It's alive!

Actually only the demo app that was preloaded in my launchpad is alive.
But it was a pain in the ass.

First I started with installing all the IDE's (there are 2 available), and then i wanted to check out the demo application.
But in my rush I forgot to instal the drivers for the launchpad... |:(

So if you are planning to use this make sure you do the next things:
1) Instal the IDE you want to use
2) Connect th launchpad to your PC
3) your PC will ask if he needs to search for drivers, make sure you can select were
4) Select "\ccsv4\emulation\drivers\msp430" (windows (even vista) will select the correct driver, so don't worry about that)
5) run the demo GUI you can find at he site of TI
6) That's it =).
This is how it looks :p

TI msp430 launchpad arrived! :)

I have some good news to anounce, today my order of TI's ADC arrived.

A first look tells me we have a potential winner were we can implement our PID controller in ;)

So the next few days I will do some 'experiments' with the launchpad to figure out how the IDE works and see what kind of stuff I can make with the launchpad.
Here is a picture of the launchpad:

To be continued... ;)

Peltiers revealed

In this post I will try to explain how Peltier elements work.

A Peltier element is a small device which basically transfers heat or cold from one side to other side.

In the industry they are widely used to cool laser modules because the wavelength depends of the temperature.
And since they are becoming cheaper and easier to get also computer enthusiasts are using them to cool their pc in the hope to get better performance.

How do they work?

A Peltier element, also called a thermoelectric module or cooler (TEC), is a semiconductor-based electronic component that functions as a small heat pump.
By applying a low voltage DC power source to a Peltier element, heat will be moved through the module from one side to the other.
One module face, therefore, will be cooled while the opposite face simultaneously is heated.

It is important to note that this phenomenon may be reversed whereby a change in the polarity (plus and minus) of the applied DC voltage will cause heat to be moved in the opposite direction. Consequently, a thermoelectric module may be used for both heating and cooling thereby making it highly suitable for precise temperature control applications.

Controlling a Peltier element

Thermoelectric coolers are DC semiconductor devices. All their standard specifications (performanceparameters) are given by manufacturers for DC current and voltage.
In many applications customers prefer to use PWM control. It means simple electronics and simple logical control.
At high frequency PWM the averaged current delivered to controlled object is estimated as equivalent of DC current of the same value.
It is true for many applications, but is a great mistake in a case of TECs.
TEC controlled by PWM operates less effectively than at DC current.
The PWM control is always less effective than TEC operation at the same average DC current and power consumption.

Neither are relays suitable to control Peltiers, these will cause a reduction of the TEC’s life time and you can’t exactly control the temperature of them, it will fluctuate too much.

DC Closed loop control is the best solution for TEC operation. It provides most effective use of TECs.In practice two control methods are in use: “Proportional-Integral” (PI) Control and“Proportional-Integral-Derivative” (PID) ControlFor most applications PI Control is enough.These PI(D) controllers can be implemented in software or done by discrete components (see my previous post)

Another important design note is that Peltier elements must always be cooled on their “hot”-side.
Otherwise you run the risk that you damage the Peltier by melting the internal solder.

Sources:
http://www.tec-microsystems.com/EN/Intro_Thermoelectric_Coolers.html
http://www.memmert.com/tekhnologii/koncepcija-temperaturnogo-kontrolja/sistema-nagrevaokhlazhdenija/
http://www.rmtltd.ru/tec_app_tips.htm
http://www.silram-cor.co.il/gp.asp?gpid=56

TI’s ADC part II + sample requests

The past few days I have been pretty busy.
First of all, we are allowed to participate to TI’s “Analog Design Contest” AND the Evaluation Modules (2x MSP430 + some other stuff) I requested will be delivered soon =).

While I was searching on Google for some information about Peltiers I suddenly came up to an application note of MAXIM-IC.
And their I discovered that they have made some IC’s especially for controlling Peltiers, in the app note was also a PID regulation drawn and explained.
So I sent some sample requests to rebuild the PID controller of the app-note:

·       MAX4475ASA                        OpAmp, Low-Noise, Low-Distortion

·       MAX4477ASA                        OpAmp, Low-Noise, Low-Distortion

·       MAX1968EUI             Power Drivers for Peltier TEC Module up to 3A

·       MAX1969EU               Power Drivers for Peltier TEC Module up to 6A

More info can be found here:
http://www.maxim-ic.com/app-notes/index.mvp/id/3318

Once I sent the sample requests I noticed that they also made Evaluation Modules exactly like in the app-note, but I wasn’t able to find the pricing/dealers.
SO I send a mail to MAXIM-IC for some more information about their Peltier-EVM’s
More info (except pricing…) can be found here:
http://www.maxim-ic.com/datasheet/index.mvp/id/3559

If we can use this, we basically only need to make a descent mechanically construction and find a good DAC, but we only need to concern ourselves about the first because at school they have a DAC of NI that can be used together with labview.

Afterwards I discovered that TI also made some IC’s for driving Peltiers. So I began to search a little more on their site and this is what I sampled at TI:

·       TMP100 - Digital Temperature Sensor with I2C Serial Interface

·       DRV592 - High-Efficiency H-Bridge (Requires External PWM)

·       TLC59108 - 8-Bit Fast Mode Plus (FM+) I2C Bus Constant-Current LED Sink Driver

·       MSP430G2231 - MSP430G2x21, MSP430G2x31 Mixed Signal Microcontroller

·       MSP430G2211 - MSP430G2x01, MSP430G2x11 Mixed Signal Microcontroller

Project specifications + TI’s “Analog Design Contest”.

Yesterday I have been mailing around to get some more information about what we may use from the previously posted open-source projects.
And what the requirement are of the system we need to design.
There are some tricky things (not blowing up the peltier, labiew interface, …), but I think we will over win them J
First something about the specifications of the system we need to design.

·        The temperature needs to be regulated stepless over a region from 10°C to 70°C.

·        The temperature must be regulated to a certain temperature within 5seconds, or if this is not possible, as fast as the Peltier can go.

·        It doesn’t has to run stand alone, but it is a bonus point =)

·        Additional sensor/actuators may be used, but are not necessary (i.e. a 7-segment display to monitor the temperature)

·        So far we have no limitation in the mechanical part (the height, width, depth, used materials, …)

·        We are free to chose the µC and which program we want to use to make the GUI on the PC

Also I have sent a mail to Texas Instruments to participate their “Analog Design Contest”, more info about this can be found here:
http://www.ti.com/ww/eu/university/analog_design_contest.html
This contest has some very cool features, you can get for 100$ of development tools and you can sample some free samples of their IC’s (that was already possible when you made an account on their site).

And if you are really going for it you can win some $$$ !!!.
The only thing you need to do for that is;

·       Use 3 analog IC’s of TI in your design

Or

·       Use a Microprocessor/controller of TI and use 2 other external analog IC’s of TI (so the internal ADC of the µC/P are not allowed :p)

The analog IC’s may be chosen from the following categories:

·     Amplifiers

·     Clocks and Timers

·     Comparators

·     Data Converters

·     Interface devices

·     Power Management devices

·     RF devices

·     Switches

·     Temperature sensors

So this won’t be a problem because we need at least one temperature sensor and a ‘switch’ to control the Peltier.
Also some Power Management Devices might be useful in our project to power the µC.
And the most beautiful part of it all, they have a small µC board (the msp430) that has a build in USB interface (I bet that it has some chips onboard to emulate a virtual COM port ;) ) for only 4,3$.
More info + a video about it can be found here:
https://estore.ti.com/MSP-EXP430G2-MSP430-LaunchPad-Value-Line-Development-kit-P2031.aspx

Our project in a nutshell

Today I finally founded some time to post on our blog.

We (me Glenn, and my teammate Dimitri) are assigned the “Bio-sensors” project.
At school they do research at bio-sensors and there for the need to be able to heat it up from 10°C to 70°C and vice versa.
We need to design that heater, and one of the main challenges, in mine opinion, is that it needs to be controlled over USB.

Our project leader had the idea of using Peltier elements, so this must be investigated further.
For our first prototype we probably will be using some of these Peltier element:http://samenkopen.net/action_product/927767/869562

And if our teacher allows us, we will be using an open source USB project for AVR microcontrollers, to provide the USB interface.
More info about this can be found here:http://www.obdev.at/products/vusb/index.html

A beautiful spin-off USB open-source project, that might be very usefull, can be found here:http://www.harbaum.org/till/i2c_tiny_usb/index.shtml
This uses a very small µC for the USB stack and needs only 2 more I/O pins to communicate with other periphery over the I2C-protocol.
So we can easily connect 1 or more temperature sensors on the I2C bus and an I/O expander to control the peltier element, even maybe some indicators/actuators like LED’s, pushbuttons etc.
The only problem we might run against to is that we run out of µC memory…

Only future will tell what problems we will have to deal with.