I just read an article on this. Analog + Digital If you decided to build a uC based tracer that emulated the real tracers, but less precise, a small screen could give you a good idea of what is going on for a trace set. I'm thinking basic basic: 10 bit DAC and ADC, not analog quality.

Article suggested a 150VDC supply, then run that through a 1MΩ resistor at the top of a voltage divider for the current source, Then switched 1% metal film resistors in 2 ranges for coarse and fine for uA to mA base drive.

The reasoning was a 1% error on the resistor wouldn't be much of an error at all after calibration, where using lower voltages would not be nearly as stable (1% of 10V is a lot more than 1% of 150V). Knowing the exact uA to mA base current is a difficult task, as measuring that low it will change it, not to mention the noise floor.

Calibrating a grid for the screen would be a bit of a task, but the pixels are known for dimensions, giving a starting point. It could be drawn by the uC itself. Maybe a bit jaggy, but drawn.

Just a jumble of ideas tossed out. I'll be interested to see how this develops.

 

Yako,
It's not all that bad. There are lots of projects out there that have interfaced with peripheral equipment.

Rather than discouraging talhaali from the project, it would be better to point out that the human interface could be left up to a personal computer, and then the problem is reduced to communication with the PC via an existing protocol, with USB being high on the list of preferred protocols.

I agree with this statement. This is clearly a school project. So it does not need to be ready ship at the date given by the OP. In its most basic form. This project will need one A/D and one D/A converter. These can be controlled by a PC that communicate with the PIC via Rs232.

 

As I stated in an earlier post, I haven't finished this. It's the Visual Basic end that I haven't written as yet. The uC and hardware end was working and spiced with a live BJT in ISIS. Attached is a very simplified block diagram of my approach.

 

sorry to interrupt you guys, we (me and my 2 co-mates) have the same problem with talhaali.
it is a school project, but it is not that easy as we all know.

These are our objectives:

1. To be able to plot and trace the characteristic curve of an n-p-n BJT.
2. To create a PC-based System Controller that would allow the users to access and vary the initial input of the current IB and the voltage VCE.
3. To implement a data transmitter and receiver, and a voltage and current source hardware interface using AT89C5021 Microcontroller.
4. To develop a PC-based software program that would output the data and the curve using the results from the hardware interface.


sorry if it sounds impossible(for just a short period of time), but i think we could have some output if we can start this project. if anyone can give advises, it would be a great help.

thank you!

 

Here's another PC-based curve tracer. It's a bit limited in range, and uses a (now hard-to-find) printer port for the interface, but it's a start.

http://pdfserv.maxim-ic.com/en/ej/EJ35.pdf
/mike

 

Here's another PC-based curve tracer. It's a bit limited in range, and uses a (now hard-to-find) printer port for the interface, but it's a start.

http://pdfserv.maxim-ic.com/en/ej/EJ35.pdf
/mike

thanks for the info sir!

 

As I stated in an earlier post, I haven't finished this. It's the Visual Basic end that I haven't written as yet. The uC and hardware end was working and spiced with a live BJT in ISIS. Attached is a very simplified block diagram of my approach.

Have any successfully completed this project??

 

Given that it is just shy a year old, probably not.

 

I wonder wat happened to CDRIVE and his project?

It looked pretty do-able, if the PIC micro reads the adc and just sends it as ascii serial data it can be logged at the PC side with any free terminal program and saved to a text file.

From there you could use Excel to chart the text data, showing multiple curves is also easy in Excel.