Author Topic: DDCSV Spindle reverse method  (Read 640 times)

Offline picclock

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DDCSV Spindle reverse method
« on: January 05, 2020, 02:38:46 AM »
It would be useful for certain operations to have a spindle reverse and I'm thinking of implementing it by using a quick on off sequence at the start of the operation.  So for normal spindle operation its just M3 .. operation .. M5, but for spindle reverse it would be m3 short pause M5 short pause M3 .. operation .. M5.

Any thoughts or advice on this most welcome.

Best Regards

picclock

Engaged in the art of turning large pieces of useful material into ever smaller pieces of (s)crap. (Ferndown, Dorset)

Offline picclock

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Re: DDCSV Spindle reverse method
« Reply #1 on: January 08, 2020, 10:37:50 AM »
M3/8/11 output current sink.

The DDCSV 2.1 manual states "The highestelectric current can be absorbed is 20mA", but tests I have done indicates that the true sink figure is far short of this.
The test was carried out with M3/M8, a 24V supply and a 2k2 resister which was pulled low when the sink output was activated by the M command.
When activated, the low level voltage measured was 5.15 and 7.4volts repectively, showing the output transistor out of saturation. This translates to an output currents of 8.6 and 7.5mA. With a 4k7 Load the current is reduced to 5mA with saturation voltages of 638/664mV respectively.

This largely appears to be by design. The opto isolators are EL 817 C devices which have a transfer ratio of 2-400%. Working this backward implies an LED drive current of ~2.5mA, which indicates a 1.6K drive resister from 5V, allowing 1.1V LED drop. On the DDCSV the drive resister appears to be  1.5K driven from a 74HC14, whose maximum drive is only 4mA.

In summation this design, as apparently implemented on my DDCSV 2.1 board is not capable of supplying the 20mA stated, but appears to work OK with loads up to 5mA.

Hope this helps out if you are using these as an interface.

Best Regards

picclock
Engaged in the art of turning large pieces of useful material into ever smaller pieces of (s)crap. (Ferndown, Dorset)