How to configure THCAD-10 arc voltage

 Hi, I am having mesa 7i92 with Chinese BOB my arc voltage pin is connected to pin 11 on BOB which is Encoder A . I am using raw arc voltage from my plasma which is 230v DC and I have used 1m ohm's resister for each leg which gives me 21:1 divider ratio but if I am cutting the THC can't sensor the arc voltage.       

I think you are going to struggle with a chinese bob IMO
the THCAD outputs a freqency bettween 120khz and ~950khz (just less than 1mhz)

They normally don't use very good optocouplers.

the inputs on the chinese bob are also expecting to see voltages between 12 and 24V...... not 5V TTL.

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Then again.... I've never tried this..... so it may or may not work. I'm just suggesting a reason why you may not get / see a voltage reading or one that is consistent over the whole range of the THCAD.

Just something for you to think about.

www.omc-stepperonline.com/download/ST-V2.pdf

obviously depends on the BOB.

you are also going to need firmware for an encoder input too on pin 10

I dont know if you can create firmware for just 1 encoder input channel or if you have to create an AB and Z / index channel

if it were me.... I would make my own bob with an IDC connector (carefully make sure you get the pin numbers RIGHT) and I would use the 2nd port of the 7i92 for the encoder input.

Note the 7i92 does not output much current on its pins and it won't like anything above 5V or below zero volts on those pins (i.e. you cannot connect them directly to a relay as the collapsing field generates a back EMF that will kill the FPGA on the 7i92)

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once you let the smoke out of the chips you won't get it back in.....

think carefully and work slowly

phillc54 wrote:

Can you post a backup of your config from the Settings tab.

 

File Attachment:

File Name: AABTECHCNC.hal
File Size:9 KB

 

File Attachment:

File Name: AABTECHCNC.ini
File Size:5 KB

 

phillc54 wrote:

I must be half asleep, I missed the bit about the BOB.
You probably need to change the THCAD jumper to 128 and the scale and offset parameters to suit.

i change the jumper to 128 and  random torch raises or dives during stable cutting was not working.