Conifirming somthing

OK hi everybody,

its the not so nob here and sadly, no question for today :frowning: :frowning:

i want to confirm something.

on the VEX wire (is that the right word for this??) you can see three wires within the hole thing (sorry if I’m a bit confusing here).

alright i know that one of them is your hot wire (positive current) and the other is your cold (negative current) and I’m pretty sure that the third one is the ground, now if I’m right i could hook up a speaker rated for <??> amount of volts or a pizo buzzer.

Now am I right about this or not??

thanks

oh look theres the spell check button!!!

yay :smiley:

oh well stupid dial up wont work right anymore…

sigh guess it happens on a windows 98 that was made in 1998

oh yay got online!!

I’m new at this too, but here’s what I think you are looking for. Please feel free to ask for further clarifications.

I’m assuming that you are referring to the cables that get hooked up to the VEX controller. Most of the cables are Red, Black and White. The red wire has +5 volts, the black is signal return and the white is data.

The data cable can either provide a digital output (on/off) of +5v or the motor outputs can provide a PWM output. These PWM outputs make a 1-2 millisecond (ms) pulse every 18.5 ms.

A buzzer may work well because you can just turn it on or off. The digital signals are good at that. I would recommend that you check the current draw of the buzzer before you hook it up though. I haven’t checked the specs on the VEX kit yet, but most microcontrollers are only capable of 25mA. If it takes more than that I’d recommend that you use a relay or transistor to switch it on and off and use something else to power it, like batteries.

You will have a lot of trouble hooking up a standard speaker directly to one of the ports for 2 reasons. First, the processor isn’t fast enough to make anything more than a simple tone. Second the you might draw too much current and damage the VEX controller. A speaker has a coil of wire so it may behave like an inductive load. Inductive loads have the ability to create power spikes significantly higher than you would expect.

As I mentioned earlier, I haven’t checked the manual yet. My numbers may be off. Hopefully I’ve got you pointed in the right direction.

Andy

The black wire is generally called “ground”.

There is no explicit negative current.

A piezo may be suited for this kind of application. But I’m not an electrical person, do your own digging.

It’s true that the black wire is often called ground. It’s a frequent mistake. Technically ground is into the earth. Most mobile robots don’t have an electrical connection to the earth.

Anyhow there are lots of terms for it. Common and signal return are both accurate. People will usually understand ground and get the right idea, but the term is not really accurate for this application.

Andy

Ok lots of help (not sarcastic) thanks a whole lot will post a pic of my setup with the buzzer when it is finished.

im a noob to vex but am an electrical genious so this is great!

Whoa whight is DATA!! :ahh: never would have guessed that!

but again thanks a whole ton guyes. :smiley: