Of Darlingtons and motor drivers...

[sputz]

Quick question on Darlington IC.. I have the Picaxe 28x project board which comes with the Darlington IC and a socket for a Motor driver IC.

If I use the motor driver, it uses output pins 4-7 from the Picaxe to drive the motors.

Can I use both the Darlington IC and the motor driver IC together if I don't access the outputs 4-7 from the Darlington IC? I mean can I use the remaining output pins from the Darlington IC?

Thanks!

 

[inglewoodpete]

Output pins 4-7 on the darlington IC will continue to operate in parallel with the motor driver chip, but there will be no adverse effect. Since the darlington outputs are 'open collector', they will switch between high impedance and 0v: just leave them unconnected.

 

[westaust55]

Darlingtons and motor driver Outputs

In short then answer is “YES” (no problems)

For a little more background:
Logic type IC’s can use one output to simultaneously drive inputs of several other IC’s. This is called the Fan-out for the IC outputs and may be around 10 inputs from 1 output.
The issue in general (particularly in industry) is one of Safety. Not a big issue on the hobby test bench but you do not in general want an output turning on two devices at once – could be poor control where not inteneded but on the other hand may be useful (for example, a bi-colour LED to indicate direction of a motor.
With the PICAXE outputs 4 to 7 via the Darlington IC you could be operating with no motors attached so no problems using all 8 Darlington outputs.
If you have motors attached and say some LED’s attached to the Darlington IC outputs then at worst you see what the signals into the motor driver IC are doing.
But if you have a motor connected across say outputs 6 and 7 and a buzzer on Darlington output 7 then the buzzer operating when the motor is under some operating conditions may be annoying.
Driving both IC’s simultaneously will not damage the Darlington or Motor driver ICs.

 

[sputz]

Thanks inglewoodpete and westaust! Those were some very detailed answers! Thank you, I had no idea I could use both.