Arduino based VCOs?

[fredrik]

To clarify, VIN should be 7-12 V and is regulated to 5 V by an onboard regulator. If you provide 5 V yourself, connect it to +5V, not VIN. See here:

Design glitches: Arduino Nano supply voltage

(thought I’d collect my nano supply notes in one place to make it easier to link to) A common design glitch in circuits that use an Arduino Nano is to connect regulated 5 V to the VIN pin instead of the +5V pin. This results in the Arduino running at a lower internal supply voltage, often 4 V or below, which may be a problem if the design depends on analog inputs or digital output levels. Voltages below 4.5 V are also out of spec for the 16 MHz clock used by the Nano. Details below, but TL;DR …

(that’s for a Nano, but Leonardo has a similar power supply, using an NCP1117 that is similar to the LM1117 and AMS1117 regulators mentioned there, with a 1.2 V drop)

The input pins have protection diodes to deal with input voltages above and below the supply rails, but they cannot handle a lot of current, so unless you have current limiting resistors on the way in, over- and undervoltages may fry them.

1222 Tuner VCO Module

The AVR chips have clamping diodes on all inputs, which keep the voltages between −0.5 V to Vcc + 0.5 V, so as long as you don’t fry the diodes, the chip will survive higher input voltages (there’s an Atmel appnote that shows how to detect zero crossings in 240 V AC with two 1M resistors and nothing else). [image]