Connect the fan to the gpio connection?

dawless · March 2, 2023, 7:33pm

I got a case for my Zynthian today and now have the display on the DSI Prort. Is it possible to connect a fan to the GPIO connection? If so, at which ports?

Greetings

tobiw · March 2, 2023, 8:34pm

GPIO pins are only designed to provide a small amount of current (typically around 25 mA). A fan will require more (yours has a rating of 160 mA) so it isn’t safe to connect it to those pins. The Pi’s GPIOs are also only 3.3V whereas the fan requires 5V so it should be directly connected to 5V and GND. A good source to lookup Raspberry Pi pinouts is https://pinout.xyz/

dawless · March 2, 2023, 8:57pm

@tobiw thanks for the information. According to the pinout, pin should be 4 (5V) and 6 (ground) or should I rather not do that? I had bought the case as a set and had assumed that this would have to work. How else should fans be connected?

Thank you for your effort.

Best regards…

dawless · March 2, 2023, 8:59pm

Oh, that’s the set:

Best regards

tobiw · March 2, 2023, 9:06pm

On the 5th picture on Amazon it looks like it’s connected to GPIO2 and 3 which doesn’t make much sense. They might have tried to use the pins on the opposite side of the pin header for the photo and got it wrong. Actually, it looks correct on the 6th photo.

You are right, using pins 4 and 6 will be fine as the current for the 5V pin comes more or less directly from the Pi’s USB power input (they are on the 40-pin GPIO header but I wouldn’t call them GPIO pins since GPIO means general-purpose input/output, whereas 5V, 3V3, GND etc are power pins).

dawless · March 2, 2023, 9:09pm

Thanks for the correction. Become a little smarter again.

wyleu · March 3, 2023, 10:43am

There is a zynthian fan mechanism on Pin 13 that might be beneficial to take advantage of.

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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It would be nice if this could be configured for other pins…

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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le51 · March 3, 2023, 11:27am

Hi @dawless ,

You should try different setup and see if fan is really needed. Cause it could be very noisy …

without fan
using GND and 3.3V RBPi headers
using GND and 5V RBPi headers
optimal solution is for sure pwm fan control based on the temperature sensor, but I could not help you that much in that direction

wyleu · March 3, 2023, 12:25pm

I can vouch for how noisy they are, and as you say the PWM way is the correct one if you are going to use a fan.
The Pi itself seems reasonably comfortable to run hot. I run hifiberry metal cases which are pre drilled for a fan and I want control of it without going to the tedium of adding a switch.
Drive from the 5V. the 3.3v line doesn’t need that fan noise, but to do so you will need a transistor to operate the fan.

Here it is from the original thread…

Fans et al…

dawless · March 3, 2023, 12:38pm

Hi,

thank you for your tips. I have now connected the fan to the 4 5v and 6 ground lines. The temperature is even between 40-50 degrees after several hours. I can hear the fan so little that it doesn’t bother me at all. I am so satisfied at first.

Best regards, Tobias