Temperature Meter Tear-down and Elastomeric Connector

 Temperature Meter Tear-down and Elastomeric Connector

The cheap temperature meter, the mysterious elastomeric connector, and reincarnation.

This part explores bare-metal working, the other two in later parts

~ Rajeev Mehndiratta

Image: 1 thermometer front case, elastomeric connector and crystal display

What's a digital thermometer?

It has a 150mm long pen-type probe, few buttons, a display, and is powered by a tiny button cell. It is a versatile temperature meter but mostly used in the food industry and your kitchen could have this.

One popular model that pops out in the web search is TP-101. It is available on almost all 

the e-stores for worth INR 150, near $2. But I don't have this exact model but is almost 

similar to TP-101 in specifications and features. This has been labeled 'Eurolabs' waterproof 

digital thermometer. Both are made in china.

Image: 2 TP-101 model thermometer Source: web

Specifications

The user manual narrates it can measure a wide range of temperatures from -50° C to +300° C (-58°F to +572°F.

• Accuracy: ± 1° C

• Sampling Rate: 1 Second

• Battery: 1.5V LR44

• Ambient Temeprature: -10° C to +50° C

Bare-Metal

It has a tiny 40mm x 15mm PCB with COB, chip on board, mounting. Few SMD resistors and few more SMD capacitors. A 2.2uF/50V electrolytic capacitor surprises with its voltage rating of 50V. I understand might be a non-availability of the lower voltage rating  capacitor or no major price difference between the lower and high voltage at the time of  assembly, but both reasons are difficult to digest.

It runs on a 1.5V LR44 button cell. No transistor or other active component can be seen on either side of the board. Understandably everything is accommodated inside the COB.

Two micro tactile switches for on/off and changing temperature mode.

It has eleven copper pads to connect with the LCD through the elastomeric connector.

A battery placeholder and sensors connections complete the PCB.

 See image 3 and 4 front and backside of the PCB.

Image: 4 Back side of the PCB

Sensor

Honestly, I ransacked the whole internet in search of the type of sensor used in the device 

to sense the temperature. But I could not get any answer to my queries. Digging more deeper

 I found one post that itself was in dilemma whether it could be a thermocouple or thermistor. 

So, I decided to sacrifice one sensor probe! :)

It has one Glass Type NTC, negative temperature coefficient, thermistor at the tip and 

connecting wires are covered with a transparent insulated rubber tube. See Image 5.

  Image: 5 NTC Thermistor

NTC

An NTC stands for Negative Temperature Coefficient. As they have a negative

 temperature coefficient the resistance decreases with the rise in temperature and increases with the fall in temperature.

See the below equation relationship between resistance and temperature:

ΔR = - kΔT

where,

ΔR, change in the resistance

ΔT, change in the resistance

k, temperature coefficient

Kindly note that the temperature coefficient k for NTC is negative because resistance decrease as temperature increases.

Image 6 showing resistance of the thermistor at near 29° C and image 7 shows 

resistance at 37° C.

Image 6 showing resistance of the thermistor at near 29° C and image 7 shows 

resistance at 37° C.

Working

As I mentioned earlier there are no active components are mounted on the board so COB 

is the big boss. As COBs don't have numbers and datasheets like ICs the working can only 

be speculated based on the experience, so don't claim it to be absolutely correct. 

At the same time, you can trust it is not absolutely incorrect! No contradictions!

Change in resistance is converted into corresponding voltage with a voltage divider 

or Wheatstone bridge. This analog voltage is converted into digital format with 

ADC and displayed on the LCD.

The button cell provides the power of 1.5V to run the circuitry. Please see the block

diagram.

Goodbye!

Rajeev Mehndiratta

15th September 2021

15:23 HRS

HITIPanel Software and Arduino In Industrial Prospect

 

HITIPanel Software and Arduino In Industrial Prospect

A third-party Arduino development software promises to develop, control and monitor professionals projects. Let's dive into the tool to see what HITIPanel software promises and how much it succeed to develop industry-grade projects.

A few months back!

A couple of months back I wrote one blog warming up discussion over a bare-metal microcontroller programmer and an Arduino developer. Blinking an LED on any microcontroller requires a dozen of lines and its 2 lines cakewalk on any Arduino series board. In your eyes who is an embedded system developer? What do you think a microcontroller-based project is more reliable and industry compliance or an Arduino one?  I know you are doing some brainstorming and would end up giving both guys equal marks! But I am not convinced it is like comparing a homemade pan maggie cooked by your mom and a 2-minute oven cooked!

A few days back!

A few days back I came across one pushed advertisement on a social media platform promising to develop professional Arduino projects. And they claim it is being used by top engineers and developers. This is HITIPanel Software.

What is HITIPanel?

"HITIPanel is a software which allow you to control and monitor your Arduino through the customizable control interface. Moreover, HITIPanel is a great development tool which helps you develop your Arduino projects faster", this is what the manager Mr.Christophe Landret says in his post.

Road Testing 

So, then I decided to install the trial version of HITIPanel to give it a try and make a comprehensive analysis.

After installation and doing some settings I was ready to go. As it uses propriety protocol so you have to add its library "HITIComm" and some required functions. See image 1, showing my setup and HITIPanel.

Control, Monitor, and Debug

There are "Panels" and inbuilt "Libraries" to control and monitor different hardware sections to see what is happening behind the curtain.

As for my setup, we will use the "Digital I/O Control Panel" to:

• Monitor digital input(a SWITCH on pin 3)
• Control a digital output(the on-board LED on pin 13)

 You can bind a name with the pin number like LED, Switch to address it by name in any other panel. To turn on the LED press the "IO" button in the command window and the inbuilt LED turns on, again pressing it you turn the LED off. See in image 1 and the Video. 

Image 1: Command Panel

This is the reverse of the above process here we toggle the switch from the breadboard and you can see toggling of the color dot in the command window.

For the above example, we used the "HITIComm.h" library and some built-in functions, see code.

/*
 HITIComm examples:  Basics / 1_DigitalInputOutput

 This sketch shows how to use HITIPanel software to:
   => monitor a switch
   => switch on/off a LED

 - switch         on pin 3
 - on-board LED   on pin 13


 More info at https://www.hitisoftware.com
*/

#include <HITIComm.h>


// pins assignment
const int pin_Switch = 3;
const int pin_LED    = LED_BUILTIN;


// run once at power on
void setup()
{
    // initialize library
    HC_begin(); 
   
    // pins mode
    pinMode(pin_Switch,  INPUT);  // pin 3  -> INPUT
    pinMode(pin_LED,     OUTPUT); // pin 13 -> OUTPUT
    
    // switch ON the on-board LED
    digitalWrite(pin_LED, HIGH);
}


// run repeatedly after setup()
void loop()
{
    // communicate with HITIPanel
    HC_communicate(); 
}

So, in this simple example, we saw to control and monitor input-output ports that can help in the debugging process also.

You can use the "chart" feature to plot up to 12 data versus time, to visualize the working and timing. I plotted one chart between time and  2 data, LED state and Switch State. You can also export all these recorded data into an excel file for later analysis. See Image 2 time and switch plot. 

                                                    Image 2: Switch Toggling Waveform

You can also monitor SRAM's occupied memory used to run your program. Stack for interrupts and function calls, Heap for dynamically allocated data. This helps to debug the program it has a memory issue. See SRAM Panel Image 3

                                                            Image 3: SRAM Allocation

One feature I liked most it to measure loop cycle timing as all of the repeating code is dumped into the loop! Here are some readings:

• Minimum Value, when no communication occurs: 20uS
• Maximum Value, when peak communication occurs: 2024uS

This can be very useful in debugging and optimizing long programs.

There is an EEPROM Panel that displays the Global Space and User Space (Boolean, Byte, Integer, Float, String). See image 4

                                                                Image4: EEPROM

There are more panels, libraries, and examples to explore. Like "Keyboard Panel" using that you can make a virtual switch.

Apart from the base library, there are libraries for Timing, Motor Control, and Signal Processing.

My Analysis or Review

In my perception, HITIPanel is more of a debugging software tool to see what's happening inside hardware and watch variables and values. This can be used as a quality control software while the product development cycle as there are many vital parameters to analyze like loop cycle time, chart plots, data logging.

This could be fine for very big programs where execution time and memory could be a serious concern in an industrial environment. For small and medium sketches it does not make any sense at all.

So, getting back to my maggie example there are more things to, cook, see and control like SRAM to see a shortage of RAM,  EEPROM  library enables management. But at the end of the day, it does not give you finer control over hardware as the microcontroller gives. Moreover, in the era of FOSS, this is a paid a maker license cost 49 bucks and a pro 99. It's not my cup of tea or maggie maybe in the context of my example. I would not make one a professional embedded system developer and a professional Arduino developer is only fun! Keep my words. 

Bottom Line

If you develop embedded solutions for industry using Arduino series of boards you may consider it if the trial version gives you productive results like increased reliability, stability, speed, performance, lesser bugs, and increased life span of the product. Here is the download link https://hitisoftware.com/hitipanel/

Kindly do give a try to this software and post it in the comment box, what others see is also important as the Arduino community is very large.

Thanks

Rajeev Mehndiratta

👾

Measure USB Current without Tears - USB Power Meter

 Measure USB Current without Tears

To measure the current running through USB wires of devices we have to cut off the wire from the middle then connect DC ammeter or Digital Multimeter. This is not only tedious to do but ruins the device sometimes. 

Fortunately, there is a handy device called with several names on web "USB Monitor", "USB Doctor", "USB Power Meter", is available in the market. Anyway, I am gonna call it a USB Power Meter as it measures the power-related parameters of the USB. See Image1.

                                            Image1: USB Power Meter connected to power bank

 It measures voltage, current, time elapsed and power delivered as well. The most beautiful thing is that using this is a layman's job. Just insert it into the USB power supplier plug like charge adapter or PC port and insert USB device or cable into its port of the meter.

                                Image2: Parameters Measured

All the parameters are displayed on its screen. Voltage, Current, Time, and Power Supplied. See image2.

As we know +5V is the standard supply voltage for all USB devices, actual measured voltage is displayed on its screen

The other parameter we are most interested in which is current is displayed in milli-ampere, ma is displayed in real-time on its screen. This makes the USB Power Meter useful stuff for an electronics engineer or enthusiast. But you have to satisfy yourself at the 2A maximum current limit of the USB Power Meter.

There is another good parameter that measures power supplied in millliampHour, mAh, over time. This can be used to record how much power has been supplied to a device, while charging a phone battery with a charger we can measure how much power the battery stores and compare with labeled mAh, and judge battery aging and quality. As this parameter is recorded into the meter memory you need to Reset it before you another round of measurement. See image3 for connections

Uptime is also displayed in HH: MM format.  

                

                            Image3: Device Connections and Measuring Parameters

I am not posting any buying link as it is easily available from famous e-commerce sites. You can google it if you need one.

Do you like this device? Post your comments, views and any doubts, queries below in the comment box.

Thanks

Rajeev Mehndiratta

👾