I've been trying to wrap my head around this for a week now....here's the low down.
+3VDC at rest, or OFF
+1VDC active, on ON
Transistor to switch low current 470omh GND signal between the two.
Make any sense?
Please provide a schematic . (hand drawn , photo of drawing uploaded)
I don't have a drawing...thats what I'm trying to come up with
KOZ:
+3VDC at rest, or OFF
+1VDC active, on ON
Is that two different signals, one of 3V and one of 1V, or a single signal that can be 1V or 3V?
I would guess something like this, but it's too simple. The Input rests at 3VDC, and needs to trigger the transistor at 1VDC. The output I need is a GND 470ohm signal.
+3VDC at rest, or OFF
+1VDC active, on ONTransistor to switch low current 470omh GND signal between the two.
If the 47
0 ohm resistor is switched between 3V and 1V, it still does not tell us what the switching signal voltage is.
It simply means that a transistor is connected from 1V to 3V and 'somehow' turned on and off.
You need to start by explaining why you are posting.
Why you want to do this and what it accomplishes and why.
If you want complete answers, you have to ask complete questions...
GND 470ohm signal.
And who knows what a 470 ohm signal is ? (since there is no such thing )
Anyone want to explain to the OP why there is no such thing as a 470 ohm signal ?
Speak English or speak Electronics.
ok...
I have an existing 5v reference circuit that consists of 4 switches. The circuit rests at 3vdc, and each switch changes the voltage sent to the computer. The switch I want to use changes from 3VDC to 1VDC when pressed.
I want to use a separate circuit to piggyback onto the existing one that will be triggered at 1VDC and provide a ground output to another device.
The main circuit is the cruise control switches in a car, that output would send a ground signal to a radar detector as a mute signal. I believe the 470ohm resistor is used to limit current.
better?
KOZ:
better?
Not to me.
I think I'm getting that the output from one of the switches is normally 3V, and goes to 1V when pressed, but that's all so far 
KOZ:
send a 470ohm ground signal
I have no idea what that might mean.
I have no idea what that might mean.
Amen
What is a 470 ohm ground output ?
Why don't you just say "I want to connect a 470 ohm resistor to ground with a 1V turn on signal ?
You only need 0.7V on the base of an NPN transistor to turn it on. That means you need a voltage
divider to drop the 1V to 0.7V, but in order to choose the resistor for that you need to know the hfe
of the transistor, and how much current is passing through the 470 ohm resistor. If it is very low,
(in the order of a few milliamps) then probably a small resistor would suffice.
The problem, as it were is that your OFF signal is 3 times the ON signal. The simple solution is screw the logic and just use an analog input pin on an Arduino and measure 1V (+/- 10%) or 3V (+/- 10%) , then
you simply measure the voltage and if it falls in the the valid range for ON or OFF then you turn on a digital
output to switch the transistor. This is a solution that works 100% of the time and requires no logic.
Or as Spock would say, "It is the only logical solution...."
KOZ:
The main circuit is the cruise control switches in a car,
OP should also be aware (although s/he might not like it) that Atmel who make the Arduino chips specifically say in the datasheet that you can't use their stuff for automotive applications [for some definition of "automotive applications].
Unless specifically provided otherwise, Atmel products are not suitable for, and shall not be used in, automotive applications.
Sorry OP but add me to the list for whom this question is not clear.
You said:
I have an existing 5v reference circuit that consists of 4 switches. The circuit rests at 3vdc, and each switch changes the voltage sent to the computer. The switch I want to use changes from 3VDC to 1VDC when pressed.
You might look at a comparator circuit. There are lots of comparators but let's say you use the TS391RILT from ST Micro. If you connect the output of your switched circuit to the '-' input of the comparator. Use a voltage reference (such as a MAX6120EUR+T) on the '+' input.
With the circuit at the "rest" voltage of 3V, the '-' input will be higher than the '+' input and the comparator output will be low. Only when the input voltage on the '-' drops below 1.2 -- resulting in the '+' input being higher than the '-' input -- will the output of the comparator go high.
The comparator I showed has an open-collector output meaning it can drive the pin to ground or let it float (you'd use a pull-up resistor to pull the level "high." So when that signal goes "high" the output ground connection is open-circuited and the pull-up resistor allows the pin to rise to your pull-up voltage.
If you sized the resistor correctly you could probably put that on the base of an NPN transistor (say, a 2N3904): (emitter to GND, base to the comparator output and pull-up resistor and the collector to the 470-ohm resistor, the other end of which is connected to the mute input of the radar detector.
Does this sound like what you want to do?
Well I guess that means an alternative analog to digital converter would need to be used.
I'm thinking of a comparator.
Give it a reference voltage of 2V and it'll produce a 5V/0V signal at 1V/3V (or the other way around depending on your wiring). Use that to switch your transistor.
Whether this works depends on the rest of your (so far undisclosed and only vaguely described) circuit. It mostly depends on what those other buttons do, the voltages available, etc.
I'm still confused by the notion of a ground signal - perhaps you mean ground-referenced signal
(which is a tautology, signals are by default assumed ground-referenced)
Please tell us from the outset what you are actually trying to do, not how you imagine it should be done,
otherwise we are going to be at cross-purposes (see xyproblem.info)
If you don't know the terminology, its important to give all the concrete details you do know,
such as identifying each piece of hardware in question, and the nature of the overall goal you are trying
to achieve.
Yeah, your right. A comparator is much more elegant solution.
I should have thought of that.
Thanks for refreshing my memory. They say that's the first thing to go when you get old. ...
(Right Larry?)