Reddit mentions: The best hall effect sensors

Yes, electronics can cost a lot, and many of the telescope manufacturers make things, that when I look at them belong in the 1990s or 2000s, in terms of the way they work, and honestly could have been $400. It's basically the TI calcuator system: https://xkcd.com/768/

People have replaced those control systems, using technology (especially things like improved stepper control) which has come about for various reasons, like 3D printers, and simply faster microcontrollers.

Here's one: https://www.youtube.com/watch?v=tCBgmgc8qiA conversion (I suspect based on that it was using one of the faster controllers, but mine can do fine with an Arduino Mega + Ramps (the cheap controller))

• SVP $300 New
  
• RAMPS kit: (https://www.amazon.com/Eiechip-CNC-3D-Printer-Kit/dp/B07BKVPZ71) $27 (Not the best drivers, but this can be upgraded if you want later probably also want a PPS source, but it can be dealt without. As can the board.)
  
• Motors (Honestly cheaper, but at 0.9 degrees these are a bit better than the normal 1.8 degrees) https://www.amazon.com/0-9deg-Stepper-Bipolar-42x42x39mm-4-wires/dp/B00W98OYE4 2x$20
  
• Pulley for mount (60 tooth) https://www.amazon.com/Timing-Pulleys-Aluminum-Printer-Wrench/dp/B07QH1ZJ9L $8 (2x)
  
• Pulley for motor (16 tooth) https://www.amazon.com/Anet-Timing-Pulley-Aluminum-Printer/dp/B07D294B2T/ $8
  
• Belts https://www.amazon.com/132-2GT-6-Timing-Belt-Closed-Loop/dp/B014QI4PU2/ $12 (I think those are what are needed, I'd have to look again to make sure. I use 110s, but have 20 tooth 1:1, as I use geared steppers, with upsides and downsides.)
  
• Bracket (3D printed) or something made: https://www.thingiverse.com/thing:2278288
  
• M6 screws and 2 nuts (<$5 at local store)
  
• Onstep https://groups.io/g/onstep/wiki/home
  
  So At 408 + a bracket (Easy and simple 3D print or easy to DIY, look at the OnStep Showcase for a number of them.)
  
  Along with a 1/4-20 screw and a dovetail (Oh look: https://www.thingiverse.com/thing:2039785) , and you've got all of the functionality of a one of the Star Adventurers, along with the ability to mount pretty much any telescope up to 8" with a vixen dovetail.
  
  Plus, unlike from what I can tell of almost all commercial ones, they don't seem to compensate for misalignment when tracking. (Ie, they only move RA, not DEC, unless guiding.) Here are some examples of unguided long exposures with dual axis compensation. (Also, He doesn't usually process them, these are per other discussions straight off the camera) https://www.flickr.com/photos/11381732@N08/albums/72157683118306836
  
  Though that uses PEC (Periodic error correction, because worm gears often have high/low spots, so it can be corrected by basically guiding a few times and storing the corrections, which are then replayed). If you want that stored, which isn't included on what I mentioned above, but can be added for the cost of a magnet or two and a hall sensor ( https://www.amazon.com/WINGONEER-Effect-KY-003-Magnetic-Arduino/dp/B06XHG9CYN/ $8 and magnet https://www.amazon.com/Personalized-Multi-Use-Whiteboard-Magnetic-Refrigerators/dp/B075PMV2BC/ $8 ) Otherwise you'd have to retrain it each time.
  
  One thing is that the microcontroller and drivers aren't the most advanced, but you can upgrade them if you want. (STM32 about 3x as fast, but it's rarely needed, except for better alignment is about $60, but add two drivers, so call it a net of +$40 extra but that the kit adds wifi ($6 and a bit of wiring to the original) and a hand controller to it. the faster processors ESP32 and Teensy cost more but are something like 14x as fast allowing better alignment. Mind if you use Howard's Sky Planetarium, it won't matter too much, and it'll be able to process on the computer.)
  
  All new, and unless you have space taken up as your main concern the above setup is in pretty much all respects better than that suggested by dan.

Making a simulated mouse trigger is very easy, get an arduino Leonardo which can be trivially programmed to emulate a USB mouse with a couple lines of code.

I am not sure what kind of IR trigger you want to implement - do you already have an IR transmitter he can trigger somehow? If that’s the case you can add an IR receiver which can receive standard IR signals from things like remote controls.

Do you need to sense something like muscular movement in his face? You might be able to hook up something like attach a small magnet with tape to his eyebrow and then position a [https://www.amazon.com/IDUINO-Arduino-Compatible-Effect-Magnetic/dp/B019GU8UY2](Hall effect sensor) nearby so he can flex an eyebrow to change the hall effect sensor reading. The hall sensor will be connected to an analog input on the arduino.

The code will look something like this:

int magnetThreshold = 300; // this value will need to be determined experimentally

void setup(){
//initiate the Mouse library
Mouse.begin();
}

void loop(){
//if the magnetic sensor is triggered send a Left mouse click
if (analogRead(1)) > magnetThreshold){
Mouse.click();
delay(1000); // wait a full second
// make sure magnet is no longer triggered
while (analogRead(1)) > magnetThreshold) {
delay(250);
}
}

There are also other kind of sensors you can use like color sensors, pressure sensors (blowing into a tube) and even tongue switches.

THANK YOU SO MUCH!! I am attempting to attach a flow meter (https://www.amazon.com/gp/product/B00HR6BTYQ/ref=ox_sc_act_title_3?ie=UTF8&psc=1&smid=A1THAZDOWP300U)
to an Arduino and gave it measure the amount of liquid that is going through it and display it on a liquid crystal display (https://www.amazon.com/gp/product/B019D9TYMI/ref=ox_sc_act_title_1?ie=UTF8&psc=1&smid=A2IAB2RW3LLT8D)
and have it display the amount of liquid going through as ounces.

If this is to much I understand but I figured this would be a great place to turn for help.

So, if I'm understanding you correctly, you simply want position feedback, and not the ability to control motors? If so, I have had good results with these encoders. They are simple and fairly inexpensive. They are relative, which means they do not report a position inasmuch as they report a rotation. It is up to you to keep track of their rotation and to zero it out. A known position + a rotation gives you a known position, but you will have to zeroize them when you start up. this could be bad if your system crashes during a performance, you'll have to physically zero out the projectors position. so you may want to look at an absolute encoder, such as this one, which I've never used.

The other problem you will run into is that unless the encoder is mounted directly onto your shaft, you will have to use a transmission of some type (belt and pulley, gear, etc) to rotate the encoder. You will have to measure the turn ratio of shaft to encoder to ensure that the values you are getting back are accurate. For example, if there is a gear reduction of some amount, your encoder will spin fewer times than your shaft, give you bad values. Since I dont really understand where you will mount it, that may or may not be an issue.

Now, others in this thread are telling you to look into an arduino, but they do not have networking capabilities, so by the time you buy a network shield and code up a working osc/udp translation layer (there's probably a library for it, but who knows), you will have spent more time and money than if you just went with the pi, in my humble opinion. Python can run osc and python is very nice for beginners, compared to c++ which you'd be using on an arduino.

As someone who just finished a semester project with an Arduino and a Hall Effect Sensor, this is brilliant but the sensor would have to be installed in-line with either the water intake pipe or underneath the drip tip where the coffee filters into the pot.....our issue was there wasn't enough pressure to get the wheel to spin fast enough to register a pulse, so this isn't that trivial.

For reference, here is the sensor I used. I can link the Python code if anyone cares.

I literally just bought these for the same purpose. They are on/off and work well. The vout needs a pill up resistor.
10 pcs New A3144 A3144E OH3144E 3144 Hall Effect Sensor https://www.amazon.com/dp/B00ATNJH20/ref=cm_sw_r_cp_api_TzkOAbDB2KAFP

I've used these in the past for a non joystick related project:

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Hall Sensor

I will have these tomorrow: https://www.amazon.com/dp/B00ATNJH20/ref=cm_sw_r_cp_apa_3VSNAbF12C59J