d123
Advanced Member level 5
Hi,
This is a very simple/rudimentary analog BJT hFE tester, quite simply it can be used to sort batches of transistors into Beta lots of e.g. 140, 180, 200, and so on. I made this at the end of 2015 and just remembered it last night and thought I'd upload it here as it is my DIY electronics.
There are far better ways of doing this kind of device, I know. Not that impressive in the age of IoT, IIoT and so on. It's a very poor cousin to a curve tracer and could perhaps be improved with a PIC/MCU for example, but it is effective for quickly sorting by Beta.
The pdf is the more legible version of the schematic, it was done in a schematic capture program that didn't export jpg versions nicely, unfortunately. There's no PCB layout as I still do my 35um solid copper FR4 boards by hand... Solid/single ground planes forever!
It can be set for 10uA, 100uA and 1mA with settings for 10R, 1R or 0R1 respectively. Has "Okay" (power good), over-range and fault LED indicators. Uses the (old) classic 7135 ADC and the rest are off-the-shelf components such as 7805s, 2N2222s and 2N2907s, 7660 and some diodes and rotary switches and buttons, basically.
Had a lot of fun learning about it all and making it.
Anyway, photos:
Salvaged schematic from pdf (sorry about the quality of image):
This is a very simple/rudimentary analog BJT hFE tester, quite simply it can be used to sort batches of transistors into Beta lots of e.g. 140, 180, 200, and so on. I made this at the end of 2015 and just remembered it last night and thought I'd upload it here as it is my DIY electronics.
There are far better ways of doing this kind of device, I know. Not that impressive in the age of IoT, IIoT and so on. It's a very poor cousin to a curve tracer and could perhaps be improved with a PIC/MCU for example, but it is effective for quickly sorting by Beta.
The pdf is the more legible version of the schematic, it was done in a schematic capture program that didn't export jpg versions nicely, unfortunately. There's no PCB layout as I still do my 35um solid copper FR4 boards by hand... Solid/single ground planes forever!
It can be set for 10uA, 100uA and 1mA with settings for 10R, 1R or 0R1 respectively. Has "Okay" (power good), over-range and fault LED indicators. Uses the (old) classic 7135 ADC and the rest are off-the-shelf components such as 7805s, 2N2222s and 2N2907s, 7660 and some diodes and rotary switches and buttons, basically.
Had a lot of fun learning about it all and making it.
Anyway, photos:
Salvaged schematic from pdf (sorry about the quality of image):
