Programmable resistors/potentiometers?

I'm looking for a cheap solution to increase/reduce the resistance at a certain position in a circuit with an Arduino.

What are my options?

edit: Yes, with an Arduino. I don't want to turn knobs or anything. I want the resistance to be changed by the code that I upload to my Arduino.

Arduino controlled or manual control? Arduino - digital potentiometer. Example, 10K resistor, 127 resistance steps, I2C interface: http://www.digikey.com/product-detail/en/microchip-technology/MCP4018T-103E-LT/MCP4018T-103E-LTCT-ND/2060161 Manual- trimpot. Single-turn, multi-turn, various orientations http://www.digikey.com/product-search/en/potentiometers-variable-resistors/trimmer-potentiometers/262968?k=trimpot&k=&pkeyword=trimpot&pv1=112&pv69=80&FV=fff40004%2Cfff80338&mnonly=0&newproducts=0&ColumnSort=0&page=1&stock=1&quantity=0&ptm=0&fid=0&pageSize=25

Arduino controlled. Okay, what exactly does "10K resistor, 127 resistance steps" mean?

127 resistence steps between 0 Ohm and 10K Ohm?

Take note that cheap digipots like the Microchip one CrossRoads linked will often constrain the input voltages to the divider to be within the supply rails.

I've seen one digitpot that could take +/- 15V on the pot pins, but I believe it needed separate analog supply voltages for that.

Arduino controlled? Yeah, digipots are what you want, and your interpretation of that spec is correct.

Good catch jiggy-ninja - I've never seen one that didn't constrain the voltages on A/B/W pins. Most of them limit you to the supply rails plus a diode drop (like the pins on almost anything). Microchip makes one that allows up to 36v between the sides of the pot - though you have to provide a V+ and V- which the voltages on A/B/W will always be between, and supply and ground have to be within that range.

"127 resistence steps between 0 Ohm and 10K Ohm?" Yes. That was just one example. You can find parts with up to 1024 "taps" or resistance steps, linear or logarithmic range in the steps, 1 to 6 resistors per package, I2C or SPI or just simple pulses to increase/decrease resistance, volatile or non-volatile (powers up to pre-loss of power) options, etc. http://www.digikey.com/product-search/en/integrated-circuits-ics/data-acquisition-digital-potentiometers/2556350?k=digital%20potentiometer

I took "in a circuit with an Arduino" to mean 5V signals.

Pot + servo + super glue. Or are you too chicken to DIY. :)

INTP: Pot + servo + super glue. Or are you too chicken to DIY. :)

Most people would consider burning an amp just to turn a servo to be wasteful.

Those people are boring.

Thank you! Man, these chips are really expensive, but well at least they exist.

I used the In-Stock filter and then sorted by price. Once you past the 3000-lot size, the 1-lot parts start at 51 cents. I wouldn't call that really expensive. Then there are price breaks at 10, 25, 100 lots depending on the part. How many did you need, and what value? Linear, Logarithmic, Pseudologarithmic (what ever that is, need to read the datasheets)?

Well 51 cents is a lot imo and it probably doesn't even include shipping. I mean for 51 cents I could probably already get an ATMEGA chip including shipping. And I have a feeling that a digital pot isn't quite as complex.

I'd really like to just buy a kit that contains all sorts of different values. But I couldn't find any... I definitely need 100, 1k and 10k.

I found offers for 1k and 10k that are, well, acceptable I guess since the shipping is free. https://www.aliexpress.com/item/Free-Shipping-Diy-Integrated-Circuits-MCP4018T-103E-LT-IC-DGTL-POT-10K-128TAPS-SC70-6-MCP4018T/32435908900.html https://www.aliexpress.com/item/Free-shipping-Ad5273brjz1-reel7-pot-Dgtl-1-K-64POS-SOT23-5273-AD5273-3PCS-LOT/32649686502.html

But I couldn't find an acceptable offer for a digital pot with 100Ohm.

Well 51 cents is a lot imo and it probably doesn't even include shipping. I mean for 51 cents I could probably already get an ATMEGA chip including shipping. And I have a feeling that a digital pot isn't quite as complex.

Oh come off it. If you think that is expensive then this hobby is not for you. Take up knitting and mone about the price of the wool.

The price of chips has nothing to do with the complexity it has to do with how many they make. What are you going to think when you get asked for $20 for a chip? Seriously you come over as a spoiled brat.

The cheap-cheap way to control resistance with an arduino is with a vactrol. Simply put, you glue an LED to a photo-sensitive resistor, wrap the whole thing up until it's lightproof, then control the brightness of the LED using the PWM outputs on the arduino.

It won't be as precise as a digipot, but it'll be cheaper and you can be proud that you built it yourself. Plus it'll get Grumpy_Mike off your back (man, he wasn't kidding when he came up with that handle).

It also will be very linear will it? My experiments with that system in the late 60s showed the actual control region was very small.

(man, he wasn't kidding when he came up with that handle).

Man I was. When ever people meet me they say "you don't seem very grumpy" to which I reply "it's my day off". However suffering fools gladly is something that is not my strong point. Their is a world of difference between someone who does not know something and wants to learn and someone who knows nothing but thinks they do.

Grumpy_Mike: It also will be very linear will it? My experiments with that system in the late 60s showed the actual control region was very small.

Vactrols are definitely limited in a lot of ways: not very precise, not very linear, and they don't tend to open or close quite all the way. That said, they're definitely cheap, and depending on the use case, sometimes they work just as well as a digipot would (or even better, since there aren't defined steps of resistance). Lots of modular synth guys love them because they allow you to replace pots with control voltages, meaning that pretty much anything can be taken apart and turned into a module; and for Arduino specifically they can be nice because they only need a two-wire connection, ground and PWM.

Really, I just wanted to mention it since nobody else had. Without knowing more details about the project OP is planning, it's tough to know what solution will work best, or at all.

Man I was. When ever people meet me they say "you don't seem very grumpy" to which I reply "it's my day off". However suffering fools gladly is something that is not my strong point. Their is a world of difference between someone who does not know something and wants to learn and someone who knows nothing but thinks they do.

I understand that there's a lot of the latter around here (or around the Internet in general), so it's pretty easy to get frustrated about it. But let's be real, the OP was just lamenting the price of a part, which I'm sure we've all done. I don't think that really justifies calling them a spoiled brat that should take up knitting instead of electronics.

In any case, I'm not trying to start a flame war or argument here. It was just a friendly jab at what I perceived to be an over-reaction. No hard feelings?

Just for grins someday... find a module that you can buy from China that is well documented (rare, but they exist, though you might have to figure out who they copied it from) and see if it has a parts list.

If the bargain version of the module costs lets say $2.00 from Aliexpress, there is a high probability that if you went to Digikey or Mouser to make 1 copy of the module yourself, the parts could easily cost you well over $10... and that does not even include the cost of the PCB.

Buying parts in less than 10 or less quantity will cost you. Specialized niche parts will always cost even more.

felic: Well 51 cents is a lot imo and it probably doesn't even include shipping. I mean for 51 cents I could probably already get an ATMEGA chip including shipping. And I have a feeling that a digital pot isn't quite as complex.

I'd really like to just buy a kit that contains all sorts of different values. But I couldn't find any... I definitely need 100, 1k and 10k.

I found offers for 1k and 10k that are, well, acceptable I guess since the shipping is free. https://www.aliexpress.com/item/Free-Shipping-Diy-Integrated-Circuits-MCP4018T-103E-LT-IC-DGTL-POT-10K-128TAPS-SC70-6-MCP4018T/32435908900.html https://www.aliexpress.com/item/Free-shipping-Ad5273brjz1-reel7-pot-Dgtl-1-K-64POS-SOT23-5273-AD5273-3PCS-LOT/32649686502.html

But I couldn't find an acceptable offer for a digital pot with 100Ohm.

If you look at most places, an ATmega328P chip is almost 4 USD in single quantities. 50 cents is not expensive.

And I can pretty much guarantee that you won't find a 100 ohm digipot for any price near what you think is "reasonable".

Grumpy_Mike: Their is a world of difference between someone who does not know something and wants to learn and someone who knows nothing but thinks they do.

Nearly half of my entire country is insane, and lining up to vote someone into the Presidency who is quite possibly the most pure instantiation of cartoon super-villain evil that I have seem in my (fairly young) life so far, someone who doesn't even hide his evil and even brags about it.

Know-nothings in an electronics forum are an annoyance; it's terrifying when they're threatening to inflict Lex Luthor on the world.

It was just a friendly jab at what I perceived to be an over-reaction. No hard feelings?

No problems.

It was just that he comes on not knowing about digital pots - which in itself is fair enough. But then when he finds out the price he is suddenly an expert in semiconductor fabrication pricing. Also the fact that he complained $0.50 does not even include postage is rather odd. In the UK it costs more than that for a simple stamp to send a letter, how much does it cost in the U.S?

The minimum amount of information given does not allow a full recommendation to be made. If you look at the wiper current for a typical digital pot you will find it is less than 5mA.

Nearly half of my entire country is insane, and lining up to vote someone into the Presidency who is quite possibly the most pure instantiation of cartoon super-villain evil that I have seem in my (fairly young) life so far

Very true and I am probably a lot older than you. The up side is that it seems to be that the way I understand the U.S. constitution, the President can do very little on their own, even if, like the current incumbent, what they want to do seems like a good idea.

1 $0.47 stamp

2 Very True... but still not very re-assuring.

Grumpy_Mike: In the UK it costs more than that for a simple stamp to send a letter, how much does it cost in the U.S?

0.47 USD currently, in all sorts of fun designs. What are you guys stuck with, just the Queen?

Even without the postage comparison, complaining that this miracle of modern manufacturing costs 50 whole cents is just weird.