The Pipistrelle can work in heterodyne mode, and also in time-expanding mode. In this latter mode, it slows down the signal to put the ultrasonic signals received from the microphone into the audio range. This way, you can hear the bat calls as they actually sound, which is completely unlike the sounds from heterodyne bat detectors.
This ability to use both ways of listening to bats makes the Pipistrelle a great product for listening to bats, and one that doesn’t really have an equivalent at even close to the price range (about £20 per device if you build a few).
While the product is great to use, it doesn’t come as a product. In fact, it doesn’t come as anything – it’s just a design and bill of materials. You have to get the PCBs manufactured and source the parts yourself. The board designs aren’t available, but are uploaded to PCBWay, so you can get them manufactured from there, but you can’t use a different fabricator.
The parts are mostly surface-mount, and it’s recommended that you get a solder stencil and solder it with a hotplate. We didn’t do this because the cost of the solder stencil would nearly have doubled the cost of our single device. If you’re soldering more, then the single stencil can be used multiple times, and it’s probably a very sensible investment.
Most of the board is fairly straightforward to hand-solder. The only exceptions are the SD card slot which needs a pointy soldering iron and a steady hand, and the microphone, which is all but impossible to solder with an iron. We placed solder paste by hand and used a hotplate. We were successful, but it’s a risky solder because if any paste gets into the microphone hole, it’ll stop working. It would have been an easier and quicker build with a stencil, but that comes at a cost.
At this point, we should mention that there’s been a new version since we tested it out, and the version we used had the microphone on a separate board, so it was easy to solder separately. The new version has the microphone on the main board, so you’ll have to solder it first if you want to go down the hand-assembly route.
The biggest problem we had was the lack of documentation. It was a bit tricky to work out how everything went together and how to get it working. The situation has improved since then, but do have a look through before you start, and make sure you’re happy with the level of documentation before committing to a build.
This is a really interesting product, and it’s a hard one to review, because should we review it based on the finished product or the build? It’s fun to play with, and the equivalent commercial product is expensive. However, this doesn’t mean it’s a toy. It can help identify bats and record their calls for later playback – it’s certainly a useful device for anyone interested in flying mammals. However, it’s a tricky build, and debugging problems is difficult. Unless you’re experienced with more complex PCB construction, it’s going to be a challenging build.
Whether or not ‘challenging’ is a good thing or not depends on what you like. For some people, this will be a fun way to push their skills. For others, it’ll be frustrating and annoying. Hopefully, you know which camp you fall into.
Because of the cost structure of the parts, it only really becomes cost-effective once you’re making a small batch (around five or ten). That’s not to say you can’t make one – we did – but to avoid the cost of the stencil, the soldering is a bit tricky.
There are certainly people for whom the Pipistrelle is a great product, but it’s not without limitations. Most of these are down to the hand assembly and, in small-batch manufacture (such as using pick-and-place machines rather than hand assembly), would go away.
A powerful ultrasonic detector, but difficult to make.