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  • pipistrelle
Picture - About pipistrelle
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
  • 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
Speech synthesiser for frequency feedback
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
  1. ​​DAC is silenced
  2. Signal analysis is halted
  3. Spectrum LEDs go dark
  4. 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

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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
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Noctule echolocating
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Myotis species bat (or Serotine - who can tell?) echolocating
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Robin singing plus Noctule echolocating

​Two recordings of Lesser Horseshoes from a field trip to Portugal, May 2022 - this shows that π•pistrelle is comfortable capturing data above 100kHz
​
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Common Pipistrelle and Lesser Horseshoe, Portugal
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At least two Lesser Horseshoes, Portugal
                                                                                        
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