Water level sensor controlling variable speed drive of a pump (big one!!)

Hi,

I have a IR depth sensor connected to my arduino uno that i want to control a variable speed drive (VSD) of a large pump. The input of the VSD allows for 4 - 20 mA to control the power delivery (speed) of the pump. Although i have seen threads on how to control a pump directly with an arduino (e.g. water a plant). I have not seen any system whereby an arduino can feed a variable output ampage based on the value of an input sensor. What would be really neat is to have a control knob that allows me to fix the water height the pump has to maintain rather than a fixed value written into the sketch. I saw something very similar here:

Any ideas how this can be done, any typical sketches? Many thanks

burt46:
I have not seen any system whereby an arduino can feed a variable output ampage

I'm not sure, but maybe a digital potentiometer? Or maybe using a PWM output could be enough?

burt46:
What would be really neat is to have a control knob that allows me to fix the water height the pump has to maintain

A manual potentiometer, or 2 buttons (increase/decrease), or a Touchscreen...many solutions :slight_smile:

Hi, the VSD what brand/model is it, some have 0 to 10V inputs as well. This would make interfacing easier.
Tom... :slight_smile:

Thanks for the replies.

I have a Mitsubishi Inverter (FR-A700) driving the pump. I found the manual and it states i can actually select between three inputs:

0 to 10V,
0 to 5V,
4 to 20mA

So i guess i can just wire in straight from a PWM of the arduino? However, i have my doubts as the PWM is not true analog? Would this cause problems? Don't fancy melting my VSD.

Look for how to low pass filter a PWM signal to make it a variable analog output. You could then use the 0-5V input to your device.

Ok, i'm getting closer. However, i made an error. The inverter cannot receiver 0 - 5V input, it is only 0 - 10V.

The other development is that i found we have an old laser sensor (INF 01D100) which gives out a 0 - 10V. Can someone assist with how i can plug the arduino, to receive the 0 - 10 V and give out a 0 - 10 V to control the speed of the pump (or 4 - 20 mA)?.

I'd like to have a potentiometer that a user can control the level of the water rather than having code that fixes the level statically. Is this possible?

burt46:
I'd like to have a potentiometer that a user can control the level of the water rather than having code that fixes the level statically. Is this possible?

One way to get 0-10Vdc is to use a PWM pin to drive the base of a transistor that is connected to a 10V source then low pass filter the output from the transistor. An npn will reverse the PWM so 0 is 100% duty cycle.

http://forum.arduino.cc//index.php?topic=65304.15