Component tester and Test Jig
I have had this multifunction component tester since Jan 2015 and it has been a useful tool as it automatically identifies discrete components and semiconductors. I have used it a lot when sorting through my junk bins of scavenged parts.
This page also shows a test jig I made for the tester for quick testing of various semiconductors especially SMD parts.
This is the component tester. There are lots of versions, designs and styles but all have the same functionality.
I chose this version since it uses the ubiquitous 16X2 LCD module so I can change it if I want to or have to.
And also having an onboard battery and USB charger means this is a standalone portable unit.
From the side.
It didn't come with a battery. Luckily I had a spare 14500 Li-ION cell on hand.
The LCD is held in by two screws. When it is removed, we get access to the main PCB.
They erased the part numbers on various chips except for the main uC which is an Atmel 328
Main uC and the voltage reference used is a TL431. It has provisions for a trimming pot but is not used. I might upgrade the resistors to a more accurate one when I get the chance.
Power management section. This area contains the USB charger and DC-DC boost converter to derive 5V from the 3.7V cell.
The DUT can be attached to the tester in several ways. 2mm banana jacks, machined pin sockets and an SMD pad.
The back of the PCB.
I tested the voltage reference and it measured around 4.9xxV. I figured a more accurate 2.5V reference is benificial according to the huge thread at EEVBlog forums which has the original circuit and firmware for this component tester.
I used a LM336-2.5 voltage reference diode (TO-92 package) shoehorned into the SOT23 footprint. It does fit but fiddly to solder if you don't have a fine tipped solder iron. I also added a trimmer pot and was able to adjust the reference to exactly 2.500V.
And now we start on the test jig. This is a 3/8 inch thick slab of aluminum that will be the base.
The back part is 1/8 inch aluminum plate drilled and tapped for screw holes.
The two plates will be joined with three screws and a couple drops of loctite to prevent movement.
A piece of polycarbonate that will hold the probe pins together.
Machined and tapped for the mounting screws.
It is coming together. I used a linear bearing which has about 1 inch of travel end to end. The polycarbonate piece moves up and down to lower the pogo pin probes onto the DUT.
A couple pieces of acrylic machined to hold the DUT in place.
It can be moved around to accept a wide range of component sizes.
Although not ideal due to ESD, I never experience it here (ESD) due to the warm, humid climate. If you plan to copy this design, a static dissipative but non conductive material should be used.
The pogo pins are soldered onto blank PCBs that are shaped to easily fit together.
An SOT89 transistor for testing.
With the pins lowered onto the DUT.
I think I need a bit more weight for a more secure contact on the DUT.
And it works.
A small perfboard and some turrets for easy connection to the component tester.
A dab of hotmelt glue on the wires for strain relief.
How about an SOT23 device.
Moved the position of the pogo pins for the new device. And it worked.
How about an SMD trimmer?
How about an SMD diode?
It works too.
SOIC-8 mosfets work too.
But only if you know which pins are the gate, drain and source.
SOT323 barely fits.
But still worked.
And then I couldn't leave it be.
This is how you cut a semicircle.
The pic should explain it all.
The holder for the probes are changed to a curved one so the screws holding them are better positioned.
The pogo pins are flat tipped.
It was a pain getting all the pogo pins positioned the same length.
And here it is ready to sort the bunch of mixed parts. These are SOT23 and SOT323 devices.
It works quite well but I plan to add a bit more weight for more contact pressure. The acrylic pieces that hold the component might also need to be changed for better grip of smaller parts.
Page created and copyright R.Quan ©17 Oct 2015.