How Can I Invert and Amplify the Output of a Rangefinder for Robotics?

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To invert and amplify the output of a rangefinder for robotics, a dual op-amp configuration is recommended, allowing for a single power supply. The goal is to convert an input voltage range of 5V to 0V into an output range of 0V to 12V, where closer objects produce lower voltages and farther objects yield higher voltages. The design may require a 2.5V reference for the op-amp's positive input, and while a single op-amp could work, using dual op-amps simplifies resistor matching. The speed of voltage change is not critical, and the motor's current requirements can be determined after selecting a suitable motor. This approach provides a solid foundation for achieving the desired motor control based on distance measurements.
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Hi folks.
I am ME/AE by profession but I love robotics and I tinker. I have pretty much zero EE experience so this question probably has a simple answer, I just don't know where to look.
Basically i will have a rangefinder with an analog output. I want to invert and multiply that output. So that farther readings will result in higher voltage to a motor. Also, the multiplication will be very small, like 5V to 12V.
Thanks.
 
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BigSteve said:
Hi folks.
I am ME/AE by profession but I love robotics and I tinker. I have pretty much zero EE experience so this question probably has a simple answer, I just don't know where to look.
Basically i will have a rangefinder with an analog output. I want to invert and multiply that output. So that farther readings will result in higher voltage to a motor. Also, the multiplication will be very small, like 5V to 12V.
Thanks.

Is multiply mean gain to you? Is the input 0 to +5V and you want the output 0 to -12V?

What speed is the voltage change? What is the driving requirement of the motor that the circuit has to drive? What I mean is how much current you need to drive the motor.

Usually all you need is a simple op-amp inverting configuration with a gain of -12/5 = -2.4 if that is what you meant but multiply.
 
Yeah, I probably didn't explain that quite right.
My sensor will output a voltage based on distance. For farther distances it will output a lower positive voltage, but I need a high (still positive) voltage to the motor. Close objects will out put a higher voltage, but I will want a lower(still positive) voltage to the motor. So a close object will approach 5v and the motor voltage should approach 0v, then a far object will approach 0v and the motor voltage will approach 12v (or whatever max motor voltage ends up being).
I don't know about motor current because I haven't purchased a motor yet. I was trying to get the design more concrete before I did. I was thinking of a 12vdc scooter motor or something similar.
Voltage change doesn't need to be anything particularly quick.
 
This is one way to do this:

25tx7ic.jpg


Input from 5V to 0V will give output of 0V to 12V. This is my understanding.

Use a dual op-amp. If you can find a rail to rail input and output op-amp, you need only a single +12V power supply. But if you have +/-15V supply, then any dual op-amp like TLO82 etc will work.

You can do it with a single op-amp, but the resistors are going to be harder to match and op-amps are cheap. I called for 5V reference driving the resistor divider just for convience. I need a +2.5V at the +ve input of the first op-amp, however which way you want to get it is up to you.
 
yungman said:
This is one way to do this:

25tx7ic.jpg


Input from 5V to 0V will give output of 0V to 12V. This is my understanding.

Use a dual op-amp. If you can find a rail to rail input and output op-amp, you need only a single +12V power supply. But if you have +/-15V supply, then any dual op-amp like TLO82 etc will work.

You can do it with a single op-amp, but the resistors are going to be harder to match and op-amps are cheap. I called for 5V reference driving the resistor divider just for convience. I need a +2.5V at the +ve input of the first op-amp, however which way you want to get it is up to you.
Thank you for the detailed answer. I probably could have never gotten that far on my own.
 
BigSteve said:
Thank you for the detailed answer. I probably could have never gotten that far on my own.

You are welcome. If you have further question, I'll be happy to help.
 
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