Post by thread:[PICLIST] [OT] Crocking Frog, People sensor

OK, their is a 100 ways to do this, but I don't want to re-invent the wheel. Are their any reference designs for something like the crocking frog that makes noise when someone walks in front of it? Are they using a photo-resistor and sensing change with a low pass filter? Are they using a photo diode? Photo Transistor? If so, how do they avoid total saturation? Best regards, Giles _________________________________________________________________ Get your FREE download of MSN Explorer at http://explorer.msn.com/intl.asp -- http://www.piclist.com hint: PICList Posts must start with ONE topic: [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads

Giles, Don't you mean 'croaking' frog? :') Either way, I haven't seen any. Regards, Jim On Mon, 20 August 2001, Giles Honeycutt wrote: {Quote hidden}> > OK, their is a 100 ways to do this, but I don't want to re-invent the wheel. > Are their any reference designs for something like the crocking frog that > makes noise when someone walks in front of it? Are they using a > photo-resistor and sensing change with a low pass filter? Are they using a > photo diode? Photo Transistor? If so, how do they avoid total saturation? > > Best regards, > Giles > > _________________________________________________________________ > Get your FREE download of MSN Explorer at http://explorer.msn.com/intl.asp > > -- > http://www.piclist.com hint: PICList Posts must start with ONE topic: > [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads spam_OUTjimTakeThisOuTjpes.com -- http://www.piclist.com hint: PICList Posts must start with ONE topic: [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads

Jim, Well, yes. I was consistent! Giles {Quote hidden}>From: James Paul <.....jimKILLspam@spam@JPES.COM> >Reply-To: pic microcontroller discussion list <PICLISTKILLspamMITVMA.MIT.EDU> >To: .....PICLISTKILLspam.....MITVMA.MIT.EDU >Subject: Re: [PICLIST] [OT] Crocking Frog, People sensor >Date: Mon, 20 Aug 2001 08:33:04 -0700 > > Giles, > > Don't you mean 'croaking' frog? :') > Either way, I haven't seen any. > > Regards, > > Jim _________________________________________________________________ Get your FREE download of MSN Explorer at http://explorer.msn.com/intl.asp -- http://www.piclist.com hint: PICList Posts must start with ONE topic: [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads

It sounds to me as though you've got the basic idea. Use a CDS cell or phototransister in a configuration where it outputs a voltage corresponding to light level. (simplified) This voltage level goes two places 1) into a diode/capacitor high pass filter which then leads to an opamp 2) through a diode into the other opamp input The output of the opamp is the derivative of the signal, ie how fast the signal is changing. A fast change (from light to dark) results in a high voltage, where a slow change results in very little voltage. A change from dark to light is a high voltage in the opposite polarity. This can go directly to a schmidt trigger. Saturation is not an issue if you pick the right components for the light levels you're expecting, and even then it doesn't matter much. If the signal is steady, the charge on the cap is equal to the signal from the light sensor, and the opamp has a difference of 0 to multiply. This is the case whether the sensor is saturated or not. If the sensor is saturated, then the light can change dramatically within the range of saturation and not trigger the device, but that is a simple problem of determining reasonable light levels to design for. -Adam Giles Honeycutt wrote: {Quote hidden}> OK, their is a 100 ways to do this, but I don't want to re-invent the > wheel. > Are their any reference designs for something like the crocking frog > that > makes noise when someone walks in front of it? Are they using a > photo-resistor and sensing change with a low pass filter? Are they > using a > photo diode? Photo Transistor? If so, how do they avoid total > saturation? > > Best regards, > Giles -- http://www.piclist.com hint: PICList Posts must start with ONE topic: [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads

The LED is sometimes there to act as a light "bias", so the circuit can be made more sensitive to ambient light. Light from the LED can be adjusted so that the usual light input causes the CdS cell to adjust its resistance such that (in series with a resistor) it produces some median voltage, like +2.5 volts. Then even small changes in ambient light can cause the circuit to produce a CHANGE of output signal that can trigger the desired activity. This CHANGE is generally measured by having a capacitor from the output coupled to a resistor tied to ground. Any AC change will impress itself on the ground referenced resistor. This signal is monitored, and when it exceeds a certain value a trigger signal is produced. A cheaper way to achieve the same end is to make the CdS series resistance variable. Cheaper but not better. To save a few pennies some of these "extra" features are left out of the final product, but the places for these components are still there on the pc boards. Fr. Tom McGahee {Original Message removed}

Adam, From what I am thinking, a op-amp would be a battery drain unless I use a high dollar low current device. Perhaps coupling the raw signal (from what ever) to a np cap directly into a port pin of a sleeping PIC. Wake on change and... Sounds too easy and cheep... A photo-transistor... If I use a high value resistance on the collector, it would limit the current draw. Or on a CDS I see one in the Allied catalog with a range of 100K - 10Meg... That is a little extreme, what is the input impedance of a PIC input.... Guess it is time to play and see what I can do.. I am trying to find the trip voltages for a PIC input and current leakage... Ok current leakage is 1 uA plus or minus. Now the trip voltage, looks like 0.15VDC & 0.85XVDD. Too large a range for passive AC coupling.. I will get back to this later when I have more spare time. Best regards, Giles {Quote hidden}>From: "M. Adam Davis" <EraseMEadampicspam_OUTTakeThisOuTUBASICS.COM> >Reply-To: pic microcontroller discussion list <PICLISTspam_OUTMITVMA.MIT.EDU> >To: @spam@PICLISTKILLspamMITVMA.MIT.EDU >Subject: Re: [PICLIST] [OT] Crocking Frog, People sensor >Date: Mon, 20 Aug 2001 21:30:48 -0400 > >It sounds to me as though you've got the basic idea. > >Use a CDS cell or phototransister in a configuration where it outputs a >voltage corresponding to light level. > >(simplified) >This voltage level goes two places >1) into a diode/capacitor high pass filter which then leads to an opamp >2) through a diode into the other opamp input > >The output of the opamp is the derivative of the signal, ie how fast the >signal is changing. A fast change (from light to dark) results in a >high voltage, where a slow change results in very little voltage. A >change from dark to light is a high voltage in the opposite polarity. >This can go directly to a schmidt trigger. > >Saturation is not an issue if you pick the right components for the >light levels you're expecting, and even then it doesn't matter much. > >If the signal is steady, the charge on the cap is equal to the signal >from the light sensor, and the opamp has a difference of 0 to multiply. >This is the case whether the sensor is saturated or not. If the sensor >is saturated, then the light can change dramatically within the range of >saturation and not trigger the device, but that is a simple problem of >determining reasonable light levels to design for. > >-Adam > > > > >Giles Honeycutt wrote: > >>OK, their is a 100 ways to do this, but I don't want to re-invent the >>wheel. >> Are their any reference designs for something like the crocking frog >>that >>makes noise when someone walks in front of it? Are they using a >>photo-resistor and sensing change with a low pass filter? Are they >>using a >>photo diode? Photo Transistor? If so, how do they avoid total >>saturation? >> >>Best regards, >>Giles > >-- >http://www.piclist.com hint: PICList Posts must start with ONE topic: >[PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads > > _________________________________________________________________ Get your FREE download of MSN Explorer at http://explorer.msn.com/intl.asp -- 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

Ray Gawronski wrote: > > Has anyone thought of using pyro detectors. These are the detectors used in > the outside security lights when they detect motion. The detection circuit > in these lights is low voltage and probably could be used. This is a great idea! I have a heap of faulty PIR units from alarm systems we used to sell, they are an RF unit and they fail regularly but I believe the PIR sensors themselves are all ok. Does anyone have info on connecting a PIR sensor to a PIC?? This would be great for devices or lighting systems that activate when you enter the room, etc. A great use for a PIC. :o) -Roman -- http://www.piclist.com hint: The PICList is archived three different ways. See http://www.piclist.com/#archives for details.

part 1 1191 bytes content-type:text/plain; (decoded 7bit) > Does anyone have info on connecting a PIR sensor > to a PIC?? This would be great for devices or > lighting systems that activate when you enter > the room, etc. A great use for a PIC. :o) > -Roman I use this for a battery-operated indoor application. It has very low power requirements (140uA @ 5V). The 5V supply comes from a PIC pin which turns the PIR off with a logic "0" after the PIR has woken the PIC from sleep. The sensors are from Murata. A proper Fresnel lens is essential - the response to PIR in the low Hz is far better than with no lens and the range (7-8 metres) is around 10 times greater. There are more sophisticated circuits in security lights, based on quad amps like the LM324. I've no need for that as occasional false triggering is no big disadvantage in my application, but there are ultra-low power around that could replace the standard type One improvement I'd like to make to this circuit is a self-settling function. Replacing the trimpot with a fixed RC filter that responds quickly to (relatively) fast wave bumps such as caused by a body but ignores drafts or increasing/decreasing sunlight part 2 4202 bytes content-type:image/gif; (decode) part 3 131 bytes -- http://www.piclist.com hint: The PICList is archived three different ways. See http://www.piclist.com/#archives for details.

Roman.B wrote: .......... >Does anyone have info on connecting a PIR sensor >to a PIC?? This would be great for devices or >lighting systems that activate when you enter >the room, etc. A great use for a PIC. :o) I mentioned using PIR a couple of days ago. Yesterday, I received my order from Hostfelt Electronics with the PIR module. It's an AMP PIRM180-200 module - $5.95/ea, Hostfelt P/N 10-110. Small device, 1.5"x1"x1.3". 180 deg field of view, high beam out to 20 feet, and low beam to 10 feet. 5v @ 2 mA, with both digital **and** analog outputs. Once I get a chance to play with it, I'll report back, but looks great. - dan michaels http://www.oricomtech.com ========================== -- http://www.piclist.com hint: The PICList is archived three different ways. See http://www.piclist.com/#archives for details.

> Where can I purchase and Fresnel lens for a PIR detector. I > am trying to improve the range of an X10 Hawkeye motion > detector(MS12A). > Ray My Fresnels come from local companies that supply security systems such as burglar alarms. The 3 I've contacted in the past have always had Fresnels in stock, at a reasonable price ($1 or so), and importing larger quantities from Asia would be no problem. You may find them at retailers like RadioSpares or Digikey, but expect to be outraged by the price. Either that or find out where old security lights go to die - perhaps you have a large service centre in your area that you could suck up to (you'd be surprised what goes in the bin !!!) . -- http://www.piclist.com hint: The PICList is archived three different ways. See http://www.piclist.com/#archives for details.

Peter, I like your creativity, that is an interesting way. Still I am wondering about a battery operated system. I don't think the self-heated would be low current. The security system methode is intersting, but again, I think they would drain a battery. I would like to find something that could wake a PIC from sleep with ultra low current for sensing. I plan to play with some photo transistors, and some photo resistors. I wory about staturation of the photo-transistors, and wory about the small swing of the photo resistors. Time to tinker. Best regards, Giles > >I have just discovered that a self heated thermistor can detect people and >large moving objects as long as they move some air past it. This should >work fine if there are no fans (or wind) blowing into it. > >Peter _________________________________________________________________ Get your FREE download of MSN Explorer at http://explorer.msn.com/intl.asp -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email KILLspamlistservKILLspammitvma.mit.edu with SET PICList DIGEST in the body

Peter L. Peres wrote: > > > I would like to find something that could wake a PIC from sleep with > > ultra low current for sensing. > > Well, if you want real low power, then you have to rely on something that > your quary produces plenty of. That would be mass (step-on mat), noise, > air movement, and electrical field disturbance (large conductive blob vs > non conductive air). IR radiation for a PIR will be low but it is well > known that it works. Good old fashioned normally-open contacts sound ideal for zero-power sensing. Many pressure mats are this type, also reed relay/magnet or microswitches. As a more high tech alternative, maybe a piezo sensor which uses zero-power but can still generate a pulse from some mechanical movement. :o) -Roman -- http://www.piclist.com hint: To leave the PICList TakeThisOuTpiclist-unsubscribe-requestEraseMEspam_OUTmitvma.mit.edu