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4-channel I2C-safe Bi-directional Logic Level Converter
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4-channel I2C-safe Bi-directional Logic Level Converter

by Virgil_Machine on Mon Sep 29, 2014 3:46 pm

Amplifier_Servo V03.1 Trinket Shifter_bb.gif
Amplifier_Servo V03.1 Trinket Shifter_bb.gif (637 KiB) Viewed 182 times
My circuit to play music and run a servoo (see https://forums.adafruit.com/viewtopic.php?f=25&t=59793 works fine. My issue now is that I've gone to a 3.3V SD micro card and smaller arduino. Since the smaller board will do 5V or 3.3V but not both, and I need 5V to run the servo. So, I need a way to get 3.3V to to SD board, uses SPI. I first thought of voltage regulator to power the board, but then I realized that the SPI pins are connected to the 5V Arduino.

I did some research, and it appears that I need a logic-level shifter like the one in the subject of this post. I want to be sure that I'm correct and that I understand how to wire it. The attached drawing shows a generic micro SD board connected to the https://www.adafruit.com/products/757 with the 3.3V pin connected to LV on the shifter, GND to GND and the SPI pins to A1-4. The corresponding B1-B4 are connected to D10-13 on the Trinket with Trinket 5V and GND connected to HV and GND on the shifter.

No additional voltage regulator required.

Did I miss anything?

Thank you.

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Re: 4-channel I2C-safe Bi-directional Logic Level Converter

by franklin97355 on Mon Sep 29, 2014 3:59 pm

The LV on the level shifter is a power input so you need to supply it with 3.3vdc. Have you considered the 3.3v Trinket?

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Re: 4-channel I2C-safe Bi-directional Logic Level Converter

by Virgil_Machine on Mon Sep 29, 2014 4:11 pm

Thank you.

I need 5V for the servo (I could supply the servo from an additional source, but I am constrained by space and need to avoid that).

The level shifter needs two inputs: 5V AND 3.3V? If that's the case, would I include a voltage regulator to take the Trinket's 5V to 3.3 to feed the LV pin on the shifter, and then wire the SPI pins as in the drawing?

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Re: 4-channel I2C-safe Bi-directional Logic Level Converter

by franklin97355 on Mon Sep 29, 2014 4:27 pm


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Re: 4-channel I2C-safe Bi-directional Logic Level Converter

by Virgil_Machine on Mon Sep 29, 2014 4:35 pm

Because it's $11 more.

Even if I do resort to that, I would like to know the answer to my question.

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Re: 4-channel I2C-safe Bi-directional Logic Level Converter

by franklin97355 on Mon Sep 29, 2014 4:46 pm

I would think that would work.

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Re: 4-channel I2C-safe Bi-directional Logic Level Converter

by Virgil_Machine on Mon Sep 29, 2014 5:09 pm

Thanks...do you mean my last update? Here's a revised drawing:

Amplifier_Servo V03.2 Trinket Shifter_bb.gif
Amplifier_Servo V03.2 Trinket Shifter_bb.gif (665.47 KiB) Viewed 165 times


Changes are:
Add voltage regulator
SD and shifter connected to output of VR
SD and Shifter (LV side) connected to common ground
VR input to 5V rail aned GND to GND

Make sense?

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