AB MicroLogix 1400 pulse train

[Christoph]

Hello All

I have a system using the ML 1400 plc. I have an encoder on HSC:1 input 4.
I want to pass this signal out on a FET output to another device
after I have scaled back making it a lower pulse rate. I need an Idea that
works. what I have come up with won't work and I am running out of ideas.

 

[VAN]

Hello All

I have a system using the ML 1400 plc. I have an encoder on HSC:1 input 4.
I want to pass this signal out on a FET output to another device
after I have scaled back making it a lower pulse rate. I need an Idea that
works. what I have come up with won't work and I am running out of ideas.

What are you trying to do?

Also, why don't you just scale the pulses on the ML and send the scaled output to whatever device?

 

[bernie_carlton]

If the rate is slow enough and the scale is a factor of 2 just use the appropriate bit of the accumulated count as a contact leading to the output.

 

[Christoph]

That's what I am trying now. took the 1000ppf / 500 then use bit 0 of that word
to toggle the output

 

[Ken Moore]

I believe Bernie is referring to the 2nd bit of your accumulated value, it should change every other count.

 

[drbitboy]

In what mode is HSC:1 configured?

I am pretty sure that Bernie provided the right approach:

If it is only counting up or down, then there is no need to divide the count; simply use one of the higher bits of HSC:1.ACC.

E.g. say the pulses are coming in at ~10kHz, so HSC:1.ACC increases by about 10,000 per second, and by about 10 per scan (assume scan time is 1ms). If you were to do something like this:

    HSC:1.ACC/12     FET_Output

-------] [--------------( )-------

Then the discrete output [FET_Output] would run at about 1.25Hz (Period = 0.8192s/output_cycle ~ 8192(input_pulses/output_cycle)/10000(input_pulses/s)) with a 50% duty cycle.

Note that bit 12 of .ACC is the 4096 bit i.e. 2^12 = 4096, so that bit 12 of .ACC has a rising edge every 8192 counts.

Cf. this link and image below (updated):