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Homebrewing a Beast. (3)

 
28 Oct

At the end of the season in 2018, I sat down with the noise maker and started looking at it, wondering what I could do to improve the odds of getting a strike on the camera at any time of the day; in the design I had the forethought to separate the input side of it to the output, so ended up cutting the back end off of it, and attaching a triggering system to it as well as building a pass through so I could daisy chain the StrikeFinder on to it.

In all, I was quite happy with that, but instead of resting on the laurels, I ended up tweaking it so it had a defined roll alongside the StrikeFinder instead of having a lot of overlap and redundancy; and after one thing and another the rig has a detection range of at least 20km (may not sound much, but trust me, it’s enough) at 1/125 of a second, F:/16 at ISO 100 and as the light decreases the StrikeFinder takes over until that’s doing all the heavy lifting on the job and the active side of is just burning batteries.

I don’t like wasting batteries for nothing, and also with the design as was, it’s still a bit cumbersome and requires a lot of extra metal work bolted on to the tripod to hold it… And seriously, it’s a bit of overkill using an Arduino Nano to read one input pin and toggle 3 outputs.

Perfect territory for an ATtiny, though…

After sitting down again with some paper, and the coffee machine, all the stuff I’d developed (initially) on a Mega, dropped on to an Uno, then downsized to a Nano with a bit of squashing even further could fit on an ATtiny85, and bring some new tricks to the party.

Everything went in to the bin, only the detection head, the LM7805 (even though the one now is beefier in the mA department) and the 1N4148s remained and off the cycle started again. Out went the LM358, in came a TL072, resistors with better heat dissipation, slightly faster discharging caps, faster opto-isolators and a ~9v rechargeable power pack (with a USB charging circuit) that fits on a standard PP3 clip so I can run it on either the rechargeable cells or a standard lead/acid (in testing this design out, the rechargeable gives me about 12 hours before it shuts down, the lead/acid about 24 before it browns).

It works by reading the shift on the sensor head (that can be swapped out for different things, it’ll even take a microphone), amplifying that, then inverting the signal so it won’t drop below 0v (or more importantly go above 5v, so no cooked pins) and the processor is just reading what shift there is in the background. And after quite a bit of bashing around, it’s can also check if the batteries are up to the job, and with the ATtiny on it when it hits the swap over threshold with the StrikeFinder, it’ll turn itself over to hibernation mode so I can get on with watching the storm instead of watching the devices and more importantly, it’s small enough to not look out of place if it is attached to the top of my little mirrorless.

Down side to all this, is I’m just waiting for the PCB’s to arrive and get it constructed properly instead of on Perf-board; but I’m unsure if I’ll get chance to offer it up as on here this year as I’ll want to field kill (test, sorry, not kill) at least one before I’m satisfied it’s fit to unleash on the internets as it looks like I’m going to be having more surgery in the next two months and it’s the same sort of time as when we get the really pretty storms.

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