Bat detector frequency counter

This text describes preliminary plans for a frequency meter for a bat detector. It measures the frequency of the local oscillator in a heterodyne type bat detector. This provides a valuable tool to help identifying the bat. The frequency is displayed on four 7-segment LED displays in xxx. x kHz format, with an estimated accuracy of better than 0. 5%
Bat detector frequency counter - schematic

. Power consumption is low at approximately 7 mA at 6V. This counter can be very useful in the determination of the bat call frequency. Just tune your heterodyne bat detector to the position where the bat call sounds lowest and read the frequency from the display. It also removes the need for a calibrated frequency scale, since you can simply read the frequency and adjust for the desired frequency. So there`s no need anymore for an ultra-stable oscillator. Using LEDs for the display has the advantage that you can read the frequency when it is dark. This also means that the light level from the LEDs can be quite low and little supply current is used. The frequency counter can be built using the popular PIC16C84 or PIC16F84 microcontrollers from Microchip. These are quite cheap to buy; development tools are freely downloadable and a simple programmer can be built out of about 10 electrical components. I don`t have a schematic of the counter yet, but it is very similar to the schematic on the right. (link to original schematic) Significant differences between this schematic and the schematic for my bat counter are: Forget about the transistors and the resistor connected to the transistors. They are not needed if you draw only a little current from the PIC. Connect RA0-RA3 directly to the respective common cathode connections of the LEDs. The resistor from Vdd to the /MCLR input is 10 kohm. The circuit expects a full-voltage...

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