I have a circuit composed of a PIC operating at 5V, a 2 stages OP-AMP(LM833) and a comparator (LM393) both operating at 9V. both are driven by 7805 and 7809 respectively.
When I measure the current at the main input of my circuit (12V DC adapter) I get 23.4mA.
When I measure the current at the output of 7809 I get 4.8mA
When I measure the current at the output of 7805 I get 5.27mA
I conclude that my circuit excluding the regulators consumes 10.07mA (4.8 + 5.27)
Since I get 23.4mA at the main input and my circuit consumes 10.07mA is it right to say that my two regulators are consuming 13.33mA (23.4 - 10.07) ?
If I use only the 9 volts regulator with resistors as voltage divider to supply 5 volts to the PIC, will the 5 volts be regulated or safe enough for the PIC ?
The PIC is driving a Piezo, a transducer at 40KHz and 2 LEDs.
Note that the LEDs and piezo were not connected when I took my measurements above.
If I use only the 9 volts regulator with resistors as voltage divider to supply 5 volts to the PIC, will the 5 volts be regulated or safe enough for the PIC ?
Len, I got your response after I wrote my message, sorry for the confusion.
I tried driving the input of the 7805 from the output of 7809 and the current went down by 0.1mA.
Mike, I am not really worried about the cost, I am trying to improve to make my circuit battery operated.
This being said if I use resistors as divider for the 5V would that be safe for the PIC?
If so, based on my browsing my circuit would last about 50 hours on a 9V battery?
Sorry,
I take out what I said, I see no way to make my circuit battery operated because although the PIC can sleep, the op-amp and comparator can't and so it is a device that will have to be on at least 50% of it full time.
I will just try to find a better way to supply 5V and 9V, maybe a regulator that can supply dual outputs to make the circuit it cleaner (in term of smaller)
For higher efficiency you could use a switching regulator such as the Black Regulator. The disadvantage is that the switching noise can affect the analog circuits so you may need extra filtering for the 9V.