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Topic: A ramp voltage with 50s or 100s ramp time (Read 1 time) previous topic - next topic

zhyf1991

My professor asked me to generate a ramp voltage with 50s or 100s ramp time by Arduino uno 3 so the ramp rate is about 5v/50s=0.1v/s or 5v/100s=0.05v/s. However I'm a little confused about whether it can be achieved. Do you have some suggestions or basic ideas or codes about this project? thx

Coding Badly


holmes4

The Uno cannot output voltages between 0v and 5v just 0v and 5v. So your first problem is to find a way of overcoming this limitation. Now as your the student.......

Mark

zhyf1991

thx for your reply.not having 5V is ok, I can amplifer it. now I don't know how to code it to make every steps keeping (50/256)s (let's say 8bit for 50s ramp time)

retrolefty


thx for your reply.not having 5V is ok, I can amplifer it. now I don't know how to code it to make every steps keeping (50/256)s (let's say 8bit for 50s ramp time)


I think you fail to understand. An arduino simply cannot directly generate a true variable analog output voltage. There is no way for you to directly have a pin output say a +2.5vdc voltage level. What you can do with external circuitry is to use the PWM outputs and wire up a low pass filter and possibly a buffer amp which will then simulate generating a true analog output voltage within the 0 to +5vdc range. Will your Prof allow such external circuitry?

Lefty

zhyf1991

thanks. yes I know this, my original plan was to build a DAC (resistive ladder)to achieve it. Is this feasible? I'm new to Arduino and my main problem is coding I guess...

retrolefty


thanks. yes I know this, my original plan was to build a DAC (resistive ladder)to achieve it. Is this feasible? I'm new to Arduino and my main problem is coding I guess...


Sure an external DAC would work fine. As far as the programming goes, it's just a matter of spacing the time internals to increment the DAC output values. The mills() function is a handy method of keeping track of elapsed time within your running program.

LEfty


Nick Gammon

I don't want to do your homework for you (then you wouldn't have any fun!) however an RC circuit with a buffer will help get the voltage out of the PWM output. Example:

http://www.gammon.com.au/forum/?id=11395
Please post technical questions on the forum, not by personal message. Thanks!

More info:
http://www.gammon.com.au/electronics

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