5i25 7i77 logic input

Hello.

In a 5i25 7i77 combo, with field bus at 24V for most of the IO (and I want to keep it like this), I have the need to receive status signals from my servos, that are only available in 5V.
Although I have almost sure that there is no way to use directly the 5V without transforming them in 24V, I am asking, as it could exist a easy way to use them directly without creating another board for matting the signals.

In the total we have x6 logic 5V signals from the servos, that must be used.

UPDATE:
It looks that I can use the available parallel port type present on the 5i25 (P2 connector) for this. I did not connected anything hoping for confirmation from the forum.

Thank you.

Hello,
maybe this thread can help you.
www.linuxcnc.org/emc2/index.php/italian/...ield-input-threshold

Frank

Thank you, but I need at least 6.
The 7i77 board can only read 4 analog inputs, so it is not a solution for now.

I'm guessing you could use a 7i87 or a 7i70 for this, but that's more expensive than just using a circuit.

There are also converters for this: www.calex.com/cis549.html

One cheap solution might be to use a regular parallel port on your control PC... assuming all you want is sensing of a digital signal.

I think if it was me I'd probably just use some DIN rail mount optocouplers for this. 5v input, 24v to field supply and the 7i77 output.

Erik

I prefer to use the current hardware.
The optocouplers are a solution, but maybe I can use the P2 in the 5i25, and no extra hardware or unnecessary confusion will exist. Can I safely use it?

The 7I77 has the hardware to do this but I'll
have to check if the firmware has the per pin
input threshold setting option supported yet

I will wait then.
And the P2 on the 5i25 is not an option?

P2 signals are usable with a couple limitations. P2 signals are just like parallel port signals: TTL levels and high speed. This means:

1. They are susceptible to high frequency noise, so you may need to use the debounce component

2. They are not protected from voltage spikes (anything over 7V or less than about -0.7V for a very short time will damage the 5I25

Both of these problems can be eliminated by using a breakout board of some kind (say the Mesa 7I75)

Or you can just be very careful with what you connect to the P2 pins

Ok, I will not use the P2 of the 5i25 for extended safety.
Can you (PCW) confirm if the individual pin threshold is implemented?

Thank you

I can tommorow