Cheap easy to build target hit sensor, adjustable

[cking]

It took 9 versions to get to this point. First was tuning the roll-off point of the piezo circuit to hear bullet strikes not just thumps. Turns out bullet strikes fall in the 500HZ to 900HZ, got this info from a military research project on a bullet proof vest that could detect a hit and its location and upload that data, so a downed soldier could be found. Next was adjusting the sensitivity so that strikes to adjacent targets didn't give false outputs, and to adjust for distinct differences velocity makes on target strikes. Turns out low velocity strikes are very easy to detect, strikes over 2000 ft/sec are more diffcult to detect. The targets, and sensor is from LE targets, however the part nos of the piezo sensor is listed and can be bought for $0.50 and it will work on wooden stake uprights, and also if attached to steel.

In my case I built a programmable moving target with three different inputs that will run three different movement patterns. The purpose of the plastic start targets is so that you do not have to walk down range until want to score the moving targets hits. So I'll attach photo's and circuit diagrams. If you have any question email me at INFO@TECD.US

Edited March 17, 2013 by cking

[jmorris]

Can you share some more details of what the targets are and exactly how you implement your circuit along with what is the output reaction?

I did something along the same line, a number of years ago using car alarm shock sensors like this, http://www.ecarsecurity.com/Scytek-Shock-SENSOR-p/shocksensor.htm and a 12v deer feeder battery along with a light that would light up when the bullet impacted with the steel or cardboard target, depending on how sensitive you had them set.

[cking]

Below you will see an early version of the reuseable activation target. Near the bottom you'll see a silver 2"X4" handy box clamped to the target upright, the orginal circuit which can be seen on the circuit board photo's {blue section, now disabled} used a car style vibration sensor. It did not work with high speed ammo namely 223. So I then purchase the sensor and strap setup you see plugged into the 2X4 Handy box in the first post pics. This is just a piezo speaker. The target, stand, sensor all come from LE Targets found in the Plastic Target section. However I still needed a latching circuit to be able to turn things on. Maybe a relay, or my case the input of a "IORelay.com" Activator relay board. It is programmable and controls the DC motor controller on my moving target. So the circuit is a latch and the RC values control how long it stays latched, my values latch the circuit on a pulse for the Piezo at 5 seconds.

The real trick of the circuit is to tune it so that it doesn't react to low frequency's. So my research into piezo circuits I found that a resistor across the output forms a RC circuit. The circuit I copied used 10MOhm across the piezo which made its -3db rolloff point down around 33Hz. I wanted to move it up to around 1000Hz. I found a sample circuit tuned for 1000Hz for a car knock sensor it showed a 200K resistor. So then I researched flexible piezo strips and found some manufactor data on how to tune the piezo. So I built another version with a 6 position switch that selected a variety of values to find a good one. For this particular piezo speaker a 100K did what I wanted. However it was still too sensitive. Since the input to a cmos circuit is almost infinity a simply pot in line wouldn't work, so I built a voltage bridge between the 2.2 Mohm resistor in series with the input and series of resistor switchable as the schematic shows. This allows you to tune in so that sensor won't react to nearby target strikes. Although it doesn't seem right the slow speed ammo delivers more energy to the target then the rifle speed ammo does. So now I can adjust it so that 100yards or 30 yards shots don't activate another target as close as three feet. The sensor will work when strapped to a standard IPSC target wood upright, and will work until the target is too shot up.

I hope this explains it better, we are going to be filiming a match shortly I'll post the video.

[Flexmoney]

Neat.

I'm not sure of your intended use? It sounds like your are going to put it on one target, which when hit will trigger/activate another?

[jmorris]

Interesting idea. The shock sensor method certainly wouldn't work on my running man target. How do you manage the wires?

Oh, I think your plan is to make a hit on the post mounted target make the running man take off.?

I did something similar on my running man target using the shock sensor method detecting muzle blase from the first shot making the shooting port take off.

Video

Edited March 19, 2013 by jmorris

[cking]

Yep, this thing will get used in IPSC match's but my first test will be a long range rifle shoot. Not too long, you'll start at 100 yards shoot the first activator white, about 2 seconds later the mover will come out and cover a 44foot long run moving about 2.75mph, it will pause about 1 second behind cover and then return same distant and speed. You will move up to 66 yards, and shoot the yellow activator, this time it will be moving about 3mph, third run will be from 33 yards the green activator and it will be moving about 3.75mph. You then go forward remove your target put up an new and next shooter will start. I can set the speeds to anything I want, even start and stop, do a shuffle whatever I program it to do. Right now the controller is limited to three starts and three programs.

I got this idea from two episodes, first was a TV show where bunch of guys were hunting hogs in Texas, they got to about 75 yards from 10 to 15 pigs in field, they went prone on bipods three of them, after all the shooting and running was over only one dead pig. Next insite was my 87 year mother, who used to be a great off hand shot at moving targets. As girl she had to shoot the varmint out of the vegetable garden and fox's out of chicken coup. She said it got too easy shooting standing targets, so she would whistle first and take them on the run! She said it was tough shooting crows on the fly with the 22lr. When she saw IPSC shooting she said you guys are fast but can you hit a moving target, who going to stand still in real world! So I want to learn to track and fire. My Dad used to take her to county fairs and she always came back with the biggest stuffed animals, and the men she beat had to buy the beers.

[jmorris]

What are you using for a controller and speed control? Do you have to hard wire to all of your activators? If I understand correctly they all activate the same running target, are they all in close proximity to one another?

[Guest]

That moving port is awesome!

[jmorris]

It gets mixed reviews every time I use it. The last time I set it up was at MVSA regionals, more than a few thought it was the best idea since sliced bread, until they shot the stage.

It was the only thing I could come up with to force people to shoot on the move without people moving slower than a grandmother using a walker.

[cking]

I'm using a 90 volt Dc motor with Dart 130LC100 variable speed fast reversing dynamic brake control, which hooks to a SPDT switch for direction and stop, a 5K rheostat for speed. The control I'm using consists of 8 relays that can be programmed, So I Switch in and out different rheostat for multiple speeds, and two more relays control on and off and direction. The activators can be a simple switch closure or the shot sensors with latch circuit I described in first post. I use extension cords, to the activators. Everything is wired to run off plain three wire extension cords. That way if the get shot easy to replace or just splice together they only have 5Volts DC in them. I exploring using the Arduino wireless transmitter and recievers to a make a wireless shock detector run them off 9Volt battery. Just have to figure out how tune them to different frequencies so I can multiple sensors. The controller board can handle 8 inputs, and they can be set to react to different voltagle levels. Next version maybe wireless control via smart phone app.

Edited March 21, 2013 by cking

[jmorris]

Do you have more information on your control system? Sounds a lot more hightech that what I did.

My low buck one uses an old 12v cordless drill with a pully I machined with two different groves machined into it with different diameters, for two of the speeds. It also has the high/low switch for the gearbox. So it can go pretty slow or out run me.

The switching is all through mechanical limit switches with little set collars on the drive string to reverse/stop and it runs off of a 12v deer feeder battery.

Here is a video of it. The springs are to allow the drill brake and reverse switching to stop or reverse without it instantly hitting a hard stop and jerking.

The sound for some reason is slower than the video, so don't let that confuse you.

Edited March 21, 2013 by jmorris

[cking]

Yours is actually more complicated than mine as far as the motor controller part. Very nice

I used a http://www.dartcontr...ols/130-series/ Dc controller and a

Relay board http://www.controlan...OR_RELAY_SERIES

PC power supply . The purpose of the hit detector is I wanted automated self resetting, system that could be shot by rifle at any distance. Thus no steel.

Controller looks like something out of 50's science project.

[jmorris]

Looked at the relay boards and my first thought was that they could take the place of PLC's for a lot of things. Then I noticed they cost more than an entry level PLC, what made you choose the relay board?

I think the controller looks just fine and you get extra points making it from a no parking sign.

[cking]

When I looked at options that IORelay offered, number of relays, inputs, timers, rotations, the ability for upgrades. It seemed to provide the best value at the time, I'm considering later to upgrade to ARM processor to allow remote control via smart phone app. Most the PLC seemed limit on inputs without a lot of expansion. I'm sure there are lots of ways to do it. Big thing now is to see if shooting at a mover will be a hit with the shooters.

[jmorris]

I am sure it will be a hit or at least they will have fun trying to hit.

Do you have a link to the ARM processor? Does it require two phones for TX/RX?

[cking]

The Arduino uses various ARMS, and is the most popular but you've got to program in Linux, which I don't run. However the one I'm going to try for various reasons is the Microsoft supported one. http://research.microsoft.com/en-us/projects/gadgeteer/default.aspx

The logic is that I can use a Windows 8 machine and visual studio and program for Window8 tablet, phone, Gadget, all with same code. So I like to use WiFi from a phone or Tablet to run the Gadget.

You don't need two phones, the WiFi, works in both directions. Plus I'm trying to find out if Microsoft can stay relavent?

[jmorris]

I am getting an error when I click on your link. Using the WiFi from a cell phone what range do you have?

[cking]

http://research.microsoft.com/en-us/projects/gadgeteer/default.aspx

Here is the link to the latest version running. Unless you have a large internet pipe, click on the "HD" on the bottom right and you will get the low res version.

vimeo.com/63033017 password is mover

Edited April 2, 2013 by cking