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***Images and link to 3D print file coming soon***
TITLE:PCB Probe Board
GOAL: Create a hands free tool for making connections to exposed pads, vias, contacts, etc on a circuit board for reverse engineering.
MATERIALS:
Sewing pins (1 per probe)
stranded copper wire (1 foot should be more than enough)
Solder
Flux
16 gauge steel wire
#10-24 coupling nuts (1 per probe)
#10-24 x 3" machine screws (1 per probe)
#10 washers
Loctite (I would go for a more permanent one like red Loctite)
Base board for mounting the probes to (3D printed) Thingiverse Link
TOOLS:
Dremel tool with cutoff disks and sanding drums
Vise/clamp to hold screws/nuts while modifying
Soldering iron
Wire cutter capable of cutting the steel wire
Screwdriver
Drill or drill press and drill bit set
Hacksaw with blade for cutting metal
PROCESS:
1) For each probe cut a piece of the steel wire that is roughly 25 cm long.
2) Make a bend about 1 cm from one end on each piece (I went with 90 degrees though I would probably use something closer to 60 or 45
degrees in the future).
3) Hold one sewing pin against the part you bent and wrap a single strand of the copper wire around both the pin and the steel wire to
hold the pin to the steel wire.
4) Apply flux to the copper wire wrap and then solder the assembly to create a good electrical connection
5) For each coupling nut cross drill a 5/64" hole perpendicular to and through the threaded hole in the middle of the nut.
6) Each machine screw will need to be cut short enough that when it has 4 washers, is put through probe board, and screwed into the
modified coupling nut, it does not block the cross drill from the previous step. (I estimated the distance by using 3 washers and
eyeballing it. If it's a bit long extra washers can be used as spacers on the bottom.)
7) clean up the cut on both pieces of each screw and then use the cutoff disk to cut a slot into the "scrap" piece you cut off each
screw to form a set screw.
8) Take a shortened machine screw and place 2 washers on it before pushing it through one of the round holes on the probe board from
below. Then place 2 more washers on the part sticking out the top of the board and screw on one of your modified coupling nuts until
it is tight enough that rotating the screw and nut relative to the board is a bit stiff but not impossible.
9) CONFIRM ONE OF THE PROBES WILL FIT THROUGH THE CROSS DRILLED HOLE AND MOVE FREELY BEFORE CONTINUING!!!
10) Remove the coupling nut and add Loctite to the screw before putting the coupling nut back on the same way it came off. (I find it
can be helpful to mark the "top" of the nut to ensure I don't accidentally put it on upside down possibly resulting in a blocked cross
drill.)
11) Repeat steps 8, 9 and 10 for the remaining coupling nuts
12) Slide one probe into each cross drilled hole and take the "set screws" created in step 7, screwing them into the top of the coupling
nuts. These will be tightened down to lock the probe in position.
13) Connections can be made from a tool to the probe using anything that will clamp on to the back of the probes I like using WAGO wire
nuts and a piece of wire that can be connected to a breadboard
UPDATES:
2024-05-14 - Increased the size of the holes in the 3D model as they were sized for #8 screws
POSSIBLE MODIFICATIONS:
- Blunt the needles slightly to reduce the risk of damage to the PCB being analyzed
- Add copper foil to the bottom of the board and solder the washer touching it to it so that traces could be made to a set of headers for
easy connection of tools like a bus pirate or arduinos