Stuck with simple motor circuit

Other Hardware Motors, Mechanics, Power and CNC
1

I am trying to build a really simple circuit in which a dc motor is controlled by a spdt slide switch. The programme seems fine and I can get it to run - trouble is, I can't get the switch to control the motor switching on and off. Any clues? I'm probably doing something stupid! Thanks.

int switchA = 7;
int motorA = 2;

void setup(){
pinMode(switchA,INPUT);
pinMode(motorA,OUTPUT);
}

void loop(){
if(switchA,HIGH){
digitalWrite(motorA,HIGH);
delay (1000);
digitalWrite(motorA,LOW);
delay(2000);
}
else{
digitalWrite(motorA,LOW);
}
}

Hopefully this link takes you to the 123d simulation circuit.

Debs

2

DON't connect a motor directly to an Arduino pin.
That will damage the pin and/or the Arduino.
Pins are only rated for 20mA (40mA absolute max).

Motors should be switched with a suitable resistor/transitor circuit with back EMF diode.

It seems you also have connected a 9volt battery to Arduino's 5volt pin.
That will smoke your Arduino.

Connect the switch to an input pin and ground. No resistor.
Enable the internal pullup resistor in pinMode.

Read this.

Leo..

3

Thankyou. I know my circuit was non-existent but it seemed to be ok without the transistor - not that I would have built it that way! Anyway, it turned out that I had an error with my code. If I changed if(digitalRead(switchPin,HIGH) to ifdigitalRead(switchPin ==HIGH) the circuit behaved properly. I assume that the first statement set the switchPin to HIGH all of the time - which is why switching on/off made no difference and the second conditional statement tests the condition of the pin to see if it is HIGH or not.

Debs

PS I have now constructed it with the transistor switching circuit too. thanks again for your help.

4

debkeys:
Thankyou. I know my circuit was non-existent but it seemed to be ok without the transistor - not that I would have built it that way! Anyway, it turned out that I had an error with my code. If I changed if(digitalRead(switchPin,HIGH) to ifdigitalRead(switchPin ==HIGH) the circuit behaved properly. I assume that the first statement set the switchPin to HIGH all of the time - which is why switching on/off made no difference and the second conditional statement tests the condition of the pin to see if it is HIGH or not.

Debs

PS I have now constructed it with the transistor switching circuit too. thanks again for your help.

But still, you should not power the motor from the +5 Volts from the Arduino.
Motors should be powered by a separate power supply and a common ground.

5 
ifdigitalRead(switchPin ==HIGH)

That line is missing a lot of brackets. It should look more like:

if(digitalRead(switchPin) ==HIGH)

The closing bracket after switchPin is really important. switchPin==HIGH is actually a valid pin number, but probably not the pin you want.

6

debkeys:
Thankyou. I know my circuit was non-existent but it seemed to be ok without the transistor - not that I would have built it that way! Anyway, it turned out that I had an error with my code. If I changed if(digitalRead(switchPin,HIGH) to ifdigitalRead(switchPin ==HIGH) the circuit behaved properly. I assume that the first statement set the switchPin to HIGH all of the time - which is why switching on/off made no difference and the second conditional statement tests the condition of the pin to see if it is HIGH or not.

Debs

PS I have now constructed it with the transistor switching circuit too. thanks again for your help.

No, the code you need is

  if (digitalRead (switchPin))

digitalRead takes a single argument the pin number, and returns a single truth value (HIGH and LOW
are synonyms for true/false and 1/0)

Don't connect a motor to an Arduino pin, the pin can't handle the current nor the inductive
voltage spikes, and will fail.