Help with a simple DC circuit for a complete novice - Page 1
Forum section: electronics / beginners

author: walsie
author_rank: Newbie
timestamp: December 21, 2020, 12:46:59 am
content: Hello everyone, im hoping you can guide me on a circuit i need to create.This may sound strange but the circuit is to illuminate an ornament from the inside. The circuit is already there which consists of a 2xAA battery pack powering a couple of LED's, but i want to add a DC power socket so i can power it from my home wall socket (mains) with a universal power supply.I have another ornament which has the full circuit and DC socket so i thought it was just a case of adding a DC PCB style power connector (5.5 x 2.1 jack socket), which in theory it is that simple, but when you have no idea what you are doing its rather confusing.I have compared the 2 circuits side by side, the only difference is that the circuit which already has the power jack socket has an extra 3 wires coming from it which im assuming is live/neutral/switch. However, there is also a tiny resistor which on one circuit is connected to the negative side of the battery pack, and on the other circuit is connected to the positive terminal of the batter pack. Now im totally confused.Ive included some pics of each circuit so you clever people can guide me on what i should do.

author: JohnnyMalaria
author_rank: Super Contributor
timestamp: December 21, 2020, 01:39:33 am
content: Have you consider something like this?https://www.ebay.com/i/284104213630?chn=ps&norover=1&mkevt=1&mkrid=711-213727-13078-0&mkcid=2&itemid=284104213630&targetid=4580771608074811&device=c&mktype=&googleloc=&poi=&campaignid=403204658&mkgroupid=1234751773358313&rlsatarget=pla-4580771608074811&abcId=9300377&merchantid=51291&msclkid=3159dce3328313a9b0cc833cceee9053

author: ledtester
author_rank: Super Contributor
timestamp: December 21, 2020, 02:03:26 am
content: This article explains why DC sockets have three terminals... if that's what you're asking about:https://electronics.stackexchange.com/questions/10731/wiring-a-dc-socket-why-three-pins

author: walsie
author_rank: Newbie
timestamp: December 21, 2020, 12:09:18 pm
content: JohnnyMalariathats a clever solution, however, i have 5 similar ornaments which are linked by a 3v power supply with a DC daisy chain cord so one power supply for all 5.Its just that one of the ornaments does not already have a built in DC socket, the other 4 do. So im looking to add a DC 5.5x2.1mm power socket (drill through the back, glue into position and wire up) but im confused about what wires go where, thinking i could just copy one of the others only to find that the resistor shown in the picture is connected to negative terminal in the battery pack but on the other its to the positive. Does this actually matter and im making it sound more difficult than it is?

author: walsie
author_rank: Newbie
timestamp: December 21, 2020, 12:19:18 pm
content: ledtesteri suspected that third pin was possibly for a switch circuit.Now on the ornament which already has the same kind of DC power socket it looks like both the negative and the 3rd (switch) pin are connected to the same pin on the batter pack on/off switch, its difficult to see exactly because of all the glue but im assuming it is. However, to me that wouldn't make sense because when the power is connected the on/off switch would work as it would be constantly on? or is the switch itself breaking the circuit.I really do apologise for my lack of knowledge. Im pretty handy at things usually but electronics baffle me.Once i get all the glue out of the way it should be clearer, its just that resistor being connected to positive on one ornament and negative on the one i want to modify thats confusing me - does it matter?by the way, im not using batteries because they only last a few hours, ornaments are really old and im guessing the bulbs are not led's but tiny halogens or something like that.

author: walsie
author_rank: Newbie
timestamp: December 21, 2020, 12:22:36 pm
content: perhaps someone could draw me a wiring diagram?- there will be 3 LED's which ive cut from an old set of battery powered Christmas lights (already know they work because ive replaced some of the lights in the other ornaments)- a battery pack (no batteries) with an on/off switch- 3 pin DC power socket (which turns the lights off even though the power is still connected