07:43 <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

07:44 <bart416> The junction in a bjt forms a better diode than a diode lol

08:07 <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

08:08 <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

08:09 <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!

08:10 <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

08:11 <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

08:13 <bart416> But size was also a constraint

08:16 <reportingsjr> huh, I don't remember it that well. *shrug*

08:17 <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

08:20 <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.

08:21 <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

08:23 <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

08:24 <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

08:25 <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

08:27 <bart416> what's the fun in that? /P

10:04 <bart416> You know what's sad

10:04 <bart416> The only well documented "discrete" design is the apollo guidance computer >_>

10:26 <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

10:29 <bart416> I blame wikipedia for this actually

12:35 <soul-d> http://www.ted.com/talks/klaus_stadlmann_the_world_s_smallest_3d_printer.html