LED's, Circuit Boards, and Buttons. Oh My! - Page 1
Forum section: electronics / projects

author: gohi777
author_rank: Newbie
timestamp: January 17, 2019, 04:02:43 am
content: So I am currently working on a big project, and I'm having some issues with the placement of some properties. I am working on a circuit board from a vape that is roughly the size of a quarter. I have two main issues currently: I need a button bypassed with wires to connect to a different button, and I need an LED moved. The button has to be pressed in different sequences for different results, and the led is multicolored and changes in result to these button presses. My main concern is that I will accidentally solder something I shouldn't, or will ruin the circuit by introducing something foreign. I have included linked photos, and would very much appreciate any help that can be provided. I also would like to note that I have other LEDs which I could try to replace the current one with. How should I go about accomplishing my goals? Thanks.https://imgur.com/a/z46ZAnB

author: bson
author_rank: Unknown
timestamp: January 18, 2019, 04:04:38 am
content: The first step would be to reverse engineer the board into a schematic, make your changes to the schematic, and then consider how to update the existing PCBs. Different LEDs have different forward voltage drops and current vs brightness, and multi colored ones will likely require additional circuitry to drive. So you may find you need to make an entirely new PCB. Fortunately there might be enough space in the enclosure for a slightly more complex board - the existing one has quite a bit of unused surface area.

author: gohi777
author_rank: Newbie
timestamp: January 18, 2019, 03:56:31 pm
content: Bson, I appreciate the suggestion, but I think I need to elaborate on my original problem. First off, I would like to make clear that I am not a great electrician. I understand basic concepts, but I can be very hesitant when trying new methods. Secondly, when I was talking about bypassing the button and LED, I was asking how to tell where the correct contact points were, so that I may be able to solder wires to them, leading off to another button. Similarly with the LED, I would very much like to be able to rip out the existing led, and connect a new one with a distance of wire, but I have no clue what type of LED I would need, as well as if doing so would ruin the entire circuit. I feel confident that bypassing the button could work, but I am unsure about the LED. How can I figure out where to connect wires to do this, and would this even work? Thank you.

author: Buriedcode
author_rank: Super Contributor
timestamp: January 18, 2019, 04:09:15 pm
content: To figure out where the switch and LED connections go, you would at the very least need a continuity tester which almost all multimeters have. However, if you're new to all this, given the size of the board, soldering wires to the correct points - perhaps even to the button and LED pads on the PCB - is quite fine work, and requires reasonable soldering experience.Removing the original LED - which looks to be a 1210 RGB LED (three LED dies) package or perhaps a bicolour ~(two LED dies on the same package) would require hot-air work.Possible? Yes. Doable for a beginner? unlikely. And with hot-air there is quite a high chance of desoldering more than just the button and LED. A small PCB heated up enough to allow removal of the LED would most likely melt almost all the solder on the board, meaning all the components will be sitting on molten solder - floating on top, and very easily moved.If you have several of these boards to practice on, that'll help. You might be able to buy up replacement boards from aliexpress or something, I imagine they would be pretty cheap.

author: gohi777
author_rank: Newbie
timestamp: January 19, 2019, 03:11:32 am
content: Thank you for your insight Buried code. I can probably make this work by leaving the LED alone, but bypassing the button is a must. Without access to a multimeter, is there any way to figure where to solder in the wires? I say this because there are four connection points, and I don't know which ones to solder to. Thanks.

author: Buriedcode
author_rank: Super Contributor
timestamp: January 19, 2019, 02:54:33 pm
content: "Tactile switches" as they are generally called often have 4 pins, with two pairs connected together - the buttons action just connects these two pairs together. The switch/button looks like these:https://www.aliexpress.com/item/100PCS-LOT-3-4-2-5mm-SMD-Tact-Switch-4-Pin-Touch-Micro-Switch-Push-Button/32696349940.htmlhttps://www.ebay.co.uk/i/283273934888?chn=psAs you can see on the underside of those, there are 4 small pads/pins. Although I don't have those specific buttons to hand, I'll bet that the "button" contact is between two pins on the shorter edge. See attached image. As these buttons are normally open - unless you wish to stop that button doing anything you could just solder wires to those pads, in parallel with the original button, for an external button.Removing it could be tricky - you can tell that the solder points are actually half under the button itself. So that would require either... hot air to heat up all four pads at the same time, or possibly destruction of the button. *sometimes* it is easier to actually destroy the component to save stress on the PCB. But this can tear the pads right off the board (a bad thing).