Monday, 6 June 2016

New Android app for the Chrony F1

I recently bought a damaged Chrony F1 from a chap that had accidentally shot it, it never ceases to amaze me how companies can design and sell things that by design you shoot at and not put adequate protection in front of the delicate electronics.

The front casing had been hit and had a large dent in it that cracked the LCD and dented the crystal body, after a suggestion from John on the Facebook group "SHOOTING CHRONOGRAPHS U.K." I looked at Radio spares for a replacement and bought this screen 184-7715, it worked like a charm and after a bit of panel beating and a lick of Hammerite Dark Green paint it looked as good as new.
Before and after
One other thing I did before shooting at it was to buy some 10mm Acrylic sheet from eBay to make some clear shields to protect the display and the rear sensor block.

So when I started to use it I realised that I'd have to write down the readings and calculate the power myself later ..... s*d that! surely there's an app for that, if not I'll write one.

So I created an app to record the readings after each shot with the option to speak the value if you prefer and automatically calculate the power using the pellet weight you entered.

I also learned of a secondary Android market called Aptoide, to which I added some of my apps so they can be downloaded from one place.

The link to my store is there are other apps there as well, if you think it's worth it buy me a beer using the beer icon :-) and I might add more features.

I found the serial communication protocol for the Chrony F1 and when I get a chance I'm going to look into adding the Chrony remote functionality to my PC software and maybe make a Bluetooth interface so your phone can talk to it.

DIY Chronograph Accuracy testing

A few people have attempted the DIY chronograph build, at least one person improved the design and made an excellent version of his own.

I had a a question asked about the accuracy of the chronograph so I setup some testing over the weekend to try and determine if it was as accurate as others out there.

I don't have access to a calibrated air rifle or similar, if something like that even exists?? so I decided to use a good quality Oscilloscope (Picoscope automotive), which connected to my laptop via USB and do a comparison with the output from the Nano (in uSeconds).

For each measurement I took a screenshot of the waveform from the Oscilloscope and the serial data from the Nano, this shows the correlation between the actual time between the first beam being broken and the second.
There is also a google sheet showing the data that was recorded during the test here you can view the data and make your own decisions, for the last few shots I added a Chrony F1 about 3m away from the rifle to see what result that gave me.

The Chrony was set up in the garage with the lights off (florescent's) because the Chrony doesn't like florescent lights, instead I had a couple of cheap battery powered LED lights on top of the diffusers.

The conclusion is that although the data for each shot was different between the oscilloscope and Nano, over the 23 shots the average from both was exactly the same 10.57 ftLbs, this compares well to the 10.48 ftLbs when I had it checked at a shop a couple of years ago.

So I'm happy to use my DIY chrono with the understanding that there's always margin for variation and if I was getting 11.9 ftLbs that would be too close for comfort but 11.5 would give me 4% 'ish headroom.

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