The port gives off eough voltage (the relay is rated at 5v, port output pins give of 5.something). The relay does not work; i dont think there is eough current.
Is it possible for me to tie multiple output pins together in some way to make the current higher while maintaining the same voltage level?
Would the parallel port itself have some sort of diode on the output pins so that electricity doesnt flow back into the circuit?
first isolate the parallel port with outside circuit for protection, then amplify the current of the signal either using opamp transisor or driving IC etc........
The parallel port pins can not drive much .. the can probably source <3mA and sink <25mA (typical currents for the 74374 output latch) ..
You will need to "amplify" the ouput "voltage" signal by using external transistors ..
Here is one example:
Code:
Vcc
|
+------+
| __|__
Relay /^\ Diode 1N4002
Coil /---\
| |
+------+
|
| /
4.7K B |/ C
parallel port >-\/\/\/\/---| NPN Transistor: BC547A or 2N2222A
data pi |\ E
| V
|
parallel port >--------------+
ground pin |
Ground
see the source and sink current of parallel port. 2mA/24mA. So it won't be able to drive a relay. If you connect relay directly to parallel port then ur port will burn. Use some transistor with it. See the link below **broken link removed** **broken link removed**