Retrofiting an old big milling machine

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12 Sep 2018 19:47 - 12 Sep 2018 19:47 #117426 by vre
The scale is glass because i saw the glass inside.
I found the VCC & GND from TL084CN 4&11 pins.
TL084CN has populated 1&7&8pin but not 14pin.
Are these 3 outputs the U1 U2 U3 ?
The remaining one wire is the 7.5V ?
That is the usage of 7.5V ?
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Last edit: 12 Sep 2018 19:47 by vre.
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12 Sep 2018 21:12 #117430 by tommylight
The TL084 is an operational amplifier so it needs a positive and a negative power supply voltage and a common ground for both of them, so it needs a + and a - 7.5V measured from it's ground in your case.
That looks to be derived from 15V supply in your case.
It can be done simply by using 2 capacitors to quite complicated voltage regulators.
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12 Sep 2018 22:14 - 12 Sep 2018 22:17 #117433 by vre
The schematic shows +15V 0V GND +7.5V
If understand correct the +15V is the +VCC the 0V is the -VCC and the 7.5V is the GND(but the TL084CN has no GND only +-VCC) right ?
I have a symmetric linear power supply +-15VDC/1A but i think the is not suitable for this case...
I need a symmetric +-7.5VDC right ?
What max current is good for powering 3 scales ?
Last edit: 12 Sep 2018 22:17 by vre.
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13 Sep 2018 05:04 #117446 by tommylight
Just a guess but they should not use more than 50mA or 0.05A. They rarely use more.
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