Easter vacation - PCB

In the Easter vacation we have made our PCB schematic.

This is a double-side PCB.
Previous week, we have send it to our teacher and he made it on the same day! What a miracle! So we could begin with soldering the PCB.

Friday evening was the print finished and we could start with testing. And Saturday, the hardware was finished: Mounting the fan & lamp , make holes for the air, holes for mount the PCB, etc.
Testing the PCB was not a succes, the circuit with the PIC don't work.
Today, tuesday, we searched together, and Joeri have located the problem. There was a problem in de design, the 2 resistors of the data-lines of USB weren't crossed. We solved this and the print had no more errors. Next friday we go test everything together. The PCB with labjack and hardware, and the PIC with hardware.

Start of trimester 3

Today we started with the 3th trimester.
It was here so quiet because we had exams.
Today we have drawed further the schematic.
It is almost done, just finish. And then can we begin if we have the components.
Earlier we can't begin drawing the PCB because we don't know al the
measurements of some components.
And today and the rest of the trimester we are going to search more about the software.
The intention is that the drawing of the PCB is finished afther Easter, than can the school
make this. And we also need to made a paper.

First total test

Tuesday was it a big day. The first version of the software was finished so we could test is with the hardware. But this was in a open classroom. But it works very well. 
The software is written in C++ because we started of an example, this was the easiest and quickest way. Joeri did well research in this stadium, because we had no C++ experience.

 

In the movie you can see a fan and a led. In the future will the led be replaced by a bigger lamp. But the led is an indication for the heating element.

When we start up the software we need to push on 'Start' and wait 5 seconds.

This is that we can measure already the temperature and than is the measured value
more correct. The lm35 needs some time to be at the correct value.

When this is done, you can see the measured temperature by the lm35.
And you can give in the temperature you want.
In our test, it was about 23°C in the classroom. So we set that we want a temperature
of 22.8°C.
Than will the fan power on and cool the lm35. When the temperature is below 22.8°C, the led turns on, because it was warmer in the class, the lm35 warms up etc, etc ...

Problems with software PIC

It is quiet here because we are trying to adapt the code of the software of the PIC.
But it is very hard for us, the code is written in C++, and we can't program that...

Hopefully we can tell you soon that we make progress with the code.

Testing with V-USB and AVR

The last days/week we were very busy with testing with V-USB and AVR.
We based us on the Powerswitch example:
http://www.obdev.at/products/vusb/powerswitch.html 

And this is our first prototype pcb:

But like you can see, it was very fast soldered with the result that it doesn't work.

So the next prototype need to build:

This time, the pcb works! So We have tested the powerswitch with the commandline software. And this was succesfull.

But afther this, we want to make a graphical software...
First we had a problem with the .dll. After this was fixed we saw that it is

on this moment impossible for us to let this work...

So probably we go use the PIC18F4550.

Our Own USB Interface

Today we have tested with the USB Data Acquisition Card of Elektor (click).
Our previous students, 2 years ago have made this PCB with the application
Ball and Beam. And the PCB was still at school.

After installing the drivers, we had a error while opening the demo software.
The problem was solved if we open the software as admin.

When this problem was solved, the PCB doesn't work anymore,
our previous students made a PCB with copper tracks with the thickness of a hair I think.
Soldering a wire and the problem was solved.
After that, we measured al the digital I/O and analog I/O.

This evening , we finished (hopefully) the list with components.
Tomorrow we hope to search how the Demo software works,
and made ourself Demo software.

A lot of progress - Prototype

Here we are after a while...
But we were very active...

First, we have coupled all the small circuits to each other to check if it is working.
This worked, but is was on breadbord.
So the next step we have done was drawing the schematic, where everthing is on it.
Al the foregoing circuits that we have maked, were small schematics.

The next step we have done, was build this circuit on a perfboard. This is also the prototype of the PWM. And the power supply is the power supply that we are going to use in the future for the project... (Adapters).

The bad quality is because it is filmed with my gsm.
While we have done those test etc, we have make a list with components.
This is almost ready, than can we give it to the school to order.

Schematic of hardware

This is a small visualization about how the klimabox probably goes look at.

Negative Supply voltage

Because we are going use the Adapters that are available in the laboratory we have only a positive voltage. For our project, the adapter needs to set to 12V.
But for the op-amps that we are using, we need a negatieve voltage of -12V.
We found a very simple circuit with a NE555. We builded it yesterday quickly and it works fine. We measured an output voltage of -11,62V. And the input voltage was 12,6V.
This is the circuit:

http://www.circuitsonline.net/schakelingen/139/voedingen/negatieve-spanning-met-ne555.html

PWM and Temperature sensor

Today was a productive day.
After a lot of testing of the PWM circuit, we had a good result.
The circuit is now working, but we only need to modify this.
We use now 4 single Op-amps (741) , in the future we go build this
with a quad op-amp IC.

This is a video of our signal:


And this evening, we are started with the LM35 Temperature sensor.
Here is also a first good result: we can read in the output of the sensor with the labjack.

This is the testcode where I send the measured signal on the input to the output but with a factor of 10 higher, so that it is easier to measure. Because the LM35 rise 10mV/°C.




---------------------------------------------



Public Class Form1
    Dim spanning As Double = 0
    Dim Checkken As Integer = 0

    Public Sub New()

        ' This call is required by the Windows Form Designer.
        InitializeComponent()

        ' Add any initialization after the InitializeComponent() call.

    End Sub


    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        Timer1.Start()
    End Sub

    Private Sub Timer1_Tick(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Timer1.Tick
        lj.LabJack.EAnalogIn(-1, 0, 0, 0, 2, spanning)
        lj.LabJack.EAnalogOut(-1, 0, (spanning * 10), 0)
    End Sub

    Private Sub Button2_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button2.Click
        Timer1.Stop()
    End Sub
End Class

---------------------------------------------
Video:

The circuit for making PWM

I told already that we are searching for a circuit to make a PWM signal with the analog output of the Labjack ( varies from 0 to 5 V ).

We found something that first makes a triangle waveform , and then makes with this triangle waveform makes a PWM signal.

Triangle waveform:

http://pcbheaven.com/circuitpages/Triangle_Wave_Generator/










PWM Generator:
http://pcbheaven.com/circuitpages/Voltage_Controlled_PWM_Generator/

But when we build it on a breadbord it seems that this is not quite stable.
So we ask our teacher of Electronics and he let us see a schematic in the handbook of Malvino. But we build it and tested it today while we have Electronics Lab. But this is only the part of making a triangle waveform.
But the circuit for making the PWM signal doesn't work yet. We need to do more tests.

The first tests

After talking with the teacher we knew that he is thinking about a temperature variation of about 2° in steps op 0,1°.

So this is normally possible with a small E10 light bulb of 3-5 Watt.

Yester we have done a first test with the Labjack. This was made a small program
in Visual Basic to turn on and off a LED on a digital output of the Labjack.
The reason of this test was that we want be sure that we can communicate from software to Labjack and turn on and off an output.
After installation of the driver and including the ".dll" we had the first test working.
This is our program code :
----------------------------------
Public Class Form1

    Private Sub Btn_aan_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Btn_aan.Click
        lj.LabJack.EDigitalOut(-1, 0, 0, 0, 1)

    End Sub

    Private Sub Btn_uit_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Btn_uit.Click
        lj.LabJack.EDigitalOut(-1, 0, 0, 0, 0)

    End Sub
End Class
----------------------------------

And this is how looks the frame with the buttons:

Also yesterday, we have removed 4 fans of old devices. So now we need only 1 more.
Today we have done the first tests with a fan and a small light bulb. We are now quite sure that it is possible to heat about 2° with a small light bulb. But the Labjack U12 doesn't support PWM, so we have to search for something else. We are now testing with a circuit that makes a PWM signal with a analog output of the Labjack.

Test of a small light bulb

A little test with a small light bulb told us that it is impossible to have enough heat.
We are now thinking of a light bulb of about 30 Watt in a E14 fitting.

Schematic of software

This is a small basic schematic of the software system.

The real object

Today, we have asked to the teacher what exactly the purpose is of the klimabox and with which materials we need to work.

The purpose is to design a nice control system. The perspex tube have a diameter of 50mm and have to be 10cm long.
The fan is a simple computerfan. (12V)
The heathingelement needs to be something like a small lamp. We are thinking about an old bicycle light. With a E10 fitting. And then 2 of these.
For the software we maybe go use a Labjack, this is easy for making an interface with usb.

Publication Project

We know now what our project is. We have to make our last choice: EA_Klimabox.
We have to make a cylinder of perspex(plexi) with a heating element and a fan.
The intention is making a circuit that holds the temperature in the cylinder constant.
And we need to design an application on the PC to show the working.