motion activated led without use of microcontroller - Page 1
Forum section: electronics / beginners

author: dennisyuki
author_rank: Contributor
timestamp: May 21, 2013, 11:50:32 am
content: I wanted to build a motion actived LED light bar. Project specs are that when some on walks by the light bar the LEDs will light up and stay on for 20 secs, then shut off. I would like to build it without the use of a microcontroller. Is this a simple circut to build without a microcontroller. I searched google, but I cannot find a circuit that would work. maybe I am not using the right search words.Your help is appreciated.

author: Rerouter
author_rank: Super Contributor
timestamp: May 21, 2013, 11:55:29 am
content: you want to detect motion or more importantly presence? if presence you could use an infrared tranciever with a very high gain, this would generate a large signal whenever something increases the reflected beam, e.g. a person, this then gets fed into an op amp peak detector, and use that buffered peak to switch on or off your leds,

author: PA0PBZ
author_rank: Super Contributor
timestamp: May 21, 2013, 12:23:54 pm
content: Get yourself a PIR (Passive InfraRed sensor). They are very cheap, all you have to do is extend the active time to 20 seconds, either in the device itself or something external like a 555.

author: EEVblog
author_rank: Unknown
timestamp: May 21, 2013, 12:38:36 pm
content: Is this a bargraph? or just a single LED strip that goes on/off?

author: Paul Price
author_rank: Super Contributor
timestamp: May 21, 2013, 03:18:36 pm
content: Here attached is a most elegant solution I created quite a few years ago, modified for this golden age.

author: dennisyuki
author_rank: Contributor
timestamp: May 21, 2013, 08:48:43 pm
content: Quote from: Rerouter on May 21, 2013, 11:55:29 amI guess just presence. I am assuming that detecting motion is more involved and this is just basic sensing.your solution is interesting I will have to look more into the parts data sheets.Quote from: PA0PBZ on May 21, 2013, 12:23:54 pmI have heard of PIR and I think this is the route I want to go to. And I was figuring I would need a 555 somewhere in the project.Quote from: EEVblog on May 21, 2013, 12:38:36 pmI am thinking of a LED strip. A bar graph would be cool. I have seen tshirts that have LED bargraphs that react to music. That would be a project for another time.Quote from: Paul Price on May 21, 2013, 03:18:36 pmI have printed the schematic. It looks cool. I need to sit down and mull over it and see if it will fit my needs. Thanks for sharing.

author: quantumvolt
author_rank: Frequent Contributor
timestamp: May 21, 2013, 09:20:30 pm
content: What you need is as old as the cow and cost less then the burger:http://www.ebay.com/itm/Pyroelectric-Infrared-PIR-Motion-Sensor-Detector-Module-/270812987833Any local electronics / home alarm shop will have them.Detecting motion by capacitance is a big science project - what you want to to is to detect rapid changes in IR. Buy one working unit as ref, and build one based on the sensor only (can be bought separately). The schematic for the PIR amplifier and 555 based triggered delay circuits are all over the web ...

author: Paul Price
author_rank: Super Contributor
timestamp: May 21, 2013, 11:15:36 pm
content: If you just need a quick, cheap solution for motion detection and are not interested in learning electronics, then you can just go down to your local store and buy an infrared or ultrasonic motion detector that lights a lamp for 30-seconds to 2 minutes for just a few bucks.But if your are interested in electronics...With my circuit, you could replace the white LED with an infrared emitting LED salvaged from a discarded remote control, and swap out the photoresistive cell with a infrared phototransistor and the same circuit can be used with its detection beam being seen. You can find phototransistors in discarded home remote controlled equipment. Every VCR or discarded CD/DVD player has one and the rest of the circuitry provides the timing for a 5-Sec on period of the LED strip and the circuit use CMOS circuitry for minimal power use and short pulses to save battery power to light the infrared emitting LED.You could even use the highly amplified output of an infrared remote control receiver to feed into the point where the photoresistive cell is now.If your intention is to mainly learn about electronics, my circuit has many common interesting digital and analog devices such as a 555 timer used as master oscillator, two 7-stage binary counterss for creating delays, op-amps to amplify and act as a comparator, and a a dual D-FlipFlop that starts and stops alarm time counting intervals. It also demonstrates how to capture a particular count using the digital counters. so as to create precision digital long period timings, and shows the use of transistors to act as a switch to turn on your LED strip .