The first was a 7 segment LED display, these come in different shapes and sizes and could still be quite portable when added to the sensor.
The backpack details can be found here
I bought one of the displays from Ebay and stuck it on the side of the sensor tube then added the code to the sketch to send the value for feet/second to the display after sending the uSecond value to the PC.
This would allow the chronograph to be used in conjunction with the PC via the USB lead or remotely with a battery pack, just reading the Feet/Second value.
Showing the feet/Second would require a lookup table to get the power from the velocity and the weight of the pellet, I suppose with a couple of small buttons added you could enter the pellet weight after power-up but before the first shot it could then alternate between the FPS and the power reading every 10 seconds?.
I then tried it out using my CP Sport Co2 pistol and it looks good.
I then used some of that PVC heatshrink, normally used for battery packs, it's really good as it shrinks using a hair drier and is quite hard when cool but can easily be removed with a pair of scissors or a knife.
Ideally I would have liked to use some clear but I only have red or white but surprisingly the LED shows through the PVC quite well.
Things to think about: -
- Writing the shot data to EEPROM for later retrieval
- Adding buttons to allow pellet weight to entered
- put together a battery pack for remote usage
- Think about power saving schemes
- Display battery power on power-up?
- Who knows?
Nano Sketch can be downloaded here you can use it with or without a PC, if you want the PC application let me know in the comments, it's still very BETA.
Fritzing file here.
More about the second option I found later.....