Cycfi NU -> ATG/GP-10 (POWER SWITCH)

[cags12]

Hi all,

I am designing a small board that will interface a Cycfi NUv2 multi pickup (Active divided pickup) with an Antares ATG luthier DSP board and/or L6 Variax. The board will include 6 trim pots to attenuate the signals coming out of the NUv2 pre-amps out to the ATG. This part is simple and I am following the same concepts as to what is described in the long thread about the External FTP adapter.

However, I am also hoping to split the signal from the NU's to a custom 13 Pin connector (https://www.cycfi.com/2019/02/roland-13-pin-to-nu-multi/) which I have done already.

The part that I need help with is with power. As you may know the NU's are active pickups and need power. I will have an onboard battery that is going to be used when playing with the ATG by itself but when connecting the 13-Pin connector, I want to automatically switch to external power from Pin 12 (+7V).

I know this would need some sort of MOSFETt switch but I was hoping someone more knowledgeable in electronics could help me with this as I do not know what type of MOSFET and how should it be wired.

Below is my Draft schematic. The Red circle shows the junction point I need to incorporate the switch (MOSFET).
Output 1: To ATG and Battery (V+)
Output 2: to 13-Pn Connector



Could anyone help me?

[CodeSmart]

Hi all,

I am designing a small board that will interface a Cycfi NUv2 multi pickup (Active divided pickup) with an Antares ATG luthier DSP board and/or L6 Variax. The board will include 6 trim pots to attenuate the signals coming out of the NUv2 pre-amps out to the ATG. This part is simple and I am following the same concepts as to what is described in the long thread about the External FTP adapter.

However, I am also hoping to split the signal from the NU's to a custom 13 Pin connector (https://www.cycfi.com/2019/02/roland-13-pin-to-nu-multi/) which I have done already.

The part that I need help with is with power. As you may know the NU's are active pickups and need power. I will have an onboard battery that is going to be used when playing with the ATG by itself but when connecting the 13-Pin connector, I want to automatically switch to external power from Pin 12 (+7V).

I know this would need some sort of MOSFETt switch but I was hoping someone more knowledgeable in electronics could help me with this as I do not know what type of MOSFET and how should it be wired.

Below is my Draft schematic. The Red circle shows the junction point I need to incorporate the switch (MOSFET).
Output 1: To ATG and Battery (V+)
Output 2: to 13-Pn Connector



Could anyone help me?

I'm not an expert but to me it sounds you want a lower voltage,(if applied), to turn OFF a higher voltage rail via a P-channel MOSFET. This means you will have to invert the 7V control logic by a second MOSFET (or transistors), so when the 7V is applied the inverter "transistor/mosfet" will conduct and pull down the gate of the 9V rail mosfet to ground so it shuts off the 9V. You'll also need a resistor or two and a third mosfet operating in none-inverted mode to allow the 7V to flow. You may also consider a couple of low voltage drop Schottky diodes instead of the third MOSFET to tie the 7V and the 9V MOSFET together towards the load.

Be careful of the current draw of the 7V. If the load is not stable you may induce noise. If noise, I recommend a 100uF capacitor and maybe also a 10 ohm resistor to low pass filter the 7V supply (meaning there's no fluctuating currents down the GK cable).

[vanceg]

I'm interested in one of the circuit boards once you get them completed!

[cags12]

I'm not an expert but to me it sounds you want a lower voltage,(if applied), to turn OFF a higher voltage rail via a P-channel MOSFET. This means you will have to invert the 7V control logic by a second MOSFET (or transistors), so when the 7V is applied the inverter "transistor/mosfet" will conduct and pull down the gate of the 9V rail mosfet to ground so it shuts off the 9V. You'll also need a resistor or two and a third mosfet operating in none-inverted mode to allow the 7V to flow. You may also consider a couple of low voltage drop Schottky diodes instead of the third MOSFET to tie the 7V and the 9V MOSFET together towards the load.

Be careful of the current draw of the 7V. If the load is not stable you may induce noise. If noise, I recommend a 100uF capacitor and maybe also a 10 ohm resistor to low pass filter the 7V supply (meaning there's no fluctuating currents down the GK cable).

Thanks, you are definitely more of an expert than myself. However, after doing some internet research and asking the lead developer at Cycfi, I have decided to take a simpler approach by using a couple of Shottky diodes in series which each power supply. This will prevent the power supplies to interfere with each other and allow the one with highest voltage (GK) to win and provide the power. Which is what I want.

Updated image above showing the diodes.

[cags12]

I'm interested in one of the circuit boards once you get them completed!

Sure, let's see how it goes. This is how it is looking so far.

[CodeSmart]

Thanks, you are definitely more of an expert than myself. However, after doing some internet research and asking the lead developer at Cycfi, I have decided to take a simpler approach by using a couple of Shottky diodes in series which each power supply. This will prevent the power supplies to interfere with each other and allow the one with highest voltage (GK) to win and provide the power. Which is what I want.

Updated image above showing the diodes.

Ahh... of course you have the 9V battery running as +/- 4.5V, now I see and agree. Yes, low voltage drop Shottky diodes will be perfect!

[cags12]

I'm interested in one of the circuit boards once you get them completed!

Hey Vanceg, I did complete this project if you are still interested.

[vanceg]

I saw that.  Yes I am. I'll PM you.