information on internal working of electronic sensors

Hi all,

I don't know if this is the correct place to ask. Feel free to point me to an other NG if this is off-topic here.

On the 27th of November, there is "de dag van de wetenschap" (the day of science) here in Belgium, and I am helping out a local fablab on this event.

This event is aimed at kids between 14 and 18. I help out in the "electronics corner"

We are working on a setup where we want to show all kind of electronic sensors. To link electronics with science, The idea is to provide the visitor with a description of the internal working of a sensor, and let them find the correct sensor in the batch.

So I am looking for information on the internal working of different kind of sensors. For certain sensors, it is well known (hall-sensor, light-sensor, ... ) and in certain cases it is described in the datasheets (laser-based CO2-sensor or fine-particle dust-sensor).

But I am looking for information on the following sensors / devices:

- temperature sensors

- air humidity

- gas (CO, VOC) that are not based on lasers

- hardware based gyroscopes


Cheerio! Kr. Bonne,

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On a sunny day (Thu, 27 Oct 2022 08:30:14 +0200) it happened kristoff wrote in <tjd8hm$2mt7c$

Did you try google <sensor type wikipedia> ?

Reply to
Jan Panteltje


Op 27.10.22 om 09:00 schreef Jan Panteltje:

Wait .. do you still use google?

I am old enough to know about "netiquette". Yes, I did do my homework before posting :-)

As said, for certain sensors, the datasheets do give me enough info to write a text for the 14-to-18 year audience.

But take -say- a BME280/BMP280, the only thing I can make out from the datasheet is that pressure is messured by a piezzo-electric element. For temperature and humidy, no info.

For the gyroscopes, I am wondering if they really messure the angular motion, or that they message lineair-motion in the x-y-z axis and then calculate angular motion based on that.

Cheeri0! Kr. Bonne.

Reply to

On a sunny day (Thu, 27 Oct 2022 09:33:35 +0200) it happened kristoff wrote in <tjdc8f$2nc2l$

Google is one of the most valuable things we have for [self]education. Of course it only works if you are interested. Combined ith wikipedia it replaces that many "Winkler Prins" I think it was encecopedia books on your hobby sheleves ;-)

Well I do not know much about evolution of the recent humming beans species but when I was about ten years old I was reading 'Zo werkt de Televisie" and "Zo werkt de radio" from Van Aisberg (you are from Begium? should know that name). In those books he has somebody (Vraagal" asking the right questions for who he then gives the right aswers. Asking the right question is a very important thing. Somebody here constantly askes the wrong ones and I gave up on educating that person. At 14 I was designing tube amps for the school band, radio transmiters, what not So it all depends on the student's interest and the teacher.

Mesuring temperature is usualy easy, almost any conductor is temperature sensitive, if it is a chip then chances are it is a silly-con and perhaps uses a diode junction that has, what was it? -2 mV / degree C or so temp coefficient, diodes make perfect temperature sensors, used those in big projects.

So google solid state humidity sensors?

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pick your choice. maybe that datasheet mentions one of those methods in the first few lines? coud well be resistive or capacitive?

You did say 'hardware gyroscope' that leaves only this:

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But if you are talking about MEMS sensors, like your [possibly smart]phone has (at least my Xiaomi has)
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etc etc

;-) fun

Reply to
Jan Panteltje

Contact the manufacturers; NXP, TI, Analog Devices, ST Microdevices, etc. Their sales reps will be happy to show up with box loads of toys. I have one sitting on my desk; a 10 year old ST Micro Mems evaluation module. A giveaway from a seminar. If you're not sure who the manufactures are go to Digikey and Mouser search for sensors. Get the info direct from the horse's mouth.

Reply to

Hi Don,

Op 27.10.22 om 10:32 schreef Don Y:

Well, the idea is that these sensors would also have some kind of display with the measurement-data from the sensor.

So by -say- moving their hands over it, or blow in them, or move a magnet over them, or move them around, they would see a change in measurements (or not).

I agree, on sight, a lot of these sensors look alike. :-)

That is an interesting point.

E.g. a laser-based CO2 sensor has a light that flickers over couple of seconds.

It's indeed a good point to mention the physical aspects of the sensor (if there are) in the description.

That's indeed what we had in mind.

Cheerio! Kr. Bonne.

Reply to

OK but you might want to think about things that either look impressive or will engage well with the teenage participants. Sensors these days are very often boring black boxes with two or more leads coming out.

Obviously there are local and modern H&S considerations that some of my suggestions below may well fall foul of. I was in the last cohort to experience a real Maxwell's spur arcing and sparking as it spun up dipped in mercury scattering tiny globules over the bench as it did so.

Another nice optical one is sellotape on OHP slide and crossed polars. A crude variant of the basic physics of many interference filters.

Any diode will do for this if opamps are around. Or thermistors.

LCD thermometer plastic sheet is impressive if your budget will stretch to it (available from the likes of Edmund).

Hot wire wind velocity is another nice one (or traditional half ping pong balls on a stick and a magnetic read off).

Stepper motor to measure angular rotation speed isn't bad either.

There are some starting around the £20 mark eg.

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Best demo by far if you have the resources to make one is a bicycle wheel on a longish spindle with lead pipe wrapped around it and a high swivel chair. Put the victim on the chair and spin up the gyroscope then when they try to move the axis of the gyroscope...

It really drives home the effect of a gyroscope to handle one on that scale. Failing that the old toy lead ones that sit on an Eiffel tower.

Tesla coil and Jacob's ladder sparks make cool if RFI dense demos too.

Reply to
Martin Brown

I suspect the gyros are acoustic and the pressure sensors are MEMS with piezo_resistive_ readouts. (Straining silicon changes its conductivity.)

One useful shortcut is to look for patent numbers in the datasheets, and look them up.


Phil Hobbs

Reply to
Phil Hobbs

Weren't fuel gauges in cars wire-wound potentiometers immersed in the fuel? They were 'safe' because the fuel to air ratio in the fuel tank was way too rich to be combustible.

I made this cork gun with a piece of steel pipe and a spark plug. Two drops of gas would pop the cork many meters into the air, but one or three drops would do nothing.

Jeroen Belleman

Reply to
Jeroen Belleman

Yes. I think that airplanes now ensure a non-combustible fuel tank.

The capacitive level sensors also have wildly redundant intrinsic safety networks, lots of resistors and zeners. Suits me, since the protection networks add a lot of capacitance that makes simulation more interesting.

Reply to
John Larkin

reckless people will run out of fingers, the cartridge is less than $100 you don't get a new finger for that ...

Reply to
Lasse Langwadt Christensen

they don't make people pay for triggering it? they either avoided injury or did something dumb (it has a test mode to test if something will trigger it)

or have people pay a small fee to a cartridge fund if they want to use the tablesaw

Reply to
Lasse Langwadt Christensen

There's a makerspace here it is ~$20/month half price for students Though they don't pay rent the location is provided by the municipality and I think they also get some subsidies by the government, like other non-profit organizations with an educational purpose

yeh, you have to plan ahead

you don't _need_ most tools, but they make it a lot easier and $50 is going to takes years to buy a decent metal lathe or table say

Reply to
Lasse Langwadt Christensen

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