The output is DC, depends on the batteries voltage. But it is usually
6.4v. Well I tried the circuit with the zener diode. I get 5v at the output. But as soon as I place the microcontroller input pin, that voltage just sink to 1.4v and the controller do not read it. If I put the input pin directly on the output of the 7805 regulator (5v) then it reads it as 5v. I used a 150ohm resistor afterwards, that did not work. why is that ?
It seems that your microcontroller input is a fairly low resistance to ground - seems strange to me, since the 8052s I use have weak pull-ups, and a plain CMOS input would be high impedance in either direction - however, I suppose anything is possible.
To solve the problem, you will need a lower series resistance than the
10K that Randy suggested to provide enough current to pull the microcontroller input high.Also, are you sure that the microcontroller pin is programmed as an input? Depending on the processor, it may be possible to use a pin as an input even if it is set to be an output, and is outputting a low.
As an experiment: put the 10k resistor back in, and connect the input end to the +5 supply for the micro.
Measure the voltage with and without the zener in the circuit.
If the voltage stays at 1.4v, you've probably got:
a) your input pin is actually programmed as an output pin b) your input pin is actually programmed as something other than a digital input (analog, clock in, etc). c) a fried input to your micro.
A working digital input is said to be 'tied high' with a 10k resistor; the voltage should be near +5. If your voltage is 1.4 without the zener, the problem is in the micro.
Can you hook a 10k to another input pin on the device to compare?
crap, my pin was set to output... thanks
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