Arduino Based Hackable Prototyping Board

Earlier in the year I needed to build a control system with the capability to detect alcohol vapour, measure fluid temperature, sound audio alarms and trigger relays. I designed a circuit board for the Atmega 328 chip and soldered all the components on to produce the finished item. It took quite a while to to this, and, whilst testing circuits on a breadboard was ok, I could really have saved myself a lot of bother if I had had a PCB that could be adapted to my needs, rather than creating a whole new one from scratch. So, after the project had finished, I thought what would I have liked to have been able to buy to have produced that project and what would I like to have to produce future projects, without the time and expense of getting batches of custom made PCBs made for the specific purpose. This was when the idea of a flexible, hackable, multi-functional PCB came to mind.

Step 1: My Previous Board

My previous board, although it worked well, would be a nightmare to hack as it's really small and compact and the tracks are not well organised. It had a K-type thermocouple circuit in the middle, an audio amplifier in the top right and a 4 x 20 LCD screen in the top left, which covered much of the board. One of the main hassles was constantly having to pull out the Atmega chip and slot it into an Uno for making pragramming changes.

Step 2: Methalyzer Project

The finished product was a bit more presentable. Note the USB slots in the foreground for attaching sensors.

Step 3: Board Layout

One of the main things that I wanted to achieve was a layout that people could understand relatively easily by physically looking at the board rather than consulting an instruction manual. For this reason, the board is laid out with the different component circuits in blocks surrounded by yellow squares with very clear exit and entry points for the relavant connections. For example, the audio amplifiers are arranged in neat blocks and the input signal, speaker outputs etc. are collected in their own little block for further connection by flying wires. All the component circuit blocks were tested in to previous project so all that had to be done was arrange them in a well organised format so that they could be understood and implemented by not only other people, but myself too!

Here is a list of all the features:

Bolt on Arduino Due
Bolt on 4 x 20 LCD
Audio amplifiers x 2
K-type thermocouple circuit (not shown below)
Relays x 6
Analog pots x 5
LCD contrast pot x 1
Momentary switches x 4
Independent power regulator with fuse
Large number of hackable pins in 1/10th inch format including DIP8 in several different patterns
USB connectors for sensors etc. x 8
PCB mounted mini speaker
Double sided, gold plated board, with very durable pin sockets for re-working
Long and easily identifiable ground and 5 volt tracks

Many of the components on the board are obvious and others, for example in the audio amplifier sections, are detailed in text on the board itself. Some of the components are surface mount, but none too small for manual soldering. A standard 40 watt soldering iron and magnifying glass are all the tools needed. The final list of components will depend on the project that is to be produced.

Step 4: Parts List

Paste this text into a basic text editor software and change the file extension to ".csv" and save it. Then open the new file in your spreadsheet software:

"Supplier","Product Code","Quantity","Pack split","Product Description","Pack Price","Total"
,,,,,,
"Rapid","62-0556",4,0.04,"1k Cr50 0.5w Carbon Film Resistor - Pack of 100","£1.17","£0.05"
"Rapid","62-0536",1,0.01,"100r Cr50 0.5w Carbon Film Resistor - Pack of 100","£1.17","£0.01"
"Rapid","11-3708",1,1,"470uF 16v Radial Electrolytic Capacitor","£0.07","£0.07"
"Rapid","11-3740",1,1,"470uf 35v Radial Electrolytic Capacitor","£0.14","£0.14"
"Rapid","11-3698",1,1,"100uf 25v Radial Electrolytic Capacitor","£0.04","£0.04"
"Rapid","08-1020",6,6,"100nf 5mm X7r Dielect Ceramic Capacitor","£0.16","£0.96"
"Digikey","929400E-01-36-ND",1,1,"header pins 16 row 2.54mm pitch male/male",1.7,"£1.70"
"Digikey","A28563-ND",1,1,"header pins 16 row 2.54mm pitch male/female Square Pin Diameter: 0.64mm",1.5,"£1.50"
,221107048515,4,0.4,"M3 x 30 bolts","£1.20","£0.48"
,190840877632,4,0.16,"M3 nuts","£1.15","£0.18"
,360611792906,4,0.08,"M3 spring washers","£1.15","£0.09"
"Rapid","60-4661",2,2,"5V RWH Series 12A SPDT Relay","£0.75","£1.50"
"Rapid","57-2251",1,1,"2004 20x4 Character LCD Module LCM White On Blue Blue Backlight ","£4.00","£4.00"
"Rapid","35-0282 ",1,1,"Piezo transducer - 1mA, 80dB","£0.87","£0.87"
"Rapid","68-0047",4,4,"10k Wr3362p 0.25 1-turn Cermet Trimmer","£0.21","£0.84"
"Rapid","71-1345 ",2,1,"470 pF 1206 capacitor 71-1345 (1206 not easily available hence 0805)",0.05,"£0.05"
"Rapid","71-0685",4,1,"100 nF 1206 capacitor 71-0685",0.05,"£0.05"
"Rapid","11-2263",4,1,"Al cap CD series SMT 10V 100uF 11-2263",0.1,"£0.10"
"Rapid","11-2264",2,1,"Al cap CD series SMT 10V 220uF  11-2264",0.1,"£0.10"
"Rapid","72-2867",10,1,"10K 1206 resistor 72-2867",0.05,"£0.05"
"Rapid","72-2597",2,1,"100R resistor 1206 72-2597",0.05,"£0.05"
"Rapid","72-2507",2,1,"1R resistor 1206 72-2507",0.05,"£0.05"
"Rapid","82-0484",1,1,"TBA820M amplifier ",0.5,"£0.50"
"Rapid","26-1568",1,1,"0.75a S/mount Polyswitch Fuse",0.37,"£0.37"
"RS","706-0217",2,2,"Connector, Rec, USB, R/A 2 Row TE Connectivity  1903815-1",1.9,"£3.80"
"Rapid","24-0351",1,1,"Re Wireable USB Plug","£0.23","£0.23"
"Rapid","20-0970",1,1,"2.1 PCB DC Power Socket.","£0.18","£0.18"
"Rapid","33-6264",4,0.16,"Round Through Hole Support PVC Ss6-2 - Pack of 25","£1.82","£0.29"
"Rapid","33-6268",4,0.16,"Round Through Hole Support PVC Ss6-4 - Pack of 25","£1.93","£0.31"
"Rapid","21-2828",2,2,"6 Way 12a 250v Side Entry Closed 5mm","£0.23","£0.47"
"Rapid","47-3313",1,1,"7805 Regulator To-220 (tru)","£0.35","£0.35"

Step 5: Gerber Plots As Zip File

Here are the Gerber plots zipped up ready to send for manufacture. It should be possible to get 5 boards made for about $120 dollars, including DHL postage, from Hong Kong. The specification to quote is: "2-Layer FR4 1.6mm 1oz Gold Immersion Green Soldermask White Silkscreen".

Step 6: PCB Populated With Shields

Here's a couple of photos of the PCB doing some work. The Arduino underneath the PCB is a Due and it's triggering a MP3 trigger shield (red) through the row of digital connections at the back.