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Spindle analogue output is not working
Posted: Mon 31 Jul , 2006 15:23 pm
by Denford Admin
My Denstep / NextStep / NextMove spindle analogue does not work - it will not change or output any analog command voltage
Posted: Mon 31 Jul , 2006 15:36 pm
by Denford Admin
This problem has been found and corrected on issue 2 and later baldor bottom boards
- Ones that look like this:
This problem seems to occur mostly on exported machines and is a component tolerance issue due to the differences in supply voltages from when the machine was built and tested at Denfords.
To check whether your bottom board requires the fix, locate resistor R31 on the bottom board (beneath the top cards' RS232 connector)
If the board has the modification, this resistor R31 will either be a link, or a 0 (zero) ohm surface mount resistor - if it has a value (eg 1003) then its likely that this bottom board is the cause of the spindle analogue failure - contact us for repair instructions
Re: Spindle analogue output is not working
Posted: Mon 24 Jan , 2011 9:36 am
by Denford Admin
Here is the information we have from someone who has repaired a Baldor with the analogue output fault:
(NB attempt any repair at your own risk, we can't offer any guarantee this information is correct)
And here´s what the fault was:
The PWM come through an optoisolator. The hot side of the optoisolator is
tied up to Vcc (13V) through a 1k resistor.
It is supposed to provide pulses that range from Vcc to nearly ground (V sat
of the isolator transistor).
Although the PWM pulses are good shaped their amplitude is just 5.4Vpk to
pk.
This is probably due to a lack of driving in the led side of the optocoupler or
that the emmiter got old, or poor design. (I discard the old option because
the customer seldom used the Novaturn since he bought it).
The pulses from the optoisolator go to a comparator unit based on an
operational amplifier whose other input is put to Vcc/2=6.5V by means of to
resistors (R42 and R41) of 100k.
Thus: the amplitude of the PWM never was enough to change the state of
the comparator, given that it goes from 13V to 13-5.4V=7.6V
The solution: a 68k resistor in paralel with R42, raising the threshold of the
comparator to 9.3V. This is working fine and has plenty of room if the
optoisolator emiter lowers its output again.
- NovaturnSpCtl1.jpg (66.19 KiB) Viewed 10776 times
- NovaturnSpCtl2.jpg (65.16 KiB) Viewed 10776 times