I'm trying to build an indicator to show acceleration either to the left or right, using a bargraph of LEDs.
The Bargraph is fairly simple, using a LM3914 bargraph driver. This device wants to see an analog voltage input on one of its pins, and, as the voltage on this pin rises, so it switches on more of the LEDs.
A solid state accelerometer along the lines of an ADXL202 delivers, amongst other things, an absolute voltage for left-right and front-back acceleration. Looking at left right acceleration, if there is a 1g left acceleration on it, it will deliver 0v. A 1g right acceleration on it will deliver 8v. Zero g acceleration delivers mid-range voltage, i.e. 4v
What I need is a circuit that can take the linear, composite 0-8V accelerometer output, and deliver two voltages, as follows:
* one which runs 0-5v (say) ON ONE OUTPUT WIRE when the accelerometer output ranges between 4v and 0v (so accelerometer output =0v/circuit output=5V, accelerometer output =4v/circuit output=0V);
*the other that runs 0-5v (as before) ON A DIFFERENT OUTPUT WIRE when the accelerometer output ranges between 4v and 8v (so accelerometer output =4v/circuit output=0V, accelerometer output =8v/circuit output=5V);
This will allow me to drive two LM3914 bargraph drivers, one which will respond in a linear manner to 4-0V, the other which will also respond in a linear manner, but this time to 4-8V.
I'm at a loss....I guess I will need to bias the circuit with a Vcc/2 battery , I maight need to use comparitors, whatever. Any body got *any* ideas???
Cheers
Jim