07/24/2017 at 19:29 •
I started working on the nev version prototype, which will be really simmilar to the Tektronix TR210. For use you will be need an oscilloscope to display the curves.
It will have:
- 2 channel
- 6 voltage ranges
- 3/6 frequancy ranges
- will work both 230V and 110V AC
I still have to finish the pcb designe, and manufacture them.
06/29/2017 at 17:05 •
It has tree main part, which are:
- Display (2.4" TFT Touch display)
- Arduino pro mini (5V 16Mhz version)
- Analog stage of the curve tracer
The display has 320x240 pixel resolution, which is perfect for this application. I only use 240x240 pixels for the curves and the other part of the screen is used to show some basic parameter, which is minimum and maximum measured voltage. These two voltage point can show you the break down points on the Zener diode for example.
When I was developing the sketch I was optimistic to use the Arduino pro mini, but end of the project I had to realise it can not handle very well the display functions and at the same time the measure functions. I ran out very quickly of the 2K RAM, so I had to do some optimalisation. In the "final" code I am using half of the program memory and almost 90% of the RAM. On the Pro Mini I had to use almost all digital and analog pin, to make it working.
For power the microcontroller and the display I used a small DC-DC converter, which I not recommend to do, because I figured out it makes a lot of noise. This noise has a very bad effect on the current measurment, that why I do not have a perfectli straight line on the display.
On the picture above you can see I hacked a button on the red probe. That button has a purpose, if you push it when you measure something, the tracer can store that curve into the memory. The stored curve showed on the display as a red curve, and same time you can measure a other component, which you want to compare it.
Part of the code was from my other project, which was a simple arduino oscilloscope I made. I never thought I can use it for anything usefull, because of the low speed, but for this project it was perfect. I modified to handle two channel, and it worked perfectly.
In this project I did not need any trigger function, because it does not matter where the drawing is starting. It just simple measure 240 point on each channel as fast as can do, and after those stored in two array, it start drawing the dots on the display.
After all this project was successful for me, I learned a lot.
A slow mo video how it works:
In the future I would like to separate the display functions from the measure functions.
I am thinking about to make a function generator for drive the analog section, and then I can change the voltage, frequency and with some other component the resistance, with I can limit the current.
04/19/2017 at 18:03 •
I was working on the auto range function on the tracker, and it is working properly now. I can set anything, and the lines now stay stable. It was a the biggest job in this project I think, because I had to do a lot of research about op-amps. After all the programming was a bit difficult, but after I figured the method, is is quite simple.
I did not make a video about the new function, becaus I last video is almost the same, one that changed, the waveform stay steady, whenever the Voltage or Resistance range changed.
The curve tracer now have:
- 25 Voltage range from 1V to 20V peak-peak
- 5 Resistance range (50 , 2k, 10k, 17k, 25k ohm ) I will expend this to 10-15 ranges, it is not to difficult.
- 6 Frequancy range from 120Hz to 1.2kHz I will expand this as well, up to 2kHz, or above.
- USB connection to PC, for save waveforms.
What do not work yet, known bugs:
- Have to press twice the main menu button to go to main menu. (bug)
- Need a front foil, with things printed on it.
- First start up, the auto range function works only, when you go to first in to the Voltage menu
- Have to make full schematic and circuit designe, to send out to the PCB fabricator
- I can make a scanner for the curve tracer, but have to think, wher can I place a connector on the front panel.
So yes I am slowly gettint closer to the end, but every working hours on it, I see more, in this project.
03/26/2017 at 20:33 •
03/13/2017 at 22:12 •
It was not to difficult and not too much work to made the second channel ussable. Whit this I can compare 2 component, and see if those have any different.
I made a little video about how it is works now.
In the video the first test was between a 6.2V zener and a 8.2V zener diode.
In the second test I used a LED and a normal diode.
03/08/2017 at 21:28 •
I have been working hard on the tracker, I built it together, so no more breadboard floating around. I found some problem with the auto ranging circuit, so it is not working yet. I also had to change the rensistance ranges, so in this state I have 5 ranges, but I would like to upgrade to 8 or more, if it is possible. I have to work on a lot of things still, so it is some photo, where is the project now.
02/23/2017 at 22:06 •
Hi everyone, I made a lot of progress since the last log. I worked on the Curve tracer like almost every day around 2-3 hours.
It is more complex then I thought in the past, it will be. Now it is sort of working, with some function.
What is working:
- I can change the voltage range between around 40Vpp - 0.5Vpp in 25 steps.
- I can change the frequency between 170Hz and 1.1kHz in 6 steps.
- It is working from the main now, but if I want I can program the microcontroller at the same time.
What does not work yet:
- I can use only one resistance range at this moment, but I am working on it. It will have 15 resistance range at the end.
- The automatic voltage level stabiliser, which will adjust the lines to the maximum screen size, when you change the voltage range.
- I need to finnish the main sreen (the big one).
- I have to fix some bug.
- The alternating mode is not finnished yet. (second channel)
- And some little stuff.
And the video ;)
02/05/2017 at 17:45 •
Recently I had not too much progress on the V2, but on this weekend I made one of the main part of the curve tracer, which is the sine wave generator. On the Version 1, I did it with a simple solution, with a transformer, which give me 12V 50Hz sine wave. It was good for basic things, but if you would like to measure electronic components with series or parallel with inductance or capacitans, you have to use higher frequancy. At higher frequancy inductive and capacitive parts shoud act differently.
This is the reason, because you have to use a variable frequancy source, to drive your front end electronic. I would like to have 6 or more steps on the frequancy range like the minimum is around 50 (60)Hz and the maximum is up to 1.5 - 2kHz.
As you can see in the video, I did managed to do the electronic, and it is more than capable to make the sine wave up to 10-20Khz, if have to.
I had some difficulty to set up the generator, because sadly I have not get an oscilloscope yet. So I had to do it differently, like I did on the Version 1, I modified the code to act like a simple oscilloscope, because if you think of it, a Curve tracer is a dual channel oscilloscope in X-Y mode, so the arduino is basically an oscilloscope in this project.
After all, I was able to develop one channel with it, so I will just have to copy the other channel from the first one and it is ready to go. It can measure a sine wave up to 1.5-2kHz so it is in the ideal range. (If I have to I will use some ADC accelerator code)
In the video the signal was free running, because I not use any trigger function. I programmed 2 main menu, which you see at the start, and that one where you can see and set the values for the Voltage, Resistance and to the Frequancy.
The left upper button is the menu button, the next to it is the Voltage selector button. When you selected a menu, it show you on the leds and on the screen which menu you ar in. The up and down button is light up that direction where you can set the value. Like if you are 0 on the voltage value it is only showing the up button with the led.
At this state where the project is, I have not figured out if I have to isolate the Arduino DUE (measure and contorl unit) from the sine wave generator completely or not, but I think I might be.
I also changed the code and now the display is smoother than before on the Version 1.
01/10/2017 at 22:45 •
So I am done with the case, and the front electronics, the screen, buttons and LEDs all works.
A little demo video, how it gonna look like.
01/02/2017 at 19:59 •
I mentioned in the last log, I had not too much time build the Curve tracer V2, because of the holidays.
In January I would like to put together the hardware section of the tracker, I did already finish the front of the device, it is looking good I think. After I got the Arduino Due I put ut together with the screen, and started work on the display functions, which is far to be done, but it is something.
The buttons will light up when you selected the mode with them.
I am planning to make a sticker for the front, to hide all mistakes what I made, and also it will looks more professional.
Some picture of the current state: