Hey all,
Fairly noob question here: Can I use diodes to allow multiple output pins to control the same actuator? In other words, is THIS possible?
I’m still fairly new to
I’m still fairly new to electronics, but I don’t see why not. Assuming of course that they’re not outputting simultaneously, but I don’t think that’s what you’re asking about.
Do a simple test … say with a blinking LED. Testing something for yourself is always the best way to learn! 
… except when you accidently blow things up. But still …
The only things I recall
The only things I recall that you’d need to consider are the 0.6 voltage drop, and that those pins are now only outputs.
Terms an’ stuff
The circuit you have above is sometimes called a “wired OR gate” showing that the result would be high or 1 regardless which output drove it or even if 2 or 3 did. It isn’t really a problem doing this.
A diode would be called a flyback diode if it was wired around an inductive device, to allow the collapsing current to “flyback” in it’s own circuit. The above jsut allows current flow to the device, not back around it when it has been shut off.
I’m guessing you want your speaker to be a little louder. What might work better is to have one output pin drive the base of a transistor, that pulls the speaker down from some voltage. Like the Darlington driver, or another single transistor circuit that had been mentioned recently for driving GM10 motors.Just put the speaker in place of the motor.
Dalington and Speaker
Actually, I was going to try to use three different sound sources, but only use one speaker (they would each perform at a seperate time) so I don’t really need three speakers to one speaker’s job.
And in all reality I probably won’t make a 3-pin sound bot, but I thought I would ask robotologist and the rest of you’s experts before I made any plans.
Don’t worry, I’ll be firing off some more schematic questions soon.
I don’t believe this will
I don’t believe this will work at all because of the capacitor. A hgh output will charge the capacitor and there is no path for the capacitor to discharge. It will work without the capacitor. You could probably add a pull down resistor and two transistors in a push-pull configuration.
Here’s a pic
Here’s a pic:
I'm not sure why I put 10K there, experiment, 1K might be better.
no path?
Can’t the cap discharge through the speaker to the ground?
I believe you would be
This might work well,
likewise if you don’t have a pnp transistor and only an npn - you can get by just having a little tank circuit with a resistor…
no, that is why it’s drawn
no, that is why it’s drawn that way ----| |----
it’s because one lead is not connected to the other
In your original drawing the cap would charge when one of the pins turned on, but it really could not discharge very well.
caps
So how DO caps ever discharge, then? (Obviously, I’m new to the circuitry thing)
I have a speaker that works fine with this circuit:
Am i doing something wrong and not realize it?
The capacitor charges and
The capacitor charges and discharges through pin 3.
When you have a high voltage on pin 3 the capacitor will charge and a current will flow through the circuit, once it is charged no more current will flow. When the voltage goes lower the capacitor will discharge and current will flow in the reverse direction out through pin 3, everything works fine and you get sound. However if there is a diode in series with the capacitor and speaker then this cant happen because it prevents the capacitor from dischanging through pin 3 when the voltage on pin 3 decreases.
I hope that explains it somewhat.
ahhhhhh
i get it. thanks!