My Homemade Chronographs
Posted: Wed May 19, 2010 2:18 am
Audio Chronograph:
Big thanks to Technician1002 for his help.
For this I used a dynamic Akai ADM-20 microphone plugged in to my Dell laptop and I used Audacity to record the audio and find out the velocity.
Originally I used a condensor microphone which was no good. To get good audio, you really need to use a dynamic microphone or have some sort of mixer to change the recording settings and bypass the computer soundcard settings.
I set my targets 5 meters away from the muzzle and placed the microphone in the middle at 2.5 meters. I also faced the microphone away from the muzzle and toward the target to get better recordings. This method of chronographing isn't very difficult though it can be harder to setup as you need a target with which the projectile can be heard impacting or a projectile that will do this. You also need to be at a fixed distance and be wary of your surroundings to avoid echo or bad accoustics.
Phototransistor Chronograph:
Big thanks to Jimmy101 for his help.
I tried this method mainly because I thought it would be interesting and a fun project, it was. For this you'll need two phototransistors. I picked the only clear phototransistors available at my local JayCar store. You'll also need something to mount these to that shields most of the phototransistor from light and keeps them at a fixed distance apart. Jimmy101's website page above was very helpful, so be sure to check it out. My phototransistors are mounted in wood with only the top of them open to the light. They are then mounted in a thin metal rail which is fixed to a flat piece of wood to stop it from being blown away. My circuit is wired in parallel with no resistors and connected to a stereo channel 3.5mm audio plug. I also used Audacity to record with.
I found this method slightly better for my purposes as I am limited in shooting space and this mehtod only requires that the projectile leaves the barrel, no target is needed, only something to stop the projectile. It will also give you a higher velocity reading because you can measure the muzzle velocity instead of the velocity from a distance. I have a very basic knowledge of electronics, yet I was able to construct this so don't be put off if it sounds difficult.
This chronograph is also very cheap to construct ($5) and easy to build. Only problems I've had with it is the lighting, it wont work under fluorescent lights as they turn on and off rapidly which will interfere with the signal. Some people use LEDs to enhance the spike generated when the phototransistor is blocked from light, I found this a bit difficult so instead I just use a cheap 500w flood lamp which does the job nicely. Though the chronograph will work great (large, clear spikes) outside as long as it isn't too dark or cloudy. I found it even worked in overcast weather fine.
Anyway, here are some results of these chronographs compiled in to a video along with some photos below:
[youtube][/youtube]
Big thanks to Technician1002 for his help.
For this I used a dynamic Akai ADM-20 microphone plugged in to my Dell laptop and I used Audacity to record the audio and find out the velocity.
Originally I used a condensor microphone which was no good. To get good audio, you really need to use a dynamic microphone or have some sort of mixer to change the recording settings and bypass the computer soundcard settings.
I set my targets 5 meters away from the muzzle and placed the microphone in the middle at 2.5 meters. I also faced the microphone away from the muzzle and toward the target to get better recordings. This method of chronographing isn't very difficult though it can be harder to setup as you need a target with which the projectile can be heard impacting or a projectile that will do this. You also need to be at a fixed distance and be wary of your surroundings to avoid echo or bad accoustics.
Phototransistor Chronograph:
Big thanks to Jimmy101 for his help.
I tried this method mainly because I thought it would be interesting and a fun project, it was. For this you'll need two phototransistors. I picked the only clear phototransistors available at my local JayCar store. You'll also need something to mount these to that shields most of the phototransistor from light and keeps them at a fixed distance apart. Jimmy101's website page above was very helpful, so be sure to check it out. My phototransistors are mounted in wood with only the top of them open to the light. They are then mounted in a thin metal rail which is fixed to a flat piece of wood to stop it from being blown away. My circuit is wired in parallel with no resistors and connected to a stereo channel 3.5mm audio plug. I also used Audacity to record with.
I found this method slightly better for my purposes as I am limited in shooting space and this mehtod only requires that the projectile leaves the barrel, no target is needed, only something to stop the projectile. It will also give you a higher velocity reading because you can measure the muzzle velocity instead of the velocity from a distance. I have a very basic knowledge of electronics, yet I was able to construct this so don't be put off if it sounds difficult.
This chronograph is also very cheap to construct ($5) and easy to build. Only problems I've had with it is the lighting, it wont work under fluorescent lights as they turn on and off rapidly which will interfere with the signal. Some people use LEDs to enhance the spike generated when the phototransistor is blocked from light, I found this a bit difficult so instead I just use a cheap 500w flood lamp which does the job nicely. Though the chronograph will work great (large, clear spikes) outside as long as it isn't too dark or cloudy. I found it even worked in overcast weather fine.
Anyway, here are some results of these chronographs compiled in to a video along with some photos below:
[youtube][/youtube]
