Mesa 7i96 Output Wiring
- Mud
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13 Aug 2020 13:56 #178098
by Mud
Am I correct thinking the diode positive (striped end) should go to 7i96 OUT+ (and can put the diode negative to OUT-)?
Replied by Mud on topic Mesa 7i96 Output Wiring
Both are correct.
If you use the second scheme you should definitely fuse the 24V supply
since a short to ground (assuming 24V common is ground)
would likely damage the 7I96 output
Note that you should have flyback diodes across the relay coils
Am I correct thinking the diode positive (striped end) should go to 7i96 OUT+ (and can put the diode negative to OUT-)?
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- PCW
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13 Aug 2020 14:05 - 13 Aug 2020 14:20 #178100
by PCW
Replied by PCW on topic Mesa 7i96 Output Wiring
No, the diode should be across the relay coil
for example
Sourcing drive:
+24V --> OUT+ --> OUT- --> COIL+ --> COIL- --> GND
or
Sinking drive:
+24V --> COIL+ --> COIL- --> OUT+ --> OUT- --> GND
Diode always goes from COIL+ to COIL- (cathode=band to COIL +)
If you are unsure, test the relay+diode with a mechanical switch
replacing the 7I96 OUT+- pins
for example
Sourcing drive:
+24V --> OUT+ --> OUT- --> COIL+ --> COIL- --> GND
or
Sinking drive:
+24V --> COIL+ --> COIL- --> OUT+ --> OUT- --> GND
Diode always goes from COIL+ to COIL- (cathode=band to COIL +)
If you are unsure, test the relay+diode with a mechanical switch
replacing the 7I96 OUT+- pins
Last edit: 13 Aug 2020 14:20 by PCW.
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- tommylight
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13 Aug 2020 14:16 #178102
by tommylight
Replied by tommylight on topic Mesa 7i96 Output Wiring
Just in case it got lost in there.Connect gnd and IN to the mesa board, they just need the input to gnd to switch over.
In case it does not work, reverse the gnd and in pins.
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- AgentWD40
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13 Aug 2020 17:47 #178121
by AgentWD40
Replied by AgentWD40 on topic Mesa 7i96 Output Wiring
Your answer is what I was confused about. Is my drawing incorrect?
forum.linuxcnc.org/27-driver-boards/3845...iring?start=0#178037
forum.linuxcnc.org/27-driver-boards/3845...iring?start=0#178037
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13 Aug 2020 18:14 #178124
by Mud
As attached?
I'm a bit gun shy about hooking up my torch switch - I plan to use a multimeter to check voltage and current, but the polarity of the 7i96 output switches keeps breaking my brain. I read in another thread that an additional relay isn't necessary (at least for a hypertherm which uses a low switch voltage/current), but I'm tempted to use one nonetheless. I assume the alternative is to just loop through an output pair since the plasma is supplying the signal voltage for the switch (assuming it's a reasonable voltage/current and I send signal+ to OUT+ and signal- to OUT-).
The manual could be more friendly, i.e.
"Inductive loads must have a flyback diode. The output polarity must be observed (reversed outputs will be stuck-on)."
I can see what you mean now, but I interpreted that as flyback diode across the 7i96 outputs (which seemed to make sense since you could force current to only flow in one direction). I was also interpreting the statement about reversed outputs with respect to a diode across the outputs, which seemed to make sense since you would short the switch if you attached the diode in one direction. Big dumb.
It also doesn't say if the polarity sign convention is current flow, or just hook neg-neg, pos-pos. Hence the confusion. I empathise with AgentWD40, I need drawings to understand
Replied by Mud on topic Mesa 7i96 Output Wiring
No, the diode should be across the relay coil
for example
Sourcing drive:
+24V --> OUT+ --> OUT- --> COIL+ --> COIL- --> GND
or
Sinking drive:
+24V --> COIL+ --> COIL- --> OUT+ --> OUT- --> GND
Diode always goes from COIL+ to COIL- (cathode=band to COIL +)
If you are unsure, test the relay+diode with a mechanical switch
replacing the 7I96 OUT+- pins
As attached?
I'm a bit gun shy about hooking up my torch switch - I plan to use a multimeter to check voltage and current, but the polarity of the 7i96 output switches keeps breaking my brain. I read in another thread that an additional relay isn't necessary (at least for a hypertherm which uses a low switch voltage/current), but I'm tempted to use one nonetheless. I assume the alternative is to just loop through an output pair since the plasma is supplying the signal voltage for the switch (assuming it's a reasonable voltage/current and I send signal+ to OUT+ and signal- to OUT-).
The manual could be more friendly, i.e.
"Inductive loads must have a flyback diode. The output polarity must be observed (reversed outputs will be stuck-on)."
I can see what you mean now, but I interpreted that as flyback diode across the 7i96 outputs (which seemed to make sense since you could force current to only flow in one direction). I was also interpreting the statement about reversed outputs with respect to a diode across the outputs, which seemed to make sense since you would short the switch if you attached the diode in one direction. Big dumb.
It also doesn't say if the polarity sign convention is current flow, or just hook neg-neg, pos-pos. Hence the confusion. I empathise with AgentWD40, I need drawings to understand

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- PCW
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13 Aug 2020 18:43 #178125
by PCW
Yes, that looks correct if I understand those relay modules
Replied by PCW on topic Mesa 7i96 Output Wiring
Your answer is what I was confused about. Is my drawing incorrect?
forum.linuxcnc.org/27-driver-boards/3845...iring?start=0#178037
Yes, that looks correct if I understand those relay modules
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13 Aug 2020 18:48 #178126
by PCW
Replied by PCW on topic Mesa 7i96 Output Wiring
Yes, those drawings are correct
OUT+ must be more positive than OUT-, otherwise the inherent diode
in the output MOSFET will conduct (so the switch will appear to be on if reversed)
This is not related to the flyback diode which is most often wired directly
across the relay coil.
OUT+ must be more positive than OUT-, otherwise the inherent diode
in the output MOSFET will conduct (so the switch will appear to be on if reversed)
This is not related to the flyback diode which is most often wired directly
across the relay coil.
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- tommylight
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13 Aug 2020 18:59 #178127
by tommylight
Replied by tommylight on topic Mesa 7i96 Output Wiring
I have those relay modules, the 5V version and they have a jumper for setting the input.
Go with PCW's version and check that the jumper is set for positive triggering.
Go with PCW's version and check that the jumper is set for positive triggering.
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- xnaron
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20 Aug 2020 03:54 - 20 Aug 2020 03:55 #178793
by xnaron
Replied by xnaron on topic Mesa 7i96 Output Wiring
5V/12V/24V Relay Module,4 Channel Optocoupler Relay Module Board High & Low Trigger (24V) www.amazon.ca/dp/B07QKLKPBJ/ref=cm_sw_r_cp_tai_rnFpFbZ9G2PSN
These relay boards are opto isolated on their inputs so I should not need a flyback diode correct?
These relay boards are opto isolated on their inputs so I should not need a flyback diode correct?
Last edit: 20 Aug 2020 03:55 by xnaron.
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- rodw
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20 Aug 2020 10:13 #178814
by rodw
Replied by rodw on topic Mesa 7i96 Output Wiring
PCW may correct me but Flyback diodes are only necessary where its an electromechanical relay (with a coil). Also I don't understand why you would bother with relay boards when the 7i96 has relays built into the outputs.
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