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'[PIC] Drive 1024 relais using 13 (thirteen) PIC18F'
2007\11\20@054955 by Luis.Moreira

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Hi Mamouda,
This is definitely possible, but you are very vague about your project. For instance how many relays per PIC, speed required, what kind of relays, which way do you want to control them? More important and useful is what's the application?
Best regards
              Luis



{Original Message removed}

2007\11\20@060145 by Alan B. Pearce

face picon face
>I'd like to drive 1024 relais using 13 (thirteen)
>PIC18F8720 which are communicating throug MSSP.
>I'd like to use Assembler as programming language.
>The master receive data through USART. The data are
>sent by software.
>Any help? any idea how to begin?

This would sound like an ideal project to have the master chip receive the
data and put commands out to the other chips on an I2C bus, using the MSSP
port.

All of the slave chips could have identical code in them, and have the I2C
address set by some DIP switches on one of the ports. It may even be
possible to have all chips use the same code, and have (say) address 0 set
the device as master, and then have that one use the serial port for the
outside communication.

This could also allow you to have more than 13 chips to drive the relays.
Currently with 13 chips, you are going to need around 78 or 79 relays per
chip. If you use 16 chips you could reduce this to 64 relays per chip. Using
such a large chip this would almost allow you to have a relay per pin, but
you would still need driver chips or transistors.

Use 32 chips will then allow 32 relays per chip. With 68 I/O pins you then
have a further 2 for I2C, and 5 for DIP switches, leaving 29 I/O pins. With
2 used for serial on the master (4 if you need handshake lines) plus
probably another 2 for the debug port (always making it available for
development purposes if the room is there, or for program upgrades if they
cannot be downloaded with a bootloader) leaves 23 pins spare. Now it is
always worth putting some indicator leds on the board for diagnostic
purposes. I would suggest about 4 or 5, one for I2C activity, one to show
'this board last addressed', one for serial activity when the PCB is the
master, and one that is available for other uses, but normally is just
showing 'power on' (it comes on after the micro does it power up). The 4
LEDs in combination can flash error codes for incorrect I2C address setting,
microcode check fail on power up, or any other errors you may want. This
will still leave some spare pins.

Personally I would allow 6 or 7 DIP switches for the I2C address - someone
is bound to want to expand the system in the future, so that would allocate
another couple of pins.

Personally I wouldn't use such a large chip (are you really going to need
128k flash memory just to drive relays?) but would use a smaller processor.
Even a 16F series as a slave device should be adequate, although I can see
that there may be a desire to have all processors the same. But even the
master processor could probably be scaled back to an 18F8520 - same chip but
only 32k flash.

2007\11\20@064114 by Jan-Erik Soderholm

face picon face
>> I'd like to drive 1024 relais using 13 (thirteen)
>> PIC18F8720 which are communicating throug MSSP.

Why use other PICs as "relay-drivers" at all ?
Why doesn't standard shift regs/latches work or maybe
a bunch of "port expanders" ? The port expanders
also talk SPI or I2C but there is no code to worry
about.

And, as Allan wrote, why use a such large PIC only
to drive relays ?

Jan-Erik.

2007\11\20@082744 by Michael Rigby-Jones

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>-----Original Message-----
>From: spam_OUTpiclist-bouncesTakeThisOuTspammit.edu [.....piclist-bouncesKILLspamspam@spam@mit.edu]
>On Behalf Of Jan-Erik Soderholm
>Sent: 20 November 2007 11:41
>To: Microcontroller discussion list - Public.
>Subject: Re: [PIC] Drive 1024 relais using 13 (thirteen)
>PIC18F8720 (Kabanga)
>
>
>>> I'd like to drive 1024 relais using 13 (thirteen)
>>> PIC18F8720 which are communicating throug MSSP.
>
>Why use other PICs as "relay-drivers" at all ?
>Why doesn't standard shift regs/latches work or maybe
>a bunch of "port expanders" ? The port expanders
>also talk SPI or I2C but there is no code to worry
>about.

My first thought as well, you'd only need one PIC with a UART and a bunch of shift registers.  Putting 128 shift registers in a daisy chain may not be a great idea (propogation delay), but it could be broken up into several smaller daisy chains with bit bashed clock/data.

Regards

Mike

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2007\11\20@090234 by David VanHorn

picon face
Using serial/parallel shift registers and ULN2003s I don't see any
need for more than one processor.

Clocking out 1024 bits can't take long, just keep the image in ram,
update as needed, and when there's a change (or on a time tick) blow
it out to the SRs and hit the latch line.

The power supply for 1024 relays, and PCB routing to keep that from
resetting the processor will be much more interesting.

At 10mA each, that's potentially 10 A being turned on and off, and
lots of inductively stored energy to dump somewhere.

2007\11\20@105035 by Dario Greggio

face picon face
Jan-Erik Soderholm wrote:
>>>I'd like to drive 1024 relais using 13 (thirteen)
>>>PIC18F8720 which are communicating throug MSSP.
>
> Why use other PICs as "relay-drivers" at all ?
> Why doesn't standard shift regs/latches work or maybe
> a bunch of "port expanders" ? The port expanders
> also talk SPI or I2C but there is no code to worry
> about.

Yep, my idea too.
Only advantage using PICs, would be that less chips would be needed...

--
Ciao, Dario

2007\11\20@115906 by Bob Blick

face picon face
> Hello !
>
> I'd like to drive 1024 relais using 13 (thirteen)
> PIC18F8720 which are communicating throug MSSP.
> I'd like to use Assembler as programming language.
> The master receive data through USART. The data are
> sent by software.
> Any help? any idea how to begin?

Where's Olin when you need him? This question begs for
his reply!

Cheerful regards,

Bob

P.S.
Your question is both full of specifics and short on
detail, so it's likely to be interpreted that you
haven't made good choices. However, if the basis for
this project is to learn assembly language, you should
start with the LED blink project first and work your
way up.

2007\11\20@150936 by Martin

face
flavicon
face
Yes that's the first thing I thought of with 1000 relays. Opto-isolation
isn't such a bad idea I think. Snubbers galore!

David VanHorn wrote:
{Quote hidden}


'[PIC] Drive 1024 relais using 13 (thirteen) PIC18F'
2007\12\03@114952 by alan smith
picon face
yes...first figure out if you want to use the MSSP or the USART interface....there is plenty of code examples for both available.  Once you have the two words in memory, that represent the bit pattern, just movff to the LATn ports.  Very simple.  But, be aware of the issues of turning on and off relay drives at the same time and how the inductive kick can affect the processors power.

mamoudaspamKILLspamweb.de wrote:  

Hello !

I'd like to drive 1024 relais using 13 (thirteen) PIC18F8720 which are communicating throug MSSP.
I'd like to use Assembler as programming language.
The master receive data through USART. The data are sent by software.
Any help? any idea how to begin?

Thanks for your help.
Regards



Jetzt neu! Schützen Sie Ihren PC mit McAfee und WEB.DE. 3 Monate
kostenlos testen. *http://www.pc-sicherheit.web.de/startseite/?mc=022220* [http://www.pc-sicherheit.web.de/startseite/?mc=022220]

2007\12\03@115253 by alan smith

picon face
Actually I didnt see the replies till I did a message sort.  If he is using I2C or SPI, why even use a processor?  Just use the MCP23017 and drive it that way.  

Luis Moreira <.....Luis.MoreiraKILLspamspam.....jet.uk> wrote:  Hi Mamouda,
This is definitely possible, but you are very vague about your project. For instance how many relays per PIC, speed required, what kind of relays, which way do you want to control them? More important and useful is what's the application?
Best regards
Luis



{Original Message removed}

2007\12\04@123108 by William Benson

picon face

Hi,

To help reduce the "Inductive Kick" look at the following LINKS:

www.coilgun.info/theory/inductivekickback.htm
www.redlion.net/Products/Groups/NoiseSuppression/SNUB/Docs/12027.pdf

I hope you found the info helpful.

BEN
> Date: Mon, 3 Dec 2007 08:49:49 -0800> From: EraseMEmicro_eng2spam_OUTspamTakeThisOuTyahoo.com> Subject: Re: RE:[PIC] Drive 1024 relais using 13 (thirteen) PIC18F8720 (Kabanga)> To: piclistspamspam_OUTmit.edu> > yes...first figure out if you want to use the MSSP or the USART interface....there is plenty of code examples for both available. Once you have the two words in memory, that represent the bit pattern, just movff to the LATn ports. Very simple. But, be aware of the issues of turning on and off relay drives at the same time and how the inductive kick can affect the processors power.> > @spam@mamoudaKILLspamspamweb.de wrote: > > Hello !> > I'd like to drive 1024 relais using 13 (thirteen) PIC18F8720 which are communicating throug MSSP.> I'd like to use Assembler as programming language. > The master receive data through USART. The data are sent by software.> Any help? any idea how to begin?> > Thanks for your help.> Regards> > > > Jetzt neu! Schützen Sie Ihren PC mit McAfee und WEB.DE. 3 Monate > kostenlos testen. *http://www.pc-sicherheit.web.de/startseite/?mc=022220* [http://www.pc-sicherheit.web.de/startseite/?mc=022220] >

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