Here ist the latest project, a cooperation with Tony Messina. We developed a bat-receiver (actually a “bat scanner”) where a microprocessor is not only being used for the frequency display, it also takes over the control of the board, implementing some interesting features. Software and board designed have already been finished. Tony is using a different case and has made his own assembly instructions.
The analog part of the receiver is still NE612-based, but the internal signal for the mixer is being produced by a PIC-processor. So the final receiver does not need any kind of adjustment (because of the tolerances of some components the analog receivers all had slightly different min/max frequencies). Currently the range is 10-80 kHz, including birds, frogs and insects in the 10-20 kHz range (step size is 2 kHz).
A two-digit display shows the frequency in kHz. Instead of a frequency dial this receiver now has three small pushbuttons “up”, “down” and “mode” for selecting the frequency, starting the scan mode and entering the configuration menu.
This is the menu structure:
- scan: stop, resume, continous
- calls: off/on (display flickers on incoming bat-calls)
- powersave: off/on (display off after 10s)
- lower scan limit: 10-70 kHz (+/- 10 kHz)
- upper scan limit: 20-80 kHz (+/- 10 kHz)
The configuration is being stored in EEPROM and restored on the next power-up.
There may be a slightly different version of the software for recording-boxes (bat receiver with VOX-operated tape recorder). This version will probably scan in 5 kHz steps, output timer beeps every 15 or 30 minutes and output of the current recording frequency when bat-calls have been detected. The timer beeps will help to find the time of most activity and the frequency markers will at least give some hints about the possible bat species. Currently this software version is just being planned, but the hardware supports it and if there is demand, I will program it.
… some hours later
Update: A small batch of professionally manufactured boards is ready now and we have been working with the first receivers in the field. The costs for a complete kit with case are about 68 Euro.
short video of the receiver in action
A nice review can be found on www.durhambats.org.uk.
seen from above: Tony (right) and Frank (left) working on a completely different project