Subj : Re: Retropi on Nespi
To   : Richard Menedetter
From : Bbsing.Bbs
Date : Wed Aug 14 2019 23:20:00

-=> Richard Menedetter wrote to Bbsing.Bbs <=-

 RM> Hi Bbsing!

 RM> 01 Aug 2019 17:01, from Bbsing.Bbs -> Richard Menedetter:

 RM>> I had a small fan. but I just bought a "Ultimate Pi cooling fan"
 RM>> for 8 USD. (simply a large heatsink with 2 cooling fans).
 RM>> Probably not needed but I liked its appearance, and it may stop
 RM>> throttling of the pi.
 BB> Is your colling fan attached to pins where you controll when the fan
 BB> turns on?

 RM> No ... same as you, fan is allways on.

 RM> CU, Ricsi

Ok I'll come up with a solution for this. 

I think a here are some parts required for minimal required build:
1) 1 560 ohm resistor
2) 1 NPN 3904 transistor
4) some wires
..) a diagram
..) some code see below
..) possibly a diode. 

I did some messing around and found a fix for this annoying fan that is always
on. .. mine is rattling a bit and if I can just turn it on when the cpu/gpu get
hot, I can prevent a lot of noise. 

The basics of the hookup:

[raspi pin 12]-(gpio18 3v)---(560 ohm resistor)---(npn3904 base) 
[raspi pin 6]-(ground)---[emitter (npn3904)]
[collector (npn3904)]-(5v)---(-){fan motor black lead}
{fan motor red wire}----[raspi pin 2]-(+5v)

The gpio readall output helps with orientation

-- CPU SIDE --
  +---Pi 3B+-+---+------+---------+-----+-----+
  | Physical | V | Mode | Name    | wPi | BCM |
| +----++----+---+------+---------+-----+-----+
| |  1 || 2  |   |      | 5v      |     |     |
  |  3 || 4  |   |      | 5v      |     |     |
H |  5 || 6  |   |      | 0v      |     |     |
D |  7 || 8  | 0 | IN   | TxD     | 15  | 14  |
M |  9 || 10 | 1 | IN   | RxD     | 16  | 15  |
I | 11 || 12 | 1 | OUT  | GPIO. 1 | 1   | 18  |
  | 13 || 14 |   |      | 0v      |     |     |
P | 15 || 16 | 0 | IN   | GPIO. 4 | 4   | 23  |
O | 17 || 18 | 0 | IN   | GPIO. 5 | 5   | 24  |
R | 19 || 20 |   |      | 0v      |     |     |
T | 21 || 22 | 0 | IN   | GPIO. 6 | 6   | 25  |
  | 23 || 24 | 1 | IN   | CE0     | 10  | 8   |
| | 25 || 26 | 1 | IN   | CE1     | 11  | 7   |
| | 27 || 28 | 1 | IN   | SCL.0   | 31  | 1   |
  | 29 || 30 |   |      | 0v      |     |     |
  | 31 || 32 | 0 | IN   | GPIO.26 | 26  | 12  |
  | 33 || 34 |   |      | 0v      |     |     |
  | 35 || 36 | 0 | IN   | GPIO.27 | 27  | 16  |
  | 37 || 38 | 0 | IN   | GPIO.28 | 28  | 20  |
  | 39 || 40 | 0 | IN   | GPIO.29 | 29  | 21  |
  +----++----+---+------+---------+-----+-----+
  | Physical | V | Mode | Name    | wPi | BCM |
  +---Pi 3B+-+---+------+---------+-----+-----+
-- USB ETHERNET SIDE --

I used Edoardo Paoloa Scalafiotti's code with minor modifications
basic code begin -- base64 begin --

IyEvdXNyL2Jpbi9lbnYgcHl0aG9uMgojIEF1dGhvcjogRWRvYXJkbyBQYW9sbyBTY2FsYWZpb3R0
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cmUgdG8gY2hhbmdlIGl0Cm1heFRNUCA9IDU1ICMgVGhlIG1heGltdW0gdGVtcGVyYXR1cmUgaW4g
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bGwgR1BJTyBwb3J0cyB1c2VkIGJ5IHRoaXMgcHJvZ3JhbQo=

-- base64 end --

run the code above using sudo:
	sudo ./raspi.fan.control.basic.py

I tested this with the above parts and code.
My system usually runs about 49 deg celcius.
I test this with stres via:
	stress -v -c 4 -t 900s

to install stress type the following:
	sudo apt update && sudo apt install stress

If you want a systemd script for this let me know. Thats probably best if you
just want the entire thing to run at startup. 

NOTE: I found if I don't slow down the execution loop that will drive the cpu
use up and increase cpu temp. I also added a sleep gate to allow the system to
cool below the threshold I set to keep the npn3904 from micro triggers.

If anyone sees and issue with the wiring setup let me know.

.... BBSING
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