I am planning to design a VERY fast laser detector to detect bb bullet pass through. BTW the bullet speed is to high and I am not sure the sensor or MCU can detect it normally. I am thinking if I add a positive 555 trigger to extend the very short 5v signal when bullet is passing.
DO you guys think if 7555 or ALD555 can handle a 43us or shorter pulse?


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I what sensor or MCU would that be? How does this 43us pulse relate to the obects speed?

And welcome to the forums.

 

I am planning to design a VERY fast laser detector to detect bb bullet pass through. BTW the bullet speed is to high and I am not sure the sensor or MCU can detect it normally. I am thinking if I add a positive 555 trigger to extend the very short 5v signal when bullet is passing.
DO you guys think if 7555 or ALD555 can handle a 43us or shorter pulse?


Moderator's Note:
Please don't hijack other member's thread, now you have your own.
This thread was split from --
555 Timer with positive pulse trigger
https://forum.allaboutcircuits.com/...h-positive-pulse-trigger.128580/#post-1121073

Check the DATASHEET of the chips of interest to find the minimum trigger pulse.

What bullet speed (estimate? 1000 m/second)?

 

Are you trying to measure the BB's speed or just detect it? They have done the speed measurement since before the advent of micro or MCU's, did it analog. The speed measurement is called a 'chronograph'. It takes two screens or sensors, not one. Google DIY chronograph. There are many circuits, and they are capable of measuring real bullets from a firearm, much faster than a BB gun.

 

I am planning to design a VERY fast laser detector to detect bb bullet pass through. BTW the bullet speed is to high and I am not sure the sensor or MCU can detect it normally. I am thinking if I add a positive 555 trigger to extend the very short 5v signal when bullet is passing.
DO you guys think if 7555 or ALD555 can handle a 43us or shorter pulse?

It sounds like you want to build a chronograph to measure the velocity of a BB or .177 Caliber (0.5mm) pellet.
Generally you would use a start and a stop sensor with a clock and timer. Velocity = Distance / Time. When the projectile breaks or triggers the Start Sensor it opens a Gate allowing pulses to start being counted. When the projectile breaks or triggers the Stop Sensor the pulses (Clock) stop being counted and since Frequency = 1 / Time and Time = 1 / Frequency the elapsed time is noted and divided by the distance the projectile traveled. For example here in the US a good BB Rifle will fire a BB at about 900 FPS (Feet Per Second) so if I place my sensors exactly Two feet apart my time should be 2.222 mSec. or 2.0 / .00222 = 900.9 FPS. Now if we want Metric we can place the sensors 1.0 Meter apart and the same applies. 1 Meter / 0.003645 Second = 274.32 meters per second.

The sensors are frequently refereed to as Sky Screens and look like the below image with actually 3 Sky Screens pictured.


The sensor spacing is critical. I have no idea how you plan to incorporate anything LASER into measuring projectile velocity. The pictured screens use a magnifier ground piece of plastic in the base with an optical transistor as the sensor. They use a Motorola MRD 3056 for daylight sensitivity. While the MRD 3056 is no longer made there are similar optical transistors and diodes out there. The above setup uning 25 year old parts and technology can measure bullet velocities exceeding 4,000 FPS.

I have seen some very new designs which use doppler RADAR but have never seen a LASER system used. BB and Pellet rifles are actually relatively slow actually. For example 304.8 Meters per second is not very fast.

Ron

 

I used to use just two thin wires in the path of the bullet. One would trigger a commercial timer to start, the other would trigger it to stop.

Needs the gun to be clamped in a fixed position, of course.

.... but that was a very long time ago...

Why complicate things with lasers?

 

I used to use just two thin wires in the path of the bullet. One would trigger a commercial timer to start, the other would trigger it to stop.

Needs the gun to be clamped in a fixed position, of course.

.... but that was a very long time ago...

Why complicate things with lasers?

The early ballistic sensors were pretty much a piece of cardboard with a single wire looped back and forth with about 0.1 inch spacing.A bullet or projectile would break the wire and that would start the timer and a second wire would break stopping the timer. That gave the elapsed time the bullet took to travel a given distance. The screens were then repaired and used until they were no longer serviceable or repairable. Then came the use of optical sensors which work well till we manage to shoot one.

Ron

 

The real early ones were two discs mounted a known distance apart turning at a known RPM. Shoot through the discs. The angle between the holes was then calculated and that was calculated into bullet speed.

Then there was the 'ballistic pendulum' to measure the energy of the bullet. All done with no micro controller.

 

The real early ones were two discs mounted a known distance apart turning at a known RPM. Shoot through the discs. The angle between the holes was then calculated and that was calculated into bullet speed.

Then there was the 'ballistic pendulum' to measure the energy of the bullet. All done with no micro controller.

My Oehler 35P was developed during the late 80s. Uses an 8 Mhz clock and when it was developed it was thee ballistic standard. No micro-controller but I would guess all the new units use a micro. It even has a little printer which prints on I think 2 1/4" register paper. It will average groups of shots It will print the Max, Min, Mean, and Extreme Velocity Spread. All with discrete components which for its time was pretty cool. Runs off a single 9 volt battery and I get quite a bit out of a single battery. One of the best gifts Kathleen ever gave me. Bummer was it was Christmas and I had to wait till spring to try it out.

One of the newest, latest and greatest uses doppler RADAR. Called LabRadar it took time for release and I hear they still have bugs. It is among the most expensive out there at $559 for the basic unit. Nice feature is it can give you velocity at 100 yards down range. The average typical chronograph today runs about $100. I also would venture most are uC based.

Yeah, the evolution of so many of the ballistic units is pretty cool stuff. Things like chamber pressure, bullet energy, velocity and other measurements have always fascinated me. I always figured if I ordered a ballistic pressure sensor someone above my pay grade might question it.

Ron

 

Actuall what I am doing is making a 32x32 laser matrix to sense the coordinate of the object pass which does not need to calculate its speed. But for a 140m/s object does anyone have idea to use must simple way to detect such SHORT period？ I will use 74hc4067 16 channel de-mux to gather 1/4 data to mcu. Sensor I try china made IS0103. But in experiment it is too slow to detect by shooting with a 70m/s airsoft but successed with throw by hand.

 

Could you upload the schematic or block diagram, please compress it to the clear resolution as 800x600 or 1024x768 jpg or gif file.

 

I will do it tonight

 

Your first post led me to think you wanted to build a ballistic chronograph. Now I do not have a clue what you are after. Since you mention "matrix" maybe you want to know the exact spot where a BB strikes on a grid square? As mentioned please try and present a drawing or similar. Obviously a ballistic chronograph was a poor guess on my part.

Ron

 

Obviously a ballistic chronograph was a poor guess on my part.

That was my guess too.

 

That was my guess too.

Oh well, the guess meter missed a few. Hey, we need to get dinner again soon. Like during the summer. Gopher and maybe Spinaker this time.

Ron

 

Here is a simple schematic. I hope you guys understand what I mean. Thanks.

https://drive.google.com/file/d/0B_Dhuks6Jp6LTWlGYnM1bmNwcEU/view?usp=drivesdk

https://drive.google.com/file/d/0B_Dhuks6Jp6LNkQ4OWd0LUdGRXc/view?usp=drivesdk

 

Please upload the pictures to the forum next time.

 

Thank you Scott.

As you can see I made a experimental case for this project. There are 16 x IS0103 on the PCB. One the other side there are also 16 x of lasers spotted on sensors. When something pass through the device it blocks laser beam to and the sensor output HIGH to 74HC4067. These is 1 set of MUX circuit and I need totallly 4 later.

 

Did you measure the IS0103, if not then you should measure it for sure when it receive the light, does it can provide a low level to the input of 74HC4067, if it doesn't then you have to add a 10K to the input of 74HC4067 to pull low.

And the picture you shown didn't like any kind of 32x32 dot-matrix, how's it goes?

 

Maybe you can draw a block diagram to show how you arrange the laser light and the laser sensor.