Vibration activated switch

[BabaOriley]

Hi everyone. First post here. Excited about finding this place. I bet you can help me with this. I know very little about electronics, and don't even know anyone who claims to know anything, so here goes...

I want to mount a metal plate on a spring. When this metal plate gets hit by a projectile, I would like it to activate 12v power to run an alarm bell for a given time, maybe 2 seconds. It would be nice if the bell ring time would be adjustable.

I suppose I would want the vibration to be more than the slightest touch, but pretty sensitive. Maybe sensitivity needs to be adjustable with some adjustment pot.

Maybe I should be open to voltages other than 12v dc, as I've found some used 120v alarm bells too. Maybe the vibration switch and ring timer could use any voltage, and activate any voltage?

Also, if you have any ideas on maybe just hitting the bell once, really hard, with each distinct vibration with some kind of hammer, that would be cool too.

As few parts, as cheap and easy to order as possible would be preferred, as my soldering skills are severely lacking.

Here's some vibration switches I found... A "start"?
**broken link removed**

This is what I was thinking for the bell... The 12v DC models. Again, I would be open to having something strike the bell just one time too. Maybe have the option to do both?
https://www.midsouthcable.com/AmsecoFireBell.htm

I am thinking 12v DC for this project, as I think I'm going to want to power the system with 12v car battery so it's portable.

Thanks!

 

[BabaOriley]

I found these vibration switches... A start...
**broken link removed**

This is what i was thiking for the bell, but would be open to a way of making it "ding" just once if we can hit it with something really hard...
https://www.midsouthcable.com/AmsecoFireBell.htm

 

[BabaOriley]

Here's some vibration switches I found... A "start"?
**broken link removed**

This is what I was thinking for the bell... The 12v DC models. Again, I would be open to having something strike the bell just one time too. Maybe have the option to do both?
https://www.midsouthcable.com/AmsecoFireBell.htm

I am thinking 12v for this project, as I think I'm going to want to power the system with 12v car battery so it's portable.

 

[ericgibbs]

hi,
The vibration sensors you have posted are not cheap.

What projectile , weight, speed etc, is it hitting what type of plate, material approx size.

A simple 'hit' detector would be a cheap microphone fixed to the plate.
Some low level of amplification 'maybe' required, send the output signal to a logic latch or monostable or relay latch.

This would drive the alarm.

EDIT: the microphone out of an 'old' style telephone mouthpiece, the type with carbon granules [resistive],
makes a 1st class 'hit' sensor, just apply a low bias voltage across the mike.

 

[BabaOriley]

hi,
The vibration sensors you have posted are not cheap.

What projectile , weight, speed etc, is it hitting what type of plate, material approx size.

The projectile would be a small piece of lead, say 40 grains in weight, travelling around 1000 feet per second, hitting a .25" thick, 10"x10" hardened steel plate. My plan was to affix some kind of vibration sensor to the plate. I also have plans to hang a larger, 1/2" thick, 16x16" plate on the larger plate, to protect it from larger, heavier projectiles hitting at anywhere up to and beyond 4000fps.

Since the plate will move at least .1 inches when hit (if it's welded onto a coil spring from a vehicle's suspension), I was thinking some kind of contact switch could activate the alarm, or bell ring, but the vibration sensor seems more reliable, with less need for adjustment.

Maybe the contact switch is the way to go. As long as it can have the contact closed several times in a split second, but only one signal sent to the bell. I just worry about a contact switch getting out of adjustment more than a vibration switch. The vibration switch, once set, would ideally not care if it was a light, or heavy impact. It would just send a signal to ring the bell once, or run the clanger alarm bell for a set period of time.

I didn't think it would be that complex.

What do you mean by expensive? $50? $200? If it's under $200 I'd be ok with it.

 

[ericgibbs]

hi,

>> As few parts, as cheap and easy to order as possible would be preferred, as my soldering skills are severely lacking
>> What do you mean by expensive? $50? $200? If it's under $200 I'd be ok with it

Contact the suppliers for prices.

The project could be done for less $50 using a simple detector.

A 'vibration' sensor is an overkill for this application.

 

[BabaOriley]

Thanks for thereply eric... I'm willing to try what you're talking about. I know I can get an old phone handset, but how would you attach it to the plate? Then what would you use to trigger the alarm bell for 1-2 seconds? Or what would you use to strike the bell? The bells usually have the clanger already mounted, but sometimes looking at used ones they don't. Can you give me the rest of how you see this coming together? Like I said, I have very little knowledge of electronics.

 

[Nigel Goodwin]

Presumably this is a bullet, hitting the steel plate? - I would imagine a simple microswitch could easily be arranged to switch under the impact of a bullet?.

 

[ericgibbs]

Thanks for thereply eric... I'm willing to try what you're talking about. I know I can get an old phone handset, but how would you attach it to the plate? Then what would you use to trigger the alarm bell for 1-2 seconds? Or what would you use to strike the bell? The bells usually have the clanger already mounted, but sometimes looking at used ones they don't. Can you give me the rest of how you see this coming together? Like I said, I have very little knowledge of electronics.

If its a 1 to 2 sec bell you want and the plate moves about 0.1nch, why not just hang an ordinary bell at the end of a piece of chain attached to the bottom edge of the plate?

 

[BabaOriley]

Presumably this is a bullet, hitting the steel plate? - I would imagine a simple microswitch could easily be arranged to switch under the impact of a bullet?.

Yes, this is a possibility. As long as it can stand up to both a slight impact, and a stronger/sharper one.

 

[Nigel Goodwin]

The plate gets the impact, the switch should receive very little.

 

[BabaOriley]

If its a 1 to 2 sec bell you want and the plate moves about 0.1nch, why not just hang an ordinary bell at the end of a piece of chain attached to the bottom edge of the plate?

Because the impact isn't going to move the plate a consistent 1 inch. A .22 caliber bullet might only move it .1 inch. That isn't going to ring the bell very loud. The shooter will have just heard the crack of a gun go off. The bell needs to be prominent in indicating a hit. A .308 might move it a half inch, hence my initial idea of a vibration sensor. I don't want to have to tweak the mechanical parts for different impacts. I just want it to sense, "Yep, there's more than this certain level of vibration, so I better activate that bell." Then the bell (12v DC) is activated for maybe 2 seconds, OR the bell is struck by something hard enough so you can hear it from 300 yards away. I can't shoot the bell. They're often made of brass, and not thick enough. Even if it was, it would wear out faster than hardened steel plate. This thing should last a lifetime.

Sorry guys, I haven't been clear enough here. If it costs $200 that's fine. There's commercially available hit indicating targets that cost well over $1000/pc. for training ranges. My buddies and I can't afford that. $200 we can afford. The ammo can cost $1 a shot when you're looking for 300 yard accuracy. We just don't like walking that 300 yards to see if we hit, or to replace the paper target.

I appreciate your creativity. Please keep the questions/ideas coming!

I'll be working on a CAD drawing of the physical idea for this thing that might help it make sense. I'll post that when I get it.

 

[BabaOriley]

Presumably this is a bullet, hitting the steel plate? - I would imagine a simple microswitch could easily be arranged to switch under the impact of a bullet?.

I think yes, if a microswitch was used, it could be set up to the plate can only move back so far until it hit a stop, and would not damage the switch. Can you post some links to an online source and model numbers for the switch you have in mind? Preferrably something at least a little weatherproof/sealed too, but i could make some kind of housing for whatever I guess.

Now I'm thinking, with the microswitch idea, I'd probably mount the plate on rubber mounts just soft enough to let the plate push the switch. Could still have a stop built in to it doesn't crush the switch if hit with a mortar or something...

The more I think about the switch idea I like it. A switch could not be activated by a shot hitting another part pf the target, like the frame, like the vibration sensor might.

I still need something the switch will activate to send power to the bell for a given length of time, OR, as I mentioned, trigger some kind of hammer to hit the bell pretty hard. Most of the bells I'm finding are set up to ring. A 1-2 second activation of the bell would probably suffice. I could also hook up a 12v light on the same circuit, stuck in the ground several yards away to give a visual indication of a hit too...

 

[BabaOriley]

Maybe this will work until I get a CAD drawing for you guys.

\\ <-smaller plate mounted behind a larger one, and have the switch mounted.
-\\
--\
___\

The large plate in front would have a hole in it, say the largest hole you'd want for long range shooting, say 10". Smaller, thinner plates could be hung to cover the large hole, and have smaller holes in them to use the target for more close range shots, with lighter calibers. Any front surface and the back plate would be angled so bullets get deflected downward. Most bullets hitting hardened steel plates shatter. It's best to use lead bullets rather than full metal jacketed ammo on these types of targets though. Higher power cartridges need to be shot from further from the target, so they've lost some energy by the time they hit. Need a bigger target though at further distances. I could see trying to hit this with high power rifles from 500+ yards. Would be great fun to try and get it to sound off...

 

[ericgibbs]

I have been searching my shelves for the past hour, looking for an old carbon mike, can I find it, no way.

Seen it twice in the past two weeks, its the project gremlins again.

IF!, the microswitch dosn't get the job done, let me know and I'll post a mike circuit.

 

[BabaOriley]

I have been searching my shelves for the past hour, looking for an old carbon mike, can I find it, no way.

Seen it twice in the past two weeks, its the project gremlins again.

IF!, the microswitch dosn't get the job done, let me know and I'll post a mike circuit.

I'm pretty sure I can find one of those old phone sets, but it seems like the microswitch would be better now. I just need the next part of the equation. Something the switch will trigger to give power to the bell for 2 seconds (maybe something adjustable). What's that called? Where do I order that and a the switch? No soldering please. Just screw down wire clamps or something...

 

[Nigel Goodwin]

I'm pretty sure I can find one of those old phone sets, but it seems like the microswitch would be better now. I just need the next part of the equation. Something the switch will trigger to give power to the bell for 2 seconds (maybe something adjustable). What's that called? Where do I order that and a the switch? No soldering please. Just screw down wire clamps or something...

You could use a simple 555 timer as a monostable to extend a single pulse to 2 seconds, easily adjustable via a preset.

 

[BabaOriley]

You could use a simple 555 timer as a monostable to extend a single pulse to 2 seconds, easily adjustable via a preset.

Like **broken link removed**?

 

[ericgibbs]

Like **broken link removed**?

hi,
>> No soldering please. Just screw down wire clamps or something...

As you just want to screw it up, then that would get the job done, hang a buzzer or bell on the Relay output.
Requires a 12Vdc supply, a 12V 7AH sealed lead acid would be ok.