Using 5V Arduino Relay to control spindle power

Mostly Printed CNC - MPCNC Hardware Development
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Hello MPCNC’ers,

I’m trying to set up using a 5V Arduino relay to power control my spindle using M105/M106 start and end gcode.

Heres a link to what I bought https://www.amazon.co.uk/gp/product/B01H2D2RI0/ref=ppx_yo_dt_b_asin_title_o00_s00?ie=UTF8&psc=1

71BX5CykEgL.AC_SL1200
71BX5CykEgL.AC_SL12001066×784 91.3 KB

I understand the fan pins use 12V by default. But can be remapped/changed in the firmware to 5V.
In this post KY-019 relay to control Router there is an explanation I’ve screenshot below.

Screenshot 2021-01-30 at 09.34.37
Screenshot 2021-01-30 at 09.34.37667×816 178 KB

I’m not clear on which of the pins in the diagram to use. If someone has a better idea of how this could work I’d appreciate any feedback. I’m in the UK and the IOT relay isn’t an option for me.

Providing this works out I plan to add an extension lead to the relay. And power the router through that.
This youtube video explains how to use the relay relay amazon https://www.youtube.com/watch?v=LLFQ8sBWc80&ab_channel=HowToMechatronics

If i’m not able to change to 5V in firmware, I could use a buck converter maybe. On the normal 12V fan pin.

Thanks!

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I would use pin 22. Alternate choices are pin 44 and pin 46. Note that pins 44 and 46 are PWM pins but pin 22 is not. This should not be an issue. Pin 45 is allocated to a laser if you ever install one. The changes are made in Marlin/src/pins/rambo/pins_RAMBO.h.

This is the section for the three fan pins:

#ifndef FAN_PIN
  #define FAN_PIN                              8
#endif
#define FAN1_PIN                               6
#define FAN2_PIN                               2

Personally I selected FAN2 for my IOT relay because it was by itself on the Rambo board.

And I’m sure you would have figured it out, but to save you a step, turning the fan on and off is M106 and M107. The ‘P’ parameter indicates which fan. M106 without a speed (‘S’) parameter turns a pin on full.

M106 P2  ; Turn on second fan pin
M107 P2  ; Turn off the second fan pin
1 Like
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Thanks for replying Robert. I just realised that the diagram is Rambo 1.4 and I’m using a Mini Rambo. Doh! Do you know what pin to use on mini rambo? I’m looking at the board now trying to figure it out.

Do you think the 5V relay would work with a 12V logic signal?

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Do you think the 5V relay would work with a 12V logic signal?

No, but they do make versions of the relay you purchased that have a 12V logic signal. One example.

First some references:

If you look at the picture, just to the right of LCD or GPIO pins is a block of pins marked P3. The schematic for that block looks like this:

P3_MiniRambo

I believe (but cannot be absolutely sure), that PH2, RX2 and TX2 are unused for the MPCNC version of the Marlin firmware. The pin numbers mapped to these ids are:

RX2  16
TX2  17
PH2  84

For remapping, I believe you need to change pins_MINIRAMBO.h in this section:

#ifndef FAN_PIN
#define FAN_PIN 8
#endif
#define FAN1_PIN 6

This is all theory based at looking at the references above and a bit of searching on the Marlin source code.

1 Like
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I wasn’t able to get the 5V relay to work. I think I will buy a 12V one and try again with the fan header.

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Just out of curiosity, did you redefine FAN1_PIN to all three values and test? Did you put a multi-meter on the pin? What g-code did you use?