# Circuit Simulation and Modeling a Motor using a Resistor

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#### Vsh3r

##### New Member
Hi,

I have a circuit that I'm simulating and would like to substitute a resistor for a motor.

I don't know much about the motor other then that it runs "kinda fast" when a 5 volt battery is connected to it... I'm not sure how much current is going through the motor and I don't have a good way to test it...

Here is the circuit that I'm using to simulate my design now...

(see attached schematic & simulation)

the current through R3 is about 100 mA... is that kinda typical for a motor?

Thanks,

#### ericgibbs

##### Well-Known Member
Thanks Eric,

Do you have any ideas what resistor and inductor values I would use?

Thanks,
V$h3r hi, Its important that you get the motor specification. If thats not possible measure the motors resistance, that will only be a rough guide. #### MrAl ##### Well-Known Member Most Helpful Member Hi, I have a circuit that I'm simulating and would like to substitute a resistor for a motor. I don't know much about the motor other then that it runs "kinda fast" when a 5 volt battery is connected to it... I'm not sure how much current is going through the motor and I don't have a good way to test it... Here is the circuit that I'm using to simulate my design now... (see attached schematic & simulation) the current through R3 is about 100 mA... is that kinda typical for a motor? Thanks, V$h3r

Hi there,

The equation for a motor includes resistance and inductance as well as rotor inertia and friction, however as Eric pointed out already if you dont know the motor spec's you cant simulate it very well.
If your application can get away with just a constant voltage however then you can get away with measuring the current and voltage when the motor has a load and when the motor does not have a load and go from there. Without any data like this however it will be impossible to get it right.

#### colin55

##### Well-Known Member
You cannot simulate a motor or a globe. Both take a very high current at the beginning and the driving device plus the power supply must be able to deliver this current.

#### colin55

##### Well-Known Member
Anyone who tries to immitate a globe or a motor is a fool.
You have absolutley no idea how the item will behave in real life.
I have had problems with both motors and globes not turning on and would not waste my time trying doing anything other than getting the actual device to work.

#### ericgibbs

##### Well-Known Member
Motors and lamps can and are simulated during the design phase of these components.
Anyone who says they cannot be simulated is the fool.

Perhaps it would be more correct so say they dont know how to use simulations to help in the design process.

EDIT:

#### Attachments

• AAesp01.gif
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• AAesp02.gif
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• motor1.zip
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#### MrAl

##### Well-Known Member
Hello,

Im sorry but i have to second what Eric says. I have used motor models in the past to analyze and design analog speed control systems and without that i would not be able to tune the components correctly. There may be limits of course, as with any theory applied in practice. The trick is to know if and when those limits are exceeded.

#### Mikebits

##### Well-Known Member
Thanks for the model Eric, this fool will use it.

#### ericgibbs

##### Well-Known Member
Thanks for the model Eric, this fool will use it.

hi Mike,
I should point out that the model is not my creation, its downloaded from the Yahoo LTspice users group.

#### Mikebits

##### Well-Known Member
hi Mike,
I should point out that the model is not my creation, its downloaded from the Yahoo LTspice users group.

At any rate, it is a nice contribution and thanks for posting it. I am a happier fool now

#### MrAl

##### Well-Known Member
Hi again,

Yes thanks Eric, too bad they got rid of that 'thank you' button

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