Assignment:
Our fourth weeks project was to solder and programme a FabtinyISP. This is the start of three conttected activites. This week I’ll be building and programming my own programmer. Next week I’ll design and mill a programmable Arduino, then the third week will be using the Pragrammer to program the Arduino and an exercise in basic programming.
Methodology:
Board Basics!
There are multiple different kinds of circuit boards, that range in complexity and use. Jumper wires and crocodile clips are the simplest form, but anything remotely complicated you’ll need a strip-board or a Printed Circuit Board (PCB) I’ll be producing a Milled PCB for this project which i will later programme.
For the sake of this project I’ll be using a pre-milled circuit board which was made by laminating a piece of copper over non-conductive resin and milling out the “Trace” (The copper track shown to the left)
The components for this board will be soldered directly onto the trace, unlike a bread board style circuit which uses larger components that are soldered through the holes to make construction simpler. The components used to product this FabtinyISP are:
1x ATtiny45 – U1
2x 1kΩ resistors – R1 and R6
2x 499Ω resistors – R2 and R5
2x 49Ω resistors – R3 and R4
2x 3.3v zener diodes – D1 and D2
1x red LED – D3 or D4
1x green LED D3 or D4
1x 100nF capacitor – C1
1x 2×3 ISP header – ISP
It’s important that these components are kept in static proof bags prior to use, and the board itself must be cleaned with soapy water to allow for good contact with the electronic components.
Each component has a specific place on the board, with the exception of the Red and Green LED’s which can be place in either the D3 or D4 locations.
ALWAYS bare in mind that some components must be facing certain directions.
Both the LED’s and the 3.3v Zener Diodes must have their Cathodes pointing towards the VCC. Their orientation is marked on the component.
Soldering Solutions!
Soldering is a craft skill that’s essential for the construction of any kind of board. Typically lead free solder with a flux core is used in electronics construction. DO NOT USE any acid core solder as this will damage the components.
Lead free solder will typically melt around 217 – 221 degree’s Celsius and people often use temperature controlled soldering irons set to between 370 – 400 degree’s Celsius. For this project i didn’t get the chance, and used a standard soldering iron with a narrow ended tip.
In order to more easily solder the board, you should first “Tip” the iron, which is melting a small amount of solder onto the tip and then removing any excess using a damp sponge, this will leave 
the end silvery and ready for use.
A good method for attaching small components more easily is to melt a very small amount of solder onto the board this and place the component on top of it, grab a small screw driver and press down on the component. Next heat the solder and the board so it melts and holds the competent in place. This makes soldering the first joint very easy.
Solder each component according to the guide above, again, ensuring correct orientation. Avoid heating the trace to closely to the component itself as this will damage it. Afterwards, create a line of solder along the Ground, VCC, NetD1-2 and NetD2-2; this will allow it to fit into a USB slot more snugly
The board should look like this when completed. For it to be programmed, that small junction above the ISP header needs to be bridged, either with wire or solder. It’s important it can be removed afterwards, as you’ll need to do that after the board has been programmed.
Be extreemly careful not to damage the traces. I did this by using too much heat on the trace while trying to solder the wire on. This caused it to delaminate.
Thankfully, this doesn’t matter so long as the junction can still be bridged!
My FabtinyISP is now built and ready to be progammed
The next step is to create a bridge between the junction (J1) this can be achieved either by a blob of solder, or something more elaborate like a piece of wire. Note: the laminated trace is extremely delicate and may de-laminate as shown below. Don’t worry if this happens though, it can be fixed with a longer piece of wire.
Programming
Cable Conundrum!
