| Electronics > Beginners |
| is it possible to mechanically trim resistors? |
| << < (3/5) > >> |
| Fred27:
https://hackaday.com/2017/04/10/hackaday-trims-its-own-resistors/ |
| jeroen79:
--- Quote from: jancumps on August 10, 2018, 05:16:19 pm ---... one of the reasons why your desired resistor isn’t there is because of the tolerance. That’s why the Exx ranges of resesistors are there. They are covering the whole range, taking tolerance in account. --- End quote --- True. You could just buy 100 resistors close to the desired value and then pick the one that is closest. |
| exe:
--- Quote from: jeroen79 on August 10, 2018, 05:44:25 pm ---You could just buy 100 resistors close to the desired value and then pick the one that is closest. --- End quote --- That's what I often do :(. Still another issue exists: the desired value is just not on sale and there is no value that would be close. Say, I need 17kOhm, it's out of stock. I could buy a ton of 15 or 18 kOhm 5% resistors, but that's just waste of resistor and tedious (and not guaranteed that I'll get the value I want). Why I sometimes need precise value? Most often is to simplify calculations and verification. While I can correct/adjust values in software, while debugging / prototyping it's good to have, say, amplifier with ~10x amplification and not 8x or 12x. Or I want save some boards space, so don't want to parallel resistor. But I got the message. SMD resistors are not easy to trim. Looks like the best solution is just to pick distributor that has required values in stock. |
| Gyro:
--- Quote from: exe on August 10, 2018, 04:45:20 pm --- --- Quote from: In Vacuo Veritas on August 10, 2018, 02:32:21 pm ---There are 49.9R resistors and there are precisely 50 ohm microwave resistors. So what's the problem? --- End quote --- Needed values are not available on my distributor's site (tme). Often values that I'd expect to be very popular. Like 50 Ohm, 9kOhm, etc. Or not available in the package I'd like (e.g. 0603). --- End quote --- Remember that it's quite easy to stack smd resistors to tweak values without extra footprints... e.g. A 1k 0603 with a 1M padding resistor soldered on top will give you 999R. You can get very fine adjustments using common values. P.S. I previously mentioned resistor calculators. I use Rescalc http://www.pmillett.com/rescalc.htm It's a good one because you can specify the Exx range and limits for the resistors that you are using - so it doesn't suggest silly values. |
| jancumps:
--- Quote from: jeroen79 on August 10, 2018, 05:44:25 pm --- --- Quote from: jancumps on August 10, 2018, 05:16:19 pm ---... one of the reasons why your desired resistor isn’t there is because of the tolerance. That’s why the Exx ranges of resesistors are there. They are covering the whole range, taking tolerance in account. --- End quote --- True. You could just buy 100 resistors close to the desired value and then pick the one that is closest. --- End quote --- If you have to do that, you're probably buying a wrong tolerance series? |
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