Tag Archives: pcb

Learning to fail

Learning to fail and how you move on from it: In my previous two posts I had designed and created a pcb layout for a simple 555 timer flasher. I thought it would be a simple thing to do because I really wanted to test the workflow on how to create a pcb from start to finish.

learning to fail
555 pcb with components

After placing and soldering all the components on my pcb, and applying power to it, I expected to see some nice flashing lights just like my breadboard model was doing. The first LED blinked on and off, the second blinked on.. and stayed on… Strange.

I double checked that the pcb matched the schematic – yep that is all correct. I turned on the circuit on the breadboard (I still have it on the breadboard as a working circuit when I created it) – and that was working. What could the problem be?

When showing off my excitement of designing my first pcb to an electrical engineering forum (EEVBlog) a kind soul (Hero999) pointed out that there was an error on my original schematic and that my circuit would not work.

After analysing it a bit further I had come to the conclusion that I had failed to copy my breadboard layout to a schematic correctly. Because this was wrong, everything else was wrong. During this time I also must have altered the breadboard circuit without updating the schematic file.

FlashingLights
FlashingLights

My original breadboard circuit was based on the one here and you can clearly see my schematic doesn’t follow this (R2 connects to +V instead of pin3).

Doh!

Learning to Fail

So what have I learnt from all this?

I was so worried about creating a perfect schematic -> pcb workflow that I didn’t spend enough time on the breadboard -> schematic step causing everything to fail.

So while I did fail – I also succeed as the pcb is a correct representation of the schematic – just that the schematic was all wrong.

I also need to pay more attention to ALL the steps in the workflow and not just focus on one step. Each step is important and can have a cascading effect if you get it wrong.

All is not lost though – the same kind soul on EEVBlog (Hero999) has also suggested that I can fix it by removing a solder joint and running a manual wire to the correct location. I’m going to give that a go the next time I’m doing some soldering.

555 LED Flasher custom made pcb circuit

My 555 LED Flasher custom made pcb circuit finally arrived. Yay!

Previously I had designed this circuit and pcb layout as a test run (see previous post) and sent it off to OSHPark for manufacturing. It turned up in the post for last night.

It took about 3 weeks from time to placing the order to me receiving it, which seems quite reasonable for a part time hack like me. I don’t need high turn around times.

555 LED Flasher
555 LED Flasher

The PCB board looks really nice and well made. I could never get this much detail or compactness if I attempted to create a PCB on my own at home (hate playing with nasty chemicals!) But the proof will be when I solder in the components.

If I get some time this weekend I might have a go at transferring the components from the breadboard and soldering them onto the PCB. Once this is done then my workflow from design to finished product will be complete.

 

My First Printed Circuit Board

Update: My first printed circuit board doesn’t work – to see how it all when wrong look here.

My first printed circuit board has just been designed. I’ve been creating a couple of circuits now on a breadboard, but each time I wanted to try something else I would either have to dismantle the circuit to reuse the breadboard, or buy another breadboard (I have 3 now).

Sure I can always put the circuit on a protoboard or stripboard, but I find they tend to get a little messy and they aren’t as neat.

To try out this workflow I thought I’d do something really simple to start with.

I will be sending off the design to be manufactured rather than etch my own board. It gives it a professional look and you don’t have to deal with usage and storage of corrosive  chemicals.

Here are the steps I used to create my printed circuit board. Hopefully it can be helpful for someone else wanted to give it a try.

Creating the schematic

555 flasher circuit schematic
555 flasher ‘railway crossing’ circuit

I created my schematic using the EagleCAD software. The ‘light’ version is free for hobby use and it works on my mac. 🙂

The circuit is just a simple 555 timer that flashes 2 LEDs. I think the secret to learning and testing a new workflow is to keep things simple. Remember that this is my ‘helloworld‘ of a printed circuit board. Don’t judge me 🙂

Breadboard the circuit

555 flasher circuit breadboardIt is important to test out your circuit by building it on a breadboard first. This allows you to swap out components and change your circuit around much easier. It also saves you time and more importantly money as it costs money to manufacture a printed circuit board externally and you want to make sure there are no mistakes.

Design the Printed Circuit Board

printed circuit boardI designed my PCB Layout using EagleCAD. This is my first ever printed circuit board design, so there are probably some things wrong with it. I’ve got a ground plane for the bottom later, and a power plane for the top layer. I managed to route all the nets on a single top layer. If anyone is interested then I’ll post up my source files.

Upload to a PCB Manufacturer

I took the final board file and uploaded to a PCB Manufacturer. I’m using OSHPark.com as I can simply upload the Eagle brd file without messing with Gerber files that most other manufacturers use. Perhaps in the future I’ll pick a different Manufacturer (suggestions anyone?).

OSHPark.com also seems to be reasonably priced given the size of the board I created (1″ squared = $5USD for a 2 layer design), and you get 3 boards for your trouble (some places want a minimum of 100 boards – who wants 100 x 555 flasher circuits?)

Now we wait…

Now that the board has been uploaded and approved I now need to wait until it gets manufactured, and delivered to me. From the website I’m estimating about 2 weeks. When it shows up I’ll take a few photos and comment on how awesome (or crap) it is.

While there is a bit of a wait, it saves me having to deal with the messy chemicals and cleanup if I was etching my own printed circuit board.

I’m rather excited to see how it turns out – Let the waiting begin…