Reedfirst wrote: ↑Tue Jan 23, 2018 11:50 pm
Hey Marty, any updates?
I've been following your threads about using the Marker Pulse for accurate homing and decided to give it a shot.
So I hooked up my oscilloscope to pin 4 on jp5 on one of my dyn4 drives and was able to verify the 5volt z+ pulse. It's just under 1ms long.
I believe you were suggesting to use a 2k 1/4 watt resistor to connected to the corresponding input that is connected to its respective drive and you seemed to have it working.
Brainstorming, I came up with the idea of using an N channel MOSFET. I just happened to have one in my junk drawer...
I connected the gate(Pin1) of the MOSFET to pin4 of the jp5 connector. The drain(pin2) of the MOSFET to Input 2 on the acorn, and the source(Pin3) of the MOSFET to ACORN Common.
I wrote a new home file, hit the "RESET HOME" button, and it worked! One thing I did notice is I'd like to clock my motors so that it is very close to the index pulse just after backing off the limit switches. (Especially on the Z axis as the travel is already limited on a bridgeport)
I'm still doing a few tests but I think this might be a viable approach. I'd like to find a popular MOSFET that will easily fit inside of a DB-9 backshell.
DMM is verifying that the 2k resistor will work long term.
Another issue is the Alarm signal, DMM pulses it and does not take it either low or high. Try it. Put everything on line and then just pull the motor encoder cable from the drive. That causes a fault. Look at input 5(assuming that's where you have the alarm connected). It pulses on and off. CNC12 does not see it as a fault. Also reported to DMM.
DMM also suggested not to power down DYN4 with a relay during Estop condition. You will loose your encoder position. Powering down just the motor power, using a relay(per The Dyn4 manual) tied to RL1(Estop relay on Acorn) and leaving the Logic power hot, seems to be the most intuitive. However, the very first time you power everything up and CNC12 closes the Estop relay, there is a motor lurch of about a quarter turn before homing. It only does this on power up.
I did update the video. I had said L1 in the .hom file referred to input 1, it does not. Cleaned up a couple other small things as well, which shortened it up a bit too.