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Can anyone explain how one would convert one voltage range to another? I'm going to need to convert a range of -10 to +10 volts into a range of 0 to +5 volts. How would this be accomplished? Thanks!
Let me say something more. Inside of a torpedo there are gyroscopes. This gyroscope give -10 volts when the torpedo have 180 degrees of deviation to the west and 10 volts when the deviation is to the east. This signal is DC, so i need to change this range a range: 0 to 5 v DC . Thanks
You could use a dual RRO op-amp (eg. AD8676) and ICL7660 as follows (single 5V supply)
simulate this circuit – Schematic created using CircuitLab
This has 0~5V output for -10~10V in. If you have to handle the -10V and +10V cases with an ADC that has a nominal 5V reference, then you may wish to increase R1 slightly to cover saturation voltage of the op-amps, resistor tolerances and so on, perhaps 5-10%. Then just scale the number from the ADC digitally.
You can bypass R6 and R7 with 0.1uF if you're worried about noise.
One advantage of this circuit is that the gain is set by two resistors (input and output gain) so you can change the input range or output range independently. For example, to change to +/-5V input, change R1 to 100K. To change the output to 0~2.5V (say you got a better reference for your ADC but it's 2.50V), change R4 to 49.9K.
Three resistors and a 10V reference supply should do it: -
simulate this circuit – Schematic created using CircuitLab
When the input is +10V the voltage on R3 will be \$10 \cdot \dfrac{2k}{2k+2k}\$ = 5V
When the input is at -10V the voltage on R3 has to be zero.
Anywhere in between the input voltage maps linearly to the output.
There's two things you need to do to your signal to convert it to your required range.
First you need to scale the signal, then you need to offset it. Or, you can offset it then scale it, the end results are the same.
There's really two ways you can go about it - passive, or active.
Passive basically means using a voltage divider to scale the voltage, the AC coupling it with a capacitor, and adding a voltage divider to apply a DC offset.
For example:
simulate this circuit – Schematic created using CircuitLab
That would scale the voltage to +/- 2.361V, then add a 2.5V offset to it. The capacitor acts as a high-pass filter, so size it accordingly for your signal.
An active solution would involve an op-amp with a split-rail power supply (say +/- 15V) with a fractional gain and a 2.5V DC bais. My brain isn't functioning well enough right now to draw this circuit and calculate all the values - maybe someone else could do it for me ;)
