Design A Simple PCB Functional Test Board (Environment)
When you finished the design and manufacturing of your board, it is important to run a test to see if everything is working as expect, for many simple boards, this is done by human eyes check, but sometimes for more complex board, it is better to run a fully functioning test. Let do it here.
For the board design:
The board should be penalized based on the test need, for example, in our this tutorial, it is the DTMF board, cell phone signal comes in from the audio jack,and display by LED indicator to tell the button pressed on cell phone. So we must consider the audio jack should be not conflict with other boards.
For PCB design, add a 3.5mm empty board outline on the side for the PCB locker to hold the board. If you are using eagle, add a rectangle on the side of the board on layer dimension 20, and nothing else need to draw. See picture below. And check how it looks like on the pictures of real PCBs more below.
- Drill, double side tape, strong fast glue – please prepare in your local store.
Most of these materials you can find it later on our store.
- Drill Bit: 0.8mm – for pin header holes drilling. 1.7mm – for drilling the insertion holes of the test pins, 3.0mm – for PCB locker and installation hole.
- Test pins – it is actually two part: a socket and a pin inserting inside the socket, for 2.54 mm pitch pin headers testing, quantity depends on how many pin headers you need to test, but this test pins normally sells 100 pcs as a small pack. The socket has a small rod to help it lock the top surface of the baseboard, it is slightly bigger than 1.7mm holes you will drill, so it can not be pressed down anymore and lock on the baseboard.
- Baseboard materials – we use the PCB type board, it is dielectric, easy for drilling and 4mm thickness to hold the test pins, red board in the picture.
- PCB locker (4PCs)- hold the side of PCBs, the yellow thing in the picture.
- Other wires for wiring up and testing, this is according to your board design and testing purpose.
So let’s start to make it, follow the slideshow and note to do so.
Tape an empty PCB on the baseboard, long edge
add some materials for protection below the baseboard when drilling, and also draw two lines next to the PCB long edge on baseboard, see next pic
drill holes for test pins with 0.8mm bit through the empty PCB, also see the PCB long edge line here
add another two parallel line out of the edge line, distance 7.0mm (distance for the locker grap), and a pair of points with distance 26mm on the line, this is for the PCB locker installation holes, need four pair of these holes for four locker
enlarge the holes for PCB test pins with 1.7 mm bit, and also drill the installation holes for locker with same bit, in this pic, the installation holes of locker is already enlarged by 3.0mm bit
drill with 3.0 mm for four corner installation holes, and also the installation holes for locker with same 3.0mm bit, install both hexagon rod and PCB locker, I only have 3pcs here, sorry for that.
detailed look again
this screw is included by the PCB locker, it is self tapped
now you are free to add the test pins, see there is a small rod on the socket pin, that stop the press down movement of the socket and lock its position, here is a problem, I don’t know why there are two holes too big for insert the pins, it is loose
I can still use the fast strong glue to glue the socket pins, also glue the rest optionally to make them not move when I attach or detach the PCB
Now you can start the design of the wires at the bottom of the baseboard, this depends how you want to test and how it can be more convenient, for demo I will make it simple here, only two power lines. Also I don’t know enough materials to assemble this PCBA
The bottom of the baseboard, free to design this for your test
running simple test.
The shape of the pins head is like a umbrella, but sharp end into the pin holes, the pins only need to touch the pads of PCB, then it is good enough, but when you drilling, try to make the holes as straight as possible.
another close look
another close look again for PCB. The side PCB gap is designed for testing.