Optocoupled DC Spindle max voltage

[Volksolive]

Hi Terjeio,

You mention in the readme that the max voltage for the optocoupled DC spindle output is limited by C7 = 30V but there is actually 2 other limiting factor.

• The high side P mosfet transistor IRLML6402 has a VDS max of 20V and VGS max is 12V.
• The low side N mosfet transistor 2N7002 VGS max is 20V.

So max voltage should be 12V because of the P mosfet but can't be more than 20V if the P mosfet is replaced by another ref. because transistors rarely have more than 20V VGS max.

BTW what is that output intended to drive? because the 2N7002 does not provide that much power? (115mA const.)

[terjeio]

Oops - I have to pay more attention to details.

BTW what is that output intended to drive? because the 2N7002 does not provide that much power? (115mA const.)

A relatively high impedance input for VFD spindle RPM control, R33/C7 act as a LP filter and R33 will limit the drive current available. A typical voltage range is 0-10V.

[Volksolive]

oh yes ok! I think the DC spindle word got me confused! I thought the intent was to drive a DC motor directly...