Latest project is as per title.
it is basically just an inverting stage where base vs collector voltages are measured and sent to pc via usb and displayed.
the curves can then be compared for a match.
the base voltage is a simple pwm into an integrator.
i use diff amps to convert between micro 3.3v and collector 9 volt supply and then back to 3.3v for a2d converter.
it is basically just an inverting stage where base vs collector voltages are measured and sent to pc via usb and displayed.
the curves can then be compared for a match.
the base voltage is a simple pwm into an integrator.
i use diff amps to convert between micro 3.3v and collector 9 volt supply and then back to 3.3v for a2d converter.
Congratulations.
Paint one transistor red and paint another transistor blue.
Test each of them every day for 20 consecutive days. How much scatter do you see in the measurements of "the same device"? How much scatter do you see in the measurements of (red minus blue)?
Paint one transistor red and paint another transistor blue.
Test each of them every day for 20 consecutive days. How much scatter do you see in the measurements of "the same device"? How much scatter do you see in the measurements of (red minus blue)?
Scatter isnt a problem over time as transistors should all be measured at same time at same temp.
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
Expanded the transistor matcher to do some different voltage simple curves too.
On the prototype I made the mistake of using same supply for pnp and npn, this caused spikes in pnp readings. So split the supply through two separate transistors and it works a treat now.
Waiting for new pcb's now.
On the prototype I made the mistake of using same supply for pnp and npn, this caused spikes in pnp readings. So split the supply through two separate transistors and it works a treat now.
Waiting for new pcb's now.
The pictures got deleted when I had a clear out.
Here it is again.
This one is the prototype, waiting for new pcb's to come in from China.
Here it is again.
This one is the prototype, waiting for new pcb's to come in from China.
First picture is transistor matcher.
Second picture is curve tracer with traces of 4 different voltages.
Second picture is curve tracer with traces of 4 different voltages.
Got latest pcb's through.
Up and running OK now, well after I replaced a transistor which was wrong way around !
Always a worry if something doesn't work first time.
Up and running OK now, well after I replaced a transistor which was wrong way around !
Always a worry if something doesn't work first time.