Post by thread:[EE:] Vibration sensor?

Hey guys and gals, I need some sensors to pick up vibration. Needs to be sensitive in two axis, and capable of detecting being bumped with less than 1/8 inch movement. It'll feed a PIC so I can work with most any output, but I only need a single pulse when it's bumped. Right now I need about a dozen, but eventually I might need several hundred. And yes I could do it with an accelerometer from analog, but I was hoping for something simpler/cheaper. Ideas? -Denny -- http://www.piclist.com hint: PICList Posts must start with ONE topic: [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads

> I need some sensors to pick up vibration. Needs to be sensitive > in two axis, and capable of detecting being bumped with less > than 1/8 inch movement. It'll feed a PIC so I can work with most > any output, but I only need a single pulse when it's bumped Can you define "bump" any better ? What frequency/repetition rate ? Can the sensor use anything else apart from its own state as a reference ? -- http://www.piclist.com hint: PICList Posts must start with ONE topic: [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads

Greetings, On Tue, 2 Mar 2004, Denny Esterline wrote: {Quote hidden}> Hey guys and gals, > I need some sensors to pick up vibration. Needs to be sensitive in two > axis, and capable of detecting being bumped with less than 1/8 inch > movement. It'll feed a PIC so I can work with most any output, but I only > need a single pulse when it's bumped. > > Right now I need about a dozen, but eventually I might need several > hundred. And yes I could do it with an accelerometer from analog, but I was > hoping for something simpler/cheaper. > > Ideas? Back in my alarm system days, we had a sensor that was simply a small weight attached to a thin strip of flexible metal. The metal strip rested on a contact, completing a Normally Closed ciruit. When there was vibration (i.e. pounding fist on a glass window or door, busting through a cinderblock wall with a drill, hammer, chisle, sledge) the contact would vibrate open. The circuit was monitored for any brief "opens" and would then latch the alarm. I believe that Radio Shack carries these devices in their stores. Would guess that they are only a couple dollars. BTW - The sensitivity was adjustable with a screw that would change the tension of the metal strip. You can mount them in various orientations to get greater sensitivity in each axis, though with intense vibration they may all go off simultaniously. Enjoy! --- Jay -- http://www.piclist.com hint: PICList Posts must start with ONE topic: [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads

Try these from digikey, pretty cheap. Hook them up to a non-inverting amp and play with the gain. You would need two for 2 axis. MSP1006-ND MSP1007-ND Hope this helps, Aaron -- http://www.piclist.com hint: PICList Posts must start with ONE topic: [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads

----- Original Message ----- From: "Denny Esterline" <spam_OUTfirmwareTakeThisOuTTDS.NET> To: <.....PICLISTKILLspam@spam@MITVMA.MIT.EDU> Sent: Tuesday, March 02, 2004 5:12 PM Subject: [EE:] Vibration sensor? > Hey guys and gals, > I need some sensors to pick up vibration. Needs to be sensitive in two > axis, and capable of detecting being bumped with less than 1/8 inch > movement. It'll feed a PIC so I can work with most any output, but I only > need a single pulse when it's bumped. > > Right now I need about a dozen, but eventually I might need several > hundred. And yes I could do it with an accelerometer from analog, but I was > hoping for something simpler/cheaper. > > Ideas? > > -Denny > I bought a cat toy that is a little ball, smaller than a golfball that has two flashing LEDs. There is a small "vertical" wire soldered to the circuit board and around it is a coil of wire. Normally the two don't touch but if you tap the ball they touch. This triggers the flashing of the LEDs for the next 30 seconds. This may not be sensitive enough for you because you can pick up the ball and wave it around and it won't start to flash. It seems to take a sharp movement to flex the coil. With the ball on the floor I can tap it with my finger and it starts to flash. I play with it more than the cat does... Her favorite toy is a length of 1/4" dowel rod. Rob Young -- http://www.piclist.com hint: PICList Posts must start with ONE topic: [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads

On 7 Mar 04, at 11:26, Robert Young wrote: > ----- Original Message ----- > From: "Denny Esterline" <firmwareKILLspamTDS.NET> > > I need some sensors to pick up vibration. Needs to be sensitive in > > two axis, and capable of detecting being bumped with less than 1/8 > > inch movement. It'll feed a PIC so I can work with most any output, > > but I only need a single pulse when it's bumped. > > I bought a cat toy that is a little ball, smaller than a golfball that > has two flashing LEDs. There is a small "vertical" wire soldered to > the circuit board and around it is a coil of wire. Normally the two > don't touch but if you tap the ball they touch. This triggers the > flashing of the LEDs for the next 30 seconds. > > This may not be sensitive enough for you because you can pick up the > ball and wave it around and it won't start to flash. It seems to take > a sharp movement to flex the coil. With the ball on the floor I can > tap it with my finger and it starts to flash. > I have seen a Piezo transducer, with a weight attached to its centre, used to produce a movement detector. Two would give your 2 axis sensing. It might be worth a try.. the ones I saw used were the very thin slivers of a transducer commonly found in small telephone handsets and "musical" greetings cards. The weight was a nut, about 0BA size, glued to the centre of the Piezo disk. hth, Mike -- http://www.piclist.com hint: PICList Posts must start with ONE topic: [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads

Mike W wrote: > I have seen a Piezo transducer, with a weight attached to its > centre, used to produce a movement detector. > Two would give your 2 axis sensing. It might be worth a try.. the > ones I saw used were the very thin slivers of a transducer > commonly found in small telephone handsets and "musical" > greetings cards. The weight was a nut, about 0BA size, glued to > the centre of the Piezo disk. I've seen similar, with one edge of the piezo disk soldered to the board, the other edge had a longish bolt (at least the diameter of the piezo element), soldered perpendicular to the disk surface. Works in three axis because piezo twist will register as well. Probably works out the cheapest option, but not the easiest (or cheapest timewise) to manufacture if you need to make many, because human assembly is required. It also could require a relatively subsantial amount of space depending on how small the case needs to be and how the piezo element is mounted. (the end of the bolt can't be resting against anything of course) -- -o) /\\ Message void if penguin violated _\_V Don't mess with the penguin Linux Registered User # 302622 <http://counter.li.org> Fido: 3:712/610 BBS/FAX: +61-2-9716-8310 Internet: .....jtKILLspam.....techniciansyndrome.org -- http://www.piclist.com hint: PICList Posts must start with ONE topic: [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads

> Try these from digikey, pretty cheap. Hook them up to a non-inverting > amp and play with the gain. You would need two for 2 axis. > > MSP1006-ND > MSP1007-ND > > Hope this helps, > Aaron > I came across these a couple days ago, they look intriguing, but the problem I see is the analog output. I'd have to set the pic up to do continuous A?D conversions and pick it out in software. That's not so much a problem, but I was hoping to put the pic to sleep and get by without a on-off switch. -Denny -- http://www.piclist.com hint: PICList Posts must start with ONE topic: [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads

> problem I see is the analog output. I'd have to set the pic up to > do continuous A?D conversions and pick it out in software. That's > not so much a problem, but I was hoping to put the pic to sleep > and get by without a on-off switch At rest the output of the accelerometer would be steady, constant or slow movements would have a gentle slope. A bump would be a higher slew rate. A basic high pass filter with a comparator or op-amp would turn this into a PIC-waking edge or level -- http://www.piclist.com hint: PICList Posts must start with ONE topic: [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads

> I came across these a couple days ago, they look intriguing, but the > problem I see is the analog output. I'd have to set the pic up to do > continuous A?D conversions and pick it out in software. That's not so > much a problem, but I was hoping to put the pic to sleep and get by > without a on-off switch. > > -Denny Use a pic with a comparator module and wake from sleep with that. I've ordered these sensors before, they are piezo's with a weight attached to the top, similar to what someone else had mentioned on the list. Aaron -- http://www.piclist.com hint: PICList Posts must start with ONE topic: [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads

> I need some sensors to pick up vibration. Needs to be sensitive in two > axis, and capable of detecting being bumped with less than 1/8 inch > movement. It'll feed a PIC so I can work with most any output, but I only > need a single pulse when it's bumped. > > Right now I need about a dozen, but eventually I might need several > hundred. And yes I could do it with an accelerometer from analog, but I was > hoping for something simpler/cheaper. Well I doubt that you will get anything simpler than the Analog Designs ones, as they will direct connect to the CCP on a PIC without any extra hardware. However the guys in out vibration facility use piezo accelerometers for doing their measurements, but I don't know that these would be any cheaper by the time you do the analog electronics to go with them. -- http://www.piclist.com hint: The list server can filter out subtopics (like ads or off topics) for you. See http://www.piclist.com/#topics

> Back in my alarm system days, we had a sensor that was simply a small > weight attached to a thin strip of flexible metal. The metal strip rested > on a contact, completing a Normally Closed ciruit. > > When there was vibration (i.e. pounding fist on a glass window or door, {Quote hidden}> busting through a cinderblock wall with a drill, hammer, chisle, sledge) > the contact would vibrate open. The circuit was monitored for any brief > "opens" and would then latch the alarm. > > I believe that Radio Shack carries these devices in their stores. > Would guess that they are only a couple dollars. BTW - The sensitivity > was adjustable with a screw that would change the tension of the metal > strip. You can mount them in various orientations to get greater > sensitivity in each axis, though with intense vibration they may all go > off simultaniously. > > Enjoy! > --- Jay Are they small enough? This entire device should fit inside a 1 inch ID tube. The tube will lie horizontal and the sensitive axis should be perpendicular to the length of the tube. I'd like some kind of commercial sensor like this, but I thought about building my own ball-in-cage type. If I used 2 pieces of PCB held parallel about 1/2 inch apart with cross wires between them and a ball inside.... Problem I see is reliability, a little corrosion would make the sensor less reliable, then I'd have to look into gold plating on the wires and ball. -Denny -- http://www.piclist.com hint: The list server can filter out subtopics (like ads or off topics) for you. See http://www.piclist.com/#topics

> Can you define "bump" any better ? > > What frequency/repetition rate ? > > Can the sensor use anything else apart from its own state as > a reference ? > We'll see if my ISP has fixed my delay problem yet (note the original message took 3 days to get to the list). I don't have any hard numbers for G force and duration on the bump, but were talking about a ~2 lbs object being hit hard enough to move it 1/8 inch or so. As to frequency, one impact will set off a led blink routine lasting 5-10 sec, then the system resets and waits for another. Ignoring any/all impacts during that time. It would be best if this could be self contained. -Denny -- http://www.piclist.com hint: The list server can filter out subtopics (like ads or off topics) for you. See http://www.piclist.com/#topics

google for nessensor, it is a vibration sensor used in some alarm systems. I cant remember what principle they work on but they are pretty cheap and should be easily available wherever you are. If you have any probs getting them give me a yell, I'm not far from the main sales office in sydney. Cheers, JJ P.S save googling here is a link www.ness.com.au/catalogue/public/pages/Ness2003-4_catalogue_page_15.p df {Original Message removed}

> > I bought a cat toy that is a little ball, smaller than a golfball that has > two flashing LEDs. There is a small "vertical" wire soldered to the circuit > board and around it is a coil of wire. Normally the two don't touch but if > you tap the ball they touch. This triggers the flashing of the LEDs for the > next 30 seconds. > > This may not be sensitive enough for you because you can pick up the ball > and wave it around and it won't start to flash. It seems to take a sharp > movement to flex the coil. With the ball on the floor I can tap it with my > finger and it starts to flash. > > I play with it more than the cat does... Her favorite toy is a length of > 1/4" dowel rod. > > Rob Young I've seen these and thought about unsung something similar. But I was hoping to not have to build the little parts myself. Seems like a pain trying to get reliable behavior out of hand made springs. And I'd need at least a dozen and a couple hundred is possible. BTW.. My cat steals pens and pencils. -Denny -- http://www.piclist.com hint: The list server can filter out subtopics (like ads or off topics) for you. See http://www.piclist.com/#topics