It is not recommended to attempt a build unless you have prior experience with 'making' or electronics assembly - assembly requires the use of solder paste and a hotplate. See Resources page for more details.
All devices are self-build, use surface-mount components for cost and compactness, and can be assembled at home using simple equipment - an inexpensive hot plate, a soldering iron, cutters and tweezers for component placing.
Build times are approximately 15 minutes for a pippyg, 20 minutes for a π•pistrelle 'batwalk', and 25 minutes for a full π•pistrelle.
Devices are best built in batches of 10, and the build cost reflects this - so '£20 build cost' means it will cost approximately £200 to build up 10 units. A single-unit build is simply not cost-effective.
π•pistrelle is a self-build heterodyne / time-expansion frequency-scanning bat detector : about £20 build cost
pippyg is a very compact, self-build bat / ultrasonic recorder : about £16 build cost
π•pistrelle 'batwalk' is very compact, self-build frequency-scanning bat detector : about £16 build cost
Common hardware features :
Processing by Raspberry Pi Pico - a low-power, high-performance, dual-core microcontroller
Knowles SPU0410LR5H-QB analog ultrasonic MEMS microphone and MicroChip MCP6022-E/SN dual op amp
Hardware high-pass filter
Powered by 3x AA cells (or 5V USB powerbank)
π•pistrelle in Bat Detector mode :
'Eyes to the skies' operation
Connect headphones or powered speaker to 3.5mm jack
Manual override and fine-tuning of heterodyne frequency via rotary controller ('classic bat detector' mode)
Switch between heterodyne and RTTX (Real-Time Time eXpansion) modes
pippyg (or π•pistrelle in Bat Recorder mode) :
Overnight / multi-night unattended field recording :
On-demand recordings when in detector mode :
π•pistrelle Bat Synthesizer mode (experimental feature) :
For educational use, volunteer training or detector / recorder testing
Simply connect a low-cost L010 ultrasound speaker to headphone output
Reproduces synthesized echolocation calls of multiple UK bat species
Programmed species to include :
Currently selected species indicated on LED display
Build cost for 10-off units (April 2023 - global semiconductor shortage makes these costs somewhat volatile) :
π•pistrelle : Approx. £20.00 per unit
π•pistrelle 'batwalk' : Approx. £16.00 per unit
pippyg : Approx £16.00 per unit
See RESOURCES page for PCB and component ordering details.
All devices are self-build, use surface-mount components for cost and compactness, and can be assembled at home using simple equipment - an inexpensive hot plate, a soldering iron, cutters and tweezers for component placing.
Build times are approximately 15 minutes for a pippyg, 20 minutes for a π•pistrelle 'batwalk', and 25 minutes for a full π•pistrelle.
Devices are best built in batches of 10, and the build cost reflects this - so '£20 build cost' means it will cost approximately £200 to build up 10 units. A single-unit build is simply not cost-effective.
π•pistrelle is a self-build heterodyne / time-expansion frequency-scanning bat detector : about £20 build cost
- Frequency-scanning heterodyne / real-time time-expansion Bat Detector
- Heterodyne bat calls / time-expanded audio / speech synthesis over 3.5mm headphone jack
- Bat Recorder - same features as pippyg
pippyg is a very compact, self-build bat / ultrasonic recorder : about £16 build cost
- Full-spectrum 384kHz / 16-bit Bat Recorder
- Programmable sleep / wake time
- Device listens to environment and only records when ultrasound is detected, maximises use of storage space on SD card
- Recordings device ID stamped, date / timestamped and geolocated
- Deployment app available for iOS to simplify multi-device deployment
- App allows setting of sleep / wake times, device ID, recording duration from 5.4s to 21.8s
- Between 3.5 and 7 days use from 2450mAh rechargeables, dependant on wake duration and bat activity
- Typically 5-6 days
- USB microphone function (384/16/mono)
π•pistrelle 'batwalk' is very compact, self-build frequency-scanning bat detector : about £16 build cost
- Frequency-scanning heterodyne / real-time time-expansion Bat Detector
- Heterodyne bat calls / time-expanded audio / speech synthesis over 3.5mm headphone jack
- Simplified user experience, just two buttons, ideal for handing out on guided bat walks
Common hardware features :
Processing by Raspberry Pi Pico - a low-power, high-performance, dual-core microcontroller
Knowles SPU0410LR5H-QB analog ultrasonic MEMS microphone and MicroChip MCP6022-E/SN dual op amp
Hardware high-pass filter
Powered by 3x AA cells (or 5V USB powerbank)
π•pistrelle in Bat Detector mode :
'Eyes to the skies' operation
- largely non-visual user interface via speech synthesis
- auto-frequency scanning, audio feedback on bat frequency detection
- allows user to track and ID bats visually while detecting
Connect headphones or powered speaker to 3.5mm jack
Manual override and fine-tuning of heterodyne frequency via rotary controller ('classic bat detector' mode)
Switch between heterodyne and RTTX (Real-Time Time eXpansion) modes
- On-board RAM limits duration of RTTX mode
- Most recent 170ms of sampled sound is played back, slowed down by a large factor
- Time Expansion factor preset to 16x - exactly 4 octaves lower than actual bat call
- If preferred this factor may be configured to 10x or 20x via configuration tool which patches firmware (requires a reflash of device)
pippyg (or π•pistrelle in Bat Recorder mode) :
Overnight / multi-night unattended field recording :
- Onboard Real-Time Clock (must be set by either pipistrelle app or AudioMothapp to allow recording) - download AudioMoth for iOS here and for Google Play here, download pipistrelle for iPhone and iPad here
- Overnight mode triggered by triple-click of right button, acknowledged by a recognisable flash pattern
- Overnight mode is immediately engaged on pippyg subsequent to setting Real-Time Clock
- Device is in low-power mode during daylight hours
- DAC is silenced
- Signal analysis is halted
- Spectrum LEDs go dark
- Ultra-slow flash pattern on single Pico LED (dim flash every 4 seconds) indicates sleep mode
- 'Wake on Bat' - during non-daylight hours, 5 second / 4MByte recordings to micro SD triggered by ultrasonic signal detection
- 3 fresh 2450mAh rechargeables typically last for 5 overnight sessions
- Battery life highly dependent on bat activity - writing to SD card is power-hungry
- Storage capacity limited by SD card size
- 8GB-16GB typically good for 2 nights' recording, may need 32 or 64GB if the night is particularly busy
On-demand recordings when in detector mode :
- On-demand single recording of 5 seconds (single click of right button)
- Or 1 minute via 12 consecutive recordings of 5 seconds each (double click of right button)
π•pistrelle Bat Synthesizer mode (experimental feature) :
For educational use, volunteer training or detector / recorder testing
Simply connect a low-cost L010 ultrasound speaker to headphone output
Reproduces synthesized echolocation calls of multiple UK bat species
Programmed species to include :
- Noctule
- Serotine
- UK Pipistrelles (Common, Nathusius' and Soprano)
- Daubenton's
- Brown Long-Eared
- Greater Horseshoe
Currently selected species indicated on LED display
Build cost for 10-off units (April 2023 - global semiconductor shortage makes these costs somewhat volatile) :
π•pistrelle : Approx. £20.00 per unit
π•pistrelle 'batwalk' : Approx. £16.00 per unit
pippyg : Approx £16.00 per unit
See RESOURCES page for PCB and component ordering details.
EXAMPLE RECORDINGS
4 or 5 species, captured in a 2 hour session in a rural garden in Wiltshire, April 2022
Recordings visualised and analysed using Kaleidoscope Free, from Wildlife Acoustics
Robin singing, Soprano Pipistrelle echolocating and communicating with social calls
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Common Pipistrelle echolocating
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Soprano Pipistrelle echolocating and social calls
Noctule echolocating
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Myotis species bat (or Serotine - who can tell?) echolocating
Robin singing plus Noctule echolocating
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Two recordings of Lesser Horseshoes from a field trip to Portugal, May 2022 - this shows that π•pistrelle is comfortable capturing data above 100kHz
Common Pipistrelle and Lesser Horseshoe, Portugal
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At least two Lesser Horseshoes, Portugal
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