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>>Dose this circuit work...

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Someone Electro

New Member
The motor shod be controled in bouth directions.

PS:
I know its a bumb post but sometimes a simulator dosent simulate right! :oops:
 

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john1

Active Member
yes its workable,
just make sure that 1 and 2 dont go high together with 3 low.
That would put both transistors into conduction.

Also you might want to put limiters in the base leads.
somewhere between 200 and 2000 ohms. (roughly)
 

Someone Electro

New Member
Thanks!

Remember that topic of mine:
Wean i reqested a circuit to control a motor

I figured out why just NPNs dont work

But i didnt want to use PNP (I dont want to risk my LPT Port)

PS:
You reply fast! :shock:
 

Roff

Well-Known Member
It doesn't work. Can you show some evidence why you think it does?
And would someone please tell me why they think PNP transistors will damage a printer port?
 

john1

Active Member
Well Ron,

I dunno why you say that it doesn't work.
Anyone would think you had tried it. :)

Don't miss that it is quite free floating,
and has two separate batteries.

It has eight possible combinations.

123 (port connections)

000
100
010
110
001
101
011
111

where 0 represents 0v (roughly)
and a 1 represents +5.5v (roughly)

With data3 hi, nothing should happen.
So thats half the options decided. OK ... ?

With data3 lo,
either data1 or data2 would have an effect by going hi.

Thats three of the remaining options decided, OK, ... ?

Last possibility,
data 1 and data2 both hi with data3 lo,
transistors may get hot, motor wont run, not nice.

Don't like the circuit at all,
but its workable.

Cheers, John :)
 

Someone Electro

New Member
That data 3 (as you think) is the ground pin (pin 25)

I just plan a 100 mA motor.


It is nothing wen there is 0V on the emitor but ven is -6V on the emitor you can kiss your port good bye!


PS:
How much mA dose the parallel port give out(data pins)(i think 3 mA)

Im simulating for 1 mA
 

Roff

Well-Known Member
No, I didn't build it, but I simulated it.
Below are the results of simulating this circuit on Linear Technology's SwitcherCAD III (a version of Spice). Note that the circuit on the right works. The circuit on the left, however, only drives 13ma through the motor instead of the approximately 100ma desired. To make matters worse, look at the currents through the transistors.
The voltages and currents in this circuit look very strange. This is because there is no ground reference in the motor circuit. Nor is there a place to add ground that will make it work.
 

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Exo

Active Member
It works, but not as you draw it...

You need a dual power supply for example +12V - GND - -12V.
The motor needs one side connected to GND and the computers ground also connected to GND, this delivers your common ground

a PNP drives the +12V trough the engine and a NPN drives the -12V
Never drive them both together.

It works , cause i have such a setup in use... :roll:
 
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