Sensor Recommendations and reference voltage

Other Hardware Sensors
1

Hello,

I'm looking to create labs utilizing the Op Amp 741 as a comparator. I'm looking for sensor recommendations to use. These sensors would need to solely be analog based since I do not want to touch any digital to analog conversations.

I've looked into the TMP37s, laser sensors, infrared sensors, a AM312 proximity sensor, a Sharp GP2Y0A21 distance sensor, and a flex sensor (acting as pressure sensor). The none specified items are just your generic Arduino sensors. I can provide links if you were curious.

Does anybody have any recommendations on the categories listed or even outside of them?

My other question is outside of sensors so I'm sorry if this isn't the correct place. Maybe someone can point me to a different forum? To set the reference voltage on the comparator, I would be just using a potentiometer. The output voltage on the TMP37 is 20mV per C. Most of the ones I found have a high voltage output starting at 2.6 V or higher so that's not an issue but the TMP is way to low. I don't even know what pot value I would need since I'd rather get recommendations first before I do the math. What temp sensor would you recommend?

Thanks!

2

Could you take a moment to explain the advantage of teaching electronics, starting with an op amp that has been obsolete for over 40 years?

5

It's a state requirement and on state testing. The government.....

That's why I'm incorporating the sensors. To start learning the process of analog readings and add actual value to this.

6

There is nothing wrong with the UA741, just very slow, prone to oscillation and far from "rail to rail" output swing. With a bipolar power supply you can work with any voltage in the range of -15V to 15V, with a bit of headroom.

If you are teaching analog electronics, it should be trivial to select a pot to use a voltage divider, e.g. setting a voltage reference as a trip point for a comparator.

Use 100K and call it a day, or clearly explain the problem.

7

The TMP36 has a 500mv offset so you can measure temperatures below 0C. At 25C it has a 750mv output. It is 10mv/C rather than the 20mv/C of the TMP37.

8

So use one of them and don't use the TMP37

9

Just for clarification, I’m trying use all types of sensors. Not just a temp sensor. All the sensors I’ve selected just have a 2.6V or higher output. Just the TMPs I was questioning but maybe someone knew a better to use for this application.

10

Very much apprecitated! I didn’t notice that in the data sheet but that makes total sense since how would you measure below 0 C. That makes things much easier. Thanks!

11

I think all of the 3 pin analog temperature sensors are 10 or 20mV/degree

12

Appreciate the info! Maybe this isn’t such a bad thing. The state is hell bent on Op Amps so maybe I’ll have students utilize the non-inverting op amp configuration to amplify the output of the TMP.