i'm trying to control a motor by parallel port, using 2 output pins which i can switch between 0v and 5v, but they cant source enough current to turn the motor. Pin 1 [0v] will turn motor clockwise Pin 2 [5v] Pin 1 [5v] will turn motor anti-clockwise Pin 2 [0v] [when both pins are the same, motor wont turn (duh)] but like i say, i cant get enough current, can anyone help me with the design of a circuit to source current, but that wont change the voltages. Thanks in advance
would simply putting two transistors onto the pins work.. if so... exactly what transistors should i be looking for, the motor is a 5v one, apparently it uses about 0.2A under load... so... meh!
Simplest way is to use a power transistor in emitter follower configuration: You will need an external 5v source (never power anything more than an LED or a low power chip off the parallel port directly). You could use a 12v external source if ya wanted to run a 12v motor etc. TIP41 will do quite a few amps. Use a 1K resistor to the base from the parallel I/O pin
Although your circuit shouldn't require a base resistor, I'd recommend placing the motor between the supply and collector to get the propper switch action (and keeping the resistor in that case). The output of a parallel port can be as low as the 3.3v mark so it would only give the motor <3v.
i have been told your circuit is incorrect, but i couldnt say that myself, but anyway, using just the one transistor wont allow me to reverse the polarity of the motor, something i HAVE to be able to do... i've been told a "push-pull" transistor circuit comprising of an NPN and a PNP transistor would do the trick, but i dont know how to actually implement one
this may or may not help you understand what i'm trying to acheive... edit: although they look like -5v in that image, its ~5v, just to clarify
Ahh i see your wanting direction control - you can't use i/o pins to source current when set to 0v. So things get more complex: This should do what ya want...logic 1 on left, 0 on right will make it go one way...1 on right, 0 on left will make it go the other. I also added some diodes in to protect the transistors (a motor is an inductive load that produces a back EMF). Use IN4001 or IN4002/3/4 etc
thanks for this, i will ask some other electronics people i know to verify this, not because i dont trust you, but because i dont trust myself, i'd like to not blow up my motherboard, looking on some other webbies, this looks like it will do the trick, oh, and it looks like you are new to the boards (post count), so welcome, and thanks
Urk @ that suggestion....Base resistor is required - you could sink too much current from the parallel port and possibly blow it...always best to not tie anything direct. And putting the motor in the collector line is a common emitter instead of common collector (emitter follower) configuration - which wont track the input voltage (he stated he wants it to be same voltage) Ripz, let me know if your wanting to output more than 5v - ya will need another 2 transistors added to that as, as it stands the motor voltage will track the parallel port logic 1 output voltage (5v). To make the motor run at what ever your external supply voltage is you will need 2x common emitter transistors to bring the logic level of the i/o pins upto your external supply voltage. Btw those resistors should be 1k (darn crap package of mine keeps defaulting em to 10k) acrimonious is right tho that some ports output only 3.3v - i've only seen that on laptops tho.
motor runs on 5v, so i wont need to up the voltage you might see the use of this in the future, tis part of my new case project , the software i'm writing will control 2 cathodes, 2 led's, the motor, and a case fan
If you use a base resistor with emitter-follower, it drops some voltage (RxI) so apart from the inevitable 0.7V drop there's an extra bit lost. Not a good way to get (almost) 5V to a 5V motor. In your example, the 200mA motor will need base current of around 5mA with the TIP41 - try putting 5mA through 1k and it drops 5V; nothing left to track. The chips used here are readily available, cheapish, and will drive a small motor directly from logic signals, forwards, backwards and stopped. Rapid sell a MIC4426 1.5A one @ £1.80.
i'm interested in doing something similar, but what i want to do is send signals to the remote control of my RC car. i can't seem to find a picture on the web, but it's the tyco 'skydriver' that came out a few years ago. it's the red one with the two huge front wheels that are controlled independantly on the controller so you can make it do a front-flip and spin around. anyways, i figured if i could control a current to the controller, i could drive it via pc, but i know nothing about using the serial or parrallel port to do this. i plan on making a new thread for this, but i searched and found this one, and "blow" seems to really know his stuff, and i think a transistor is what i'll need to use, and this seemed like the only way to get "his" attention. thanks for your time and help. let me know agent
I think you misunderstood what he was after. You don't want an emitter follower because you can't get an analogue voltage from the parallel port, and as cpemma stated, the base resistor will drop even more voltage. That TC4424/4426 is a nice simple solution for someone not too familiar with electronics.
sorry for the threadjack and revival of an old thread. my new thread with pictures and as close to detailed explanation as i can come is here: http://forums.bit-tech.net/showthread.php?p=1037793#post1037793
