Hi everyone,
I have a course project where we need to design and build a system to measure the temperature of water in a geyser. One constraint is that we are not allowed to use microcontrollers or development boards (Arduino, ESP32, etc.). We’re expected to implement the measurement and display using basic analog/digital building blocks instead.

My current idea is:

• Use an LM35 temperature sensor
• Add signal conditioning with op-amps
• Feed the signal into an ADC or ADC + display driver IC
• Drive a 7-segment directly from that

I’m also considering adding comparators for over-temperature cutoff or alarm.

Does this seem like a reasonable architecture?
Are there better sensors, ADC/display ICs, or simpler approaches you would recommend for an MCU-free design?

Any suggestions or example circuits would be really helpful. Thanks!

 

hi guy,
Welcome to AAC.
As this is homework we need to see your best attempt at answering, then we can help you.
Post a simple sketch showing your draft circuit.
E

 

Hi everyone,
I have a course project where we need to design and build a system to measure the temperature of water in a geyser. One constraint is that we are not allowed to use microcontrollers or development boards (Arduino, ESP32, etc.). We’re expected to implement the measurement and display using basic analog/digital building blocks instead.

My current idea is:

• Use an LM35 temperature sensor
• Add signal conditioning with op-amps
• Feed the signal into an ADC or ADC + display driver IC
• Drive a 7-segment directly from that

I’m also considering adding comparators for over-temperature cutoff or alarm.

Does this seem like a reasonable architecture?
Are there better sensors, ADC/display ICs, or simpler approaches you would recommend for an MCU-free design?

Any suggestions or example circuits would be really helpful. Thanks!

Hi,

I think the LM35 isn't too bad of a choice, but the first thing to do with any component is to look up the data sheet, which tells you a lot about the part and often how to use it too.

These days most part data sheets are available online. Back in the day, you had to have a library of data books that took up a lot of room.

 

I’m also considering adding comparators for over-temperature cutoff or alarm.

Are there better sensors, ADC/display ICs, or simpler approaches you would recommend for an MCU-free design?

Signal conditioner AD597

• Operates with Type J (AD596) or Type K (AD597) Thermocouples
• Built-In Ice Point Compensation
• Temperature Proportional Operation – 10 mV/°C
• Low Cost
• Temperature Setpoint Operation – ON/OFF
• Programmable Switching Hysteresis
• High Impedance Differential Input

 

I asked Google whether the LM35 includes internal signal conditioning. Here is the answer:

Yes, the LM35 temperature sensor includes
basic, built-in signal conditioning, allowing it to output a voltage directly proportional to the Celsius temperature without needing external linearization or calibration.
However, for many applications, additional external signal conditioning is often added to improve accuracy or resolution.
Here is a breakdown of the signal conditioning aspect of the LM35:

Built-in Signal Conditioning (Internal)

• Linearity: Unlike thermistors, which require complex circuits to linearize their output, the LM35 provides a linear output of 10 mV/°C.
• Calibration: It is pre-calibrated to measure Celsius temperatures, requiring no external trimming.
• Low Output Impedance: The sensor acts like a voltage source, making it easy to connect directly to microcontrollers (like Arduino) without complex buffering.

External Signal Conditioning (Optional but Common)
While it works out of the box, you may need additional circuitry to enhance the signal:

• Amplification: To increase resolution (e.g., if using an ADC with a high reference voltage), an operational amplifier (op-amp) can be used to increase the 10mV/°C sensitivity.
• Noise Filtering: A 10 nF capacitor is often added between the output and ground to minimize noise and improve stability.
• Negative Temperature Support: To measure temperatures below 0°C, an external resistor and a negative power supply (or a voltage divider) are required to shift the output signal.

In summary, the LM35 is an integrated circuitthat does the heavy lifting of signal conditioning internally, but external components are usually added for specific application needs.

So, what signal conditioning do you intend to add?

 

A thought,
KISS..
do you need a digital display ?
how about a good old analog meter ?

 

hi,
The TS has stated this:
We’re expected to implement the measurement and display using basic analog/digital building blocks instead.

 

hi,
The TS has stated this:
We’re expected to implement the measurement and display using basic analog/digital building blocks instead.

thanks, got that, but I cant see it saying the display needs to be digital,

 

Whatever approach you take, go for incrementalism in your implementation. Don't worry about displaying something in a finished form until you have something worth displaying. Initially, start off with just your temperature sensor and the bare minimum of analog circuitry to get a voltage that you can display on a multimeter. Don't go any further than that until you have that circuitry working the way you want it to.

What are your basic specs? What are the min/max temperatures you need to be able to measure? How far away from the water stream (I'm assuming you plan to put the sensor directly in the stream as opposed to using infrared or other remote sensing approach) will the electronics be? How accurate do you need the reading to be? If you weren't given those as criteria, do a bit of research and come up with your own, trying to establish goals that are reasonable.

Finally, don't worry about bells and whistles until you have the basic requirements met. I've seen students fail in projects because they spent all their time focused on features that weren't asked for and ended up with something that couldn't do what was.