Battery powered PIR LED light strip with timer - Page 1
Forum section: electronics / beginners

author: smh
author_rank: Newbie
timestamp: November 12, 2023, 02:43:24 am
content: Hello everyone,First just a small bit about me - I'm from the UK and I'm a mechanical engineer spending most of my time designing jigs and fixtures at work, in my spare time I get sucked into projects at home mostly making use of my FDM and resin 3D printers. I have a basic knowledge of electronics but really the last time I touched on it properly was at uni over ten years ago, and at college 8 years before that. I try my best to research things I dont know how to do, watching youtube, reading forums, using google, the usual, because learning is the fun part and my autism usually requires me to go down rabbit holes of wanting to know way more than I actually need to.My latest project has evolved to a point that I really am not sure if a) I'm doing it right/efficiently or b) if what I have done will even work, I just feel like I'm heading down a rabbit hole and have some extreme inefficiencies in what I have come up with so far. So I was hoping some willing people of the community would see what I've done and just give some helpful advice please?To describe it - I am designing and have part made a light up fairy skeleton frame that I want to be portable and not tied down to a mains socket (its a christmas present for someone who really loves this sort of design). Imagine a picture frame (3D printed of course), inside is a skeleton with wings pinned to the backboard (also 3D printed and painted), also built into the frame is a PIR motion sensor that is part of an RGB LED strip light system. The PIR is mounted to the front of the frame border and the LED light strips will wrap around the inside of the frame border so the lights point towards the skeleton hopefully lighting it up real nice. So, this project started off as an idea that in my head sounded pretty simple, just some LED lights plugged into a battery (20,000mAh) that would light up whenever someone walked past the frame. However I quickly came up to the first hurdle....when the lights were not on, the PIR didn't draw enough power from the battery and after a time (around 30 seconds) the battery would auto-off, and after this point the PIR would not activate again without first hitting the push switch on the battery (the battery is essentially a powerbank btw with a powerbank management board built in). So to tackle this I did some searching online and found a few suggestions but the one that seemed to be most reasonable was to buy a USB monitor and modify it a little (involving soldering a couple of 200ohm resistors in parallel over the USB output contact points) to essentially keep a constant minimum draw on the battery to stop it from auto turning off. OK so it does contribute to running the battery down, but it works and the draw down on the battery isnt ridiculous (V draw is 5.1V so current draw is ~50mA with the resistors soldered in place). I left it plugged in without activating the LEDs and it drained the battery in about 5 days. This means theres quite a bit of draw elsewhere, the lit up display showing the Vin and maybe the heat on the resistors? (its not dangerously hot, just warm) must add to the drain. After this test, I put the battery on charge back to 100%, and came across another hurdle. Once the battery died on empty, everything connected also powered down. Even though I charged the battery back to full, the lights wouldnt turn on. The "always on" usb monitor had turned off and remained off, and the only way to intiate it again is to press the push switch on the battery circuit board. This is a problem because the battery and board are going to be mounted into the back of the frame and not accessible unless a cover is unscrewed and the battery pulled out. So I desoldered the tiny push switch that was mounted to the board, and instead fitted another push button with a length of cable so that I can mount it through a hole in the side of the frame. This by the way may also be used to turn the entire system on and off should it be required to disconnect the battery.Anyway, for info, the PIR/LED control circuit is set up from the factory so that it works on a selectable timer, 4 times to be precise, 38/75/150/300 seconds, so once activated the LEDs will come on for the chosen time and then turn off again until the PIR is activated again. This seemed ok to me at the time, but it now bugs me that it cant be actived for longer. So I started looking into making my own PIR with delay that I can set myself. The circuit board that came with the LED strip lights has the PIR and LED colour management built into it, so if I made something myself my thinking is that I would need provision for both those things.I also do like the idea of a timer but I would like to choose the time myself, so I thought about using a Trigger timer module that would activate when the PIR is triggered.I'm not so good at drawing standard circuit drawings, so I have included an image of how I think everything would be connected up and images of each of the circuit boards/components in this project. I also added a picture of the framed skeleton idea in a draft position that made me think this would be a good idea to delve into in the first place. Each board has its own selection of resistors, capacitors and transistors (and other components), so if I just made my own board with everything required on it, I'm not sure I would know how to tell what I do and dont need to keep.All I wanted was some portable pretty lights for the skeleton frame I designed haha, but my ambition went a bit wild.Apologies that this post is so long, but I tried to include as much detail as I could so anyone has a chance of giving me some helpful advice of making this work (or not if my requirements are just unobtainable).Thank you so much in advance.SophieSkeleton light circuit.pdf(146.45 kB - downloaded 91 times.)

author: jwet
author_rank: Frequent Contributor
timestamp: November 13, 2023, 02:39:29 pm
content: I feel your pain. The effect is pretty cool, dark but cool.Here is what I would do. All on amazon for about $35. Get a 12v Sealed Lead Acid battery. A 7 amp hour cell is about $20 and once bucked down with a switching power supply will give you something like 15 amp hours or capacity at 5V/usb. Get a switching supply that will take in 12v and make 5v, these are about $8 for a 3 amp one. This would work fine. Finally buy a small charger that you can charge the battery with. These batteries are often used in Childrens' ride on toys, anything that puts out about an amp will charge the battery over night. Wire it up.Have fun. You can PM me if you need more details.