Mapping output voltage range of infrared rangefinders

Thread Starter


Joined Dec 7, 2013
Greetings all,

I have some Sharp infrared rangefinders. They return 0-5V. I am using them to control VCAs. I used to use vactrol based VCAs, but now I'm using Mitsubishi M5207L01 ICs. They work great, much more linear, but with the rangefinders, they're more sensitive than the vactrol based VCAs. I'm finding the Mitsubishis pass signal at a much greater distance before passing no signal. In other words, objects need to be much farther from the rangefinders for the VCAs to pass no audio signal. I'd like to be able to variably shorten the range, presumably by scaling the voltage. 5V would still be 5V so I don't want to scale down around ground with a voltage divider, but the other way around. So, for example, say I want to "map" 3V-5V from the rangefinder to 0V-5V going into the VCA, effectively shortening the sensitivity distance. Close range would still provide 5V, but as the object moves away, by the time the rangefinder output hits 3V, the VCA will see 0V. I could use a microcontroller and map voltage values to a PWM pin and use a D to A converter, but I think that would lose a lot of resolution if your mapping a narrow range of 8 bit values to the full 0-255 range. Is there a way to accomplish this with transistors or an op amp? Thanks for listening!