Accurate adjustable resistor?

I need a simple, low cost, small device capable of 10 different resistance settings, and must be capable of mechanically reproducing them exactly, on command.  It cannot be a potentiometer, as it is innacurate without some sort of  measurement device (which I cannot use), nor a rotart switch or encoder (too big and expensive, cannot use digital).  Basically, is there some alternative <$2 that will do this.  Again, no digital stuff or measuring position, only going between several set resistance settings (but any incrament thereof is okay).   

sort by: active | newest | oldest
Libahunt4 years ago
Set of resistors and a crocodile clip might be the cheapest option. Connect all resistors together in one end, label them and use crocodile clip to connect to other end of one of them. Wise and sturdy mounting makes the usage experience better.

By the way, what is the purpouse of this device and the reason for so small budget? Educational? Why the size restrictions? All this information may help developing better answers.
jduffy54 (author)  Libahunt4 years ago
Sorry for the lack of specificity, but unfortunately, when an idea is on the Internet, anyone can claim and use it. I need mine to stay that way until at least early June. (It's for an engineering class). Once it's done, ill post an instructable on the whole thing.

As for this part, it needs those things as I may need to make as many as 20-30 of them, which must fit in the same footprint that other parts of it do. An alligator clamp won't really work, this should feel like an end-user product, so a professional-looking switch/sensor of some kind is a must. However, do you know where I can get a cheap dec thumbswitch? Those seemed like exactly what I want, but they're all >$8, and that's for a coded one.
Thanks for the responses through,
Get a small rotary switch, and use surface mount resuistors - I can get a switch << 0.5"

jduffy54 (author)  Libahunt4 years ago
Never mind, i just found this, which though a little too tall should work just fine (when they're separated). Though I will have to trim off the PCB at the end. The rest should work fine.
Best you can do is a rotary switch with the resistors you want. But nothing you do will be in the $2 range. Not to mention very accurate resistors are not very cheap either. You might be able to build your own selector switch to go along with the +/-1% resistors you need to use.
jduffy54 (author)  mpilchfamily4 years ago
it's not set what the pull-up resistor will be, so I can use whatever value (though I know you mentioned tolerance), usually even +-5% will usually be within an ohm or two. In a voltage divider to measure it, thats not a lot. It doesn't really need 1-2 ohms, just basically not more than 10% or so.
(That does NOT mean that im using 10-20ohm resistors, just that it needs to be within a few thousandths within a voltage divider.)
How small does it have to be that a single 10 position or a pair of 5 position selector switches can't be used? With 2 of the right 5 position switches you can get it down to the size of an altoids tin. With 1 large switch you can make it smaller. Its all in your layout.

You do know there are resistor selector boxes on the market for around $20. You can make one yourself by sourcing your own parts and may be able to get it down to around $10.
jduffy54 (author)  mpilchfamily4 years ago
I forgot to mention the footprint, which must be <1"x1"x3/4". An altoids tin or even normal rotary switch will be too big and expensive. a bunch of switches will be too big.
jduffy54 (author)  jduffy544 years ago
Also, I found this which should work fine.