Fried my THCAD-10

@Hi Rodw,

It can be bad luck. If you have the new card. Check for sure your electrical ground status of your machine. Sometimes machine's get static if grounding is not attached.
For example painted floors can be dramatic for plasma machine's. If your grounding is okey you don't have
to worry about getting the plasma + (=ground) over your pc or your electrical devices.

PCW wrote:

26LS31 is fine, its still RS-422 differential so no jumper changes
the 26LS31 just has a bit lower voltage swings (but is much easier to find)

Peter thanks, I did find the 5V one on Digikey but $25 freight v's free through RS Components. How do they ship a single $3.00 chip for free? (I ordered 2 just for good luck.)

Rod

I have bought from DK for close to 40 years, they have always had handling and extra shipping fees for less than minimum orders. In spite of this I have bought from them both personally and business wise over this period. Their professionalism and depth of stock has always been hard to beat. In the US they have quick shipping because of their central location.

I am sure that RS is carrying stock in OZ and by using post for small orders has low shipping cost. Also remember that the chip costs RS less than a $ in the quantities they buy. RS is counting on your return order for higher margin goods. I can remember when living in the UK in the late '70s when RS was really the only game in town for less than industrial scale orders, they were awfully expensive compared to buying the same thing in the US.

I hope you get your THCad and 7I76E sorted out soon, I am looking forward to news on your progress. I have patched together a new PP and hope to do some cutting tests next week. The plan is to be able to set cutting parameters though G code or from the GUI. I have a pair of radio buttons on the GUI to make the selection. There is a bit of conditional Gcode that gets set at the start of each program that reads which set of cutting parameters are used and sets post variables accordingly. Have a good weekend, it is pissing rain and cold (8C)here.

John

John, Thanks for the support. RS have been here for years and there was a time that I could walk into a local branch. If they did not have it, it would be there the next day ex Sydney. Believe it or not, my RS order is being fulfilled from the UK and their promise is 5 day turnaround! Element 14 (previously Farnells) have also been good to deal with. Digikey is a new comer to our market. Mouser fulfils from Hong Kong. I suspect RS must have decided it was cheaper to ship for free than run branches.

Yes, this problem is very frustrating. I've been so careful powering off things when I change wiring and to get caught like this is bloody annoying. Anyway my mate who offered to do any SMD soldering is away for a week so maybe by the time he gets back, the part will be here. I've already updated the bit file.

Really hats off to Mesa becasue of the amazing support on this thread. I'm sure anybody else would have said bin the parts and buy some new ones! Thanks again Peter. At least if the THCAD repair does not work, it will only cost $100 to get a new THCAD over here.

Still quite warm and humid here. 25 deg C. Its been an unusually wet summer and we have not had any cold nights yet which is a bit unusual.

Well that was a bit disappointing. The replacement chip arrived yesterday and my SMD solderer also arrived back home so we swapped the chip over this morning. The THCAD is still not functioning. We checked it on a CRO with no result and I reconnected it as well but no luck anywhere.

Peter, whats the best way to get a replacement? Through you or back through John where I purchased it from originally?

Well, my replacement THCAD-10 turned up today and thanks to Peter's great support providing patched firmware to use the other encoder input, it looks like we are back in business!

It looks like I did not need to buy the new 7i76e that I ordered with it. I just figured with the costs and distances involved, I had to make sure I had all bases covered.
I hope to cut something soon!

Hi Rodw,

Good luck with your installation.
Soon your table will cut like a formula 1 car !!
I saw your youtube video yesterday of piercing test.

Thanks Grotius,

OT for a minute now. This was the most successful cut with external offsets THC control (2mm mild steel) There was probably a 20mm rise on the last side cut.


After that we tried to improve THC velocities and accelerations and Dewey found a bug and we did not get very far. We've now added a deadband to external offsets so are very hopeful it will help. I wanted to do some test cuts at different heights and log the results to a file. From there, I want to graph the results in a spreadsheet. If what I've observed with a few points is replicated with a data set of a few thousand points, we should be able to identify the best cut height from one cut about 150mm long using a 3rd order polynomial trend line. Scary stuff!

The next couple of weeks are very busy for me but I hope to be able to work full time on this in a month or so.

Hi Rodw,

Good work !!
For your info, a proma is switching in about 5 volt difference for up and down. Is that wat you mean with deathband?

I can make a drawing with external offsets. It wil follow everything you say.
I just merged an update for negative value speedcontrol.py widget. Haha github is easy !!

Grotius wrote:

Hi Rodw,
For your info, a proma is switching in about 5 volt difference for up and down. Is that wat you mean with deathband?

Thanks, Yes thats right. The external offset barnach included the eoffset_pid component
github.com/LinuxCNC/linuxcnc/blob/dgarr/...nts/eoffset_pid.comp

A pin has been added to control the deadband. If say the deadband pin is 2 volts then the PID adjustments made in func() are ignored unless the actual volts is more than 2 volts difference from the commanded voltage.