Latest project is a transistor curve tracer.
As it stands the software can input upto 5 transistors data and display a trace on the PC screen in a different colour for each transistor.
The hardware simply applies a voltage from 0 to 10 volts through a 1k resistor into the base/gate and the drain/collector voltage is read in via an A2D.
The drain/collector has a 100r resistor to 10 volts to apply a current.
Instead of just the usual set "scope" screen I have used a CAD type screen where you can zoom and pan around to get in close to the action.
The microcontroller uses PWM to set the gate/base voltage through an x3 gain op amp. The micro has a USB interface for passing data to pc.
You can save/load traces and print them out.
As it stands the software can input upto 5 transistors data and display a trace on the PC screen in a different colour for each transistor.
The hardware simply applies a voltage from 0 to 10 volts through a 1k resistor into the base/gate and the drain/collector voltage is read in via an A2D.
The drain/collector has a 100r resistor to 10 volts to apply a current.
Instead of just the usual set "scope" screen I have used a CAD type screen where you can zoom and pan around to get in close to the action.
The microcontroller uses PWM to set the gate/base voltage through an x3 gain op amp. The micro has a USB interface for passing data to pc.
You can save/load traces and print them out.
I havent got the hardware yet but here is a sample random trace showing voltages on a grid background.
An externally hosted image should be here but it was not working when we last tested it.
Close up. The software allows zooming and panning of the traces.
An externally hosted image should be here but it was not working when we last tested it.
PCB's arrived today and built one up.
The PIC software I had written wouldn't work with the USB bus.
Couldn't work out what the problem was so resorted rewriting it based on a previous project that uses same PIC. It then burst into life.
Waiting for some mosfets now so I can test the software and hardware.
The PIC software I had written wouldn't work with the USB bus.
Couldn't work out what the problem was so resorted rewriting it based on a previous project that uses same PIC. It then burst into life.
Waiting for some mosfets now so I can test the software and hardware.
I progressed quite a bit with the hardware and software today.
The PWM into an RC filter was a bit slow at changing so I changed 10K resistor in filter to 1K and that makes it much faster.
The software has been a bit tricky at times getting all the levels right and making it user friendly.
I used 10 volts originally for the drain/collector supply through a resistor but this was inaccurate. So I reduced it to 9 volts which works better with the 3V3 microcontroller.
I can multiply or divide by the 3 to get close to the 9 volts or 3v3.
The pc software now not only does markers or the collector/drain voltage but also for the gate/base voltage. You can read off the screen the same base/gate voltage for different transistors.
You can also run markers along the collector/drain voltages to trace the curves.
The software can now save traces to disc, print them out for save to a bitmap file.
The PWM into an RC filter was a bit slow at changing so I changed 10K resistor in filter to 1K and that makes it much faster.
The software has been a bit tricky at times getting all the levels right and making it user friendly.
I used 10 volts originally for the drain/collector supply through a resistor but this was inaccurate. So I reduced it to 9 volts which works better with the 3V3 microcontroller.
I can multiply or divide by the 3 to get close to the 9 volts or 3v3.
The pc software now not only does markers or the collector/drain voltage but also for the gate/base voltage. You can read off the screen the same base/gate voltage for different transistors.
You can also run markers along the collector/drain voltages to trace the curves.
The software can now save traces to disc, print them out for save to a bitmap file.