Probe Interface Board Design (resistance switching)

It is a REALLY nice probe. It is supposed to fix the issues with the Renishaw-style probe where there is a bias due to the three legs that contact the balls. Blum shows a drawing that indicates their probe does not have a 3-lobed sensitivity pattern, and responds equally in every direction. This is all down in the microns, and is nothing I would ever be concerned about, however. I stumbled over this probe on eBay while looking at other Renishaw-style clones.
As for details of my interface design, it is QUITE specific to the Blum probe. But, the IR interface is fairly standard stuff. One problem with IR is that almost all the IR devices are specific to the 38 KHz frequency used for TV remote controls. I had to search pretty hard to find opto devices that did NOT have the 38 KHz filtering in them. The IR receiver device is a QSE159 the transmitter (to the probe) is 6 units of the LTE-4208.
Jon

@jmelson 
Why do you use FPGA? this job is probably for a simple microcontroller ?
What is the frequency of data transmission in this interface?

besriworld wrote:

@jmelson 
Why do you use FPGA? this job is probably for a simple microcontroller ?
What is the frequency of data transmission in this interface?

 

Well, I am mostly an FPGA guru.  And, I make a bunch of products that have FPGAs on them, so I had suitable boards to repurpose.  The data rate is not high.  Yes, a fairly simple micro could do it.
Jon

Thanks ! You have done a great job! It is not an easy job to debug the interface.
I have a probe of Renishal with a cable. On my to-do list is to make a wireless interface for this pendant. Then I will be able to rotate the probe and touch on the same side of the round ball ...So there will be a small error.

Progress has been made... A Wheatstone bridge to help 'tune out' residual resistance in the probe contacts & cable, I finally learnt how to flash a bare metal ATtiny85 from PlatformIO. Still have to 'calculate' the usual random resistor values - some are confirmed but others are a bit finger in the air.
This was originally planned to be my first SMD project but the my brain put the electronics in the 'quite hard' pile, so possibly a step too far. Maybe. Even with THT the PCB is 32mm wide x 84mm tall so should be DIN rail mountable.
 

Well, that's depressing. My 21 year old Renishaw TP6 has given up the ghost. It was always a little dodgy on one of the 3 lobes but now it seems to have given up permanently. I think the internal spring mechanism was broken when I bought it as turning the adjust screw never changed the tension.The errant lobe never moved as far as the other two so possibly something has moved (again) inside.

Anyone ever disassembled one?

Ho hum image missing /media/kunena/emoticons/sad.png

Edit: @Mecanix - Any chance of buying one of your spares?