Post by thread:[EE]:Tilt sensor

> Can anyone give me some recommendations on sensors for detecting tilting? I > hope to have a sensor that can detect when a car is being jack up, or towed. You could use a single accellerometer looking at the down component of gravit. However, that will be rather innaccurate at small tilt angles. A more sensitive system would use two or a dual axis accellerometer looking at the horizontal components of gravity. ***************************************************************** Embed Inc, embedded system specialists in Littleton Massachusetts (978) 742-9014, http://www.embedinc.com -- http://www.piclist.com hint: PICList Posts must start with ONE topic: [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads

On Fri, 17 May 2002, Olin Lathrop wrote: >> Can anyone give me some recommendations on sensors for detecting tilting? >I >> hope to have a sensor that can detect when a car is being jack up, or >towed. > >You could use a single accellerometer looking at the down component of >gravit. However, that will be rather innaccurate at small tilt angles. A >more sensitive system would use two or a dual axis accellerometer looking at >the horizontal components of gravity. Automotive applications use electrolytic tilt sensors. See my previous posting on this. Peter -- http://www.piclist.com hint: PICList Posts must start with ONE topic: [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads

How about a pair of simple mercury tilt-switches? -Neil. -----Original Message----- From: pic microcontroller discussion list [spam_OUTPICLISTTakeThisOuTMITVMA.MIT.EDU]On Behalf Of Alan B. Pearce Sent: Friday, May 17, 2002 6:17 AM To: .....PICLISTKILLspam@spam@MITVMA.MIT.EDU Subject: Re: [EE]:Tilt sensor Check out the Analog Devices accelerometer series, specifically the ADXL202 devices and their application notes. They will do this for you. -- http://www.piclist.com hint: PICList Posts must start with ONE topic: [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads -- http://www.piclist.com hint: PICList Posts must start with ONE topic: [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads

>How about a pair of simple mercury tilt-switches? >Check out the Analog Devices accelerometer series, >specifically the ADXL202 devices and their >application notes. They will do this for you. Well the ADXL devices have the advantage that when you turn the car off they can remember the current angle of the car (well your software would be doing this) and then if that changed before the car was started again then the alarm goes off. An allowance would need to be made for the car rocking in the wind or any other activities .... no lets not go there .... and it then means that it does not need manual calibrating if parked on a hill. -- http://www.piclist.com hint: PICList Posts must start with ONE topic: [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads

On Fri, 17 May 2002, Alan B. Pearce wrote: >>How about a pair of simple mercury tilt-switches? > >>Check out the Analog Devices accelerometer series, >>specifically the ADXL202 devices and their >>application notes. They will do this for you. > >Well the ADXL devices have the advantage that when you turn the car off they >can remember the current angle of the car (well your software would be doing >this) and then if that changed before the car was started again then the >alarm goes off. An allowance would need to be made for the car rocking in >the wind or any other activities .... no lets not go there .... and it then >means that it does not need manual calibrating if parked on a hill. As a general rule alarms operate when the car is not operating. Why would you store the 'previous' 'horizontal' level ?! There is a 'slight' price difference between the ADXL devices and electrolytic tilt sensors, also, the ADXL is more sensitive to impacts, shaking from wind, etc. Peter -- http://www.piclist.com hint: PICList Posts must start with ONE topic: [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads

>As a general rule alarms operate when the car is not >operating. Why would you store the 'previous' >'horizontal' level ?! You do not want to store the previous 'horizontal' level, you want to store the current level when you park, so if you do park on a hill you do not need to go and tweak some control to level the sensor. -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email listservKILLspammitvma.mit.edu with SET PICList DIGEST in the body

There's the original pinball machine tilt sensor - a pendulum (contact 1) in a wire hoop (contact 2) Mercury or mercury-alternative tilt switches, that might not be sensitive enough if the car is lifted only slightly to get in on a towing platform under the back wheels The problem you'll have is that you may not be parked on a horizontal surface. Whatever sensor you use has to take its reference from whatever the orientation the car is in and that you want it to stay in. A self-levelling gimbal housing the sensor that locks in place when the ignition goes off ? Perhaps an accelerometer on the whole body or IR sensors that measure the distance between the top of the tyre and the mudguard, or something like that which detects changes to the wheel heights as the suspension moves -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email .....listservKILLspam.....mitvma.mit.edu with SET PICList DIGEST in the body

On Mon, 20 May 2002, Alan B. Pearce wrote: >>As a general rule alarms operate when the car is not >>operating. Why would you store the 'previous' >>'horizontal' level ?! > >You do not want to store the previous 'horizontal' level, you want to store >the current level when you park, so if you do park on a hill you do not need >to go and tweak some control to level the sensor. Yes but why in eeprom ? Or did I misread your posting ? Peter -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email EraseMElistservspam_OUTTakeThisOuTmitvma.mit.edu with SET PICList DIGEST in the body

> -----Original Message----- > From: Alan B. Pearce [SMTP:A.B.Pearcespam_OUTRL.AC.UK] > Sent: Monday, May 20, 2002 9:39 AM > To: @spam@PICLISTKILLspamMITVMA.MIT.EDU > Subject: Re: [EE]:Tilt sensor > > >As a general rule alarms operate when the car is not > >operating. Why would you store the 'previous' > >'horizontal' level ?! > > You do not want to store the previous 'horizontal' level, you want to > store > the current level when you park, so if you do park on a hill you do not > need > to go and tweak some control to level the sensor. > I guess a potentiometer with a weighted arm hung off the end would do the trick? Regards Mike -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email KILLspamlistservKILLspammitvma.mit.edu with SET PICList DIGEST in the body

At 09:43 AM 5/20/02 +0100, Michael Rigby-Jones wrote: > > >I guess a potentiometer with a weighted arm hung off the end would do the >trick? Even better: one of those fairly inexpensive quadrature encoders from Bourns: 256 pulses per rev with ball bearing shaft. Reset an up-down counter to 0 when the ignition is turned off and sound the alarm when the count exceeds some pre-set value. Using a quadrature encoder and up-down counter helps ensure that swaying and wind gusts don't cause the counter to just climb to the trigger value. I'm not sure if the sensor from a mouse has enough resolution but that may also be worth a try. dwayne Dwayne Reid <RemoveMEdwaynerTakeThisOuTplanet.eon.net> Trinity Electronics Systems Ltd Edmonton, AB, CANADA (780) 489-3199 voice (780) 487-6397 fax Celebrating 18 years of Engineering Innovation (1984 - 2002) .-. .-. .-. .-. .-. .-. .-. .-. .-. .- `-' `-' `-' `-' `-' `-' `-' `-' `-' Do NOT send unsolicited commercial email to this email address. This message neither grants consent to receive unsolicited commercial email nor is intended to solicit commercial email. -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email spamBeGonelistservspamBeGonemitvma.mit.edu with SET PICList DIGEST in the body

Hi all, I have look at the Electrolytic sensors and also the ADXL202E accelerometer. The electrolytic sensors seems to be what I need. The only problem is, in my opinion, one need to invest some time to produce a tilt sensor module from it. The electrolytic sensors need to be powered by an ac and that means you need to have some sort of dc to ac converter ( not sure if it need a sine wave or a square wave). In addition you also need a controller to interpret the data from the sensor and perform calibration to the module (so does the accelerometer). And if I am not wrong, the electrolytic sensor is slower than the accelerometer. My intention is to get hold of a ADXL202E and try to construct a dependable tilt sensor module. Dependable here means that there should not be any false alarms from winds, thunder, kids sitting on top of the car and immune to automotive noise and must be rugged. The datasheet states that the ADXL202 should not be subjected to shock more than 1000g, and it continues saying - " Drops onto hard surfaces can cause shocks of greater than 1000 g and exceed the absolute maximum rating of the device. Care should be exercised in handling to avoid damage." Any advice, please? In addition, are there any accompanying notes that aids one in understanding those terms in the ADXL202E datasheet ? I am totally lost in those terms and metrics used. Appreciate if anyone can point me to any of these links of information describing these terms. Some terms here - Measurement Range 1 2g Cross-Axis Sensitivity 12 % Noise Density Acceleration (Any Axis, Unpowered for 0.5 ms) . . . . . . 1000 g Acceleration (Any Axis, Powered for 0.5 ms) . . . . . . . . . . 500 g Thanks and have a nice day. Rgds, Pang -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email TakeThisOuTlistservEraseMEspam_OUTmitvma.mit.edu with SET PICList DIGEST in the body

>Yes but why in eeprom ? Or did I misread your posting ? I never mentioned storing in eeprom. Perhaps it could have been read that way, but what I was meaning was an algorithm along the following lines. 1. remember current tilt angle when engine switched off (in suitable ram location) 2. allow settling time for tilt to change as occupants leave vehicle. This can probably be denoted by vehicle being locked. 3. allow a small rapid change in tilt value for short time to allow wind or draught from passing vehicles to rock car. This can probably be recognised readily by knowing the natural resonant frequency of the suspension system. 4. Sound alarm if long term slow rate of change in tilt (car being jacked/lifted for towing) or large amplitude natural resonance oscillation (car being attacked by joyriders/rioters etc). An accelerometer of the type made by Analog Devices would be ideal for doing something like this. -- http://www.piclist.com hint: To leave the PICList RemoveMEpiclist-unsubscribe-requestTakeThisOuTmitvma.mit.edu

>> You do not want to store the previous 'horizontal' level, you want to >> store >> the current level when you park, so if you do park on a hill you do not >> need >> to go and tweak some control to level the sensor. >> >I guess a potentiometer with a weighted arm hung off the end >would do the trick? Well it could do for a simple system I guess. See my previous posting on what I envisaged one could do with an accelerometer. Got a couple of these things, must give it a go :) -- http://www.piclist.com hint: To leave the PICList piclist-unsubscribe-requestEraseME.....mitvma.mit.edu

On Tue, 21 May 2002, Pang wrote: >Hi all, > >I have look at the Electrolytic sensors and also the ADXL202E accelerometer. >The electrolytic sensors seems to be what I need. The only problem is, in my >opinion, one need to invest some time to produce a tilt sensor module from >it. The electrolytic sensors need to be powered by an ac and that means you It is not so hard. You can use a square wave, f.ex. a PIC output pin, and read using two opamps per axis connected as precision rectifiers. Then you use four PIC A/D inputs to interpret the data. You can request application notes and recommended schematics etc from the makers. The questions about the ADXL sensor data sheet will be answered by others, I just want to add that the ADXL requires significant lowpass filtering for your application afaik. Car body noise and fast passing vehicles could do strange things to your system. The electrolytic sensors can be ordered with different time constants as needed. Peter -- http://www.piclist.com hint: To leave the PICList EraseMEpiclist-unsubscribe-requestmitvma.mit.edu

I've repaired some commercial car alarms etc, the standard system is very cheap and simple. Usually using a fine spring about 3cm long with a weight at the end. The other end is soldered on a piezo or in some systems the spring goes through a metal loop, so when it vibrates it touches the loop and provides a closed circuit. These work very good and are cheap and easy to make, you really can't bang the car, or jack it up at all (even horizontal jacking) without the alarm being triggered. -Roman Alan B. Pearce wrote: {Quote hidden}> > >> You do not want to store the previous 'horizontal' level, you want to > >> store > >> the current level when you park, so if you do park on a hill you do not > >> need > >> to go and tweak some control to level the sensor. > >> > >I guess a potentiometer with a weighted arm hung off the end > >would do the trick? > > Well it could do for a simple system I guess. See my previous posting on > what I envisaged one could do with an accelerometer. Got a couple of these > things, must give it a go :) -- http://www.piclist.com hint: PICList Posts must start with ONE topic: [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads

However you can drive by it real close and failry fast with a van or bus and have alarms. If the bus runs on shedule all hight there will be a crowd of fans looking for you (the designer of the alarm) fairly soon. About 5% of the installed car alarms are too sensitive and go off for no reason (thunder, bus, fat cat jumping on hood etc). Peter On Wed, 22 May 2002, Roman Black wrote: {Quote hidden}>I've repaired some commercial car alarms etc, >the standard system is very cheap and simple. >Usually using a fine spring about 3cm long >with a weight at the end. The other end is >soldered on a piezo or in some systems the spring >goes through a metal loop, so when it vibrates it >touches the loop and provides a closed circuit. >These work very good and are cheap and easy to >make, you really can't bang the car, or jack it >up at all (even horizontal jacking) without the >alarm being triggered. >-Roman > > >Alan B. Pearce wrote: >> >> >> You do not want to store the previous 'horizontal' level, you want to >> >> store >> >> the current level when you park, so if you do park on a hill you do not >> >> need >> >> to go and tweak some control to level the sensor. >> >> >> >I guess a potentiometer with a weighted arm hung off the end >> >would do the trick? >> >> Well it could do for a simple system I guess. See my previous posting on >> what I envisaged one could do with an accelerometer. Got a couple of these >> things, must give it a go :) > >-- >http://www.piclist.com hint: PICList Posts must start with ONE topic: >[PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads > > > -- http://www.piclist.com hint: PICList Posts must start with ONE topic: [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads

Any idea of how much these cost? Joe -----Original Message----- From: pic microcontroller discussion list [RemoveMEPICLISTEraseMEEraseMEMITVMA.MIT.EDU]On Behalf Of Ken Evans Sent: 21 May 2002 09:29 To: RemoveMEPICLISTspam_OUTKILLspamMITVMA.MIT.EDU Subject: Re: [EE]:Tilt sensor Also check out Memsic MXD2020, can take 50,000g. http://www.memsic.com ADXL202 can be easily broken. see below for more Ken ----- Original Message ----- From: "Pang" <RemoveMEklpangTakeThisOuTspamAICM.COM.MY> To: <EraseMEPICLISTspamspamBeGoneMITVMA.MIT.EDU> >I am totally lost in those terms and > metrics used. Appreciate if anyone can point me to any of these links of > information describing these terms. > > Some terms here - > > Measurement Range 1 2g 1g is the gravitational acceleration. If you point the accelerometer sensitive axis (see data sheet) down or up, you will get + and - 1g. Useful for calibration. > Cross-Axis Sensitivity 12 % The device in question is a dual accelerometer. Its 2 accelerometers measures acceleration in 2 axes nominally at right angles to each other. However each has a small reponse to acceleration along the direction (axis) at right angles to its own axis - cross axis sensitivity. > Noise Density residual noise expressed in spectral terms. Can be reduced by suitable low pass filter. > Acceleration (Any Axis, Unpowered for 0.5 ms) . . . . . . 1000 g beyond this the device will be permanently damaged. ie the silicon breaks ! > Acceleration (Any Axis, Powered for 0.5 ms) . . . . . . . . . . 500 g as above. {Quote hidden}> > Thanks and have a nice day. > > Rgds, > Pang > > -- > http://www.piclist.com#nomail Going offline? Don't AutoReply us! > email RemoveMElistservKILLspammitvma.mit.edu with SET PICList DIGEST in the body > > > -- http://www.piclist.com hint: To leave the PICList piclist-unsubscribe-requestSTOPspamspam_OUTmitvma.mit.edu -- 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

I remember seing somewhere on the ADXL202 costing some USD12. As for memsic, ahem....... MXD2020A/B, MXR2500AL, MXA2500AL all cost USD14.50. Minimum quantity order is 85 pieces and then there is the minimum order value at USD500. ( quotation from local supplier ) Even if I managed to get some samples from them, this product will be difficult to sell due to the price. Ideas from earlier posting suggest using encoders and also ball bearing potentiometer. But having difficulty getting local supplier for these parts. have a nice day. Rgds, pang ----- Original Message ----- From: "Joe McCauley" <spamBeGonejoe.mccauleySTOPspamEraseMETCD.IE> To: <KILLspamPICLISTspamBeGoneMITVMA.MIT.EDU> Sent: Thursday, May 23, 2002 11:31 PM Subject: Re: [EE]:Tilt sensor > Any idea of how much these cost? > > Joe > > {Original Message removed}

On Tue, 4 Jun 2002, Pang wrote: >I remember seing somewhere on the ADXL202 costing some USD12. As for memsic, >ahem....... >MXD2020A/B, MXR2500AL, MXA2500AL all cost USD14.50. Minimum quantity order >is 85 pieces and then there is the minimum order value at USD500. ( >quotation from local supplier ) > >Even if I managed to get some samples from them, this product will be >difficult to sell due to the price. Ideas from earlier posting suggest using >encoders and also ball bearing potentiometer. But having difficulty getting >local supplier for these parts. If you still haven't found what you are looking for I'd look into building the items locally. Surely you have inexpensive subcontractors. Electrolytic tilt sensors are relatively simple to design and build if the required precision is low. The only trick is the electrolyte and here a chemist will help. You get what yuo pay for ... Peter -- http://www.piclist.com hint: To leave the PICList EraseMEpiclist-unsubscribe-requestEraseMEmitvma.mit.edu

> >I remember seing somewhere on the ADXL202 costing some USD12. As for > >memsic, ahem....... MXD2020A/B, MXR2500AL, MXA2500AL all cost > >USD14.50. Minimum quantity order is 85 pieces and then there is the > >minimum order value at USD500. ( quotation from local supplier ) > > > >Even if I managed to get some samples from them, this product will be > >difficult to sell due to the price. Ideas from earlier posting > >suggest using encoders and also ball bearing potentiometer. But > >having difficulty getting local supplier for these parts. ST have released a device called the LIS2L01, dual axis 1g, 30Hz. Find it from http://eu.st.com/stonline/index.shtml Looks like it might be cheaper but I don't know the price. -- Brent Brown, Electronic Design Solutions 16 English Street, Hamilton, New Zealand Ph/fax: +64 7 849 0069 Mobile/txt: 025 334 069 eMail: @spam@brent.brown@spam@spam_OUTclear.net.nz -- http://www.piclist.com hint: To leave the PICList spamBeGonepiclist-unsubscribe-requestKILLspammitvma.mit.edu