Are they detecting heat? Or are they detecting something else? Is there a way to move so discreetly that a motion sensor wouldn’t detect your movements?
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Many detect warm things moving. Some use ultrasound, or radar. Mythbusters did an episode about fooling security systems, and found some methods that worked on the heat and ultrasound types: https://mythresults.com/episode59
A lot of the times basic ones just use a simple camera. If something has changed between picture 1 and picture 2 then that signifies movement.
Obviously if you wanted something super advanced you could use Lazer beams and detect if something has broken the Lazer signal
A lot of the times basic ones just use a simple camera. If something has changed between picture 1 and picture 2 then that signifies movement.
Obviously if you wanted something super advanced you could use Lazer beams and detect if something has broken the Lazer signal
Many detect warm things moving. Some use ultrasound, or radar. Mythbusters did an episode about fooling security systems, and found some methods that worked on the heat and ultrasound types: https://mythresults.com/episode59
A lot of the times basic ones just use a simple camera. If something has changed between picture 1 and picture 2 then that signifies movement.
Obviously if you wanted something super advanced you could use Lazer beams and detect if something has broken the Lazer signal
Many detect warm things moving. Some use ultrasound, or radar. Mythbusters did an episode about fooling security systems, and found some methods that worked on the heat and ultrasound types: https://mythresults.com/episode59
One of the most common motion sensors is PIR (passive infared). These are those sensors you see with a white plastic dome or visor strip for automatic lights and security systems. That white plastic acts as a lens. It focuses infrared light onto a sensor. That sensor has a lot of different sections. Its waiting to sense a rapid change in temp across 2 or more of those sections. It only looks for rapid changes to avoid a false alarm from an environmental temp change.
This leads to a few different methods of not tripping them.
One is called “slothing”. Its just moving extremely slow, like a sloth. The intent is to spread the temp changes you create on the sensor over longer time periods so the sensor treats them like background temp change. This technique works, but is a lot harder than you’d think. People are not very good at moving extremely slow for long time periods.
Another is shielding. A large piece of glass (glass is opaque in IR) or something ambient temperature is held up between you and the sensor. You can move faster this way, but anything peaking around the shield will trigger the alarm.
You can also stay in the “shadows”. This means you pretend the sensor is a flood light and you only move in the spots behind objects that would create a shadow. Basically figuring a path that keeps you out of sight of the sensor.
One of the most common motion sensors is PIR (passive infared). These are those sensors you see with a white plastic dome or visor strip for automatic lights and security systems. That white plastic acts as a lens. It focuses infrared light onto a sensor. That sensor has a lot of different sections. Its waiting to sense a rapid change in temp across 2 or more of those sections. It only looks for rapid changes to avoid a false alarm from an environmental temp change.
This leads to a few different methods of not tripping them.
One is called “slothing”. Its just moving extremely slow, like a sloth. The intent is to spread the temp changes you create on the sensor over longer time periods so the sensor treats them like background temp change. This technique works, but is a lot harder than you’d think. People are not very good at moving extremely slow for long time periods.
Another is shielding. A large piece of glass (glass is opaque in IR) or something ambient temperature is held up between you and the sensor. You can move faster this way, but anything peaking around the shield will trigger the alarm.
You can also stay in the “shadows”. This means you pretend the sensor is a flood light and you only move in the spots behind objects that would create a shadow. Basically figuring a path that keeps you out of sight of the sensor.
One of the most common motion sensors is PIR (passive infared). These are those sensors you see with a white plastic dome or visor strip for automatic lights and security systems. That white plastic acts as a lens. It focuses infrared light onto a sensor. That sensor has a lot of different sections. Its waiting to sense a rapid change in temp across 2 or more of those sections. It only looks for rapid changes to avoid a false alarm from an environmental temp change.
This leads to a few different methods of not tripping them.
One is called “slothing”. Its just moving extremely slow, like a sloth. The intent is to spread the temp changes you create on the sensor over longer time periods so the sensor treats them like background temp change. This technique works, but is a lot harder than you’d think. People are not very good at moving extremely slow for long time periods.
Another is shielding. A large piece of glass (glass is opaque in IR) or something ambient temperature is held up between you and the sensor. You can move faster this way, but anything peaking around the shield will trigger the alarm.
You can also stay in the “shadows”. This means you pretend the sensor is a flood light and you only move in the spots behind objects that would create a shadow. Basically figuring a path that keeps you out of sight of the sensor.
There’s three main types of motion-sensors:
1. Doppler radar (using microwaves)
2. Ultrasonic (technically also Doppler radar, but using high pitched sound)
3. Passive infra-red (PIR)
Microwave Doppler radar emits low-power microwave (radio) energy, an detects disturbances in the reflected energy. They are primarily sensitive to motion towards or away from the detector. They can detect motion down to a centimetre or so.
Ultrasonic emits high pitched sound, and again detects disturbances in the reflected sound. Although they are primarily sensitive to motion towards/away from the sensor, because sound bounces around a room, in practice they will often detect any motion. These will give false alarms if there’s much air motion, drafts etc, and cannot be used outside. They used to be popular intruder detectors 30+ years ago, but have gone out of favour since. Used in car alarms though.
PIR detects heat radiated by the body (think thermal camera), but they are far simpler. Owing to the way they are designed (with little segmented mirrors), they are primarily sensitive to motion across the field of view (and less sensitive to towards/away motion). If you wore thermally insulating clothes and/or draped yourself in a foil thermal blanket you may be able to evade detection from PIR, but not reliably!
Some systems use a combination of Doppler radar and PIR, to reduce false-alarms.
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