Reddit mentions: The best variable resistors

Welcome!

Take this with a grain of salt because, I still don't really know what I'm doing (although I'm not sure anyone feels like they ever do); but, here's my experience.

For recommendations - skip to the -------------- Bottom Line ------------------ below

My first project was this little breadboard prototyping pedal box thingy I made out of stuff I bought at RadioShack (before all the stores closed):

https://www.youtube.com/watch?v=lJ5ws-Y9OPQ

There are much better ways to do this and I regret my potentiometer selections for this box but, I was really green and the Shack didn't have board mounted pots (I don't even think I knew there was such a thing at that point).

But, on that box, I built circuits that I found online and I was instantly hooked.

Fast forward many "wasted" hours and here's where I am:

https://www.youtube.com/watch?v=zGNmA1YM3n8

Hah! - still building distortion boxes :P - well - and this:

https://www.youtube.com/watch?v=iPrLFpkO9no&feature=youtu.be&t=48

----------------------------------------------------- Bottom Line -----------------------------------------------------

After all that here are the things I can suggest you stock up on (and I would bet you can find cheaper versions of any of these - but what's in them is what matters):

For IC's:

http://smallbear-electronics.mybigcommerce.com/op-amp-ic-kit/

For Potentiometers:

https://www.amazon.com/Logarithmic-Linear-Reverse-Potentiometer-Assortment/dp/B07SVMC3VK

Then you'll want a grab bag of diodes and transistors - look at different schematics of fuzz and distortion pedals and get an idea of what they're using - I just bought a bunch at RadioShack and some I got from Mammoth (also now defunct) and Small Bear (still rolling). I have em in a box and I swap em out on the breadboard to see how it changes the sound. That's the best part to me. When I'm on a breadboard - if I replace this guy with that guy how does the sound change? Definitely not the intelligent way but I enjoy that pseudo-creative process.

Finally - you should get some resistor and capacitor kits. My wife got me kits from amazon that have a label "JoeKnows Electronics" on the boxes. I haven't come across anything I've wanted for that wasn't in those two boxes.

Oh - as an added bonus:

https://www.harborfreight.com/toolbox-organizer-with-4-drawers-68238.html

This is my favorite storage box - find you a super coupon and grab one or two of these.

Anyway -

My sincerest congratulations and my deepest condolences for the path on which you are about to embark.

The 50K should be log, but I don't see any such indication on the 20K. Maybe a different pot would help? I did exactly what you're describing with these: http://www.amazon.com/gp/product/B002IABLF8/ref=oh_details_o00_s00_i00?ie=UTF8&psc=1

I did mine with a receiver, so I think the input impedance may have been higher. I'm pretty sure you want the pot value to be between the impedance values, so the DAC looks like a short and the amp looks like an open, but I'm not positive.

You are going to want to balance tools and parts.

TOOLS (must haves)

• Multimeters (At least two, I suggest starting with one cheapo ($5-$10) and one in the $30-$50 range)
  
• Variable regulated power supply with current limiting (Skip the cheap/dangerous chinese crap and get a used HP/Agilent/Keysight one off ebay like this or this.)
  
• Breadboards (several)
  
• Jumper wires
  
• Wire strippers and cutters
  
• Decent soldering Iron ($50-$100) (DO NOT CHEAP OUT ON THIS)
  
• Desoldering pump and/or wick (The ctrl-z of the soldering world)
  
• Heat shrink tubing for sealing connections (Especially if you are going to be doing outdoor stuff)
  
• Microcontrollers (I suggest starting with an Arudino Uno since it has the largest amount of online support material, you could get an Uno kit, any of them will be fine)
  .
  .
  TOOLS (eventually)
  
• Logic Analyzer (Let's you see the logic signals in your circuit which is super helpful for debugging, I have a bitscope micro which is decent, but the software kinda sucks and is more than just a logic analyzer)
  
• A function generator (variable voltage and frequency for sine, square and triangle waves) (Again I suggest used off ebay, something like this.)
  
• Oscilloscope (a really amazing tool for actally seeing what is going on in your circuit)
  .
  .
  PARTS (vaguely in order of usefullness)
  
• Elenco Resistor Kit
  
• Elenco Capacitor Kit
  
• Elenco Transistor Kit
  
• Elenco Diode Kit
  
• Elenco LED Kit
  (Of couse you don't have to get the Elenco kits, those are just the ones I use and really like)
  
• Voltage regulator ICs (Great for providing regulated power to things that need more than what your arduino can provide)
  
• Trimmer Potentiometer Kit (really useful to have around for many projects)
  
• Old electronic equipment to scavenge parts out of (Many of my parts have come from old equipment or broken ATX computer power supplies. Tearing stuff apart is both fun and yields great parts.)
  .
  .
  .
  I think that's all for now...

You are on the lower side of what I would use for cannabis but yes. Properly placed side lighting will help increase yields throughout the whole plant.

If you want flexibility you can always get a dimming LED driver. With a Vero 18 at 1.12 amps max you'll be able to dial in the lighting levels continuously from darkness to about 1400 uMol/m2/sec for a five gallon bucket.

https://www.mouser.com/ProductDetail/MEAN-WELL/HLG-40H-36A?qs=DNaZHaGatO3z1WYl%2FZR5Ng%3D%3D

For this dimmer you need a 100K linear potentiometer for the dimming function:

https://www.amazon.com/Uxcell-a11120800ux0026-Terminals-Rotary-Potentiometer/dp/B011BHHY0E/ref=sr_1_18?keywords=100k+potentiometer&qid=1558419199&s=gateway&sr=8-18

As a disclaimer, some of the very latest Vero 18 generation 7 COBs being sold are about 5% better than the version of the generation 7 COBs I'm testing with.

You have a 12V fan but a 5.5V power supply? This sounds like a problem to me. I'd recommend a 12V, 0.5A adapter - I use this one - with a 500 ohm potentiometer.

I usually have to turn the rheostat up about half way to get past the fan's stall speed, and then it runs very slowly, and ramps up smoothly to top speed as I turn the dial. At top speed the vortex is so strong the stir bar gets caught in it and jumps the field.

It also helps to use very strong magnets, spaced exactly as far apart as the ends of the stir bar. If your drive magnets are half an inch apart, don't bother with a 1 inch stir bar.

>How wide is your maple? Something to consider: I have a 12" 5hp Belsaw planer at my shop in Hagerstown, I'd be willing to give you access to for lumber trade. Also, I noticed you need a motor for your lathe, I have 4 electric motors that I don't use, I think most have pulleys. I purchased this a while ago as a speed controller, it works great.

>Those slabs sound amazing. How did you get those milled?

I also have a 12" planer. Some of the board are over 18 or 20. I think I'll be ripping most of them down anyways. Thanks for the offer on the motor, I recently picked up 2. I just need to get a belt that fits now.
The slabs I had done by 2griffins. They had an Alaskan chainsaw mill. That was really cool to watch. If you ever want to come see some of it, let me know.

In the past I've used a large box type thing to control the heat output of my 1500w element. It got VERY VERY hot, and burnt out, because apparently i should have put a giant heatsink on the back (Why would it NOT come with one?)

Anyway....looking up motor controllers again, I see nothing but these guys. Rated at 2kw should be good for a 1500w element, but I'm not sure if PWM is a good thing, compared to plain old analog tuning. I guess it depends on the pulse width, right? 10hz compared to 0.1hz might be fine.


Edit: this is what I had which apparently is a FAN controller, and obviously analog (rheostat)

off the top of my head around 120-150 but thats assuming you buy everything online with free shipping and assuming you have access to alot of tools.

Pi Zero https://www.adafruit.com/product/2885 $5.00
LCD https://www.amazon.com/BW-3-5-Inch-Monitor-Automobile/dp/B0045IIZKU/ $15.50
USB Sound Card https://www.amazon.com/Sabrent-External-Adapter-Windows-AU-MMSA/dp/B00IRVQ0F8/ $6
USB HUB https://www.amazon.com/Adapter-Converter-Android-Samsung-Transformer/dp/B00OZDUTMM $6
Volume Potentiometer https://www.amazon.com/16x2mm-Double-Taper-Duplex-Potentiometer/dp/B00O9Y6Z70 $6
Mono 2.5w amp https://www.adafruit.com/products/2130 $3
ABXY PCB http://store.kitsch-bent.com/product/common-ground-dmg-button-pcb-a-b-x-y-version $11.75
Power Boost 1000C https://www.adafruit.com/products/2465 $20

Female micro usb https://www.adafruit.com/products/1829 $1
female usb socket https://www.amazon.com/uxcell-Female-Degree-Socket-Connector/dp/B00FH85SGG Free or $6
Stereo Jack https://www.amazon.com/uxcell-Plastic-Stereo-Socket-Connector/dp/B00GLQAF7A $6
Slide switch https://www.amazon.com/uxcell-SS12F32-G7-Position-Switch-Solder/dp/B007QAJWYW $6
Membrane set http://store.kitsch-bent.com/product/silicone-buttons $2.75
Extra button set http://store.kitsch-bent.com/product/custom-buttons $2
28mm Speaker https://www.amazon.com/Metal-Inside-Magnet-Player-Speaker/dp/B00O9YG9GM $6.50
two single button pcb http://store.kitsch-bent.com/product/easy_buttons $4.30
2300mah Battery http://www.microcenter.com/product/458057/2,300_mAh_Li-Po_Battery_and_Charger $15.00

Yep! Pretty straightforward mod. You desolder the trim pot, then solder three wires to the pads where the trim pot was. After that, solder the other end of the three wires to your potentiometer and you're done as far as the sound's concerned. For usefulness/cosmetcs, I cut a hole in my Walkman case to run the wires out, then poked a hole in the side of an Altoids tin, sanded away the rough edges, and threaded the other end of the wires through. Then I drilled a hole in the top of the Altoids tin big enough to get the potentiometer shaft to fit through and spin freely while still being snug. When I was sure of that, that's when I soldered the wires to the pot. Then I hot-glued the pot into the backside of the tin's top lid (it's too small to glue to the tin bottom), being careful not to cover any wires or pads, closed the lid, put down the numbered dial position circle thing (with some gorilla glue to make sure it'd stay in place), and finally put the potentiometer's knob on. Here's the exact pot I used and the Ouija Altoids tin.

The reason I don't trust my handiwork is I didn't have a Dremel for the Walkman case hole, and had to use wire-cutters to snip off bits instead. I sanded it down a little, but I could've done a better job. I'm worried it'll cut the wires over time. The wires themselves are also pretty long (about 18") and prone to tangling. The length is enough that I can keep the Walkman on a belt-clip while holding the Altoids tin at waist-height, but I mostly use it on my desk, so it's pointless. If I make another, I'll halve the length and add a few bands to keep the wires straight and tangle-free.

Thats true, and definitely an option, but I wouldnt know which resistance to get, or pretty much anything about them. I'm not particularly familiar with electronics, other than the things strictly associated with my printers. Would something like this work? What pins would be used, there's 3.. how do you hook one up?

> Would a 220v controller still be under the router speed controller category?

I don't think they make commonly available 220v router speed controllers. I think they were referring to purpose built controllers. The SSR style voltage regulators aren't that expensive. Something like this with this pot and some kind of box, and some 10ga wires, and you have a controller. You can add a volt/ammeter, and switches, etc. Shouldn't cost more than $30. I posted a link to a kit above as well.

You can also use the Chinese SCR voltage regulators, lots of people use them for this purpose. Something like this or this. The second one has a fan, which will help it run cooler.

How wide is your maple? Something to consider: I have a 12" 5hp Belsaw planer at my shop in Hagerstown, I'd be willing to give you access to for lumber trade. Also, I noticed you need a motor for your lathe, I have 4 electric motors that I don't use, I think most have pulleys. I purchased this a while ago as a speed controller, it works great.

Those slabs sound amazing. How did you get those milled?

Sure. Does yours have a 2 pin or a 3 pin plug?

Something like this should work fine.

Photo of the label on the tray would help.

It's very easy, it's just 2 parts and some wires. The manual that comes with the SSVR is pretty self explanatory too.

You can see in the photo of my SSVR (a spare I bought), it has a power input side, and a load output side. You just connect the 2 live wires from your circuit breaker, or GFCI, to the power input side, and then run the load output side to your heating element.

Then you connect 3 wires from the pot to +5V, COM, and 0-5V. If you don't have a digital multimeter, you might want to pick one up.

But yeah, it lets me manually adjust the voltage going to the heating element, and thus adjust the amount of power it is using to heat the element.

I can draw a simple diagram on that photo I took. Here is the potentiometer I bought. The dial doesn't match exactly what the pot is doing, 0 - 7.5 is about from minimum to max, it doens't go all the way to 10. But that's fine with me.

Here is a simple diagram. If you buy the same pot that I use, it has the numbers stamped on the bottom, but they are all the same, you connect COM (0V) and +5V to the outside pins, respectively, and the middle pin (aka the wiper) is the signal that ranges between 0V and 5V. That goes to the 0-5V pin on the SSVR.

Here's a $4 part (datasheet) that will produce a stable, low noise, 5V reference.

Use your favorite low-noise precision op-amp (The OPA227 might work well datasheet but there are certainly cheaper options) with precision resistors in noninverting configuration to convert the 5 V to +1 V.

Use another in inverting configuration to convert the 5V reference to -1 V.

A summing amplifier can be used to add or subtract a fixed voltage to your signal.

I would use this as an excuse to pick up an assortment of trimmer potentiometers such as this.

​

Edit: recommended a higher voltage opamp

RV24YN20S 200ohm B200 - Link
Yeah its kinda ridiculous, but it has a nice feel to it. sort of requires a bit of force to turn, but turns very smoothly. like the knobs on an old wooden tv set or something.

If you don't mind modding one you can get good value for money by buying this:

http://www.voxamps.com/us/pedals/wahwah_v845/

replacing the inferior pot with this

http://www.amazon.com/Jim-Dunlop-ECB24B-Potz-Crybaby/dp/B000EEL5W4

Then modifying it for true bypass with these instructions:

http://stinkfoot.se/archives/561

I've done these steps and got a good result.

That is probably the best way tbh.this or this might be a better style of pot than the usual kit type.

It's pretty simple - for a digital (on/off) all you need is a cheap zero delay usb encoder like this:

https://www.amazon.com/Reyann-Arcade-Encoder-Joystick-Fighting/dp/B00UUROWWK

Get a microswitch and stick it to the side of the handbrake (even double sided tape works), so the bolt slider presses the switch when you pull the lever back. Wire the microswitch to one of the connections on the USB board and there you have it - a plug and play handbrake.

On the mechanical side of it, you just need to replace the master cylinder with a spring.

Analogue gets a bit trickier, but basically you mount a slide potentiometer to the side of the handbrake:

https://www.amazon.com/BOURNS-PTA4543-2015DPB103-POTENTIOMETER-SLIDE-10KOHM/dp/B005TBCVXY?ref_=fsclp_pl_dp_4

When you move the lever, it moves the slide in the potentiometer. Wire this to the analogue input of an arduino and use a joystick library to map that input to a joystick axis output:

https://github.com/MHeironimus/ArduinoJoystickLibrary

If you go down the arduino path, you can also wire the microswitch to one of the digital inputs and use that library to program it as a joystick button, and thus have both digital and analogue.

Ok, almost any 80mm computer fan will work (provided that it has a flat face to it):
http://www.amazon.com/KingWin-Long-Bearing-CF-08LB-Black/dp/B002YFSHPY/ref=sr_1_11?ie=UTF8&qid=1421330687&sr=8-11&keywords=80mm+fan
http://www.amazon.com/Bgears-b-Blaster-80mm-Bearing-Extreme/dp/B0043GQC6S/ref=sr_1_32?ie=UTF8&qid=1421330791&sr=8-32&keywords=80mm+fan

Magnet suggestion:
http://www.amazon.com/Neodymium-Magnets-inch-Disc-N48/dp/B001KV38ES/ref=pd_sim_k_3?ie=UTF8&refRID=100B2PQECYWG45ZYYRMR

Project box:
http://www.amazon.com/Hammond-1591ESBK-ABS-Project-Black/dp/B0002BSRIO/ref=pd_sim_indust_4?ie=UTF8&refRID=1B7JFAHDACTFVK2AZ15M
(Get the ES model, it's bigger, which means more room for your flask)

Switch:
http://www.amazon.com/gp/product/B0002ZPBRA/ref=as_li_ss_tl?ie=UTF8&camp=1789&creative=390957&creativeASIN=B0002ZPBRA&linkCode=as2&tag=socimumb-20

Rheostat:
http://www.amazon.com/gp/product/B009QFU9H4/ref=as_li_ss_tl?ie=UTF8&camp=1789&creative=390957&creativeASIN=B009QFU9H4&linkCode=as2&tag=brewprof-20

Stirbar:
http://www.amazon.com/gp/product/B001ACNFDQ/ref=as_li_qf_sp_asin_tl?ie=UTF8&camp=1789&creative=9325&creativeASIN=B001ACNFDQ&linkCode=as2&tag=socimumb-20

Power Supply: (Most people use an old cell phone charger, I used a usb cable, plugged into a modern phone charger)
http://www.amazon.com/PowerLine-90367-Universal-Power-Adapter/dp/B00CWR39TI/ref=dp_ob_title_ce

Toss in some super glue to hold it all together, a couple of nuts and bolts to mount everything with, and that should just about get you there.

The dimensions of the box are 17in x 7.5in
The switch, potentiometer, and display was all one piece which was sourced from amazon. It’s in a previous post of mine on this page.

I had to use a different potentiometer than the one from the kit. The top plywood for the box was too thick for the knob to reach so swapped it out for these (https://www.amazon.com/Uxcell-a15011600ux0213-Linear-Rotary-Potentiometer/dp/B0171M5SRE)

The fans were two of these (https://www.amazon.com/ARCTIC-F12-Standard-Configuration-possible/dp/B002KTVFTE)

The magnets were bought off eBay. (Rare earth magnets, neodymium)

Washers for spacing the magnet from the fan were already owned.

Used clear epoxy for any gluing that was needed.

12v dc power plug, which was an old cell phone charger. I split the power supply to both PWM speed controllers.

That’s it for parts!

Deadmans switch would be real easy,

just grab something like https://www.amazon.ca/Three-Trigger-Switch-Electric-DZKS-11-4/dp/B007Q9XVUO/ref=sr_1_2?s=hi&ie=UTF8&qid=1506536689&sr=1-2&keywords=electric+trigger

and then one of these https://www.amazon.ca/uxcell®-Wirewound-Potentiometer-Adjustable-Resistance/dp/B01N8TFXVX/ref=sr_1_84?s=hi&ie=UTF8&qid=1506536751&sr=1-84&keywords=potentiometer

wouldn't even need fancy wiring, just run the input through the trigger to the potentiometer. have it mounted to be held by the index finger and then the dial for thumb control?

I've had good luck with a router speed controller. You can find them at most hardware stores for very little money.

In a pot there's a wiper on a thin disk of material. As the wiper moves along the disk, the value of the pot changes. If you move the pot a lot, eventually you'll start wearing down the disk. When this happens, the pot will make scratching sounds when you move it.

Normally this is not a big deal, you don't frequently play and move a knob at the same time. But, with Wah pedals it is, since the foot pedal is attached to a pot - when ever you move it it will make scratching noises.

edit: and because this is a common problem with Wahs, it is usually pretty easy to buy a replacement for ~$25 link (you may be able to find them for less somewhere)

Find yourself an old fan motor or an old plug in drill and hook it up with something like this http://www.amazon.com/TruePower-Electronic-Stepless-Controller-Brush-type/dp/B009KAEP7A

So a router speed controller would not work?

What about a device like this?

https://www.amazon.com/TruePower-Electronic-Stepless-Controller-Brush-type/dp/B009KAEP7A

500 ohm surface mount pots:

http://www.ebay.com/itm/500-OHM-Linear-Taper-Rotary-Potentiometer-B500-Pot-/280672832335

http://www.ebay.com/itm/Alpha-500-OHM-Linear-Taper-Pot-B500-Split-Shaft-Solder-17mm-Potentiometer-EO-/121183474239?_trksid=p2054897.l4275

http://www.amazon.com/Parts-Express-500-Ohm-Potentiometer/dp/B0002KRE16

add a fancy guitar knob of your liking

Box

Fan

Power

Switch

Potentiometer

Stir bar

Small Flask

Bigger Flash

Mason Jars, as if you couldn't go to WallyWorld to get these

I am using this one: https://www.amazon.com/dp/B00O9Y6Z70/ref=cm_sw_r_cp_apa_xFcSAbSZCMY49

You need a potentiometer.

You need 1k ohm resistance and a linear taper (some will be listed as audio taper and won’t work well).

Hook your dimmer leads up to the center and a side pin on the pot and you’re done.

Wouldn't something like this work

https://www.amazon.com/gp/aw/d/B009KAEP7A/ref=pd_aw_fbt_121_img_2/163-7575233-3411138?ie=UTF8&psc=1&refRID=E5DJJXXPZKDYCS0FNTZR