Relay

[Stoneww]

Hey I've been trying my best to get this relay circuit working for about a week now, help would be very much appreciated

I've managed to get the comparator working as well as the transistor. However the transistor wasn't enough to power a motor. I've tried the motor with a relay but even after numerous guides I couldn't do it. As I understand the principle is that if the coil is powered an EM field will pull a switch and activate a circuit which has a different power source.

I haven't been able to successfully connect this on my breadboard. Could anyone show me how it would be done? Below is a circuit diagram of how I think it works and also a diagram I used as a reference.

 

[Harald Kapp]

Your diagram is o.k.
What's missing is: where does IO1 or IO2 come from? This should be a signal that switches between 0 V (relay on) and open circuit (relay off). An I/O port of a microcontroller will not work. You'll need a more powerful driver, e.g. a transistor.

By the way: do not use the breadboard for the mains side of the relay. A breadboard isn't menat to be used with mains voltage. Use some wire and solder it t o the relay's terminals, then connect only the coil side to the breadboard.

 

[Minder]

The .png pic shows it, you could also use a 2n7000 fet if driven from a comparitor.
M.

 

[Stoneww]

Your diagram is o.k.
What's missing is: where does IO1 or IO2 come from? This should be a signal that switches between 0 V (relay on) and open circuit (relay off). An I/O port of a microcontroller will not work. You'll need a more powerful driver, e.g. a transistor.

By the way: do not use the breadboard for the mains side of the relay. A breadboard isn't menat to be used with mains voltage. Use some wire and solder it t o the relay's terminals, then connect only the coil side to the breadboard.

Oh dude not that diagram, I mean't the diagram that I have left as an attachment

 

[AnalogKid]

The circuit will work better if you swap the two comparator inputs (to change the output logic polarity to go high when you want the motor to run) change the transistor to an NPN (with base resistor) or N-channel MOSFET (2N7000, 7002). The gate or emitter goes to GND and the collector or drain goes to the coil. This drives the relay with a saturated switch instead of an emitter follower. This reduces power dissipation in the transistor and puts more voltage across the relay coil.

ak

 

[duke37]

You need a npn transistor (2N2222) or n channel fet.(2N7000)

Edit. Nothing like saying the same thing twice

 

[Stoneww]

The circuit will work better if you swap the two comparator inputs (to change the output logic polarity to go high when you want the motor to run) change the transistor to an NPN (with base resistor) or N-channel MOSFET (2N7000, 7002). The gate or emitter goes to GND and the collector or drain goes to the coil. This drives the relay with a saturated switch instead of an emitter follower. This reduces power dissipation in the transistor and puts more voltage across the relay coil.

ak

Thanks for the help , turns out the problem was just that 9V wasn't enough for the coil but 18V did the trick.

 

[Minder]

The relay didn't have a rating on it??
M.

 

[Stoneww]

The relay didn't have a rating on it??
M.

It did but clearly I am blind