NerdKits - electronics education for a digital generation

You are not logged in. [log in]

NEW: Learning electronics? Ask your questions on the new Electronics Questions & Answers site hosted by CircuitLab.

Basic Electronics » Connecting to external control voltages

April 19, 2011
by kayrock
kayrock's Avatar

I have a synthesizer keyboard that outputs 0-5v depending on what key is pressed. Is it safe to connect that voltage directly to an adc pin or will I need to use an opto-isolator chip? Conversely, is it safe to connect the pwm output directly to a 0-5v cv input on the same keyboard? My nerdkit is powered by a different power supply than the keyboard.

April 19, 2011
by Hexorg
Hexorg's Avatar

5v is the typical power supply for the nerdkit, so it should be save to connect your keyboard to the ADC pin. However, make sure that 5v IS the maximum voltage from the keyboard. As far as I know, analog sound data usually goes from 0-1.4v, not 0-5v. It'd still be safe to plug it in, you just won't get any ADC readings higher then about 287.

Also, make sure that the ground of the keyboard is connected to the ground of the nerdkit too, otherwise you won't be able to read the voltages correctly.

April 19, 2011
by kayrock
kayrock's Avatar

Thanks. I measured the voltage coming out and it is indeed putting out 0-4.98v on my multimeter. I am trying to read a control voltage from a Roland SH101, so it is not audio.

April 19, 2011
by bretm
bretm's Avatar

is it safe to connect the pwm output directly to a 0-5v cv input?

PWM output isn't 0-5V, it's 0V or 5V, switching rapidly back and forth between them. If that's not what you want, you have to use a low-pass filter.

Post a Reply

Please log in to post a reply.

Did you know that there are Power MOSFETs for switching big loads on and off? Learn more...