Hi everyone please help. I'm using an LM358 op. amp.
1. R in =25k ohms ~ 65k ohms (flex sensor)
2. R f = 75k ohms
3. Vin = 1.6V
The problem is actually involved in the choice of Vcc.
so for the voltage supply of this circuit: I put 4.5V for Vcc, and ground the GND.
I was getting Vout = 2.81V, as I increase R in, Vout goes down a little bit (which makes sense).
But Vout should be at lease 3+V from my calculation.
Thus, I figured that my Vcc maybe is too small. Then I changed it to Vcc=9V. However, Vout is constant even though
I change R in. Vout stayed about 8V even though I didn't hook up V+ and V-.
Then I changed Vcc into 6V. Similar thing happened: Vout is constant again!!..
Obviously I do not know how to choose the right Vcc. Can someone please teach me how? And teach me how to read
this graph, please. *I'm a rookie in circuitry*
(Here is the op. amp. .....and some graphs from the datasheet..... and a similar graph about voltage range [Please teach me how to read this])