On 01/31/2017 10:10 PM, Tom M wrote:
We almost almost finished configuring our cnc build at the makerspace I
belong to.
Since the G540 has a charge pump, we thought we would take advantage of it.
(We we're debating if we even need to since we don't think the bbb has
the start issues that a pc parallel port does.
My understanding is that the G540 needs a charge pump frequency of 10Khz
It is my understanding that the frequency is much less important than
the drive current. The pump input circuit has a DC blocking capacitor,
diode bridge, and charge capacitor that needs to be charged. I found
that a 5 Volt pull-up resistor or a buffer IC than can source 24ma works
well. This should allow going down to 500Hz or just about any convenient
frequency. I have some notes here:
http://wallacecompany.com/machine_shop/G540/
I seem to recall that the scope traces that got above 3Volts worked.
Such as the motherboard port set to EPP worked:
http://wallacecompany.com/machine_shop/G540/g540_mb_epp.jpg
But set to SPP didn't:
http://wallacecompany.com/machine_shop/G540/g540_mb_epp.jpg
I did a little bit of circuit tracing here:
http://wallacecompany.com/machine_shop/G540/G540_upper_bottom_z-1b.png
Pin 16 is the input, C is the series DC blocking capacitor, next comes
the half-wave diode bridge (KL4 Y8), a filter capacitor on the output
(two bottom pins), and the opto-coupler input LED and current limit
resistor (201) to ground.
I haven't done any work with the Beagle Bone but I suspect any buffer
circuit that can convert the BB low voltage to 5Volts at 24ma should
work at any convenient frequency.
--
Kirk Wallace
http://www.wallacecompany.com/machine_shop/
http://www.wallacecompany.com/E45/
--
website: http://www.machinekit.io blog: http://blog.machinekit.io github:
https://github.com/machinekit
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