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International Journal of Mechanical Engineering and Technology (IJMET) Volume 8, Issue 11, November 2017, pp. 403–412, Article ID: IJMET_08_11_045

Available online at http://www.iaeme.com/IJMET/issues.asp?JType=IJMET&VType=8&IType=11

ISSN Print: 0976-6340 and ISSN Online: 0976-6359

© IAEME Publication Scopus Indexed

INTEGRATION OF HEATING SYSTEM USING

OUTPUT SIGNAL OF MYDAQ CONTROLLED

BY LABVIEW

Vipul Kumar Sharma

Research Assistant, Drexel University, Philadelphia, PA, 19104

Ajeet Kumar

Assistant Professor, Guru Nanak Institute of Technical Campus, Hyderabad

ABSTRACT

In this paper, a Heating System is proposed by using output signal from myDAQ.

To achieve this aim, Labview is used to execute a series of program to analyse set of

data, with an aim to achieve a perfect result. Instead of thermocouple a thermistor is

used to determine the temperature as myDAQ lacks CJC terminal. To evaluate the

program consistency a thermometer is used in parallel which compares the outputs. It

is found that myDAQ can be used as a controller, which can also be used to give

output.

Keywords: myDAQ

Cite this Article: Vipul Kumar Sharma and Ajeet Kumar, Integration of Heating

System Using Output Signal of myDAQ Controlled by Labview, International Journal

of Mechanical Engineering and Technology 8(11), 2017, pp. 403–412.

http://www.iaeme.com/IJMET/issues.asp?JType=IJMET&VType=8&IType=11

1. INTRODUCTION

DAQ known as data acquisition are the device which collects live signals from any device and

interpret it into digital form. It can measure small electrical signals as well as physical

phenomenon. It contains sensor and hardware and needs a computer program. The software

used here is Labview. It contains firmware for DAQ from which a significant program can be

made. As both the hardware and software are made by National Instruments, so they are

compatible. DAQ is mostly used to acquire and read the signal but it can also be used to

output voltage. The output voltage has a very low current. The output power is very less and

can’t be used for high power requirements. To fulfill the need, an outside power can be used

while the output of the DAQ can actuate small electronics.

In order to achieve this aim, a circuit has to be built which can fill the requirements.

Integration of Heating System Using Output Signal of myDAQ Controlled by Labview


2. THERMISTOR

Thermistor which is derived from more descriptive term “thermally sensitive resistor” is a

type of resistor which depends on temperature change. The relation between temperature and

resistance of a thermistor is depends upon the material used. Basically, two types of

thermistors exist namely NTC & PTC.

• In NTC, resistance decreases as temperature rises.

• In PTC, resistance increases as temperature rises.

For this project two thermistors were tested one is Vishay 10k and the other is Honeywell

100K thermistor. The 10k thermistor gives quite a satisfactory result with the temperature

range of - 40 to + 125 °C while 100K thermistor, which has a higher temperature range and

operating temperature ranging from - 60° C to 300° C.

Figure 1 a) Vishay NTCLE-100E-3103 10k thermistor

b) Honeywell 135-103FAD-J01 100k thermistor

3. STEINHART–HART EQUATION

Steinhart–Hart Equation is a resistance model of semiconductor at different temperatures. It

can be written as follows

1

. ln/ C. lnR/Rt D. ln/

Where: T = degrees Kelvin, R = Calculated Resistance, Rt = Thermistor resistance

While A, B, C and D = coefficients derived from measurement

To know the coefficients A, B, C and D measure the thermistor at four different

temperatures. The temperatures should be evenly spaced. Then by using these four

temperatures, it is easy to derive and solve these equations. These equations help to derive A,

B, C and D which remains same for the given temperature range. By knowing A, B, C and D

of the thermistor allows the use of Steinhart and Hart equation.

For 10k thermistor, (REF 5)

A= 3.354016E-03 B= 2.909670E-04

C= 1.632136E-06 D= 7.192200E-08

4. myDAQ

Data Acquisition Devices allows to measure live signal as input commonly used as plug-and-

play computers-based lab instruments, including a digital multimeter (DMM), function

generator and oscilloscope. It can perform experiments and exercises with the arbitrary

waveform generator, dynamic signal analyzer (fast Fourier transform), digital input, and

digital output. With LabVIEW software, it can analyze signal as input and project output

data.

Vipul Kumar Sharma and Ajeet Kumar


Figure 2 Pinouts myDAQ

This myDAQ has a major problem that it does not have CJC (Cold Junction

Compensation) which is required for all measurements of temperature as a reference.

Thermocouples just measure a temperature between two points and it’s not absolute

temperature. So, a thermocouple cannot be used to precisely determine the temperature,

instead a thermistor can be used.

5. CODING myDAQ WITH LABVIEW

The myDAQ can be connected to a thermistor and can be used to measure temperature. The

desired thermistor is wired in a circuit as a resistor. It requires a positive input on one side

and a negative input on the other side where the orientation is not important.

Figure 3 (REF 18) Wiring thermistor to myDAQ

Now with a simple program in Labview putting Stein Hart Equation into a loop resistance

can be converted to temperature.

The program is made for 10k thermistor and can be further updated according to use. To

change the program according to the thermistor rating, update DAQ configuration and

Steinhart Coefficients. Updating myDAQ can be done by configuring the DAQ with the 100k

thermistor using internal IEX source and 2 wire configurations. Putting 1 sample on demand

will take resistance value at an instance.



Figure 4 Steinhart Equation in a loop

Figure 5 DAQ upgradation for 100k thermistor

In LabVIEW, the program should measure the resistance value coming from the

thermistor of 100Ω to 100kΩ. This value is then converted to a temperature using the

polynomial equation from the thermistor specifications referenced at the end of this

document. Finally, the output is the result to a numeric indicator and a temperature chart on

the front panel.

Inside the while loop on there is the DAQ Assistant. It’s configured to read a single value

from the myDAQ DMM terminals at the time it executes. Once a value is read it is passed

down the wire, it is divided by 10000 and then the natural log is taken of the quotient before

being again passed into the formula node. The resistance is then further converted into a

temperature in Kelvin using the Stein Hart polynomial equation and constants from the sensor

specifications.

6. GRAPHICAL METHOD

Another idea is to take up the resistance vs temperature chart of thermistor and put these

points in the Labview. This gives a T vs R graph which is exponentially decaying. Now

merge the graph with the exponentially decaying graph, which are quite close. Now try to

interpolate the points, as the myDAQ can measure resistance, it can give the corresponding

value of the temperature.



Figure 6 Thermistor graphical method

This interpolation gives quite a result even better than using stein hart equation. The

temperature always has a tolerance of 1.25 degree, which for higher temperature measurement

is outstanding.

Table 1

Graphical Method Thermistor

(Reading)

Thermometer

(Reading)

Sample 1 111.0 112.7

Sample 2 67.5 68.4

Sample 3 53.4 54.0

Sample 4 27.9 25.8

This is measured from a thermometer to check if the result is consistent. The result is

always consistent and has a gradual decrease or increase in the temperature.

Figure 7 Result comparison with graphical method

Now, one part of the loop is complete as till now it is only able to read temperature. To

control the temperature, integration of Matlab script into the Labview should be done.

7. INTEGRATION OF MATLAB INTO LABVIEW

Here the temperature can be controlled from the program. For this there will be integration of

Matlab script with the Labview. The condition is specified into the Matlab script which in

turns gives the output voltage as required. The condition is such that if the desired

temperature value is less, then it will have to output voltage on a certain selected pin. While if

the temperature is high, then there won’t be any voltage.



Figure 8 Integration of matlab with labview

This can be seen in the following figure that the temperature will be constant by applying

this coding. To read and verify temperature, thermometer is added.

Figure 9 Controlling temperature

Now checking the pins for output voltage. As the selected output voltage was 10V, so

there is high enough voltage, but the current is very low, as low as 2mA, which is very

difficult to run a heating element. The heating element requires at least 10W to work.

8. myDAQ AS CONTROLLER

As a result, taking graphical method and combining with Matlab completes the whole circuit.

As known the output voltage is very low, so using transistor as a triggering and relay as a

switching device to complete the circuit.

The DC supply used is a Protek dual dc supply, which can give up to 30V and 1.5 A,

which is high enough for the heating element. As this can give up to 45 watts of power, which

is enough for a small heating pad whose requirements range from 10-15 watts.



Figure 10 Protek dual dc supply

Now the relay which is going to be used is HY1Z-5V, Signal Relay. It has a coil

resistance of 125ohm with a contact current of 1A. This coil needs a 5-volt battery. The

highest contact VDC is 30V. This simple N.C and N.O contact will be triggered through

transistor which will allow relay to switch on and off during the process. This will bypass the

required current for the heating element through DC supply.

This has a common terminal which connects directly with N.C without being charged and

connects with N.O when it’s given current.

Figure 11 (REF 9) HY1Z-5V Signal Relay

The transistor that will be used is 2N3906 or 2N3904 PNP. It has an emitter base voltage

of 5V which is sufficient for its working with DAQ.



Figure 12 (REF 12)2N3906 PNP transistor

The transistor will allow to trigger relay, as the transistor collector is connected with the

relay, which provides its high voltage. The base is connected with a 1K resistor and the

emitter is connected to the ground.

Now, comes main part of the heating system is the heating pad. This 12V 10W Polyimide

Flexible Membrane Thermo Foil Heater Heating Film has an internal resistance of 15ohm

with the working temperature of 140 degree Celsius. It is a polyamide thermos foil heater

which has a high rating of 10 watts that generates high temperature range of 230 to 300-

degree Celsius maximum.

Figure 13 (REF 16)12V 10W Polyimide Flexible Membrane Thermo Foil Heater Heating Film 80mm

x 10mm

9. PROPOSED HEATING SYSTEM

The proposed heating system is a loop which acts on triggering. The relay is connected to a

5V battery supply to energies it. The transistor base is connected to 50K resistor which is then

connected to a 5V output of the myDAQ. The emitter is connected to the negative of the

battery as well as the negative terminal of the myDAQ. Where on the other side, collector is

connected to the relay coil which completes one half of the circuit.



Figure 14 Proposed heating system

The other half of the circuit is connected to a DC power source which gives around 10V

and 1A for the heating element. The myDAQ is directly connected to Labview which is run

through the loop. This system is checked with both the transistors 2N3906 & 2N3904. The

result is best derived from 2N3906 transistors.

10. CONCLUSION

The output signal of DAQ can be used for many purposes. The DAQ can be used not only for

data acquisition but also as a controller. It can be used in different fields. Some of the uses of

flexible heating system can be seen in 3D printing, domestic blankets, jackets. To be sure that

heating system should be fully functional a large amount of open and closed source software

in conjunction with microcontrollers to get it operational.

The transition of hardware and software through the development of a GUI which can run

by LabVIEW. The experiment shows very satisfactory results for any type of heating system.

The only part required is the fully integration of all sort with the Labview. The plan on

continuing the development of the GUI and the development of a firmware for use with a

fully functioning and integrated heating system.

11. FUTURE WORK & DEVELOPMENT

Although this project has a lot of scope to develop, future plans has to continue development

into the final finished product. The goal is to build a fully functional heating system which

can be only controlled by LabVIEW. The flexible heaters can be used in domestic as well as

industrial purposes.

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