Bat Detector
This is the first project that I've attempted to document for construction on a breadboard. The documentation tools available aren't brilliant yet, but they are getting better so I thought it was worth giving it a try.
If you haven't yet read Breadboard initial setup, I would go do that now.
At the end of this page, you will find artwork and other files that you can download.
So, first up is the parts list. If you are in the UK, you can get
Qty Part Number Description Rapid Part Number
1 C1 22nF Capacitor 08-1065
2 C2, C6 10uF 25v electrolytic capacitor 11-0220
2 C3, C10 220uF 35v electrolytic capacitor 11-0260
1 C4 47nF 08-0237
4 C5, C7, C8, C9 100nF 08-0235
1 R1 150 ohms (Pack of 100) 62-0350
3 R2, R5, R6 10 ohms (Pack of 100) 62-0326
1 R3 220 ohms (Pack of 100) 62-0354
1 R4 2.2K (Pack of 100) 62-0378
1 VR1 5K preset 67-0410
3 IC1, IC2, IC4 LM386 82-0266
1 IC3 CD4020
1 RX1 40KHz ultrasonic receiver 35-0180
1 LS1 8 ohm loudspeaker 35-0128
Additional items:
9v battery
battery clip 18-0080
Breadboard 840 Tie-Point 34-0655
The CD4020 IC is no longer stocked by Rapid Electronics but you will find them for sale with other suppliers or even on Ebay (which may be a good option for a single IC since you typically don't get stung for high postage charges because of minimum order values).
If you haven't yet read Breadboard initial setup, I would go do that now.
At the end of this page, you will find artwork and other files that you can download.
So, first up is the parts list. If you are in the UK, you can get
Qty Part Number Description Rapid Part Number
1 C1 22nF Capacitor 08-1065
2 C2, C6 10uF 25v electrolytic capacitor 11-0220
2 C3, C10 220uF 35v electrolytic capacitor 11-0260
1 C4 47nF 08-0237
4 C5, C7, C8, C9 100nF 08-0235
1 R1 150 ohms (Pack of 100) 62-0350
3 R2, R5, R6 10 ohms (Pack of 100) 62-0326
1 R3 220 ohms (Pack of 100) 62-0354
1 R4 2.2K (Pack of 100) 62-0378
1 VR1 5K preset 67-0410
3 IC1, IC2, IC4 LM386 82-0266
1 IC3 CD4020
1 RX1 40KHz ultrasonic receiver 35-0180
1 LS1 8 ohm loudspeaker 35-0128
Additional items:
9v battery
battery clip 18-0080
Breadboard 840 Tie-Point 34-0655
The CD4020 IC is no longer stocked by Rapid Electronics but you will find them for sale with other suppliers or even on Ebay (which may be a good option for a single IC since you typically don't get stung for high postage charges because of minimum order values).
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This is a diptrace format file of the circuit diagram. A free version of diptrace is available here
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This is a JPG version of the circuit diagram
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This is the breadboard layout source file. You can download free Fritzing software from here
You will notice that the source file contents are slightly different from the picture I've included. This is due to some limitations in the Fritzing software so I can to do a bit of "hacking" of the final image. | ||
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This is a high-resolution version of the breadboard layout after I've manipulated the image slightly.
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Circuit description
The circuit is operated from a 9v battery so make sure that any electrolytic capacitors have a working voltage of at least 10v;16v is better.
Mounting the ultrasonic transducer will probably require you to solder extension wires to the two pins. Likewise with the loudspeaker.
Mounting the ultrasonic transducer will probably require you to solder extension wires to the two pins. Likewise with the loudspeaker.
Bats use ultrasonic frequencies to echo locate and the frequencies vary from species to species. The 40KHz transducer used in this design is reasonably sensitive to the frequencies that most UK bats transmit. That said, the output level from the bats is quite low so to detect them quite a high gain (amplification) is required, so a high gain audio amplifier consisting of ICs 1 & 2 boosts the weak output signal from the transducer.
The first amplifier IC is configured to give a gain of around 20, with the second IC providing a gain of around 10; this gives a combined gain of around 200.
The bats transmit ultrasonic frequencies around 40 KHz, but that's too high a frequency for us humans to hear.
IC3 counts the number of pulses that are received and for every 64th pulse, a pulse is sent to the main audio amplifier; IC4 and this has the affect of dividing down the input frequency.
The audio amplifier IC drives the loudspeaker allowing you to hear an approximation of the ultrasonic sounds the bats are generating.
The first amplifier IC is configured to give a gain of around 20, with the second IC providing a gain of around 10; this gives a combined gain of around 200.
The bats transmit ultrasonic frequencies around 40 KHz, but that's too high a frequency for us humans to hear.
IC3 counts the number of pulses that are received and for every 64th pulse, a pulse is sent to the main audio amplifier; IC4 and this has the affect of dividing down the input frequency.
The audio amplifier IC drives the loudspeaker allowing you to hear an approximation of the ultrasonic sounds the bats are generating.
Breadboard construction
Construction should be straight forward enough. Try and keep link wires as short as possible, and make sure that bare component leads don't touch things they shouldn't. Check the polarity of the electrolytic capacitors; the lead with the vertical stripe is usually the negative.
You may also notice a few slight differences between the photograph of my version of the project, and the breadboard layout image. I made these changes purely to make documenting the breadboard layout clearer for the reader. Electrically they are the same.
Operation and in use
I've had pretty good results with this project, but it requires patience in use. The bats near me have a sixth sense and don't seem to like performing too often when I'm monitoring them. The circuit is also pretty good at picking up other "stuff" going on in the neighbourhood.
If you turn the level of the audio amplifier up via VR1 too high, you can end up with the project producing oscillations or other distortions. You may also find the project picking up radio broadcasts or other local interference from florescent lights or other RF noisy sources.
As a test, try jingling a bunch of keys in front of the transducer and listening to the sounds the project produces.
If you turn the level of the audio amplifier up via VR1 too high, you can end up with the project producing oscillations or other distortions. You may also find the project picking up radio broadcasts or other local interference from florescent lights or other RF noisy sources.
As a test, try jingling a bunch of keys in front of the transducer and listening to the sounds the project produces.