Electronics Question About 3-Wire Ports

[Sylvie]

This is with both V5 and PIC.

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What is the strength of the signal wire on a digital out port?

Is it possible to turn the power on/off to an LED strip plugged into the Signal and Ground wires?

Is it possible to give variable power to the LED strip via the signal wire and ground wire? i.e. analog output.

What would be the minimum number of 3 wire ports to fully control the color of an R, G, B, Ground light strip?

Is it possible to power a 5V light strip from the Brain or PIC without an MC29?

[jpearman]

This info was specific to the cortex, but the V5 is similar. Due to the series resistor and the fact that the control signal is connected to a microcontroller, almost no current is available,

Cortex digital IO ports and the pneumatics driver

I’m going to try and explain why we sometimes have problems with the pneumatics firing and why different programming options are behaving differently. To understand what’s going on some background knowledge is needed on how the digital IO ports are configured by firmware and what features the specific micro controller in the cortex has. To start, lets look at the simplified schematic of a digital IO port from the cortex user manual. [cortex_digital_port.jpg] This shows the 1k ohm series res…

[Sylvie]

So, an MC29 is needed for the LED strips?

What I’m taking from that is that the signal is only just enough to make the VEX LED piece turn on.

[jpearman]

Yes, the control line can only source or sink a few mA of current.

[Andrew_Strauss]

I did some poking around at the V5 ADI ports a little while ago and this is what I ended up with. It’s a pretty standard affair with a voltage divider to bring the 5V input signal down to 3V for analog readings. While most of the pins on the MCU that’s handling the ADI are 5V tolerant, this isn’t the case when the pin is in analog mode.