Motion sensing can be quite effective when taking photographs of wildlife. But how can one be sure that the motion was at the center of the frame? A PIR sensor picks up motion in its entire viewing range. It’s not really something that can be aimed. But if you use two PIR sensors you can monitor a focused area for motion.
The trick is to use a logic circuit. By building an AND gate you can trigger based on motion in the area which is overlapped by both of the sensors. In this case the AND gate is built from a voltage divider. The outputs of the PIR sensors are connected above and below the divider’s connection to the photo trigger. Both have a protection diode, and the divider is tuned so that both PIR outputs must come one in order to raise the trigger input above the voltage threshold. So much for never crossing the streams.
[Ben] has a raccoon problem. It seems that it’s not uncommon for him to come face-to-face with a pesky raccoon in the middle of the night, in his living room. We think most people would solve the problem by preventing the raccoon from entering the home. But [Ben] just seems hell-bent on catching him. Most recently he’s added motion-sensing to a live trap which he installed…. in his living room.
So [Ben] has cat’s which that to roam at night. They have free range thanks to a cat door which the hungry pest has been exploiting. Apparently the masked robber has a taste for cat food and that’s what keeps him coming back. [Ben] has been using the cat dish as bait but up to this point the live trap hasn’t worked. You see the raccoon isn’t going inside to get the food, but reaches through the cage and pulls pieces out one at a time. The solution is to put up a solid surface around the cage, and hope that the motion sensor will get him this time. Although we’ve linked the most recent post above, you’ll want to page through his blog for the whole story.
Wouldn’t it be better to install some kind of automatic lock that only lets in the kitty?
Continue reading “Are you smarter than a raccoon?”
This light is a rather dim LED module whose purpose is to give you a very small bit of illumination when using the restroom at night. If you rely on it instead of using the overhead lighting in the bathroom, you’ll be able to find your way back to bed with your night-vision undisturbed.
[Fred] built the project as a way to learn more about using MSP430 microcontrollers. The protoboard seen above has a pair of female pin headers designed to accept an MSP430-PIR board, which uses the low-power microcontroller to monitor a PIR motion sensor. The chip can be reprogrammed and [Fred] did just that, using the USB dongle side of the eZ430-F2013 dev stick. Now when the sensor detects motion the chip first checks the light-dependent resistor on the protoboard to see if it’s dark in the bathroom. If so, it switches on the LED and sets a timer to shut if off again.
The system runs on a 9V battery, which is a bit under-powered for the 12V-spec’ed LED module. But [Fred] says the light it produces is just the right intensity.
[Brad] was asked by his Sister to design a motion-based alarm that would help her catch her son sneaking out of the house at night. Obviously this didn’t need to be a long-term installation so he decided to throw something together that is only active at night and can be battery-powered. What he came up with is a light-sensitive motion sensor that uses very little power.
He knew that an Arduino would be overkill, and decided to try his hand at using the Arduino to develop code for an ATtiny85. It has an external interrupt pin connected to the output of the PIR module, which triggers action when motion is detected. The first thing it does is to check the photoresistor via the ADC. If light levels are low enough, the buzzer will be sounded. [Brad] measured the current consumption of his circuit and was not happy to find it draws about 2.5 mA at idle. He spent some time teaching himself about the sleep functions of the AVR chips and was able reduce that to about 500-600 uA when in sleep mode. Now all he has to do is find a nice place behind the house to mount the alarm and there’ll be no more sneaking around at night.
If you’re trying to keep a tight leash on your own kids you could always make them punch the time clock.
This hardware is used to keep a computer monitor awake when there is motion in the room. The monitor displays important information for firefighter in the vehicle bay, but only needs to be on when they are getting ready to go out on a call. The solution is a simple one, a PIR sensor combines with a mouse for motion sensitive input. When the PIR sensor detects motion it causes a mouse button click via a 2N3904 transistor. Now the monitor will not waste power or have burn-in over the long term, but whenever someone is in the room it will be displaying the information that the emergency workers need to know.
[Muris] is pumping out the home lighting hacks. He developed this motion sensing module as an add-on to the IR switch we saw last week. There’s some kind of fuse box above his entry door and its white cover, which you see above, is where he mounted an IR distance sensor to detect movement and switch on the lights. The RC5 infrared protocol is used to transmit the necessary signal to turn the lights on, then when a set amount of time has passed it will turn them back off again.