultancy, development, PICmicro products
docent Hogeschool van Utrecht: http://www.voti.nl/hvu

2008\06\20@113223 by Robert Young

picon face


>
>
> I'm making an electronic portable Connect4 game that will run on
> batteries. It started out as a project for college but now I'm just
> doing it over the Summer for fun.
>

Non-standard schematic conventions make it a bit hard to read.  Contrast and size of some of the text on the background makes this one hard to read.

That said here we go:

1) RB6 / RB7 are the programming and debug pins.  Yes, you can use them as I/O but you will loose your ability to use them as debug pins.  Furthermore, you call out RB6 on your oddly shaped PIC twice.  

2) Component values not labeled in many cases.  What FET/MOSFET are you using?  Where is the value for the high and low side drivers?  Etc.

3) No component numbering, again this can be a cause for confusion.  U1, U2, D1, D2, R1, etc are quite helpful.  -- Wait I retract part of that statement.  I found some components are labeled but so small they are hard to see.  And in some cases there are nets running through the text.  And finally some have a "number" but most just have "?".

4) Non-standard component shapes.  "L" shaped PIC is a bit odd.  Use buses to show large groups of lines.  Sometimes it helps to make things like microcontrollers in shapes other than a simple rectangle or to split them up into multiple shapes.   Or to group the pins by function instead of numeric order.   But in this case I think a simple rectangle with buses to show the signal groups would have been more readable.

5) Power?

6) Ground?

7) Supply bypass caps?

8) Reset component values?  Not familiar with the 16F887 but in general, for the "newer" PICs (16F and 18F) I was of the impression that a single pull-up resistor on MCLR/VPP is OK for the reset if you also have the POR bit set.  For a production unit I'd think a bit more about the reset vs power supply turn on but for hobby and play seems OK.

9) Pins for the 7-seg?  Are you going to use something like a 74HC595 and SPI bus to control them?

10) I've never been a big fan of the weak-pull ups in PORTB and unless I'm really pressed for power consumption I like a nice stiff pull up resistor.  Again, _personal_ preference but I generally use a 47K for pull ups on a 5V design unless I need to minimize power and then I go through the exercise of computing currents versus expected duty cycle of the signal vs. input current HI/LO logic for the given PIC and its operating environment.  For the one you have indicated on E1, what value?  

11) What is hanging off of E2?  

12) Internal oscillator?  If nothing else, a quite note in the corner of the schematic about that.  

13) Un-used inputs on your driver chips should probably be tied to ground.  Maybe through a resistor so you can use them later if you decide you want them.  

14) If you switch to a common cathode 7-seg you could use your two spare high side drivers instead of the discrete FET/MOSFETs shown.



Rob

2008\06\20@120045 by Tomás Ó hÉilidhe

picon face


Wouter van Ooijen wrote:
>> Here's a link to the current schematic of my project, I'd appreciate if
>> you'd take a look and see what you think, give me advice! :-D
>>    
>
> Nice project, do publish it somewhere on the web when you are finished.
> (extra points for selecting the 887 instead of an older chip) If you
> have no web space available call James.
>  

Thanks. I've already got a working one finished and it's great... except
I was very cavalier with it, leaving out current-limiting resistors and
so forth. This time arround, I want to make a "bulletproof" product.

> You used a funny style for the schematic, which probably makes it more
> readable for absolute beginners, but less for more experienced persons.
> Some details are omitted (power decoupling, reset circuit values).
>  

I don't know what "power decoupling" is.

As for the reset circuit values, well I haven't even thought about them
yet. I'll get my board made, populate it with 99% of the components, and
then I'll take the time to think about the resistor and capacitor values.

> You are reserving RB6/7, that's required when you want to debug, not
> when you just want to program.
>  

To be honest I'm being as braindead about it as I can be so that I don't
make mistakes. I won't to use the "standard" interface to the Pickit2
and be done with it because I'm perfectly happy with how the Pickit2
works with my demo board.

> Depending on the currents, I might have selected a HC595 for the low
> side driver, saving some PIC pins.
>  

Somebody mentioned this chip to me already. I looked it up and go its
datasheet but I couldn't make any sense of it. Haven't a clue what it does.

> What's that thingy on RE2, an SMD LED? Without series resistor?
>  

It's a piezo speaker! I'm not the greatest artist :-P

2008\06\20@120124 by Nicola Perotto

picon face
Hi Tomás,
you can save some pin by using a HC589 8 bit input shift register and
driving it with only 3 pins.
- check the pin numbering for the pic: vpp/re3 is number 1 not 13 (maybe
there are more wrong).
- the HC595 can be cascaded so you can have 8*5 = 40 output with only 3 pin
Cheers
     Nicola



Tomás Ó hÉilidhe wrote:
{Quote hidden}

2008\06\20@120753 by Tomás Ó hÉilidhe

picon face


Robert Young wrote:
> 1) RB6 / RB7 are the programming and debug pins.  Yes, you can use them as I/O but you will loose your ability to use them as debug pins.  Furthermore, you call out RB6 on your oddly shaped PIC twice.

Are you sure I have RB6 on it twice? I had a look around the chip and
can't find the second instance of it... please let me know!

> 2) Component values not labeled in many cases.  What FET/MOSFET are you using?  Where is the value for the high and low side drivers?  Etc.
>  

I don't need any of those details on the schematic. I'll get my board
made and then I'll have a think about it.

> 3) No component numbering, again this can be a cause for confusion.  U1, U2, D1, D2, R1, etc are quite helpful.  -- Wait I retract part of that statement.  I found some components are labeled but so small they are hard to see.  And in some cases there are nets running through the text.  And finally some have a "number" but most just have "?".
>  

I'll get around to that. Protel has this "auto numbering" thing that
will assign numbers for me. Where appropriate, I'll change the names to
something more intuitive.

> 5) Power?
>  

At the moment I'm think of going from a 9 V square battery into an
LM7805. I'll get around to that in due course.

> 6) Ground?
>  

Em... eh... the negative of the supply...  ?

> 7) Supply bypass caps?
>  

What are they?

> 8) Reset component values?  Not familiar with the 16F887 but in general, for the "newer" PICs (16F and 18F) I was of the impression that a single pull-up resistor on MCLR/VPP is OK for the reset if you also have the POR bit set.  For a production unit I'd think a bit more about the reset vs power supply turn on but for hobby and play seems OK.
>  

I don't know about this stuff. I'll ask questions in due course.

> 9) Pins for the 7-seg?  Are you going to use something like a 74HC595 and SPI bus to control them?
>  

Do you see the net names I put on the pins for the seven segs? Those
nets go to the output of the high-side driver. (I originally did it by
just drawing wire but it was way too messy).

> 10) I've never been a big fan of the weak-pull ups in PORTB and unless I'm really pressed for power consumption I like a nice stiff pull up resistor.  Again, _personal_ preference but I generally use a 47K for pull ups on a 5V design unless I need to minimize power and then I go through the exercise of computing currents versus expected duty cycle of the signal vs. input current HI/LO logic for the given PIC and its operating environment.  For the one you have indicated on E1, what value?
>  

Haven't thought about it yet. I'll wait til I get my board. Probably
something like 10k though.

> 11) What is hanging off of E2?
>  
It's a piezo speaker :-D

> 12) Internal oscillator?  If nothing else, a quite note in the corner of the schematic about that.
>  

I still have RB6 and RB7 free so I'm thinking of hooking up some sort of
20 MHz yoke-a-ma-jiggy to it.

> 13) Un-used inputs on your driver chips should probably be tied to ground.  Maybe through a resistor so you can use them later if you decide you want them.
>  

Nice, thanks for that. It would have slipped my mind.

> 14) If you switch to a common cathode 7-seg you could use your two spare high side drivers instead of the discrete FET/MOSFETs shown.
>  

VERY NICE! Never crossed my mind! I'll look into it  :-D

2008\06\20@121812 by Apptech

face
flavicon
face
>> What's that thingy on RE2, an SMD LED? Without series
>> resistor?

> It's a piezo speaker! I'm not the greatest artist :-P

Be aware that tapping a piezo speaker that is directly
attached to a pin can generate enough voltage to make the
PIC play Connect none thereafter. For extra points you can
protect it from being touched but have it squeezed or hit by
dropping/knocking :-)




           Russell

2008\06\20@123219 by Tomás Ó hÉilidhe

picon face


Apptech wrote:
> Be aware that tapping a piezo speaker that is directly
> attached to a pin can generate enough voltage to make the
> PIC play Connect none thereafter. For extra points you can
> protect it from being touched but have it squeezed or hit by
> dropping/knocking :-)

Piezo speakers can generate a voltage? :-O

So what do I do, stick a diode in series with it?

2008\06\20@124509 by Alan B. Pearce

face picon face
>
>As for the reset circuit values, well I haven't even thought about them
>yet. I'll get my board made, populate it with 99% of the components, and
>then I'll take the time to think about the resistor and capacitor values.

You really should reverse the order of thinking here (see next point). While
being able to think about values of components you have already made
allowance for could come later, you may find that you need a different size
footprint on the PCB if you change capacitor value - especially for
electrolytic capacitors.

>I don't know what "power decoupling" is.

<VBG> this is why I say you need to think about what goes on the PCB before
you make it.

You will require capacitors across the power supply to make the circuit run
reliably, especially when the battery gets near the end of its life.
Typically you will require a 47nF or 100nF ceramic chip capacitor across the
VDD and VSS pins of the PIC - or at least as close as you can reasonably get
it. It will probably also require some amount of 'bulk filtering' in the
form of an electrolytic capacitor (most people prefer a tantalum capacitor
for this) around 10 to 22uF, somewhere across the 5V supply.

2008\06\20@125757 by Alan B. Pearce

face picon face
>Piezo speakers can generate a voltage? :-O

Sure can - they are 'just' a crystal microphone being used in the reverse
direction.

>So what do I do, stick a diode in series with it?

The 'approved' way is to use a separate transistor that can withstand any
voltage that it is likely to generate. It is also possible to get higher
volume from the speaker doing this as well, but that is a separate issue.

2008\06\20@130006 by Robert Young

picon face


> Robert Young wrote:
> > 1) RB6 / RB7 are the programming and debug pins.  Yes, you can use them as I/O but you will loose your ability to use them as debug pins.  Furthermore, you call out RB6 on your oddly shaped PIC twice.
>
> Are you sure I have RB6 on it twice? I had a look around the chip and
> can't find the second instance of it... please let me know!

I could be reading it wrong, the text is pretty darn small so B's can look like E's and vice versa.  Size and contrast ratio are your friends.

>
> > 2) Component values not labeled in many cases.  What FET/MOSFET are you using?  Where is the value for the high and low side drivers?  Etc.
> >  
>
> I don't need any of those details on the schematic. I'll get my board
> made and then I'll have a think about it.

Yes you do need these details on the schematic...  One day you will wonder what those parts are.

>
> > 3) No component numbering, again this can be a cause for confusion.  U1, U2, D1, D2, R1, etc are quite helpful.  -- Wait I retract part of that statement.  I found some components are labeled but so small they are hard to see.  And in some cases there are nets running through the text.  And finally some have a "number" but most just have "?".
> >  
>
> I'll get around to that. Protel has this "auto numbering" thing that
> will assign numbers for me. Where appropriate, I'll change the names to
> something more intuitive.
>

No experience with Protel.  Some schematic entry number as you go, some auto number.  Personally I use Eagle and it autonumbers as I go but then I can go back later and change manually or run a script to renumber from the schematic or the board.  My preference is to renumber from the board so that things start in the upper left corner and read in increasing order left to right / top to bottom.

> > 5) Power?
> >  
>
> At the moment I'm think of going from a 9 V square battery into an
> LM7805. I'll get around to that in due course.

It will be important eventually...

>
> > 6) Ground?
> >  
>
> Em... eh... the negative of the supply...  ?

Yep.

>
> > 7) Supply bypass caps?
> >  
>
> What are they?

In the grand tradition of the PICLIST, RTFM. :)  All kidding aside, you should bone up on that topic ASAP.

>
> > 8) Reset component values?  Not familiar with the 16F887 but in general, for the "newer" PICs (16F and 18F) I was of the impression that a single pull-up resistor on MCLR/VPP is OK for the reset if you also have the POR bit set.  For a production unit I'd think a bit more about the reset vs power supply turn on but for hobby and play seems OK.
> >  
>
> I don't know about this stuff. I'll ask questions in due course.

I think most PIC datasheets have a little section on reset signal generation.  May not be sufficient information if you aren't familiar with what can happen though.

>
> > 9) Pins for the 7-seg?  Are you going to use something like a 74HC595 and SPI bus to control them?
> >  
>
> Do you see the net names I put on the pins for the seven segs? Those
> nets go to the output of the high-side driver. (I originally did it by
> just drawing wire but it was way too messy).

Again, I missed those due to the size of the text.  Does Protel have a BUS function?  You can collect several related signal names, say LED0 to LED7 into something like LED[0..7] and then use a thicker BUS line to indicate they all run along parallel.

{Quote hidden}

I think you mean RA6 and RA7.

{Quote hidden}

Rob

2008\06\20@141040 by Joe Bento

face
flavicon
face
Tomás Ó hÉilidhe wrote:
> Piezo speakers can generate a voltage? :-O
>  

Oh yes!  Think of a barbecue or cigarette lighter. (the ones that
"click" and not with a flint wheel)  The piezo crystal element in the
igniter is essentially the same thing as in the piezo speaker.  If you
are adventurous, it is actually possible to make a piezo speaker from
the igniter in a lighter.

Regards,

Joe

2008\06\20@142142 by Marcel Birthelmer

flavicon
face
Tomas,
may I suggest the book "Designing Embedded Hardware" by O'Reilly. It's not
as thorough as some other books on the subject, but it gives a nice overview
of the basics of embedded circuits - how crystals/piezos work, layout,
common devices, bypass filters, etc.
There's a website associated with it here:
http://oreilly.com/catalog/9780596007553/
Rgds,
- Marcel

2008\06\20@142946 by Nicola Perotto

picon face
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Tomás Ó hÉilidhe wrote:
> Wouter van Ooijen wrote:
>   >> Depending on the currents, I might have selected a HC595 for the low >> side driver, saving some PIC pins.
>>   >>     >
> Somebody mentioned this chip to me already. I looked it up and go its > datasheet but I couldn't make any sense of it. Haven't a clue what it does.
>
>   Here a small sample.
You can also chain more device.
Have fun
     Nicola


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2008\06\20@151553 by Clint Sharp

picon face
In message <spam_OUT485BB467.10401TakeThisOuTspamlavabit.com>, Tomás Ó hÉilidhe
<.....toeKILLspamspam@spam@lavabit.com> writes
>I've decided to use the three-pin LED's that are called "tri-colour",
>but I'll only be using them as bi-colour (i.e. I won't ever have both
>colours lit at the same time).
Why not have both lit to indicate the winning line or have a 'hint' mode
for younger players?
>

--
Clint Sharp

2008\06\20@151959 by Dario Greggio

face picon face
Wouter van Ooijen wrote:

>>Here's a link to the current schematic of my project, I'd appreciate if
>>you'd take a look and see what you think, give me advice! :-D

Nice indeed! I'd use a 18F PIC though, and C language.

--
Ciao, Dario

2008\06\20@154819 by Tomás Ó hÉilidhe

picon face


Dario Greggio wrote:
> Nice indeed! I'd use a 18F PIC though, and C language.

The whole program is in C, I've written less than 50 lines of assembler
in my entire life.

What's the benefits of using a 18F over a 16F?

My program runs in the following eternal loop:

   for(;;)
   {
       ColI i = GetRawPushButtonInput();    /* Check to see if a button
is pressed */

       DisplayScan();   /* Flash the display multiplexer */
           
       if (BAD_COL != i)    /* If a button is actually held down */
       {
           if ( !ProposePlacement(i) ) continue; /* Check if column is
empty, and if so place a chip */

           IncrementAndUpdateSegs();   /* Increment the number shown on
the seven seg displays */
         
           CheckForConnection();  /* Check to see if we've achieved
Connect 4 */
         
           if ( CheckIfConnectionValid() ) IndicateGameWon();  /* Game
is finished, this function doesn't return */
         
           ProgressNextPlayer();  /* Move on to the next player's go */
       }
   }

2008\06\20@161141 by Dario Greggio

face picon face
Tomás Ó hÉilidhe wrote:

> The whole program is in C, I've written less than 50 lines of assembler
> in my entire life.

I see :)

> What's the benefits of using a 18F over a 16F?

Oh, I supposed you were using assembler on PIC16, since they're not much
optimized for C language. But of course you can do that.
That was my main reason for using 18F.

--
Ciao, Dario -- ADPM Synthesis sas -- http://www.adpm.tk

2008\06\20@203921 by Jinx

face picon face
> I don't know what "power decoupling" is

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

See Transient Load Decoupling section

http://www.seattlerobotics.org/encoder/jun97/basics.html

Mention of it in two of many Microchip documents

ww1.microchip.com/downloads/en/DeviceDoc/power.pdf
http://ww1.microchip.com/downloads/en/AppNotes/00763b.pdf

Most people would probably put a 10uF and 0.1uF close to the
micro, 0.1uF ceramics around the circuit and possibly a bulk
electrolytic too, perhaps 100uF or 470uF, something like that

> Somebody mentioned this chip to me already. I looked it up and
> go its datasheet but I couldn't make any sense of it. Haven't a clue
> what it does.

Well, an HC595, like other serial-parallel convertors, turns serial
data into parallel data. This means that you feed it a clock and an
8-bit byte of data into two pins, and the contents of that data byte
appear on the output pins in parallel format. Look at the timing
diagrams carefully

The HC164 is another shift register. This circuit drives 28 LEDs
with just 2 pins

(apologies for white-on-black images)

http://home.clear.net.nz/pages/joecolquitt/2wireled.gif

448 LEDs with a 16F628

http://home.clear.net.nz/pages/joecolquitt/message.html

> It's a piezo speaker! I'm not the greatest artist :-P

A piezo often has the same schematic symbol as a crystal

You can save 4 pins by multiplexing the buttons with diodes, as per

http://home.clear.net.nz/pages/joecolquitt/chaser.gif

Note that the logic is the reverse polarity of your pulled-up-and-
grounded inputs. For a 7-to-3 multiplex, eg no buttons pressed
<b2:b0> = 000, button1 pressed <b2:b0> = 001, button2 pressed
<b2:b0> = 010 etc up to <b2:b0> = 111 for button7

> At the moment I'm think of going from a 9 V square battery into
> an LM7805. I'll get around to that in due course

Very wasteful, and particularly so because the whole circuit is running
on 5V, AFAICT. If you have to use 9V, then at least run the LEDs
on the unregulated 9V, rather than the regulated 5V. For parts that
actually need 5V, a 78L05 or LDO would. Although given the number
of LEDs (56 by my count), any reasonably-portable battery-based
power supply you choose won't last long. It's quite possible that you
might be drawing an average of 250mA. You will, of course, be very
popular at the battery shop

2008\06\20@222817 by Jinx

face picon face
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>So what do I do, stick a diode in series with it?

The usual way would be to isolate the piezo from the PIC and
a diode won't do that effectively

Attached are some drivers I use with piezo elements, and the
schematic of a high-volume two-tone piezo alarm for comparison.
This sound bomb has enough dB to be most uncomfortable to
the ears. "piezo_drive.gif" is easily heard throughout the house

Note that piezo elements are capacitive in nature, hence the 1k
across it. If you don't include that, the sound will be quite weak

Be aware that a piezo might impress electrical noise onto Vdd
and should be well decoupled

Two-terminal self-contained 'beepers' have both drive and HV-
generation (often around 30VDC) circuitry built-in. You might
also find that smaller ones have a magnetic core for better drive

A simpler method is to put the piezo between two I/O pins and
drive it with reciprocating pulses (ie o/p1 high, op2 low, then o/p1
low, o/p2 high) at the resonant frequency



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2008\06\20@225748 by Jinx

face picon face
> You press the push button and a chip falls into that column

So the "falling" will be animated ?

I've not used bi-colours much, but when I did, those I could
find were relatively expensive and not particularly bright. If it
were me making this, I'd be looking at a couple of cheap high-
intensity SMT or leaded LEDs instead. Carefully placed under
a diffuser (which could be a thin sheet of transluscent plastic
under the front panel) you wouldn't know the difference. Apart
from the $$$ saved. And being easier to see. And using less
current. And being easier to assemble. And having more colour
combinations to choose from. But apart from that .... ;-)

2008\06\20@230618 by Jinx

face picon face
BTW, you want cheap SMT LEDs ?

A friend at Vodaphone is grabbing me a box of old mobiles
for the spare parts box. LEDs, keypads, batteries, beepers,
many probably exotic and unuseable ICs, chargers, all free,
lovely stuff


2008\06\21@063829 by Jinx

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> Piezo speakers can generate a voltage? :-O

Attached is another practical example (igniters and microphones
already mentioned)

Hit the piezo and the peak voltage is stored in the 1u cap. Can
be used as an impact sensor. In this case it's one pad of a MIDI
percussion unit, output going to a micro's ADC



part 2 1174 bytes content-type:image/gif; (decode)


part 3 35 bytes content-type:text/plain; charset="us-ascii"
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2008\06\21@125258 by Charles Rogers

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Jinx:
The schematics you send with your replys is really good. What
CAD program do you use?  Also what OS do you use?


Charles R.

2008\06\21@125322 by Charles Rogers

picon face
Jinx:
The schematics you send with your replys is really good. What
CAD program do you use?  Also what OS do you use?


Charles R.

2008\06\21@201945 by Dennis Crawley

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On Saturday, June 21, 2008 7:34 AM [GMT-3=CET],
Jinx  wrote:

>>> Piezo speakers can generate a voltage? :-O
>>
>> Attached is another practical example (igniters and microphones
>> already mentioned)
>>
>> Hit the piezo and the peak voltage is stored in the 1u cap. Can
>> be used as an impact sensor. In this case it's one pad of a MIDI
>> percussion unit, output going to a micro's ADC
>>

I love this stuff, Jinx!.
My wife played as a drummer in her band, I'd like to make a percusion
instrument in the future,... with a good pair of headphones :P

Dennis.



2008\06\21@203219 by Jinx

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> The schematics you send with your replys is really good. What
> CAD program do you use?  Also what OS do you use?

Thanks. It's just a picture of collected symbols I Copy/Paste with
any handy graphics program (Paint Shop Pro, MSPaint, etc)

CAD programs are Eagle and Altium with XP Pro. I prefer my
smaller b/w gifs to multi-coloured schematics in some instances
(email and web pages for example)

I've just uploaded the latest revision of the symbols

http://home.clear.net.nz/pages/joecolquitt/symbols.zip

2008\06\21@203552 by Jinx

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> I love this stuff, Jinx!.
> My wife played as a drummer in her band, I'd like to make
> a percusion instrument in the future,... with a good pair of
> headphones :P

Haha. But you love your wife's drumming really don't you ?

Well, I'll keep you updated with what I'm working on and pass
on construction details when it's done

2008\06\21@213013 by Jinx

face picon face
>> Hit the piezo and the peak voltage is stored in the 1u cap. Can
>> be used as an impact sensor. In this case it's one pad of a MIDI
>> percussion unit, output going to a micro's ADC

> I'd like to make a percusion instrument in the future,...

Actually, a thought I had last night harks back to the h/w vs s/w
issue that was raised in another thread - do you get fancy with s/w
or do you add a little h/w ?

You'll notice in the piezo sensor schematic that there's a pre-set
pot. That is the sensitivity control and is to set the impact force
required to register as a genuine hit. Each sensor goes to its own
ADC pin. The ADC pins are scanned and sampled under a timer
interrupt, and any that exceed pre-set EEPROM values are then
processed and output as MIDI data

Now, if each pad had an associated comparator (1/4 LM339 for
example), then the digital output of *that* would be the trigger to
sample (as a general INT event), thus relieving the micro of the,
admittedly minor, task of repetitive and usually resultless scanning

Not really an issue in this application as the micro has naff all else
to do, but a little simple h/w can make life easier when timing gets
cramped

2008\06\21@221707 by Gaston Gagnon

face
flavicon
face
Dennis Crawley wrote:
> On Saturday, June 21, 2008 7:34 AM [GMT-3=CET],
> Jinx  wrote:
>
>  
>>>> Piezo speakers can generate a voltage? :-O
>>>>        
>>> Attached is another practical example (igniters and microphones
>>> already mentioned)
>>>
>>> Hit the piezo and the peak voltage is stored in the 1u cap. Can
>>> be used as an impact sensor. In this case it's one pad of a MIDI
>>> percussion unit, output going to a micro's ADC
>>>
>>>      
>
> I love this stuff, Jinx!.
> My wife played as a drummer in her band, I'd like to make a percusion
> instrument in the future,... with a good pair of headphones :P
>
>  
Hi Dennis,
There was a DIY project in Electronic Musician magazine a while ago on
this subject.
I think the project has been distributed by PAiA in kit form since.
Anyway, you may be interested to read this article:
http://www.paia.com/ProdArticles/drumsens.htm

Gaston

2008\06\22@013737 by Jinx

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> Piezo speakers can generate a voltage? :-O

I bumped into a friend of a friend this morning which reminded
me that I made some modifications to their baby monitor. It was
a couple of small piezos that went under the baby. Each was
sandwiched between plastic plates about 200mm square, and
they generated suprisingly high AC voltage peaks, ~40V IIRC,
from moderate movements

Tomas, you are going to write some annoying little tunes for the
game aren't you ?

2008\06\22@073306 by olin piclist

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Jinx wrote:
> CAD programs are Eagle and Altium with XP Pro. I prefer my
> smaller b/w gifs to multi-coloured schematics in some instances
> (email and web pages for example)

You can certainly generate black and white schematic GIFs with Eagle.

********************************************************************
Embed Inc, Littleton Massachusetts, http://www.embedinc.com/products
(978) 742-9014.  Gold level PIC consultants since 2000.

2008\06\22@081449 by Jinx

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> You can certainly generate black and white schematic GIFs
> with Eagle

You certainly can. And it's not unknown for me to output as .tiff
for photographic purposes

2008\06\22@221102 by Jinx

face picon face
> Hit the piezo and the peak voltage is stored in the 1u cap. Can
> be used as an impact sensor

PS, noticed that LM324 Vss shown as -9V. Should be/can be 0V


2008\06\23@064412 by Dennis Crawley

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On Sunday, June 22, 2008 11:09 PM [GMT-3=CET],
Jinx  wrote:

>> Hit the piezo and the peak voltage is stored in the 1u cap. Can
>> be used as an impact sensor
>
> PS, noticed that LM324 Vss shown as -9V. Should be/can be 0V

If somebody wants to connect to a PIC, yes. It must be -0.3 to +6,5V.
I´ve also used LM358.

Rgds.
Dennis

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