use low source to switch higher source??

[daaaaay]

Ok.

My problem is that i have a source that is to small to move this motor that i have. My source is about .5 volts when low and about 4 volts when high. Is there a circuit that will allow my source of .4 - 4 volts to switch a voltage of about 10??

im open to any options

thank you

 

[j.p.bill]

A logic level FET like a VN10LP might be just the item.

 

[Hero999]

What current does the motor draw?

I'd go for something like the IRL540A as pretty popular.

 

[dknguyen]

Yup. A logic level MOSFET (a transistor) is just what you need. Don't forget a schottky diode anti-parallel to the source-drain to protect the transistor from motor inductive flyback (voltage spikes from switching something inductive like a motor), especially if your motor draws higher currents and you are switching it on and off frequently/quickly.

 

[daaaaay]

ok that makes scince to use the transistor but i am not sure how to get the secondary source to the motor. the computer is connected to the base, source connected to collector, and emitter is the output to the motor?? i would still get the voltage from the comptuer. i am not sure on the circuit

i am using a TIP31C as i dont have many electronics stores in my area

thank you

 

[dknguyen]

One terminal of the motor is connected to the COLLECTOR and the EMITTER is connected to ground. The other terminal of the motor is connected to +V.

YOu will need a resistor between the computer and the BASE since this is a BJT transistor of the NPN type and not a MOSFET. Also, remember that the BJT will drop 0.7V since this is a BJT and not a MOSFET.

YOu also need the diode I was speaking about especially since this is a BJT and not a MOSFET (a MOSFET has a bad anti-parallel diode built into it which lets you sometimes get away without using an external one, but a BJT does not so you definately need one).

 

[Hero999]

You still haven't answered the important question?

What current does the motor draw?

The base current needs to be 1/10 of the motor current which your source might not be able to supply.

 

[dknguyen]

Private Message From the OP indicates the motor is a stepper motor.

Thank you for all the help so far. but i am still having problems with this project. i did what you said and it worked but now that i am programing it. when i send a high to the base of the transistors in order it does weird things. like does small steps and moves backwards. I can manually do it by taking one of the inputs and touching the resistor and it works perfect. do u have any idea?

So yeah, you are going to need a more complicated setup with more transistors for each winding of the stepper motor (you will also need to find how what wire is what on the stepper motor). We had assumed you were using a DC motor where you just apply power to the two terminals and it spins. In a stepper motor you have to manually select which windings are being energized to make it move forward, otherwise it will move to the winding energized...and just hold there. Google stepper motors to understand how they work.