Reading a thermocouple ?

if you just need frequency reading you just need 1 pin per channel (the encoder "A" signal)
so you dont really need 4 or 8 more encoder channels (8 encoder channels is 24 signals)
for example if you have a 6I25, you could have a config that used the second 6I25 connector
as 17 encoders all with just channel A brought out

PCW wrote: if you just need frequency reading you just need 1 pin per channel

The MAX31855 component only needs 1 pin per channel too, but also needs 2 on top of that for clock and data.

ok so one config I was thinking of may require another 7I76 to get another stepper motors for what I am thinking

can I setup the second 7I76 inputs to encoders and just break out the A channel as suggested ?

if that is the case what is a good input scheme for the thermocouple output. I am going to put a micro controller between the thermocouple and the 7I76.

so if I want a 0-600C range for temp
what is a good frequency range to map that too ?

ideally I want to plug this into a PID loop in linuxcnc and control the temp that way

Thanks for all of the suggestions

C

If you just need more step motor outputs a second 7I76 is overkill, you could use a 7I85S and gain
4 additional stepper outputs and 12 inputs

Any frequency from a few KHz to maybe 1 MHz or so should be OK

An all "A" encoder connection would require custom firmware but its a pretty simple change

Can I repeat my suggestion of using the MAX thermocouple chips and the dedicated HAL component?
You can get them pre-mounted if that is the problem.
www.adafruit.com/product/269
(Adafruit are out of stock, eBay has them, search for max31855)

Andy, that is a very solid point. I went back and re looked at the hal component you linked to.
so if I wanted to get 4 separate temp readings, could I use the set of pins on a mesa card to read the input ?

this actually seems like less work because I do not need to modify the firmware to get A channel only encoders

any idea what the refresh rate would be ?

Thanks Guys

C