Post by thread:Cheap Accelerometers

For output and size, nothing beats Kynar film produced by AMP in Valley Forge PA. They have a demo device which is a 1/2" x 3" piece of film, laminated between two sheets of light mylar, and a neon bulb riveted on one end. You hold it between finger and thumb and wiggle, and the neon fires about ten times in each direction, causing an arc of orange flashes in a dark room. I used the stuff for sensitive microphones, hydrophones (buried in urethane) and motion detectors. It is not a static pressure detector, only works on derivatives. I have had comments in the past that my postings contain weird trailers. Could someone let me know if this problem has been fixed? John Shreffler New Directions

Firstly "Thanks to all who responded to this thread so far" Your Ideas have been an insperation. In fact I have now concluded that I probab;y don't actualy require an Accelerometer but a 3 DOF movment detector, I am trying to build a small device that I can attach to my snowboard that will sound a LOUD alarm if anybody tries to "Borrow" it without my permission. It will have a small keypad to arm/dis-arm it and must be about the size if a ciggarett packet. it will run of a 9V battery. I have most of the keypad and I/P O/P code sorted so far it's based on a 16c84. So if anybody has any ideas on motion dectection please let me know. It dosent have to be linear just digital will do. IE motion /no motion but the sensivtivity must be quite good. Thanks again for all the help so far ....... Cheers Peter ............

On Wed, 24 Sep 1997, Peter Baines wrote: > Firstly "Thanks to all who responded to this thread so far" Your Ideas have > been an insperation. In fact I have now concluded that I probab;y don't > actualy require an Accelerometer but a 3 DOF movment detector, I am trying > to build a small device that I can attach to my snowboard that will sound a > LOUD alarm if anybody tries to "Borrow" it without my permission. It will > have a small keypad to arm/dis-arm it and must be about the size if a > ciggarett packet. it will run of a 9V battery. I have most of the keypad > and I/P O/P code sorted so far it's based on a 16c84. So if anybody has any > ideas on motion dectection please let me know. It dosent have to be linear > just digital will do. IE motion /no motion but the sensivtivity must be > quite good. > > Thanks again for all the help so far ....... > > > Cheers Peter ............ > PTM: Make a small cage of wires that are insulated of each other. Three wires should be enough. Connect the to a sounder. Put a metal ball in the cage. When you move the cage, the ball rolls and makes new connections. -------------------------------------------------------------------------- PTM, spam_OUTpasi.mustalahtiTakeThisOuTutu.fi, .....ptmustaKILLspam@spam@utu.fi, http://www.utu.fi/~ptmusta Lab.ins. (mikrotuki) ATK-keskus/Mat.Luon.Tdk OH1HEK Lab.engineer (PC support) Computer Center OI7234 Mail: Turun Yliopisto / Fysla, Vesilinnantie 5, 20014 Pt 02-3336669, FAX 02-3335632 (Pk 02-2387010, NMT 049-555577) --------------------------------------------------------------------------

At 08:20 24/09/97 +0100, you wrote: >Firstly "Thanks to all who responded to this thread so far" Your Ideas have >been an insperation. In fact I have now concluded that I probab;y don't >actualy require an Accelerometer but a 3 DOF movment detector, I am trying >to build a small device that I can attach to my snowboard that will sound a >LOUD alarm if anybody tries to "Borrow" it without my permission. I have several suggestions. The traditional tilt switch is a mercury switch. It comprises a ball of mercury and some contacts. If it's tilted the mercury moves breaking the contact. The main disadvantage is that it only covers a small range of angles so you would need to stow your board the same way each time. Another neat trick is to use a spring and weight system, similar to those used in pinball machines to detect tilting. These are particularly sensitive to sudden movements. You need a piece of piano wire which is fixed at one end, and passing through a ring at the other. In the middle you attatch a sliding weight, and adjust it so the wire doesn't quite touch the ring. Any sudden movement and the piano wire touches the ring. I'll try and sketch it here... ____ . | |---------WWWW-----(-)- | | | ------+--+-------------------+----- This will detect motion along two axis, and two of them, along each side of a box for example, should detect acceleration along any axis. Main weakness is that they don't detect very small forces. Hope this helps, Keith. ------------------------------------------------------------ Keith Dowsett "Variables won't; constants aren't." E-mail: kdowsettKILLspamrpms.ac.uk or .....kdowsettKILLspam.....geocities.com WWW: http://kd.rpms.ac.uk/index.htm www.geocities.com/CapeCanaveral/Lab/8979

On 24 Sep 97 at 8:20, Peter Baines wrote: > Firstly "Thanks to all who responded to this thread so far" Your > Ideas have been an insperation. In fact I have now concluded that I > probab;y don't actualy require an Accelerometer but a 3 DOF movment > detector, I am trying to build a small device that I can attach to > my snowboard that will sound a LOUD alarm if anybody tries to > "Borrow" it without my permission. It will have a small keypad to > arm/dis-arm it and must be about the size if a ciggarett packet. it > will run of a 9V battery. I have most of the keypad and I/P O/P code > sorted so far it's based on a 16c84. So if anybody has any ideas on > motion dectection please let me know. It dosent have to be linear > just digital will do. IE motion /no motion but the sensivtivity must > be quite good. There's something like that built into my alarm clock - its a 2 part one - slides apart - one side is conventional quartz clock and 'normal' pip pip type alarm - other side is an 'industrial strength' - "747 at 10 metres" variety. Anyway, when you split it, the industrial strength alarm has a slide switch on it, and a short length of cord. Idea is - you hang it on a motel door, to warn of onexpected entry. I suspect the device is using the very loud piezo as both a mike and a sonalert - cuts down on parts. Its ultra-sensitive, there's absolutely no way you can remove it from door without triggering it. (it has a long attack envelope for the volume - otherwise it'd be impossible to disarm.) MikeS <mikesmith_ozNOSP*M.relaymail.net> (remove the you know what before replying)

> > On Wed, 24 Sep 1997, Peter Baines wrote: > > > Firstly "Thanks to all who responded to this thread so far" Your Ideas have > > been an insperation. In fact I have now concluded that I probab;y don't > > actualy require an Accelerometer but a 3 DOF movment detector, I am trying > > to build a small device that I can attach to my snowboard that will sound a > > LOUD alarm if anybody tries to "Borrow" it without my permission. It will > > have a small keypad to arm/dis-arm it and must be about the size if a > > ciggarett packet. it will run of a 9V battery. I have most of the keypad > > and I/P O/P code sorted so far it's based on a 16c84. So if anybody has any > > ideas on motion dectection please let me know. It dosent have to be linear > > just digital will do. IE motion /no motion but the sensivtivity must be > > quite good. > > Pasi Mustalahti wrote: > PTM: Make a small cage of wires that are insulated of each other. Three > wires should be enough. Connect the to a sounder. Put a metal ball in the > cage. When you move the cage, the ball rolls and makes new connections. > You can buy this type of tilt switch at many discount parts distributors. Check out: http://www.allcorp.com/sw008.html#TILT This is the All Ecectronics web page. They sell this switch for 50 cents. I think Marlin P. Jones also carries this switch but it is only in their catalog not on their web page: http://www.mpja.com/ Keith Keith D. Kotay Ph.D. Candidate Dartmouth College EraseMEkotayspam_OUTTakeThisOuTcs.dartmouth.edu http://www.cs.dartmouth.edu/~kotay

> LOUD alarm if anybody tries to "Borrow" it without my permission. It will > have a small keypad to arm/dis-arm it and must be about the size if a > ciggarett packet. it will run of a 9V battery. I have most of the keypad > and I/P O/P code sorted so far it's based on a 16c84. So if anybody has any > ideas on motion dectection please let me know. It dosent have to be linear > just digital will do. IE motion /no motion but the sensivtivity must be > quite good. > Try this: Take two concave glas circles. (Used in chem labs, don't know the fancy name). I used ones about 1" in diamiter. Put a drop or two of mercury on one and cover it with the other. Now you have a conductive liquid runing around in an enclosed space. Now you slip a couple of dozen contacts inbetween the two edges and glue everything shut. As this gets bumped and tilted it makes and breaks contacts like mad. I read this with a PC where I could dedicate 32 lines, but there must be an trick with resistors and A-D's that lets you get away with less. Or just put in only say 12 wires. Hook them up alternatly to + , input , gnd, input. Gives you six I/O's used and probably more than enough sensitivity. Keep scanning the pins and when it moves the bitpattern will change. Nic

Hi What about using a piezo electric cable or bi-morph element (available in the RS sensors section) or more cheaply, use a mercury based vibration sensor (like a tilt switch) these work in any orientation (3 DOF) and cost about £1 UKP. Tim At 08:20 24/09/97 +0100, you wrote: {Quote hidden}>Firstly "Thanks to all who responded to this thread so far" Your Ideas have >been an insperation. In fact I have now concluded that I probab;y don't >actualy require an Accelerometer but a 3 DOF movment detector, I am trying >to build a small device that I can attach to my snowboard that will sound a >LOUD alarm if anybody tries to "Borrow" it without my permission. It will >have a small keypad to arm/dis-arm it and must be about the size if a >ciggarett packet. it will run of a 9V battery. I have most of the keypad >and I/P O/P code sorted so far it's based on a 16c84. So if anybody has any >ideas on motion dectection please let me know. It dosent have to be linear >just digital will do. IE motion /no motion but the sensivtivity must be >quite good. > >Thanks again for all the help so far ....... > > >Cheers Peter ............ > > ------------------------------------------------------------------ Personal Web Pages: http://web.ukonline.co.uk/members/tim.kerby/ Email: tim.kerbyspam_OUTukonline.co.uk ------------------------------------------------------------------

On 26 Sep 97 at 19:02, Tim Kerby wrote: > At 08:20 24/09/97 +0100, you wrote: > >Firstly "Thanks to all who responded to this thread so far" Your Ideas have > >been an insperation. In fact I have now concluded that I probab;y don't > >actualy require an Accelerometer but a 3 DOF movment detector, I am trying > >to build a small device that I can attach to my snowboard that will sound a > >LOUD alarm if anybody tries to "Borrow" it without my permission. It will > >have a small keypad to arm/dis-arm it and must be about the size if a > >ciggarett packet. it will run of a 9V battery. I have most of the keypad > >and I/P O/P code sorted so far it's based on a 16c84. So if anybody has any > >ideas on motion dectection please let me know. It dosent have to be linear > >just digital will do. IE motion /no motion but the sensivtivity must be > >quite good. > > > >Thanks again for all the help so far ....... > > > > > >Cheers Peter ............ > > > ------------------------------------------------------------------ How about a Mercury Switch? Regards, Christof

Hi everybody ... Christof wrote: > > On 26 Sep 97 at 19:02, Tim Kerby wrote: > > > At 08:20 24/09/97 +0100, you wrote: ... > > >ideas on motion dectection please let me know. It dosent have to be linear > > >just digital will do. IE motion /no motion but the sensivtivity must be > > >quite good. ... How about a paltform with 2 or 3 mercury bubble switches (organized on an ortogonal structure). When arming the device you can read the current status of the switches, and them react to any change on taht staus. best regards Jorge F