Why are pins on a component placed so awkwardly? - Page 1
Forum section: electronics / general

author: MrOmnos
author_rank: Frequent Contributor
timestamp: January 23, 2018, 09:17:05 am
content: From previous post you guys might know I have trying to make a watch. So far, I have tested my components and written some code. My first try at etching PCB for the watch was pretty good. The toner transfer worked (somewhat) despite being the size of 26mm x 26mm. But my major problem is routing. Routing has turned out to be very frustrating for me. At first I just connected the nets I could and left that I couldn't. Then I soldered thin magnet wires to make the rest of the connections. Which again was very frustrating. I don't know how many times I felt like shoving my cheap soldering iron into my laptop screen. It was even more frustrating soldering small pins looking through this ghetto lens contraption.But at last I was able to solder the remaining connections required to test the ATmega32 and 74HC595 ICs.And surprisingly it worked even though it doesn't look like it should wok. But trust me it works.Now I want to make a proper board which won't require me to use magnet wires to make connections but I have run into a problem again. Why are pins placed in such inconvenient positions?For example I need to connect all the GND pins and VCC pins in above image. But as you can see, they have place PIN 5 VCC above PIN 6 GND and there is no way I will be able to connect all the VCC and GNDs without overlapping each other.How do people route stuff? Is there some rules, tips and tricks I need to learn? How do I learn it. I have tried placing the components closer, farther, rotated 45 degrees, created GND planes but nothing works for me. Is is not possible to make single sided 26mm x 26mm single sided PCB at home? I am very frustrated.How do people route? Where do I learn to route?This is my current progress. But I know, I am at a dead end.

author: llkiwi2006
author_rank: Regular Contributor
timestamp: January 23, 2018, 09:39:06 am
content: I'm not very experienced with routing pcbs either, but I suggest if you must use single sided boards, design your pcb with places for placing jumper links, not just add them in as an afterthought. But you should consider getting double sided pcbs from chinese manufacturers for very cheap prices (just long shipping times).Btw, you should really be using decoupling caps with your microcontroller. Check the datasheet for their recommendations.

author: donotdespisethesnake
author_rank: Super Contributor
timestamp: January 23, 2018, 09:40:11 am
content: I think you have picked a pretty impossible task. SMDs really only work with 2 layer boards. If you have a lot of PCB space then you could arrange to use some wire jumpers to simulate another layer, but if you want a small PCB area then you really need multi-layer.For DIY, you might consider etching two 0.8mm PCB and sticking them together. Personally I would just order boards from China...

author: tszaboo
author_rank: Super Contributor
timestamp: January 23, 2018, 09:48:50 am
content: Quote from: MrOmnos on January 23, 2018, 09:17:05 amNot on 1 layer. Yes, usually default rules in your PCB designer software should be a good start for rules.You learn by doing it, or watch Dave's video routing his nixie clock.Yes, you should not design single layer SMD boards. Just dont. Its like trying to power an Audi A8 with a tuk-tuk engine. Even if it works, it is not OK. Also, capacitors? Did you learn nothing from Dave's videos? If you see a teardown of a product and it has a billion small capacitors, do you think your watch is not going to need it?There is so many issues with the way you design, I dont even know where to start.

author: mavu
author_rank: Contributor
timestamp: January 23, 2018, 10:04:45 am
content: Esiest way: route 2-layer pcb and order from china, probably very cheap ( less than 10 currency units probably)If you do want to make it yourself:Do you really need the giant atmega32? Wouldn't maybe a attiny do?If you really need the components you selected there, you can make vias yourself. ("vias" are shortcuts from one side of the board to the other)drill a hole under the chip, before you solder it down, and either route a wire from the pad or trace through the hole to the other side, or make a pad in your design and solder a wire to it that comes up from below.you will need to keep it very flat though.About missing components. your parts list does seem to be missing some things, but hey, if it works. why not. you will over time learn what would have been a good idea in the first place. Best way to learn. not the most painless, but certainly not something you forget easily again if you learned from your mistakes.

author: nctnico
author_rank: Super Contributor
timestamp: January 23, 2018, 10:59:31 am
content: Quote from: NANDBlog on January 23, 2018, 09:48:50 amYou can but you have to use 2 sided boards. If you use the solder side as a solid ground plane you can achieve a lot IF you plan ahead. Here I used 1206 jumpers and a few wires. Under the CPLD there is a 3.3V copper pour.But if you have time then using a cheap Chinese is a very good option.

author: tszaboo
author_rank: Super Contributor
timestamp: January 23, 2018, 12:18:56 pm
content: Quote from: nctnico on January 23, 2018, 10:59:31 amOK, so according to nctnico, you can design one layer boards, if your design is two layer.I stand corrected.

author: plazma
author_rank: Frequent Contributor
timestamp: January 23, 2018, 12:28:33 pm
content: It helps much if you place GND and Vcc planes on other side. No need to etch. Just cut planes with a knife and make vias by drilling and soldring a wire through it. Easy to solder decoupling caps between planes. Route most signals without jumpers. Route the rest so you can use non overlapping jumper wires (place round testpads where you solder the jumper wire).

author: MrOmnos
author_rank: Frequent Contributor
timestamp: January 24, 2018, 11:44:26 am
content: Thanks you guys! It is always nice to come here and ask for help. I am using Atmega32 because I had those on hand. I didn't use any caps because I didn't have SMD caps. I just wanted the damn thing to work. Do I need to use caps between all the GND VCC? For final build I will use Atmega328PB.The thing is I need to control 22-35 leds because I am making two watches, one in English and one in Spanish for my friend. The English version needs 22 leds and the Spanish version needs 33.The 32.768Khz crystal will need two 2 pins and the push button will require 1.So, for english version I will requires 25 pins and for Spanish I will need 36 pins.ATmega328PB has 27 I/O pins and draws 1.3micro Amps in Power Saver mode with RTC running. And also works at voltages as low as 1.8v which also great because I will be using CR2032 battery.Hence for spanish version I decided to use 74hc595. Is 74hc595 a good choice? I also decided to upload my board files tohttps://jlcpcb.com. It says they can do 10 boards for 2 bucks. Ofcourse before sending it to them I will post here.

author: Zero999
author_rank: Super Contributor
timestamp: January 24, 2018, 12:02:35 pm
content: Of course decoupling capacitors are required across the VDD and VSS pins.The 74HC595 is fine and is specified to work down to 2V.

author: 3roomlab
author_rank: Frequent Contributor
timestamp: January 24, 2018, 12:15:47 pm
content: im very curious what is this device in the/your photo?

author: tszaboo
author_rank: Super Contributor
timestamp: January 24, 2018, 12:47:24 pm
content: Quote from: 3roomlab on January 24, 2018, 12:15:47 pmWordclock. Probably not english.

author: @rt
author_rank: Super Contributor
timestamp: January 24, 2018, 01:06:58 pm
content: Love your style, but you’re no better off than having used a single protoboard, or a couple of stacked QFP breakout boards... well except for some CAD experience, which I guess was part of the goal.Regarding the iron.. do yourself a favour. I don’t see anything terrible there considering the pitch, but in general..I used a crap pencil for 35 or so years, and an expensive Goot (after using a JBC at work), and am kicking myself.It was never worth the torture.If you’re in Australia, there’s a yellow pencil iron at Jaycar with a temp control on the side.It’s probably the best of the cheap pencil irons to use, but will last 3 months for a serious hobbyist.I went through 7 of these.. I considered them worth it a the time for what they cost.

author: MrOmnos
author_rank: Frequent Contributor
timestamp: January 24, 2018, 01:32:44 pm
content: Quote from: 3roomlab on January 24, 2018, 12:15:47 pmHi. Thanks for your curiosity. That is the watch I am trying make. The front face with letters was designed in solid works and was cut using a laser cutter. It is in Spanish. The base part was made by my self using a Woodworking Gouge. I had designed the base in solid works but I couldn't find a CNC to cut it in my country. So had to make it by hand. Looks hard to do but if you chose a good wood anyone can carve it provided that you invest time and patience. I decided to make this because I sawhttps://imgur.com/a/TNoh2this post on imgur and really liked it. OP took the project to Kickstarter.https://www.kickstarter.com/projects/182337072/wooden-word-watchSince, I couldn't find any design files online and didn't have money to buy from kickstarter, so I thought I would give it a try and make it myself. So, far It seems I am on the right track.Here's the front face in more detail.

author: Yansi
author_rank: Super Contributor
timestamp: January 24, 2018, 02:13:06 pm
content: Quote from: NANDBlog on January 23, 2018, 09:48:50 amIn Altium they never are.