| bart416 | btw, somebody asked in here a few months ago why you should use a bjt as a temperature sensor instead of a regular diode | 07:43 |
|---|---|---|
| bart416 | I think I figured it out | 07:43 |
| bart416 | The BJT responds faster to temperature changes as well as current changes | 07:43 |
| bart416 | The junction in a bjt forms a better diode than a diode lol | 07:44 |
| reportingsjr | bart416: I remember that and as soon as I read your second to last sentence (I read from bottom to top sometimes) I thought of that | 08:07 |
| bart416 | I'm not sure why I didn't remember it either at the time | 08:08 |
| bart416 | But was going over a schematic of a temperature sensor once more and came to me heh | 08:08 |
| reportingsjr | I don't think the reason is what you stated | 08:09 |
| bart416 | it was a discrete component | 08:09 |
| reportingsjr | I think the reason is that it's most likely much more accurate than a thermistor and it's also much, much cheaper than a thermistor | 08:09 |
| reportingsjr | err | 08:09 |
| bart416 | It's not cause it's easier on IC scale :P | 08:09 |
| reportingsjr | that last thermistor should be a ... | 08:09 |
| reportingsjr | fuck | 08:09 |
| bart416 | Also, in terms of accuracy a PTAT source is better | 08:09 |
| reportingsjr | I can't remember the name of anything today | 08:09 |
| reportingsjr | thermocouple! | 08:09 |
| reportingsjr | with a thermocouple you need to buy the thermocouple (fairly costly compared to transistor) and also stuff to amplify its' signal. | 08:10 |
| reportingsjr | and with common transistors temperature effects on them are extremely well documented | 08:10 |
| bart416 | Actually, in this application that part of it wasn't a problem | 08:11 |
| bart416 | It's just that it also had to be precise at cryogenic temperatures | 08:11 |
| bart416 | semiconductor junctions will do that | 08:11 |
| bart416 | But size was also a constraint | 08:13 |
| reportingsjr | huh, I don't remember it that well. *shrug* | 08:16 |
| bart416 | If you want precision and ease and don't care about power use, go for the 4 transistor ptat source | 08:17 |
| bart416 | If size and power usage is an issue, use a diode or transistor | 08:17 |
| superkuh | How does one use a transistor as a temperature probe? I have a temperature controller using a platinum RTD I am not exactly satisfied with. | 08:20 |
| superkuh | Obviously I can't just switch it out, the temperature controller wouldn't be compatible. But building something else is fine. | 08:21 |
| bart416 | Fairly easy, your transistor (like any other semiconductor) actually has an exponential curve largly dependent on the thermal voltage | 08:21 |
| superkuh | Oh. I should've figured it wasn't linear. Still interesting though. | 08:23 |
| bart416 | http://www.eecg.toronto.edu/~kphang/papers/2001/haft_ref.pdf | 08:23 |
| bart416 | sort of explains it | 08:23 |
| superkuh | Thank you. | 08:24 |
| bart416 | ask me again in about 12 hours, then I'll be closer to my notes from a few years ago heh | 08:24 |
| bart416 | Got a really nice reliable design | 08:24 |
| horizontally | wait dude i worked on something related to this recently | 08:24 |
| bart416 | Did require a transistor array though | 08:25 |
| horizontally | why isn't the platinum RTD not working? | 08:25 |
| horizontally | a thermocouple / RTD is much easier to setup but more expensive than a transistor / diode temperature sensor | 08:25 |
| horizontally | you could also buy a linearized diode / transistor temperature sensor like an LM35 or (better yet) LM36 | 08:25 |
| bart416 | what's the fun in that? /P | 08:27 |
| bart416 | You know what's sad | 10:04 |
| bart416 | The only well documented "discrete" design is the apollo guidance computer >_> | 10:04 |
| bart416 | fucking retards | 10:26 |
| bart416 | master slave flip flops are NOT edge triggered | 10:26 |
| bart416 | An edge triggered latch is something completely different | 10:26 |
| bart416 | A master slave simply uses a delay to respond to level changes | 10:26 |
| bart416 | I blame wikipedia for this actually | 10:29 |
| soul-d | http://www.ted.com/talks/klaus_stadlmann_the_world_s_smallest_3d_printer.html | 12:35 |
| --- Mon Dec 12 2011 | 00:00 | |
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