Quick explanation: seed gets blown with air from a holding bin to units that place them in soil, via 1' pipe. 1 pipe at holding bin, gets distributed to 50 pipes and then to planting units
Goal : building a monitor that could notify tractor operator(me), that 1 or more pipes are blocked, therefore not planting seeds
There are many commercial available systems out there, that uses different ways to sense seed-flow (hit-, infrared-sensors), but the one that is most effective is one using a sound sensor, 'hearing' seeds bounce of a membrane.
I've build a working prototype using a microphone and 555timer, switching on/off red and green leds, but I don't like the idea of having a harness with 50+ wires running from back of seeder all the way to tractor cab, and quick connector blocks malfunctioning.
So arduino with wifi it is!
I have done some research, and found many ways of doing this, so much so that I think it best to ask the pros for advice before I start and do it wrong, or more complicated than needed.
Coding I'm sure would be doable and I'll spend many nights learning (noob!),
Hardware are my question:
Sound sensor- KY-038 x 50 (?)
Interesting project. Wifi seems like overkill unless the tractor already has it. There's plenty of other short range radio options though.
I would start with a wired connection though - run the fifty wires to a mega on the planter and have it talk over serial using two or three wires to an Arduino on the tractor. That one will have a display to tell you which pipes are blocked.
Yes, a serious and interesting project. I agree with @wildbill.
As a professional designing and maintaining the computer controlling 8 ton forklift trucks mainly indoors, running on hard concrete floors I know that vibration is a hard enemy. Tighten the cables well or they fail in more than one way. The same difficulty applies to the controller and the entrance of the harness, the connections, to the controller.
Know that solder spreads into a multi strain cable and hardens that piece. That's an invitation for cables to break.
Premature post there!
Next
Arduino uno with expansion board DI024-ARDProcessing: dio24-ard_manual.pdf...
Or arduino mega
Or arduino uno stacking multiple sensors data to single pins?
Wifi (NRF 24) or
Bluetooth (HC- 08)
What other short range radio options, hc-12?
Im not sure if bluetooth would be strong enough with obstacles in between (cab glass, steel holding bins)
Also I might want to have multiple master arduinos(uno) with each 6-7 sound sensors, tranmitting to 1 slave(mega), with all the red and green leds, as the monitor.
Could this be done?
I can only find tutorials of one master, multiple slave, not the other way around?
In addition to the stuff you already mentioned, there's the cheap 915MHz stuff, X-Bee (or Zigbee if you prefer), LoRa and no doubt others. Bluetooth might do it, but the environment is pretty hostile.
Having a number of master Arduinos could well work and make it easier to swap out if one fails. You can get the tutorials to work for you if you reverse your terminology - the unit on the tractor is the master and the ones on the planter are slaves. The master will ask them for the health of the pipes they monitor one at a time and alarm if any of them report a problem.
I am something of a farming expert, having watched all six episodes of Clarkson's Farm, so it seems to me that getting all this wired up reliably and weatherproofed, especially if the planter stands idle outside for much of it's time, is going to be tricky 
Thanks I'll have a closer look at LoRa
Excellent!
Now next question:
My master will be a Mega and I'll need 50 green leds, 50 red leds and 50 yellow leds( I'm guessing I could write the code so that yellow leds could go on when there is a difference in sound intensity at sensors when some pipes are partially blocked?)
That's 150 pins, + one more for a buzzer
Without any additional hardware (transistors),what's the best way to do this?
That many individual LEDs sounds very painful to wire up. If you're determined to have such a solution, look perhaps instead at Neopixel strips from Adafruit.
My inclination would be to use a display screen of some sort that gives overall status and just indicates a list of pipes that are problematic.
Adafruit (I don't work for them) has some nice OLED displays that could work. Nextion comes up here quite frequently with their touch sensitive screens. I haven't used one, but be aware anecdotally that they're considered a bit tricky to write code for. @PerryBebbington can probably give more concrete advice in this area.
Hi,
I agree with @wildbill you only need to know when a pipe is blocked, and LED display of all 50 is really not practicable.
A simple sound alarm and a pipe number(s) indicator would suffice.
Your wiring from sensor to controller would be best of a microphone shielded cable to keep the noise pickup of relatively long cables.
The only thing I would try first is just a single unit on a machine to check for machine vibrations/bumps causing pickup problems.
Tom... 
Well, it is dead easy with a MAX7219!
Yes, but all you will see is bars that most of the time will show minimum and then 1 or 2 or 3 go up to show blockage.
Waste of LEDs.
Anyhow the OP knows what he wants, it will evolve.
Tom...
I thought I had replied to this, but I must have gotten distracted.
Bluetooth (BLE, anyway) should be fine. I worked for a company that designed a lot of ag equipment and all our communication with the hardware was via BLE 4.0 to a tablet in the tractor cab.
That said, I prefer Wi-Fi where possible. The main reason is that there's less code to write. If you go with BLE, then the User Interface also needs an App written for the communication. By using an ESP8266 or ESP32, you can have the processor itself serve up a simple web page and then all you need to view the data is a browser on your phone. No need for 50 LEDs.
So, my head is still stuck at my original prototype with 555 ic where I would have had the top view of the planter ingraved onto aluminum box with red and green leds at every plant-unit, +buzzer
Obvious arduino gives so many more options, but still like this display layout
I would use rgb leds to save and simplify space
Painful wire job? - I love a challenge
Now this is interesting!
I can run 50 rgbs from only 4 arduino pins.., but this is the deep end of the code writing pool, for a noob like myself? I'll have to start my studies!!
Thanks for getting undistracted!
If wi-fi is less code, then I should start their.
I've looked into using a app. Creating one that displays image of planter on a tablet, illuminating each unit according to its state, would be the best, but that looked to difficult for me?
To be clear, this would not need internet connection? (no reception where I plant) Does it use arduino code or similar? I need to do more research on ESPs
Please bear with me, as you can see, I know almost nothing, and that should disinterest you, but my whole purpose with this thread is to get to the best way of doing this, so I don't waste time running with wrong ideas first.
I want to build my(our) own pipe blockage monitor, and be proud of it!!
I'm aware that you're a farmer and obviously that means that you can fix almost anything with a hammer and some baler twine.
However, it seems to me that the long pole in the tent here is wiring up all the hardware on the planter and keeping it working.
The comms and the software are trivial by comparison I suspect. If you can get a reliable reading from each of fifty sensors to an Arduino on the planter, I or others here can help you present that data in the tractor.
Correct. The ESP can be put in a mode wherein it creates its own Wi-Fi network and your device can connect to it. No external router, or internet service required. Lots of information online about setting it up as a web server.
I have one here that I was using to monitor the temperature in my garage. Temperature updates about every 5 seconds or so.
The MAX7219 requires only three Arduino pins unless I am very much mistaken. 
Plus 5 V power and ground.
Well, the ESP can make its own local "intranet" (Access Point) to which you can connect via WiFi with a phone (or PC etc.)
I hope my link posting works!
Am I on the right track, could it really be that simple, hardware-based?
The coding for a rgb matrix looks like hieroglyphs thow!
My KY-038 module (6/ESP or Arduino) are nicely packed a dustproof container with rubber tubes running from each mic to the dtainless
The reply button is on wrong place(finger to thick 
)
... to the stainless steel membrane pipe module (3d printed)
This way there is very little noise interference from out side and if I use wifi, no noise pick-up from long cables?
What power regulator would be best to bring down 12v dc (tractor battery), to 3,3v esp or 5v arduino?