# Torch height control problem



## Electrical-EE (May 4, 2017)

Dealing with a THC at my workstation. I am using CNC plasma cutter. The machine alone works perfectly when THC has activated it goes up to 20 mm (which it should not, instead it should go to the set value). Specs Three isolated inputs and two isolated outputs Requires Mach 3 Rev2 and second printer port Fused 5V and 24V power supply, from this divider 
I calculated the resistors to be 150 k and 2.55 k. The circuit looks like this for control (Not exact caps). 









Any suggestion to change or guide on whats wrong with it?


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## RePhase277 (Feb 5, 2008)

I have zero experience with Mach3 for plasma cutting, but I am familiar with it in router mode. Are sure you haven't overlooked a safe-Z checkbox or setting somewhere? What does the circuit you posted have to do with torch height?

If it is a consistent 20 mm, I'd bet it's software related. On my CNC router, the Z axis has a different number of steps per mm than the other axes. Start there.


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## Electrical-EE (May 4, 2017)

I am actually using a power voltage divider to supply the module. The divider has two resistors.


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## RePhase277 (Feb 5, 2008)

I get it, I think. In my opinion, using a voltage divider to supply power to a device is a bad idea. The voltage will vary depending on the load. Voltage dividers are good for sensing purposes but terrible as power supplies. You could use an op amp configured as a voltage follower (aka "unity gain buffer") with your divider, or, better yet, give this device it's own power supply.

Switching power supply units are dirt cheap and can take a wide range of input.


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