Miscellaneous circuit - for robot

[George L.]

Hello,

I am working on a circuit which will be used with a robot competing in the FIRST robotics competition.

Basically I do the electrical stuff...There are three inputs on the controller we are issued for the robot, +5V, Ground ,and Signal. Signal has an internal pull up resistor, 10K.

I need to make a circuit that will pull the signal input low, basically ground it, so that the input will read 0 to the controller. Fairly simple.

The circuit below is supposed to do this but doesnt work the way I want it to. The idea of the circuit is to indicate whether the input is high or low by lighting up the corresponding LED, only one LED is lit at one time.

In the circuit below, which is on my breadboard, doesn;t work properly,

The 10K resistor represents the Signal input.

when the switch is closed , the blue LED is on, the red is off and the meter should read no voltage.

when the the switch is open red LED is on, the blue is off and the meter should read a voltage.

Does anyone know what is wrong with my design...I would really appreciate some help.

thanks,
George L.

 

[audioguru]

It will do what you want if you change it a little: