Probe Interface Board Design (resistance switching)

I have a renishaw omp60 but i don't have the wireless ir-receiver so it is useless.
Knows soneone the comunication ptotocol to impement a receiver or
if it is posible mod it and use it with wired connection?

Up until it broke, the contact resistance was a bit variable (probably because of the lack of spring tension) but operated fine at 5v with the 'check if still open loop' able to detect closed at 0.5v. Now I've removed the chrome, my '3D printed special' shows similar characteristics.

i played with a few renishaw probes a while back - namely TP6, TP1s. yes, the resistance can be quite high and variable. but PI4 and MI8 interface units i had could reliably detected it. AFAIR, they supply 10 VDC at 0.5 mA to the probe. resistance less than about 3 kOhm considered as a seated probe.

The probe must triggered not by resistance absolute value but by increase in resistance.
So must have mcu with a voltage comparator?

vre wrote:

I have a renishaw omp60 but i don't have the wireless ir-receiver so it is useless.
Knows soneone the comunication ptotocol to impement a receiver or
if it is posible mod it and use it with wired connection?
 

That is a very nice probe. There's a lot of information on the Renishaw site here but predicatably no information at all the protocol. Reading the IR outputs from the probe would be fairly(!) trivial with an IR reader/oscilloscope/Arduino but without the OMM receiver,  the IR inputs to the probe would be challenging to say the least.

I suspect it would not be prudent to convert the probe to wired - there's a whole lot of electronics packed inside!

dm17ry wrote:

i played with a few renishaw probes a while back - namely TP6, TP1s. yes, the resistance can be quite high and variable. but PI4 and MI8 interface units i had could reliably detected it. AFAIR, they supply 10 VDC at 0.5 mA to the probe. resistance less than about 3 kOhm considered as a seated probe.

 

Thank you Dmitry, that is very useful information. It validates my decision to implement a Wheatstone bridge to be able to 'tune out' the probe resistance but only up to 2K atm!

I'm using 5VDC with 10K resistance (2x 20K in parallel in the bridge) which fortuitously turns out to be 0.5mA! Happy camper.

Philip

i've found some old notes when was playing with an MP700 optical interface:

The probe turns on after receiving 500Hz for 1/4 sec.. it has internal a switch for selecting auto power of or power of with the same signal that turn it on.

Once turned on, the probe sends out a 19.2K baud byte every 16 ms, and when there is a change of state of the probe tip. When not triggered, the byte is :
01010100 (with 1 meaning LED lit)
on the first transmission after the probe is deflected it sends:
11010100
after the first transmission of a trigger, it sends
10010100 as long as the probe is still deflected
The last bit goes to a 1 when the battery is low.
The start bit of the data is not shown above, it is with the
LED lit.