Mesa 7i78
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27 Aug 2021 22:26 #218942
by PCW
Replied by PCW on topic Mesa 7i78
What supplies the voltage between SPINDLE+ and SPINDLE- ?
Does the 5V supply droop when loaded?
Does the 5V supply droop when loaded?
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28 Aug 2021 16:06 #219016
by COFHAL
Replied by COFHAL on topic Mesa 7i78
Not, is ok all time 5 volt.
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28 Aug 2021 16:14 #219017
by PCW
Replied by PCW on topic Mesa 7i78
What is the load resistance? The 7I78 should be OK down to ~5K ohm loads
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28 Aug 2021 16:22 #219018
by COFHAL
Replied by COFHAL on topic Mesa 7i78
Is only 133 ohm
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28 Aug 2021 16:36 #219019
by PCW
Replied by PCW on topic Mesa 7i78
OK that cannot work.
What are you driving that has that low of an input impedance?
What are you driving that has that low of an input impedance?
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28 Aug 2021 16:40 #219021
by COFHAL
Replied by COFHAL on topic Mesa 7i78
XMT500C, Previously I used a PWM to DC converter and it worked very well.
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28 Aug 2021 17:20 #219029
by PCW
Replied by PCW on topic Mesa 7i78
I mean, what does the 7I78 drive? 133 Ohms is a very low impedance for an analog input
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28 Aug 2021 17:22 #219030
by COFHAL
Replied by COFHAL on topic Mesa 7i78
Can't add an electronic circuit that avoids loading the output of that electronic potentiometer?
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28 Aug 2021 17:24 - 28 Aug 2021 17:24 #219031
by PCW
Replied by PCW on topic Mesa 7i78
The 7I78 has an op-amp buffer but 133 Ohms is _way_ too low a load resistance
Last edit: 28 Aug 2021 17:24 by PCW.
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28 Aug 2021 17:24 #219032
by COFHAL
Replied by COFHAL on topic Mesa 7i78
But originally the speed of the spinlde was controlled analogously with a potentiometer.
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