What is the maximum input voltage level on 660x devices?

[Daniel_Chile]

Until now, I have used my 6602 board to power (+5v) and read signals from an encoder. Now, I need to read the signals coming from an encoder that's already linked to (powered and read by) another device, which uses +24v level. Can I direcly connect this signal to my 6602 or I need to lower the voltage level first? I mean, what is the maximum voltage level that a 660x device allows?
Also, there's another matter: should I connect the encoder GND to my 6602 GND? When I did power the encoder with my board this was straigthforward, but now I have doubts about if this is correct.
Hope you could help me.

Daniel Ramirez

[gus]

You should only use 5V signals with the 6602, so I would suggest you lower the voltage level first. I'm no expert on grounding issues, but I would suspect that you should still connect the ground from your encoder to the 6602 device, even if you're powering it off of a different power source.

Alternatively, you might take a look at the 6624 (http://sine.ni.com/apps/we/nioc.vp?cid=12501〈=US). It is an industrial version of the 6602 with isolated inputs. Follow the link for more information.

gus....

[Daniel_Chile]

Hi, Gus.
Regarding the voltage level, I understand that 660x devices are TTL/CMOS compatible and that CMOS voltage level is higher than TTL's 5V, but I'm still not quite sure about what is the maximum voltage that the board supports. I only know that it's higher that 5V.
About grounding, I'm not an expert, too, and I think that I should connect the grounds for better signal integrity, but I don't know if this could eventually damage my board.
Thank you.

[Bill B]

Hello Daniel,

The absolute maximum voltage that the 6602 board can handle is 5.5V. When the specifications state that the board is CMOS compatible, that means that it can interface to CMOS devices, but the maximum input voltage is still limited to 5V even though some CMOS devices can operate at higher voltages.

As far as the ground is concerned, you may not want to connect the ground of your 24V encoder to your 6602 if you plan on placing some type of isolation circuitry between your encoder and your 6602. However, if you just plan on using some type of simple resisitive voltage divider to reduce the voltage level, then you will want to connect the ground of your encoder to the ground of your 6602. The ground on your 6602 is internally con
nected to the ground of your PC power supply which is connected to the ground of your power outlet which is connected to earth ground.

Regards,
Bill B

[Daniel_Chile]

Thank you, Bill. Now it's much cleaer.

Daniel

[FrankHS]

I have a similar question. What is the maximum voltage that a 6602 counter input can take without damage to the 6602? If the voltage briefly went as high as 12 or 18 volts, would this damage the board.  I don't need to count during these periods of high voltage.