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2004-11-09 by Dave Mucha
Hi all, I am looking an alarm type switch and am thinking of using a Tiny11 to generate a pulse of something like 10khz and then send that thru the 6 to 10 switches (in series) and then use the same Tiny11 to detect that pulse. Any switch opens and the pulse is lost. An alternate is to use a pair, one to generate and one to detect. BTY, does anyone know if there will be another group buy ? Dave
2004-11-09 by Leon Heller
----- Original Message -----
From: Dave Mucha To: AVR-Chat@yahoogroups.com Sent: Tuesday, November 09, 2004 2:42 PM Subject: [AVR-Chat] alarm switch Hi all, I am looking an alarm type switch and am thinking of using a Tiny11 to generate a pulse of something like 10khz and then send that thru the 6 to 10 switches (in series) and then use the same Tiny11 to detect that pulse. Any switch opens and the pulse is lost. An alternate is to use a pair, one to generate and one to detect. BTY, does anyone know if there will be another group buy ? I doubt if Chetan will be organising another, as he's got all he needs. Why not organise one yourself? Leon
2004-11-09 by Dave Mucha
> > BTY, does anyone know if there will be another group buy ? > > I doubt if Chetan will be organising another, as he's got all he needs. Why > not organise one yourself? > > Leon If I remmeber correctly, someone went to a seminar and after the seminar, attendees were offered an 'all you can buy' price of 25 cents each. I'm not sure if that offered one specific chip and package or some variations ? I know of some people that buy PIC's in the thousands, but then you are locked into their specific chip and package. Always seems to be an odd chip. I wonder if there is interest in a group buy ? Dave
2004-11-09 by Dave Mucha
Correct, it is a series loop. It is for a machine where the wires can be cut or vibrate open or be shorted. The current or pulse would offer a more accurate way to verify that the switches are in the circuit. Dave --- In AVR-Chat@yahoogroups.com, Dave VanHorn <dvanhorn@d...> wrote: > At 09:42 AM 11/9/2004, Dave Mucha wrote: > > > > >Hi all, > > > >I am looking an alarm type switch and am thinking of using a Tiny11 > >to generate a pulse of something like 10khz and then send that thru > >the 6 to 10 switches (in series) and then use the same Tiny11 to > >detect that pulse. Any switch opens and the pulse is lost. > > This is just a series loop, right? > No need for pulses, just give a current of 10-20mA and detect open/closed > with debounce of about 100mS. Protection of your inputs and outputs is more > interesting. > > For a moment, I thought you meant addressable switches, as in "which switch > is open". > > Years and years ago, I did something like this in discrete logic (yecch!) > It sent a wide sync pulse, then narrow polling pulses down a single conductor. > Another conductor carried back answering pulses from each switch. > > Today, a single Tiny-11 at each switch point could work, but you'd have to > program in their address ranges. A micro with more pins would allow a > dipswitch to set that. Four pins for a 0-F dipswitch, and four switch > inputs, plus two pins for data, would be nice.
2004-11-09 by Dave VanHorn
At 09:42 AM 11/9/2004, Dave Mucha wrote: >Hi all, > >I am looking an alarm type switch and am thinking of using a Tiny11 >to generate a pulse of something like 10khz and then send that thru >the 6 to 10 switches (in series) and then use the same Tiny11 to >detect that pulse. Any switch opens and the pulse is lost. This is just a series loop, right? No need for pulses, just give a current of 10-20mA and detect open/closed with debounce of about 100mS. Protection of your inputs and outputs is more interesting. For a moment, I thought you meant addressable switches, as in "which switch is open". Years and years ago, I did something like this in discrete logic (yecch!) It sent a wide sync pulse, then narrow polling pulses down a single conductor. Another conductor carried back answering pulses from each switch. Today, a single Tiny-11 at each switch point could work, but you'd have to program in their address ranges. A micro with more pins would allow a dipswitch to set that. Four pins for a 0-F dipswitch, and four switch inputs, plus two pins for data, would be nice.
2004-11-09 by slaw999
Dave, Sounds like a failsafe design is required. Most failsafe implementations require switches that have both a Normally Open and Normally Closed contacts. This would require 2 conductors, wired in series, to each switch. Depending on the type of switch, the contacts are either "make before break" or "break before make". In either case the intermediate "break" state is usually not more than a few ms. You would then monitor both the Normally Open and Normally Closed circuits, requiring 2 inputs. If both circuits remain Open or Closed then we have an indeterminate state that should be handled as if the machine cover is open and an indication that maintenance to repair the problem is required. --- In AVR-Chat@yahoogroups.com, "Dave Mucha" <dave_mucha@y...> wrote: > > Correct, it is a series loop. > > It is for a machine where the wires can be cut or vibrate open or be > shorted. > > The current or pulse would offer a more accurate way to verify that > the switches are in the circuit. > > Dave > > > > > > > --- In AVR-Chat@yahoogroups.com, Dave VanHorn <dvanhorn@d...> wrote: > > At 09:42 AM 11/9/2004, Dave Mucha wrote: > > > > > > > > >Hi all, > > > > > >I am looking an alarm type switch and am thinking of using a Tiny11 > > >to generate a pulse of something like 10khz and then send that thru > > >the 6 to 10 switches (in series) and then use the same Tiny11 to > > >detect that pulse. Any switch opens and the pulse is lost. > > > > This is just a series loop, right? > > No need for pulses, just give a current of 10-20mA and detect > open/closed > > with debounce of about 100mS. Protection of your inputs and outputs > is more > > interesting. > > > > For a moment, I thought you meant addressable switches, as > in "which switch > > is open". > > > > Years and years ago, I did something like this in discrete logic > (yecch!) > > It sent a wide sync pulse, then narrow polling pulses down a single > conductor. > > Another conductor carried back answering pulses from each switch. > > > > Today, a single Tiny-11 at each switch point could work, but you'd > have to > > program in their address ranges. A micro with more pins would allow
> a > > dipswitch to set that. Four pins for a 0-F dipswitch, and four > switch > > inputs, plus two pins for data, would be nice.
2004-11-09 by Jim Wagner
Dave - I don't see your reason for using pulses. Why not just a soft pull up at one end (say, the receiving end), a hard pull down at the other. Then, if any switch opens, the pull-up end goes high and you have it. Jim On Tue, 09 Nov 2004 14:42:23 -0000 "Dave Mucha" <dave_mucha@yahoo.com> wrote: > > Hi all, > > I am looking an alarm type switch and am thinking of > using a Tiny11 > to generate a pulse of something like 10khz and then send > that thru > the 6 to 10 switches (in series) and then use the same > Tiny11 to > detect that pulse. Any switch opens and the pulse > is lost. > > An alternate is to use a pair, one to generate and one to > detect. > > BTY, does anyone know if there will be another group buy > ? > > Dave > > > > > > > > > > > > > > > > Yahoo! Groups Sponsor > > > ADVERTISEMENT > > > > > > > > > > > > > Yahoo! Groups Links > > To visit your group on the web, go > to:http://groups.yahoo.com/group/AVR-Chat/ > To unsubscribe from this group, send an email > to:AVR-Chat-unsubscribe@yahoogroups.com > Your use of Yahoo! Groups is subject to the Yahoo! Terms > of Service. > > > > > > > > > > > --------------------------------------------------------------- The Think Different Store http://www.thinkdifferentstore.com/ For All Your Mac Gear ---------------------------------------------------------------
2004-11-09 by Jim Wagner
A pulse won't help you. Vibrated open or short situations will still be an open or short circuit. I suggest that you use a steady-state voltage as I suggested in my earlier post, then digitally filter. That will do a LOT more for you than pulsing. Jim On Tue, 09 Nov 2004 15:21:18 -0000 "Dave Mucha" <dave_mucha@yahoo.com> wrote: > > Correct, it is a series loop. > > It is for a machine where the wires can be cut or vibrate > open or be > shorted. > > The current or pulse would offer a more accurate way to > verify that > the switches are in the circuit. > > Dave > > > > > > > --- In AVR-Chat@yahoogroups.com, Dave VanHorn > <dvanhorn@d...> wrote: > > At 09:42 AM 11/9/2004, Dave Mucha wrote: > > > > > > > > >Hi all, > > > > > >I am looking an alarm type switch and am > thinking of using a Tiny11 > > >to generate a pulse of something like 10khz and > then send that thru > > >the 6 to 10 switches (in series) and then use > the same Tiny11 to > > >detect that pulse. Any switch opens and > the pulse is lost. > > > > This is just a series loop, right? > > No need for pulses, just give a current of 10-20mA > and detect > open/closed > > with debounce of about 100mS. Protection of your > inputs and outputs > is more > > interesting. > > > > For a moment, I thought you meant addressable > switches, as > in "which switch > > is open". > > > > Years and years ago, I did something like this in > discrete logic > (yecch!) > > It sent a wide sync pulse, then narrow polling > pulses down a single > conductor. > > Another conductor carried back answering pulses from > each switch. > > > > Today, a single Tiny-11 at each switch point could > work, but you'd > have to > > program in their address ranges. A micro with more > pins would allow > a > > dipswitch to set that. Four pins for a 0-F > dipswitch, and four > switch > > inputs, plus two pins for data, would be nice. > > > > > > > > > > > > > Yahoo! Groups Sponsor > > > ADVERTISEMENT > > > > > > > > > > > > > Yahoo! Groups Links > > To visit your group on the web, go > to:http://groups.yahoo.com/group/AVR-Chat/ > To unsubscribe from this group, send an email > to:AVR-Chat-unsubscribe@yahoogroups.com > Your use of Yahoo! Groups is subject to the Yahoo! Terms > of Service. > > > > > > > > > > > --------------------------------------------------------------- The Think Different Store http://www.thinkdifferentstore.com/ For All Your Mac Gear ---------------------------------------------------------------
2004-11-09 by Dave VanHorn
In the alarm industry, this is called a supervised circuit. A resistor at the far end sets the loop current. At the panel, a window comparator checks that against high and low limits. shorted loop alarms high, open loop alarms low, short to ground or panel power also alarms. Design for ANY conductor to withstand short to panel power if it's in the same cable.