Arduino Project 9

My circuit works perfectly fine, but i’m trying to understand what causes my motor to work. As you can see in the attachment provided the positive end of the motor is connected to the 9v battery, while the negative end is connected to the output signal from the transistor. My question is how exactly is the circuit closed? Does a change in voltage from ground, caused by the transistor allow the motor to draw power from the 9v battery? Thank you for your support.

IMG_0498.JPG

IMG_0497.JPG

Please post an actual written schematic. That is just too unclear to analyse.

If you're talking about what I think just Google "transistor low side switch" and you'll find all the explanations you need. It sounds like you may have roughly the right idea.

Steve

tstewart30:
My circuit works perfectly fine, but i'm trying to understand what causes my motor to work. As you can see in the attachment provided the positive end of the motor is connected to the 9v battery, while the negative end is connected to the output signal from the transistor. My question is how exactly is the circuit closed? Does a change in voltage from ground, caused by the transistor allow the motor to draw power from the 9v battery? Thank you for your support.

It looks like you're using an npn transistor, and may start with pin9 set low. When you press the switch it tells the arduino to set pin9 high which turns on the transistor, allowing current to flow from the motor to ground. The resistor from the switch to ground, just makes sure that pin2 stays low rather than float. At least that's what I'm deriving from the pics.

Hi,
The way that they get you to wire the "transistor" without a "base" resistor, tends to make me think they are using a MOSFET.
IMG_0498.JPG
Can you tell us the part number printed on the component please?

Thanks.. Tom.. :slight_smile:

TomGeorge:
The way that they get you to wire the "transistor" without a "base" resistor, tends to make me think they are using a MOSFET.

That's kinda what I thought at first too since it would make more sense. But the way the pins (position) are being used it made me more inclined to think transistor. It would make even more sense if pin9 was used as analogout.

edit: coincidentally, here's almost the exact same schematic (I thnk it's close) here.

My question is how exactly is the circuit closed? Does a change in voltage from ground, caused by the transistor allow the motor to draw power from the 9v battery? Thank you for your support.

Because a transistor or MOSFET can act like a switch and control the passage of current.

Your 9V battery is completely overloaded by driving a motor with it, I suspect its only holding 6V or less
under such load and will rapidly flatten. Small 9V batteries are unsuitable for powering motors (certainly
under any kind of load that is).

justjohn:
That’s kinda what I thought at first too since it would make more sense. But the way the pins (position) are being used it made me more inclined to think transistor. It would make even more sense if pin9 was used as analogout.

edit: coincidentally, here’s almost the exact same schematic (I thnk it’s close) here.

Most TO220 cased N-CH FETs are configured so that they would fit directly into that circuit layout.
B - C - E
G -D - S
Tom… :slight_smile:
PS does it have a part number in it?

TomGeorge:
Most TO220 cased N-CH FETs are configured so that they would fit directly into that circuit layout.
B - C - E
G -D - S
Tom... :slight_smile:
PS does it have a part number in it?

Bygolly you're right. Thanks for the "heads up."

Look at this it may clear up some of your q's.

http://www.gammon.com.au/motors

jackmanjls:
Look at this it may clear up some of your q's.

I think it's about time the OP cleared up something.