Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.
Welcome to our site! Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.
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?
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.
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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