Using Mesa 7i47S as TTL (not RS422) is possible?

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21 Jun 2011 19:17 - 21 Jun 2011 19:25 #10726 by machete
I plan to use 7i47S for spindle control using something like this:
www.delta.com.tw/product/em/drive/ac_mot...p?pid=1&cid=1&itid=2
(this is good;-)


But, also i have a lot of sensors (for tool changer etc.) with 12V logical "1" output.

How i can connect it to 7i47Sinputs (it have RS422 type differential inputs)?

As well, how can i connect 7i47S outputs to "solid state relays", like this, for controlling solenoids:

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Last edit: 21 Jun 2011 19:25 by machete.

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21 Jun 2011 21:03 #10737 by PCW
Normally the 7I37TA or one of our newer serial interfaced remote I/O devices is used for 12-24V I/O

The 7I47/7I47S is mainly designed for differential encoder/serial/step+dir I/O but its possible (though quite awkward) to use the inputs for single ended signals.

For example for 12V inputs, what you could do is this:

1. Disable termination on the input (jumper option)
2. Connect one input pin of the input pair to a reference voltage (say 5V since its there)
3. Connect the other input of the pair to the center node of a voltage divider
(say two 1k resistors in series, 12V switch signal to R1 pin1, R1 pin2 to R2 pin1 and 7I47S input and finally R2 pin2 to ground )

This works because the RS-422 receivers are basically comparators. With the above values the input to the resistor divider needs to be above 10V to change the receivers output state. You can change this threshold by using a different resistor divider ratio, for example using 1k for R1 and 3.3K for R2 gives a close to 6V (= 1/2 way up fo 12v signals) threshold

Whether this is worth the trouble or not I don't know...

The 7I47S outputs swing to 5V and will drive solid state relays directly (~20 mA max however)
Just chose the correct output of the pair so your solid state relay is off at power up

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22 Jun 2011 11:44 - 22 Jun 2011 11:45 #10761 by machete
PCW wrote:

Normally the 7I37TA or one of our newer serial interfaced remote I/O devices is used for 12-24V I/O

The 7I47/7I47S is mainly designed for differential encoder/serial/step+dir I/O but its possible (though quite awkward) to use the inputs for single ended signals.


I understand, but 7i47S is only one way i find to control spindle...

For example for 12V inputs, what you could do is this:

1. Disable termination on the input (jumper option)
2. Connect one input pin of the input pair to a reference voltage (say 5V since its there)
3. Connect the other input of the pair to the center node of a voltage divider
(say two 1k resistors in series, 12V switch signal to R1 pin1, R1 pin2 to R2 pin1 and 7I47S input and finally R2 pin2 to ground )

This works because the RS-422 receivers are basically comparators. With the above values the input to the resistor divider needs to be above 10V to change the receivers output state. You can change this threshold by using a different resistor divider ratio, for example using 1k for R1 and 3.3K for R2 gives a close to 6V (= 1/2 way up fo 12v signals) threshold


OK is that correct?



(blue box is my sensor)
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Last edit: 22 Jun 2011 11:45 by machete.

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22 Jun 2011 11:49 #10762 by machete
PCW wrote:

The 7I47S outputs swing to 5V and will drive solid state relays directly (~20 mA max however)
Just chose the correct output of the pair so your solid state relay is off at power up


Like this?



And should i leave R1=360 Ohm, like in case with TTL +5V logic?
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22 Jun 2011 13:53 #10765 by andypugh
machete wrote:

I understand, but 7i47S is only one way i find to control spindle...


PWM to voltage conversion is fairly simple. You could just connect a resistor and capacitor to one of the 7i37 output drivers, feed it PWM and get voltage out. As they are isolated outputs you could even source the 10V from the high-side pot terminal on the drive (assuming you are using a standard VFD)

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22 Jun 2011 14:40 #10768 by PCW
On the inputs, yes its OK though I would probably use 3.3K for R2 so the threshold is closer to 6V (with the current 1K,1K, and the added 330 series resistor, the threshold is a bit too high

On the outputs, that will work fine except you will reverse drive the SSRs LED when off. If the SSR has a reverse input protection diode, this is fine. If not you can use just one of the TX outputs and ground to drive the SSR

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22 Jun 2011 14:48 #10769 by machete
andypugh wrote:

machete wrote:

I understand, but 7i47S is only one way i find to control spindle...


PWM to voltage conversion is fairly simple. You could just connect a resistor and capacitor to one of the 7i37 output drivers, feed it PWM and get voltage out. As they are isolated outputs you could even source the 10V from the high-side pot terminal on the drive (assuming you are using a standard VFD)


I spent a loot of days trying to find an example of PWM->VFD signal convertor, but i don't find even one... (stupid)

Maybe you can post some link(s) with some already working examples???

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22 Jun 2011 15:15 #10770 by machete
PCW wrote:

On the inputs, yes its OK though I would probably use 3.3K for R2 so the threshold is closer to 6V (with the current 1K,1K, and the added 330 series resistor, the threshold is a bit too high

On the outputs, that will work fine except you will reverse drive the SSRs LED when off. If the SSR has a reverse input protection diode, this is fine. If not you can use just one of the TX outputs and ground to drive the SSR


So, this version must be perfect?

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22 Jun 2011 15:57 #10775 by PCW
yes, looks right to me

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