I am trying to run a pump (see link) that is operated by a DC motor. It is the NF 25 TTDCB-4 version. It needs a supply voltage between 10 and 28 V. I have a 24 V (1 A) DC power supply. The speed is controlled by a separate voltage signal (Vctrl) between 0 and 5 V.
So far I connected my 24 V power supply to the two supply voltage wires of the DC motor. If I then connect the white (Speed control – input signal) and green (Frequency output – output signal) wire the pump will run. But, of course, I can not control the speed of the motor.
I tried to connect the white wire to the output pin 6 on my Arduino Uno and sent a PWM signal. I used the following code (this is only the important part):
int OutPin = 6;
void setup()
{
pinMode(OutPin, OUTPUT);
Speed = 100; // value between 0 and 255
analogWrite(OutPin,Speed);
}
However, the DC motor doesn't react to any value that I choose for Speed. It makes some noise, but the pump does not seem to transport any liquid. What did I do wrong? I also have the adafruit motor shield (link) here that I could use.
You need an ANALOG voltage (0-5V) to drive the pump controller.
The PWM outputs are DIGITAL (Pulse Width Modulated) - which can be put through a filter to generate a low-current pseudo analog voltage.
You will be better off using a separate Digital-to-Analog converter chip/module to generate a stable voltage signal based on the value you set from the Arduino.
I found this information in the manual:
In the case of type NF25 DCB-4, the supply voltage is not designed for operation with pulse-width modulated voltages (PWM).
However, a PWM signal (frequency ≥ 500Hz ) can be used to control the control voltage.
No I have not. I think that could be the missing piece.
So that means I have to connect the black wire (- Supply voltage, GND) with the minus of the DC power supply (already done) AND the GND of the Arduino (the one next to digital pin 13)?
Thanks!
I attached the drawing. I am not familiar with those drawings though, sorry. The dashed line is the missing connection, I think.
I attached the drawing. I am not familiar with those drawings though, sorry. The dashed line is the missing connection, I think.
That very much looks like a missing link. Without it, it won't work (though if you have connected the grounds of the two power supplies together, that should be enough - but you didn't draw that part).
You may also be able to improve the control by adding a smoothing cap on your PWM output, which helps to convert your PWM blockwave into a fairly constant DC voltage.
