use of the signal wire in "prototype breadboard"

Would someone enlighten me about the signal wire used in “prototype breadboard”?
No-one seemed interested in answering my question in that thread.
“I understand the 5V, resistor, LED, and ground. I don’t follow how the signal wire fits in. Is it acting like a switch, somehow?”
If you were making an actual circuit (without the breadboard), where would you put the signal wire? Please explain how the signal wire would work. Wouldn’t the same circuit work without the signal wire, or does the power only go to the circuit when there is a pulse on the signal wire?:confused:

You mean the “Servo Wire” mentioned in the Top Post of the Thread??

The “prototype breadboard” allows one to try different circuts, before making a “permanent” circut, or lets one try different components before settling one a given one.

The “Servo Wire” lets you connect the LED to an Output on the Vex Control Modue, in the place of a Servo or Motor.

MarkO, No, I meant the signal (white) wire part of the servo cable. The rest, I know.

IIRC, you have +5Volts, Gnd, and the “signal”, which can be Digital Input, Digital Output or Analog Input.

EasyC 1.1 defaults to Analog Input on ports 1-4, Digital Input on ports 5-10, and Digital Outputs on I/O 11-16.

Here is an LED Circuit with 3 LED is series (verses parallel), and a resistor to lower the Current to the level that won’t burn out the LEDs.

For the LED, it you connect the +5Volts to the Gnd, the LED would be on all the Time. But you set the “port” to Digital Output (like Port 11), and connect it to the LED, then you can turn on and off the LED when you place in your program a call to EasyC function “SetDigitalOutput ( 11 , 1 )”

MarkO, very interesting. You managed to answer everything BUT what I asked. I didn’t ask about the programming side. I didn’t ask for an LED circuit. I asked how the signal wire is used, how it acts in a circuit, and where it would be placed in a non-breadboard application like the one shown in “prototype breadboard”. I tried to make it clear that the only part I don’t understand is the signal wire. I have a little experience with breadboards, but none of my experience has dealt with incorporating a PWM line into a circuit.

MarkO, please let someone else answer my posts.

Sorry , I obvously don’t understand your question… I was hoping to answer your question since no one else was trying…

MarkO, thanks for trying. No-one else seems to want to give it a try. I made two separate posts and sent a PM to the original author = no answer. After rereading my posts, I don’t know how I could have made it more clear.

The signal wire (the white wire) is being used to provide the positive voltage to the LED.

The circuit looks like this:
WhiteWire <-> resistor <-> +LED- <-> BlackWire(GND)

The red wire is not connected to anything in the circuit. It is plugged into the bus strip along the edge of the breadboard, but nothing else is plugged into that strip.

The PWM signal in the white wire alternates between a positive voltage and ground. The relationship between the length of on (positive voltage) and off (ground) pulses determines when the LED will be lit. The longer the ratio of on to off, the brighter the LED will appear.

If the signal wire were used as a digital out (full on or off), then the LED would just be turned on or off - but there would be no variable brightness. The brightness of the LED would be controlled only by the size of the resistor.

A great explanation!!

Also see this Parallel Thread

First: Look at this picture:

In the +5 (Vcc) wire, the scope trace would look like a flat line at the +V point. Similarly, the ground would look like a flat line on the x-axis (0 V).

In Pulse-Width Modulation (PWM), like that used in the vex controller, alternating an output on and off corresponds to a value between full off and full on. So, for example, in the picture, the second row (which appears to be about 50% PW) would correspond to a value of ~ 127 being sent to the PWM ports.

In a led, what is actually happening is that the led is blinking on and off very quickly. The top trace (in the picture I linked to) would provide a weak light, as the led spends most of the time off, and just a tiny bit of the time on. Similarly, the bottom trace would be at almost full brightness as the led spends most of the time on, and just a little bit of the time off. The center trace would (logically) have a brightness somewhere in between.

HOWEVER, when used with the servos, the PWM serves a slightly different purpose. Just as the code in the controller represents a particular pulse width with an 8-bit value (0-255), a servo can decode a PWM signal back to its 8-dit digital value, and then move to that numbered position. That is why the servo can be so precisely positioned.

If you have any other ?s please PM me.

~ Christopher