to reduce a dynamically defined percentage of the voltage.
What is the output impedance of the sensor? Is it constant and stable regardless of the sensor reading? Trying to drag down a low impedance output that isn't designed for it is a bad engineering practice.What is this mystery sensor? Is there some reason you must conceal its identity from us? Not fully explicating the problem will definitely impact the quality of the answers you get.Also, this forum is for Arduino questions. Where is the Arduino in this circuit?
I have a sensor that outputs 0~5V and I want to be able to hook up a circuitry onto that signal wire in order to reduce a dynamically defined percentage of the voltage.
But let's forget about all that. I'm not worried about toasting anything I'll find that out later. Can somebody please show me a way that for instance, I can simply tap into a 2.5V line and reduce it to let's say 2.2V. Is it possible?
Can somebody please show me a way that for instance, I can simply tap into a 2.5V line and reduce it to let's say 2.2V. Is it possible?
Many auto systems that utilize a reduced voltage system for sensors use an isolated supply to do so. Connecting a resistor to body ground will not complete the circuit.
Hi xgrapher,From your first post I think you want to scale the output as a function of something an arduino calculates.So for instance if your scale factor goal is 0.9 then a normal 5V out would be 4.5V and a 3V output would be 2.7 V. Am I understanding you correctly?I've worked with this sensor some years ago in a fuel tank leak system and recall the output was proportional to input voltage. So I see two options:If you don't require a large range of scale factor you could simply modify the input voltage (Vcc). This may not meet your "don't cut a wire" goal.Load the sensor output with resistors. Some DAC's can be wired this way but I don't know if they can handle the current needed (which is unknown at this point). Alternatively you could 4 Mosfets, each grounding a resistor tied to the sensor output. This would give you 16 combinations. I believe it will not damage the sensor as all automotive sensors must be capable of extended short circuits on their outputs. Caveat, the sensor output impedance may not be constant for all conditions (especially temperature)Good Luck.
Yes, that is possible. But then you no longer get any data from the sensor. The Arduino is loading it down to 2.2V and you cannot possibly know if the sensor has changed from 2.5 to some other value.Now there may be some ways which this is useful - for example, you never want to see any value greater than 2.2V so you can brick-wall it at that value, allowing any lesser voltage to pass through unmolested.The thing is, it's not just a sensor. It's a delicate sensor which produces a signal in the microvolt range plus an amplifier which brings it up to the volt range. That amplifier will have feedback. That means that if its output is not at the right voltage, it will apply more power to bring it up. You can load it down by exceeding the power available to that amplifier. And that is the point where you're no longer reading the sensor, you're just applying the voltage that you want to that wire, using your more powerful amplifier.You could add another sensor and use that output to overload the original sensor but I suspect if your goal is not cutting wires, then bolting a new sensor on is not in the picture.
Hi,A potential divider will work, but you will have to cut into the wire.Using shunt method is not recommend as the sensor is not designed for that sort of loading.Here is the typical output characteristics of your map sensor.It has an output impedance of <50R.It can only Source 0.1mAAs you can see, if you use shunt scaling you will be sourcing 6mA.Tom..