Welcome to our site!

Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.

  • Welcome to our site! Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.

Impact sensor ideas

Status
Not open for further replies.

turbid

New Member
I'm in the early process of trying to make an impact sensor for steel targets used in long range shooting competition.

At the moment I'm messing with what I hope is the easy route by using an Automotive Impact sensor. In fact it's This One. It not too expensive, and it's a simple mechanical sensor. That operates by having a "V" shaped cup mounted on a spring with a post that you can adjust in or out for sensitivity.

The way it works is that it has a + and a - line in and a sensor line out. The sensor line simply grounds the circuit when an impact is felt.

What I'm trying to figure out is the best way to make use of this information.

What I get is a very quick jump to the voltage I have applied. It's so quick that it doesn't allways show up on my multimeter, but if I hook it up to my digital O-Scope set for TTL input it picks it up every time.

So what would be your ideas on making use of this information. All I really want to do with it is to operate a relay that activates a camera flash.

As I said. I'm at the very beginning of working this out, so any and all ideas will be appreciated, including different sensor ideas. I have also considered using Piezo Vibration Sensor like THIS, but I think that might really complicate things.

Thanks for any ideas.
 

DSGarcia

New Member
What exactly are you trying to accomplish. What are you photographing--where the bullet is hitting the target?

The vibration sensor you are considering, though inexpensive, produces a very small signal that will need to be amplified before you can do anything with it.

You could feed the impact sensor output into a one-shot (555) and have that drive your [solid-state] relay circuit (a mechanical relay may prove to be too slow). You may find that the photo shows the aftermath and not the impact.

Could you mount the target on a spring and use a tilt sensor? You can feed this into a one shot (no pun intended) or you could feed it into a latch to trap the 'hit' then reset the latch to prepare for the next 'hit'.

I think you really will need a pre-trigger (also no pun intended) that starts the shot [as in photo, not gun shot] prior to actual impact.

Dale
 
Last edited:

Sceadwian

Banned
turbid you're going about this the wrong way, by the time the sensor has recorded the impact there's nothing to look at as the bullet has already hit and passed through it's target, even if you have a super fast camera. You're giving a very complex idea of how you think whatever it is you want to be done without actually stating your goal which makes it impossible for us to help you.

If you want to photograph an event at high speed you'll need to know two things. When the object gets to a specific point, and how fast it's traveling, and you need to get this information to the camera with enough time for it to react to take an image at the exact point you're looking for, this is just about always before the event takes place. That's what Garcia meant by pre-trigger. In order to react to an event at macro time scales you have to know when the event is going to occur, BEFORE it does.


So what are you trying to actually DO.
 

turbid

New Member
So what are you trying to actually DO.


Hopefully answering this question will clear things up. I'm sorry I didn't explain better.

I'm not trying to take a picture. The camera flash (or a flash unit I might build) is just a visual confirmation that the target was hit. I'm not trying to take a picture of the target or anything like that.

The problem is that at longer distances it is sometimes hard to be sure the target was hit just by the sound. So if the target is hit and a flash is seen it would be easier to be sure during shooting competition when knowing for sure is pretty important.
 

Boncuk

New Member
In that case I suggest to use the impact sensor of your choice and ignite the flash using a transistor.

A transistor circuit reacts much faster than a relay. The minimim delay time for a good quality relay is about 10ms. A transistor can perform much faster (µsecond range).

All you have to do is amplifying the weak sensor output signal to control the transistor (preferrably a MosFet).

Instead of an impact sensor you might consider using IR barriers 90 degrees angled off. The crossing point will be the predicted impact point. If both barriers are interrupted simultaneously with the crossing point on "bull's eye" it is going to be a 100% hit.

Place the IR barrier as close as possible to the target to avoid false triggering caused by wind influence of the bullet.

Using IR barriers instead of a physically hit target sensor you might save cost. If someone uses supersonic ammo the impact sensor might be destroyed when being hit.

Boncuk
 
Last edited:

stevez

Active Member
If you have some crystals, out of a computer, from a radio, etc you might try and experiment or two to see if the shock will generate sufficient voltage to be useful.

As an alternative, you could wire up very low power crystal oscillators and listen with a receiver. If you tune the receiver for zero beat you might expect to hear a chirp as the target is struck momentarily shifting the operating frequency.

I can explain more but this might be sufficient for you.
 

turbid

New Member
Wow, some interesting ideas so far. Thank you guys, I will look into the ideas you have to see what might be feasible.

I would still like to hear some more creative sensor ideas like the IR and crystal ideas, but also more ideas about using the info I am getting from the sensor have.
 

ke5frf

New Member
Are these steel tagets moving, the kind that spin or tilt like at a carnival or fair? Are you just interested in confirmation of hitting the target as a whole, or a specific area, like a bullseye or shot group pattern?

If the target moves, I was thinking something like a tilt switch might work to trigger your visual indicator (as a simple solution).

How far down range are the targets and how large? My questions may be rather naive if they are close enough to actually see the target move when the are hit LOL
 

turbid

New Member
Some are stationary, some hang and may swing back a bit when hit, but none of them are the spinners or anything like that.

It doesn't have to detect where it was hit like a bullseye, just if it was hit.
 

turbid

New Member
In that case I suggest to use the impact sensor of your choice and ignite the flash using a transistor.

A transistor circuit reacts much faster than a relay. The minimim delay time for a good quality relay is about 10ms. A transistor can perform much faster (µsecond range).

All you have to do is amplifying the weak sensor output signal to control the transistor (preferrably a MosFet).

Instead of an impact sensor you might consider using IR barriers 90 degrees angled off. The crossing point will be the predicted impact point. If both barriers are interrupted simultaneously with the crossing point on "bull's eye" it is going to be a 100% hit.

Place the IR barrier as close as possible to the target to avoid false triggering caused by wind influence of the bullet.

Using IR barriers instead of a physically hit target sensor you might save cost. If someone uses supersonic ammo the impact sensor might be destroyed when being hit.

Boncuk


While I am interested in all the additional ideas you guys are providing that I might use instead of the sensor I have, I think I'm gonna start here with the part in red. Mostly because whatever sensor I choose, I think I will need this.

Let's see if I can describe my problem with the required circuit.

The sensor I have has a signal line that is basically just a switched ground. I think this might cause me some problems, but I'm not really sure how to describe what I mean. I'm gonna run up to Fry's and grab a Mosfet and a few other parts then see what I can work out. When I get back I'll try to draw up a schematic that points out what I see as a problem.

Thanks again for all your help.
 
Last edited:

shortbus=

Well-Known Member
Most Helpful Member
Hi Turbid, maybe a little more than you need , but go to; Auto Target

You wouldn't need the CCTV part. Just use the mic to pick-up the thud(clang) to a op amp. Then that signal to a flip flop turning on a LED. Then a push button switch to the flip flop to reset for the next shot.

Cary
 

The Mad Professor

New Member
Ball bearing glued to the end of a spring from a disposable ciggarette lighter makes the basis of an effective and very inexpensive 'trembler' switch. Use this as the input to a 555 in monostable mode to switch the 'hit' lamp for the required number of seconds.
 

turbid

New Member
Ball bearing glued to the end of a spring from a disposable ciggarette lighter makes the basis of an effective and very inexpensive 'trembler' switch. Use this as the input to a 555 in monostable mode to switch the 'hit' lamp for the required number of seconds.


That is in it's very basic form what is inside the sensor I have, and what I may very well copy.

I was thinking a copper tube with on end plugged with epoxy and the spring+ball standing in the middle of the epoxy kinda like an upside down bell clanger. Then I could run a screw inside the spring that as it was screwed up and down would adjust the sensitivity.
 

turbid

New Member
Here is where I'm currently stuck. I know there must be a simple answer, but I not seeing it.

This is a very basic idea (using a crappy smart draw schematic) of what I have.

9145-switch1.jpg



The problem is that the sensor trigger is ground.

If it was not ground and actually gave me a voltage then I would just hook everything up, the sensor trigger line would drop voltage across the gate and it should work. But I'm not sure how to do this with the sensor trigger line being ground.
 

mneary

New Member
Invert the signal. The 10k resistor can be just about any value ± an order of magnitude.
 

Attachments

  • Sensor.png
    Sensor.png
    31.9 KB · Views: 250

turbid

New Member
mneary,

Thank you for taking the time to actually draw that up, but I'm still stuck on the fact that all the sensor trigger will do is ground the gate on impact.
 

Mr RB

Well-Known Member
Instead of a weight glued to a spring you could use guitar strings, ive seen "feelers" and bump sensor made out of these for robotics use. You can bend them to hold a specific shape and they are springy and won't corrode much. You pass the guitar string through an eye rivet (or an eye made from a loop of guitar string too) and it will sense any decent knock.
 
Status
Not open for further replies.

Latest threads

EE World Online Articles

Loading
Top