Hello Forum.
I'm hoping some folks can help me with a project I've been hacking at for some time. I have a CNC table that uses a plasma torch to cut various designs out of various metals.
As the torch cuts the metal it introduces heat into the material thus warping it upwards which decreases the distance to the torch head. This fluctuating distance results in undesirable cut quality.
The premise:
The plasma is a constant current source and as the material warps it decreases the voltage between the work piece and torch (electrode).
I'm trying to sample that voltage and adjust the torch height accordingly.
My setup as of now:
The converted values from my ADC jitter a by couple volts (+/-) 5-8 dc out of a 50-200dc output scale. It's not horrible but does limit the speed at which I can cut.
As a beginner my understanding of the analog side of things is extremely limited.
I've read that plasma output is very noisy and has high frequency signals that I assume are making there way into my ADC.
I've been reading about two stage Pi LC low-pass filter because that's what commercial units use with success.
I just purchased an oscilloscope and could acquire some data but not exact sure what I'd be looking for just yet not to mention leery about hooking up to the plasma leads. I remember reading a warning about ground potential differences.
My Plea:
Does anyone have experience with two stage Pi LC filters and willing to share some knowledge?
I've been studying these commercial circuits and trying to visualize what is transpiring underneath but I'm in over my head.
Here's a pic of the circuit on the and what I think may be happening in the underneath.....
I'm hoping some folks can help me with a project I've been hacking at for some time. I have a CNC table that uses a plasma torch to cut various designs out of various metals.
As the torch cuts the metal it introduces heat into the material thus warping it upwards which decreases the distance to the torch head. This fluctuating distance results in undesirable cut quality.
The premise:
The plasma is a constant current source and as the material warps it decreases the voltage between the work piece and torch (electrode).
I'm trying to sample that voltage and adjust the torch height accordingly.
My setup as of now:
- tapped leads fed into a 50 amp bridge rectifier
- simple voltage divider (50:1) feed into lowpass rc filter
- 0-5vdc feed into 12-bit MCP 3201 ADC
- ADC values feed to Atmega328 MCU over SPI
- ADC values used in if/else control function calculations which are encapsulated via modbus and sent to CNC controller
The converted values from my ADC jitter a by couple volts (+/-) 5-8 dc out of a 50-200dc output scale. It's not horrible but does limit the speed at which I can cut.
As a beginner my understanding of the analog side of things is extremely limited.
I've read that plasma output is very noisy and has high frequency signals that I assume are making there way into my ADC.
I've been reading about two stage Pi LC low-pass filter because that's what commercial units use with success.
I just purchased an oscilloscope and could acquire some data but not exact sure what I'd be looking for just yet not to mention leery about hooking up to the plasma leads. I remember reading a warning about ground potential differences.
My Plea:
Does anyone have experience with two stage Pi LC filters and willing to share some knowledge?
I've been studying these commercial circuits and trying to visualize what is transpiring underneath but I'm in over my head.
Here's a pic of the circuit on the and what I think may be happening in the underneath.....