Simple help required - motion/vibration sensor for LED circuit. - Page 1
Forum section: electronics / beginners

author: simon_h
author_rank: Newbie
timestamp: September 22, 2025, 12:49:32 pm
content: This is for a airsoft project so space is very limited.I have 4 3.2 forward voltage LED's with appropriate resistors to allow me to use either a 7.4v or 11.1v lipo battery, I would really like to add a movement/motion sensor so that if the replica is motionless then power is stopped, but when it is picked up the LED's light up again.I have no idea where to start - for ease these are two different replicas hence the two different batteries.many thanks in advanceSimon

author: voltsandjolts
author_rank: Unknown
timestamp: September 22, 2025, 01:18:18 pm
content: Simplest solution would be a motion sensor likethisorthisand a 555 re-triggerable monostable to drive the LED.Or DIY:https://electronics.stackexchange.com/questions/13071/accelerometer-switch-to-trigger-led-fadeThisseems to be a ready-made module using the above sensor. A bit big, but you could chop the relay off. Have a look for similar on Alixepress, they are normally good for cheap pre-made modules.Otherwise, you would probably need an accelerometer IC and a microcontroller to read it and switch the LEDs as appropriate. I guess you would need someone to help you with that, although arduino platform is quite accessible and might have something ready-to-go.

author: simon_h
author_rank: Newbie
timestamp: September 23, 2025, 01:39:12 pm
content: Thanks for that - I think I can make that work

author: RJSV
author_rank: Super Contributor
timestamp: September 24, 2025, 05:34:46 am
content: Using 555 is good. I just don't like'm, but that's my bugaboo.I just rather be enjoying design with TTL 7474 dual latch, or even just connecting a pair of NOR gates or NAND pair,...explicit flip-flop using two out of the four in an IC package.The 555 is very versatile, but then you're faced with decisions, which of the literally hundreds of applications and unique circuits, which is why it's so popular. (I just never understood the timer IC modes of connection, in full).Advantage of 555 is the analog ramps and other analog characteristics, when you need analog portions for a timer (ramp).If forced, I would prefer to only generate the oscillating clock, and go with TTL or CMOS family logic gates. Especially if I have to explain or teach the '555 as it applies to my particular circuit:"Well, I copied the circuit out of a 555 Timer book, so it should work."Going the route, of 'least number of IC's' introduces more subtle complexities...often nice on the budget, but an individual might use 3 ICs versus 5 or 6,...saving $3 dollars and creating an inscrutable tricky circuit. In my opinion.

author: Terry Bites
author_rank: Super Contributor
timestamp: September 24, 2025, 08:33:35 am
content: I just don't like'm either because they are a jack of all trades and master of none.The inner workings of the 555 are not complicated.It is a "window comparator," a flipflop and a transistor switch.

author: RJSV
author_rank: Super Contributor
timestamp: September 25, 2025, 04:28:20 am
content: Specifically, (thanks to a reader here), the 555 in many repeat pulse situations will have a first pulse or delay, that is noticably different, from the chain of pulses.Charging the cap. up from zero volts, in the first timing, but then subsequent pulses ramp up from 1.1 volts, and so the repeating pulses are shorter, due to less ramp time spent. Not exactly, but something similar to that.