This simple project is a little breakout board that uses a ZIF socket to provide safe access to modules that are wider or longer than the typical 14- or 16-pin DIL ICs. It does much the same job as a solderless breadboard, but with the difference that the ZIF socket enables the module to be inserted and removed without any force, and without risk of breaking the module or its pins. It is particularly suited to very small modules that tend to use very thin PCB material, such as logic level converters, LiPO charger modules and step-up or -down voltage converters. It can also be used with the small 128x64 or 128x32 OLED display modules, which are extremely fragile, and with modules that are sensitive to poor connections, such as the cheap clone mini MP3 players.
The board has connections for each of the ZIF socket pins, as well as a small bus for both 5v and Gnd, but of course it could be built to any configuration.
ZIF socket. There are many variations available
and the most appropriate can be chosen to match the type of module
typically used. This example uses a 28-pin (2x14) socket that
can accommodate modules with a pin width of 12 to 14mm. Note: this
does not fit an ATMega328 28-pin chip, but versions of the ZIF are
available in that size.
Prototyping board.
Headers: 2 x 14-pin, 2 x 6-pin. Female headers have been used for
consistency with the usual arrangement of MCU prototyping boards.
Mounting feet, or case.
The ZIF, or zero insertion force, socket is designed for the
insertion and removal of dual in-line chips and modules, usually in larger
sizes, with zero stress on the chip or its pins. The socket is
opened by raising the lever, so that the chip or module can be inserted
into open connectors. When the lever is closed the connectors
squeeze the pins, creating a secure connection. The chip or module is
removed by raising the lever and opening the connectors.
Any suitable configuration and size can be used, but
the most convenient will have traces organised in a 'ladder' configuration
where the ZIF solders to rungs on separate rails of the ladder and the
rungs provide connections to adjacent headers. Ensure that the rungs
are far enough apart, or long enough, to allow the headers to be placed
alongside the ZIF without the need to run connections to an adjacent rung.
Apart from bringing each ZIF pin out to an adjacent header, the arrangement of the breadboard will depend on the expected usage. In the example here, the 5v supply is from a two-terminal connector and a USB-C socket, each connected to a pair of female headers. The USB_C socket is fastened to the board with stakes, providing one pair of male headers, as well a a very secure mounting. (The socket board also has extra holes which can be used for stakes or a wire strap.). There is also a variable step-down power supply with its own headers for an external supply. This is also mounted using stakes. Depending on the expected usage it may be worthwhile to provide fixed 5v and/or 3.3v regulators powered from a 12v connector. The example provided here will likely be expanded based on experience with using it with developing projects.
The
parts are laid out on the prototyping board in a form that uses the
pattern of traces to the best advantage. In this case the only additional
wiring required is for the second 5v connector and the several different
ground points (as the projects it will be used with will not require
floating power supplies). These additional connections can be run across
either the top or bottom (copper) side of the board..
If it is necessary to cut the traces then the simplest method is to drill out an intermediate hole to a larger size from the copper side. This gives a clean and obvious disconnect. If the trace needs to be cut between two holes then use a sharp knife and be sure to peel or scrape away a small segment of track, ensuring that no stray piece of copper can bridge the gap.
Before soldering components scrub the copper side thoroughly to give a clean surface so the solder wicks to the copper easily. Prototype boards vary widely in the quality of the copper coating, but usually require good cleaning, and often need a light sandpapering to get clean bright copper.
Holes should be drilled in each corner of the board for mounting stand-offs so that the traces and wiring on the back of the board are raised from the working surface to eliminate any risk of shorting out on anything sitting on the workbench. In this example one hole of the USB socket has been used for a support, to add extra security to the socket mounting. If metal supports are used be sure to include insulating washers between the copper traces and the support base. If the USB socket hole is used for a mount then an insulating washer is also required for it.
The image shows the board being used with a MP3 player module. For reasons that are not clear this module is particularly sensitive to poor connections, so the ZIF socket makes a big difference in reliability and consistency during prototyping.
The board is also very useful with the Arduino Pro Mini, particularly when the Pro Mini is configured with only a few pins. Although the Pro Mini is quite sturdy, it can be damaged when removing from the solderless breadboard. If it is soldered into the final circuit before the damage is detected then a lot of effort is involved in removing and replacing it. The ZIF socket virtually eliminates any risk of damage.
