Help with some components

[Nozza]

Hi

I'm building a hall effect magnetic sensor but the design I have seems a little unspecific about the exact components needed...or rather I'm not experienced enough to know what I need at any rate. I've attached a circuit diagram.

I know which hall sensor to get as it specifies A1301UA
The IC op amp is LM358N
What I'm not sure aboutare:

1.The diode (what specifications do I need to look for?)
2.The 1M variable resistor - there is a pic of the finished item in the guide and it looks like THIS - is that correct?
3. The two resistors - I assume any resistors of that resistance will do?

Many thanks for any help you guys can offer.

 

[duke37]

1. The diode should be capable of passing the motor current but it only does this during the actual turn off. The common diodes are 1N4001 to 1N4007, these are rated at 1A but can pass more than this for a split second.
2. The 1M potentiometer looks right.
3. Any small resistor of the right resistance will do.
4. The transistor needs to be able to pass the motor current and, if this is large, may need a heat sink.

 

[Nozza]

Thanks mate,

So it's chiefly dependent on how much power the motor draws?

Would a motor like this be OK electronically speaking?

I think these are the ones mentioned in a similar guide by in the series, but they are only 3V? I see the battery is 6V but I don't know all of that is applied across the motor.

As you can tell I've not clue about how to work this stuff out at this stage.

 

[duke37]

You need to drop about 3V at 100mA (0.1A) so will need a 27 or 33 ohm resistor in series with the motor.
Ohms law V=I*R , voltage = current * resistance

 

[Nozza]

Looking at the circuit it appears that the voltage getting to the motor is controlled by TR1 and its output as a resistor on it. So how can one tell if the resulting voltage applied across the motor terminals ever gets to 6V?