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Topic: Devices to salvage thermistors from? (Read 492 times) previous topic - next topic

brodbord

Jan 12, 2021, 04:35 pm Last Edit: Jan 13, 2021, 02:06 pm by brodbord
Hi,

I am trying to find out in what devices I may find thermistors (10k I guess is optimal) in. I found some in old intercom phones [EDIT: it was not intercoms. It was some kind of thermostats. Sorry.].
I got quite a bit of electronic junk, but I am not sure what is inside. I opened a few ac to dc power supplies but I did not find any.

If this is too of topic I apologize, please let me know where to ask.

Cheers

DVDdoug

Quote
I found some in old intercom phones.
OK, but I don't know why there would be a thermistor in an intercom!  Of course there is some kind of temperature sensor in a thermostat, or refrigerator, etc.

Smajdalf


MarkT

Protection circuitry for audio amps sometimes has a thermistor on the heatsink.
[ I DO NOT respond to personal messages, I WILL delete them unread, use the forum please ]

hammy

Thermistors are one of the cheapest items to buy !

PerryBebbington

Quote
I don't know why there would be a thermistor in an intercom
I don't know specifically about an intercom but old dial phones used negative temperature coefficient resistors (tungsten filament) to regulate the line current.

brodbord

#6
Jan 12, 2021, 11:16 pm Last Edit: Jan 12, 2021, 11:24 pm by brodbord
These intercom things, I found them all smashed up in an old barn, the plastic had been burned by... something... but the thermistors seems to work. :D

brodbord

...I prefer to use junk to avoid shipping stuff around the globe. When it is possible.

Pc power supplies are supposed to have thermistors too.

WattsThat

Pardon the expression but harvesting unknown thermistors from scrap equipment is just pissing into the wind.

Harvesting resistors and capacitors and other similar things with markings can be useful. Thermistors are not one of those things. Is it an NTC part? PTC? What's the β parameter? These things matter unless of course you just want to watch a number change on your ohmmeter when you heat them with a torch.

 
Vacuum tube guy in a solid state world

larryd

Why? you can get 20 X 10k thermistors for $7 on Amazon.





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DrAzzy

#10
Jan 13, 2021, 07:21 am Last Edit: Jan 13, 2021, 07:35 am by DrAzzy
Why? you can get 20 X 10k thermistors for $7 on Amazon.






What a ripoff - you're really paying for the fast delivery time on that >.>

10 for 52 cents on aliexpress, plus $1.42 shipping for up to 7 lots (70 resistors), $2.63 shipping for more (when the value of a line item on an order is above a threshold that's around $4, aliexpress requires the seller to ship it by nothing worse than "aliexpress standard shipping" - which unfortunately isn't really any better than the dirt-cheap shipping options, it just costs more)

For cheap parts from china, you can't beat aliexpress...

I used to scrap stuff for parts (and my father still does)... but I stopped a while back. You want to know why? I had this project I made. It worked real good. I wanted to make a few more of them... And there were all these parts I couldn't identify, which meant, basically, another prototype stage. Not worth it. Another time, I wasted a bunch of time with something that wasn't working right and I couldn't figure out why... well, the pull I'd used was bad. And why shouldn't it be? It's not like it was pulled from working equipment! Back when parts were expensive, using pulls could be cost justified... but with parts as cheap as they are, it's just not worth it. I still pull a few things (crystals at real odd-ball speeds for stock and juicy power resistors come to mind; my father justifies saving inductors by their relative cost, but he has so goddamned many now that even if my future kids get into electronics, they will still have leftovers. I also snag diodes in MELF packages larger than those tiny ubiquitous ones; they're expensive and look oh-so-slick. the larger MELF surface mount resistors for the same reason - SMD resitors with the colored bands on them? Yes please... but not at the price they cost new!).
ATTinyCore and megaTinyCore for all ATtiny, DxCore for DA/DB-series! github.com/SpenceKonde
http://drazzy.com/package_drazzy.com_index.json
ATtiny breakouts, mosfets, awesome prototyping board in my store http://tindie.com/stores/DrAzzy

brodbord

#11
Jan 13, 2021, 09:46 am Last Edit: Jan 18, 2021, 02:45 pm by brodbord
It is really good to know this, thanks. However, my purpose is probably way more primitive than what you are relating to. I am an artist and finding usefulness in the discarded is one of my central themes. It is not about money.
I intend to connect a few thermistors straight into analog inputs and then use the arduino as a serial interface to use with software sound synthesis. It becomes an interface you have learn to use by exploring it, just as a music instrument. The inconsistent becomes a feature.

Here is one of my works, to illustrate:
Modular Trash System example
and more here

Paul__B

Pc power supplies are supposed to have thermistors too.
Not that would be much use to you, I fear.  These are NTC thermistors which heat up when several Amps are passed through and dramatically lower their resistance so they limit the initial current, but they are a very low resistance value to start with and I doubt the heat you are proposing to detect would result in much effect.

PerryBebbington

Quote
I am an artist and finding usefulness in the discarded is one of my central themes.
Ah!
I have a friend who did an art degree, while he was doing it he was very interested in old circuit boards for their appearance, not their function.

brodbord

#14
Jan 13, 2021, 02:05 pm Last Edit: Jan 13, 2021, 07:07 pm by brodbord
I got a working prototype now.

Here is the harvest: thermistors

And here is the interface

Thanks for the input!


And, oh, sorry. It was not intercom phones, it was some type of thermostats... :/

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