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The Projects Forum Working on an electronics project and would like some suggestions, help or critiques? If you would like to comment or assist others with their projects, this is the place to do it.

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  #1  
Old 06-26-2013, 05:23 PM
ImmortalPr1nce ImmortalPr1nce is offline
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Default PIR Motion Sensor Project

Ok so this is my first post. I layout circuit boards for a living but im a complete noob when it comes to making schematics so i thought maybe some of you pros could help. Basicly i want to make a motion detector using a PIR sensor. when tripped i want it to sound an alarm until reset. i would also like a low battery light and maybe a remote controlled on and off. Any and all help would be greatly appreciated.
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Old 06-26-2013, 05:43 PM
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Dodgydave Dodgydave is offline
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You can buy a ready made pir sensor , and attach a timer/tone generator (555) to the output, as for remote control again ready made modules are available what is your price range?
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Old 06-26-2013, 06:03 PM
ImmortalPr1nce ImmortalPr1nce is offline
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I really want it all to be on one board/ schematic (obviously remote would be its own). i would prefer to stay away from ready made if possible.
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Old 06-26-2013, 06:18 PM
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Your better getting the module sensor ready made rather than building your own, costs are far lower, as for all on one pcb its easy,
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Old 06-26-2013, 06:29 PM
elec_mech elec_mech is offline
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Welcome to AAC.

While I'm not overly familiar with PIR options, I can't recall seeing PIR sensors by themselves. More often than not, they come on a small board with basic circuitry to allow you use them right away. They're often so cheap, I won't think it would be worthwhile to attempt to get the sensor alone and design a driver circuit for it.

That said, you can add a set of female headers to your board and just plug the sensor into it. I've helped others use the Parallax PIR sensor which you can pick up at RadioShack if you're in the U.S. If space is an absolute premium, you could buy the PIR sensor, reverse engineer the small board, buy the components and desolder the PIR sensor itself to use on your custom board.

You can take a look at this thread to get you started on hooking up a PIR sensor. You can use a flip-flop to keep the alarm going once PIR sensor is tripped and until someone presses a reset button.

I haven't done a low battery indicator before, but I'm sure we can help you find something.

When you say remote control are you referring to a wired or wireless remote? If the latter, you can use a children's RC toy. Will depend on the range you want though.
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Old 06-27-2013, 11:57 AM
ImmortalPr1nce ImmortalPr1nce is offline
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digikey has some of the PIR sensors by them selves. but yes you both are right the pir with the board would probably be the best option. yes i was thinking flip flop for the alarm but am unsure on how to hook up the reset. as for the remote i was thinking almost like a car alarm key fob you point it at the unit push the button and it turns it on and off. again was thinking flip flop for this to would that work?
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Old 06-27-2013, 10:14 PM
elec_mech elec_mech is offline
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For the remote, another member recently found this. If we understand it correctly, you can set each channel to act as a momentary or latch switch. You could set up one channel as a latch to turn the circuit on and off and another as a momentary for the reset portion. If you want to keep it dirt simple, the on/off can be reset - turn the power off then on again to reset the circuit.

The simplest approach that comes to mind is an SCR. Once the PIR sensor trips, it will turn on the SCR which would be connected to your alarm. The SCR then remains on (and thus the alarm) until power is removed. I haven't used one of these myself, so perhaps someone else can suggest a part, but if not, I can research something for you.
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Old 06-28-2013, 04:31 AM
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Default PIR preamp example

This is from an old project. The PIR detector P/N is lost to history but it was a raw PIR in a TO-5 can with a window on top. Anyway, similar devices are likely available still.

These generate a SLOWLY changing, HiZ output with changes to detected body heat.

The circuit comprises a 2 stage AC coupled amplifier. The output (U3-7) swings slowly around in response to sensed heat. In this circuit, the output is fed into a window discriminator (HISENSE/ and LOSENSE/) which went to a microcontroller. The SENSITIVITY pot moved the high and low thresholds apart to set where the movement was enough to signal the code that motion was happening. Motion was defined as a voltage excursion in the high or low direction.

I don't remember much else about it except that I got stiffed on the project so quickly lost interest in archiving it - hence no BOM. .

EDIT:
I think the sensor was something like the Murata IRA-E700ST0 (Digikey) The circuit looks familiar..
All said, I agree with the others that an integrated sensor, off the shelf setup is pretty attractive..
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Old 06-28-2013, 12:01 PM
ImmortalPr1nce ImmortalPr1nce is offline
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Thanks everyone for the help so far. looking at that last schematic I realize this project is a bit above me. so the question is what would someone charge to make me a schematic? well 2, 1 for the main board and one for the remote (preferable in diptrace) that does what I want it to do? with little to no coding.
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Old 06-28-2013, 12:20 PM
elec_mech elec_mech is offline
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If you're okay using a ready-made PIR module, you won't need anything quite as involved as John's schematic - he's, in effect, showing you what is on the boards of the ready-made PIR sensors - hence the advice of the rest of us to stick with ready-made.

Are you trying to put this into a tiny-as-possible package or would a small package work? If the latter, use a ready-made PIR module and we can help you design the schematics to do what you want. This becomes dirt simple using a PIR module with an SCR and an alarm - three parts and a few passive components.

The battery indicator will add some parts, but I don't foresee that being complicated either. How do you want that to function? Green LED when battery is good, yellow for low, red for dead? Or just a red LED to indicate when the battery is low (thereby prolonging the battery life)?

Remote module will probably be the biggest item if you go with something simple and cheap. Even then, I'd guess you could fit everything into something the size of soup can (maybe a little bigger). Would this work?
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