Friday, 19 April 2013

Chronograph - Part 4

The PCBs arrived, at last!

They look good and after assembling the parts, the design works, well I've not tested the 868MHz transceiver yet but the LCD display connected to the Arduino Mini Pro clone works fine and when connected to the sensor fitted to the gun all seems to be OK.

I used a scope to check the calibration of the value sent from the Arduino and it looks pretty good.
Front View - LCD and switches

Back View - the Mini Pro plugged in
Various part plugged in
The PCB is essentially a carrier board for the processor and the display and the 5V step-up converter.
Using an oscilloscope I fired some pellets with my pistol through the sensor tube and compared the timing reported by the Arduino, via serial to the PC, with the measurements taken with the scope.

Scope display showing time between pulses
As you will see from the picture the timings are not exactly the same but this could be due to rounding or the fact that the Arduino only has a 4uS resolution for the micros() function.  I will do some calculations to see what the effect on the final FPS or FPE values would be.

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