Last year, we produced the 'Box of Swifts' for attraction call playing and we deployed about 35 of them. The component costs were quite high, and it took a couple of hours of volunteer skilled soldering to assemble them, and, at the price we sold them, we ended up losing money, because of ullage and our decisions to donate them in situations with no budget.
Requirements of an attraction system
The requirements that the BoS satisfied were:
1. Simple installation: this was achieved by having a small 1.5 inch car tweeter on the end of a single piece of speaker cable. It is easy to attach to a nest-box 6 metres high, and there is no need to get mains power to it.
2. Simple operation: the BoS starts playing when the power is on and stops when it is off. There is no messing around with clamps on play buttons, nor having to restart the thing manually after a power failure.
3. To this we would add one other thing, that volume control is on the ground; for the BoS, this was not an issue because it was always set to maximum because of the limited power of its amplifier.
The biggest problem for us with the BoS was the component cost and the time taken to assemble them.
New Plan for 2013
So we have a new plan. We found an off the shelf SD card player, for about £12 that does everything the BoS does, except it doesn't have an amplifier. It is intended for use in an automated telephone answering system. So we then went searching for an amplifier, and found a good one for £9. Add in some bits of cable, a power supply and a speaker, the complete component cost comes to less than £40 per kit, with only one soldered connection to connect the speaker to the speaker cable.
The resulting kit does everything that the BoS does, but can deliver considerably more volume. The only disadvantage is that it doesn't come in a neat little black box.
|AfSAK assembly diagram|
Sourcing the components
Most of the components come from China, and apart from the SD card player, you can't buy things in singles. Amplifiers come in batches of 5, splitters in batches of 20, power supplies in batches of 5, speakers in 2's (but you may want to drive 2 speakers) and speaker cable in lengths of 100 metres. The only thing you need in addition is a 240 volt digital timer with battery back up (rough cost £8).
Depending upon whether you have 1 or 2 speakers (the amplifier has sockets for 2 speakers) and the volume setting, the AfSAK consumes between .3 and .5 amps at 12 volts. So on a fully charged 60 amp hour car battery it could run continuously for between 120 and 200 hours. So, if one rationed the playing to, say, 4 hours per day, using a 12 volt timer (rough cost £18), it could keep going for between 30 and 50 days. Add a solar panel and it could keep going indefinitely.
We are happy to let anyone have the sources of all the components,
If you have any comments or suggestions or want to know more contact us at firstname.lastname@example.org