TinyG v8 coolant pin not working

Started by skillhoarder on Sep 22, 2017 in TinyG Support. 1 reply, last activity Sep 22, 2017.

skillhoarder Sep 22, 2017 #

Hi there,

I'e been using my tinyG for a couple years with pretty much zero problems. Today I finally decided to run my coolant relay from the coolant pin! But alas, no joy.
When I use M7 or M8 to turn on coolant, I don't get the ~3v that I expected like I get from the spindle pin.

On further inspection with a multimeter, M7 does absolutely nothing but M8 does bring the pin voltage from 0v up to 144mV! Even weirder: after calling M8, entering M7 will bring the voltage back to 0 just like M9...

The coolant LED also does not illuminate. When I check it's voltage, the coolant LED also goes from 0mV to 144mV with M8 just like the pin. I also checked R21 (wred to coolant pin), and it measures 150ohms, which I'm assuming is correct because R18 and R19 (wired to spindle and direction pins) are built to give the same HIGH/LOW output as the coolant pin and also use a 150ohm resistor. R20 has a 3Mohm resistor, but it's for PWM, so that's understandable.

So as far as I can tell by eyeballing the board and poking it with probes, the physical layer seems to be in ok shape unless there's a broken trace somewhere out of sight or a bad connection to the microcontroller.

So maybe I have a bad setting in the firmware? That could explain why I get different functionality for M7 and M8 - but only kinda. Again I get no signal with M7 and a super weak 144mV signal with M8.

Are there any settings that would affect this? Have any other suggestions?

cmcgrath5035Staff Sep 22, 2017 #

Here is the schematic, which is consistent with your description above

https://github.com/synthetos/TinyG/blob/master/hardware/v8schematics/v8h/tinyGv8h%20-%20schematic%20page1.pdf

The last time I played with my tinyG coolant line, I noticed that M7 did not turn it on, M8 did and M9 turned it off. Bug? First I have noticed, but then don't use it.

Does your coolant relay have a damping diode? If not, the first time you turned it off may have fried it.

There are no FW parameters associated with this function.

For jollies, you could tie a 10K or so resistor from coolant pin to 3.3V (J6 Pin 2, see schematic), see if perhaps the active pullup on the output gate is weak. Maybe, just maybe, you might have enough pulldown to make it work (M8/M9).

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