#avr Logs

Mar 06 2022

12:21 AM WormFood: Have any of you guys ever turned a regular resistor into a precision resistor? I just turned a 470 ohm resistor into a 700 ohm resistor. I was shooting for 680 ohms, and overshot it a bit.
08:08 AM Smidge204_: All resistors are precision, it's just the markings that lack resolution.
08:10 AM Thrashbarg: A wizard is never late, Master Baggins, nor is he early, he arrives precisely when he means to.
08:11 AM LeoNerd: Eh... Yes and no. At any moment in time, a resistor will have a very precisely-defined value. The point of a "precision" resistor is more that its value doesn't -change- as much over time/temperature/etc... as regular ones
08:11 AM * Thrashbarg goes woosh!
08:12 AM LeoNerd: E.g. I have some Vishay Zfoil resistors in boxes that I use for calibrations.. they're 50ppm per degree C of tempco. So basically you can entirely ignore that
08:12 AM LeoNerd: The value is e.g. 1.00000k ohm, and prettymuch nothing will change that
09:25 AM cehteh: how about resistors with tolerances in +/- Ohms not % :D
09:26 AM cehteh: touch with bare finger and they are off
09:26 AM * qu1j0t3 resists commenting
09:30 AM cehteh: lol
10:46 AM rue_bed: I made a resistor substitution box
10:47 AM rue_bed: I wanted to use 0.01% resistors
10:47 AM rue_bed: so I trimmed my own in series/parallel
10:47 AM rue_bed: WOW I learned a lot
10:47 AM rue_bed: there are *no* 470 ohm resistors
10:48 AM rue_bed: they shoot for 474 and the rejects become 5%
10:48 AM rue_bed: iirc
10:48 AM rue_bed: there were other values too, you could tell the standard 5% value was not the target
10:49 AM rue_bed: going thru a whole box of like 300 resistors to find one with the value I needed
10:49 AM rue_bed: my meter too, and its resolution, ugh
10:49 AM rue_bed: could tell the areas were its rez was low
10:50 AM rue_mohr: and yea, if the whole thing warms up a lot its slightly out
12:08 PM cehteh: calibrate it at 150°C ... make an PID controlled oven for that
12:08 PM cehteh: and hope that these resistors never need to dump higher loads
11:11 PM rue_bed: hah, its signal resistors
11:12 PM rue_bed: have you seen it?
11:12 PM rue_bed: http://ruemohr.org/%7Eircjunk/projects/resistorbox/slide.htm
11:13 PM rue_bed: whats great is the placement of the E on the screen lets me to E12 or E24, etc
11:13 PM rue_bed: I haven't coded in the standard value stepping tho
11:14 PM rue_bed: havn't made use of the usb control let
11:14 PM rue_bed: yet
11:23 PM rue_bed: it does two resistors at once, same value
11:23 PM rue_bed: so if you have a circuit where you need two matched, it does that
11:23 PM rue_bed: which was kinda an almost-free bonus