Using Pimoroni fan shim with no software control

harrylnorris · November 20, 2022, 8:32pm

Just wondering whether anyone has successfully installed a Pimoroni fan shim on the current hardware (full kit) with the included metal heat sink?
Two aspects - 1) will it fit mechanically (preferably keeping the included heat sink) ?
2) when not intending to use any fan control software (i.e. just have it run continuously) does the current software manipulate a GPIO that will affect the operation of the fan?
Harry

Lanfranco · March 22, 2023, 3:55pm

I had tried to mount the Pimoroni fan, but I’m poor in programming and I opted for a very silent fan and with the 3D printer I made a duct that brings the air directly to the Raspberry…

wyleu · March 22, 2023, 4:25pm

It kind of sounds like it might well interfere with things if it’s to taken at it’s word.

Lanfranco · March 22, 2023, 4:28pm

I also have the GPIO full since I have the encoders connected directly to the raspberry… I therefore preferred to insert a good fan. If one day I feel like it (but I don’t think so) I could insert a sensor that starts the fan only when needed…

wyleu · March 22, 2023, 4:30pm

Not sure quite how the fanshim controls the fan, normally yiu just need to specify a pin and the rest is all handled in the raspi-config software because the Pi itself has an internal thermometer and uses this to do the switching.

Zynthian does include this mechansism.

Lanfranco · March 22, 2023, 4:39pm

So the Raspi can start the fan by itself?
The Pimoroni string is this:
git clone GitHub - pimoroni/fanshim-python: Python library for the Fan SHIM for Raspberry Pi
cd fanshim-python
sudo ./install.sh
cd examples
sudo ./install-service.sh --on-threshold 50 --off-threshold 40 --delay 2

Lanfranco · March 22, 2023, 4:42pm

My fan runs at 12V because I have a power supply with a circuit that lowers the voltage to 5.1V and the fan is connected to the power supply… I could put a small relay (I have microscopic ones) and control it with the raspi… .

wyleu · March 22, 2023, 4:49pm

Yes the install service command will install a systemd service which is started up and managed by systemd, the great and glorious does everything on startup programme.

The zynthian has a fan pwm control if you know where to look …

github.com

zynthian/zynthian-sys/blob/testing/etc/systemd/zynthian-pwm-fan.service

[Unit]
Description=Zynthian PWM controlled fan
After=multi-user.target

[Service]
Environment=PATH=/usr/local/bin:#ZYNTHIAN_SYS_DIR#/sbin:/bin:/usr/bin:/sbin:/usr/sbin
Environment=HOME=/root
#Environment=ZYNTHIAN_LOG_LEVEL=10
Environment=ZYNTHIAN_DIR=#ZYNTHIAN_DIR#
Environment=ZYNTHIAN_UI_DIR=#ZYNTHIAN_UI_DIR#
Environment=ZYNTHIAN_SYS_DIR=#ZYNTHIAN_SYS_DIR#
Environment=ZYNTHIAN_CONFIG_DIR=#ZYNTHIAN_CONFIG_DIR#
WorkingDirectory=#ZYNTHIAN_SYS_DIR#/sbin
ExecStart=/usr/bin/python ./zynthian-pwm-fan.py

#-- :0 vt3
TimeoutStopSec=8
Restart=always
RestartSec=5

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This starts up the zynthian-pwm-fan.py code…

github.com

zynthian/zynthian-sys/blob/testing/sbin/zynthian-pwm-fan.py

#!/usr/bin/python
import RPi.GPIO as GPIO
import time
import os
import signal

#Configuration Items
fan_pin = 13
fan_freq = 100
fan_startup = 30.
fan_min = 30.
poll_sec = 1 

#Linear interpolation from 2 points upper_temp, lower_temp, upper_speed, lower_speed
temp_1 = 70.
temp_2 = 30. 
speed_1 = 100.
speed_2 = 1.
smooth_beta = 0.025

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This specifies a pin that controls the fan

But I don’t know if the fanshim uses this pin. Presumably the fanshim has a transistor or similar for controlling the fan.
I don’t use this pin for instance I use pin 14, and I like this context to all be in the zynthian setup files…

You can do this using the PWM mechanism which the zynthian implementation provides which will allow the fan to be speed controlled as well so it wont hammer away with full ferocity if it doesnt need to.

You would need to see the schematiac of the fanshim to be able to fully answer the question.

Lanfranco · March 22, 2023, 4:52pm

Genius…