14v input tolerant ardu board

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Exidous
 
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14v input tolerant ardu board

Post by Exidous »

Hello,

I'm looking for a board that's tolerant of power at 14v and can accept the same 14v as an input.

My project is to replace an old blower motor in a car with a brushless version. I need to convert the 0-4 speed switch(vbat output from alternator) to a PWM output for a brushless motor controller. Speed is normally controlled via a large resistor to creat the appropriate voltage drop. I want to remove the resistor and create a plug in replacement.

I noticed the metro 328 was 16v tolerant on the power but what about the inputs? Is it 3.3 and 5 logic level only? Ideally, I'd like the smallest board possible.

Cheers,

Patrick

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Exidous
 
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Re: 14v input tolerant ardu board

Post by Exidous »

Alternatively, I can rewire the switch to go to ground but I'm guessing the inputs would need a pull up to 3.3 or 5v. Built in pull up preferred.

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Re: 14v input tolerant ardu board

Post by adafruit_support_mike »

I don't know of any microcontroller whose IO pins can handle more than about 6V.

You'll probably need to run the microcontroller in a 3.3V or 5V environment, and use external circuits to handle the 16V side.

Most brushless motor controllers work that way though: they have a low-voltage control side and a higher-voltage power side. The DRV8871 H-bridge, for instance, can handle motor power up to 45V:

https://www.adafruit.com/product/3190

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Re: 14v input tolerant ardu board

Post by Exidous »

What about ground switched inputs? Does the metro mini have built in pull ups to switch to ground?

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Re: 14v input tolerant ardu board

Post by adafruit_support_mike »

That sounds like what's commonly known as 'open drain' outputs: instead of switching between high and low voltages, a pin switches between high-resistance and low-resistance connections to GND. Those are usually paired with pull-up resistors to hold the signal line's voltage high while the connection to GND is in its high-resistance state.

Microcontrollers usually don't do open-drain output as a single output option, but can get the same effect trivially: you switch the pin configuration between INPUT (high-resistance) and OUTPUT,LOW (low-resistance). That's how they handle the I2C protocol, which requires open-drain outputs.

Many microcontroller pins have built-in optional pull-up resistors. They're mostly used when the pin is configured as an INPUT, but can double as open-drain pull-ups.

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Re: 14v input tolerant ardu board

Post by Exidous »

I only need a single output to control a servo/rc style brushless motor controller.

I'm only concerned about the inputs. The switch latches to ground. Ideally, 4 inputs. Are the internal pull ups activated in software?

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Re: 14v input tolerant ardu board

Post by adafruit_support_mike »

Yes, you can enable internal pull-ups in software. In the Arduino environment, you do that by setting the pins to INPUT_PULLUP.

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Re: 14v input tolerant ardu board

Post by Exidous »

Got it, thanks.

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