Need help, creating training aid for my army unit

Thread Starter

Goofoff5

Joined Mar 13, 2018
16
I am in the national guard, our budget is almost non existent. I am want to create training aids for my guys. I am creating pressure plate booby traps. I have the plates made hooked up to a piezo disk and a 9 volt. I want to add a LED (should be easy. But I want the LED to strobe and the buzzer and LED to stay on once triggered and I am not sure. I have read alot on the 555 chip and believe it should do what I am looking for but not sure. I should need the buzzer and LED tonstay on for more than 30 minutes and with no delay when they go off.

Is all this possible, I would rather do the work myself since this is coming out of pocket. Directions or a diagram would be a life saver.
 

Thread Starter

Goofoff5

Joined Mar 13, 2018
16
Just realized my typos. Let me clarify.

-instant on
-LED to strobe and buzzer
-doesn't need to stay on for more than 30 minutes
 

dl324

Joined Mar 30, 2015
11,317
In theory a 555 timer could do 30 minutes. You can buy blinking LEDs, but don't know if they have super-bright varieties.

From Jameco.com:
upload_2019-4-15_9-46-12.png

If you need super-bright, you'll need an oscillator plus the timer.

Is the piezo disk the pressure sensor? Or is it the buzzer?
 

AnalogKid

Joined Aug 1, 2013
8,540
Do you need to be able to clear the alarms manually before the 30 minutes runs out?

A 555 can do this, but even the CMOS version will not be very accurate at 30 minutes. If you don't mind +/-5 minutes variation from one device to another, then the 555 is good because it has a beefy output stage that probably can drive your lights and buzzer without an external power transistor.

If by "LED strobe" you mean that the LED flashes while the buzzer is on continuously, then you'll need two 555's or some other circuit that combines the functions.

What have you selected for the switch, LED(s) and the buzzer? Datasheets? Links?

LED color and brightness are key parameters of your project. There are low power LEDs that are self-oscillating. Very convenient for your product (back to only one 555), but not very bright.

What is your skill set for assembling a small circuit on perf-board?

ak
 
Last edited:

Thread Starter

Goofoff5

Joined Mar 13, 2018
16
In theory a 555 timer could do 30 minutes. You can buy blinking LEDs, but don't know if they have super-bright varieties.

From Jameco.com:
View attachment 175022

If you need super-bright, you'll need an oscillator plus the timer.

Is the piezo disk the pressure sensor? Or is it the buzzer?
It's the buzzer, I made a variety of plates for fitting under rugs and door ways as the trigger. And, yes, I may need to clear it out before the 30 minutes runs out. +/- 5 minutes is fine. Just need it to be long enough to drive them nuts while they train on first aid for whoever's set it off.
 
Last edited:

Thread Starter

Goofoff5

Joined Mar 13, 2018
16
Do you need to be able to clear the alarms manually before the 30 minutes runs out?

A 555 can do this, but even the CMOS version will not be very accurate at 30 minutes. If you don't mind +/-5 minutes variation from one device to another, then the 555 is good because it has a beefy output stage that probably can drive your lights and buzzer without an external power transistor.

If by "LED strobe" you mean that the LED flashes while the buzzer is on continuously, then you'll need two 555's or some other circuit that combines the functions.

What have you selected for the switch, LED(s) and the buzzer? Datasheets? Links?

LED color and brightness are key parameters of your project. There are low power LEDs that are self-oscillating. Very convenient for your product (back to only one 555), but not very bright.

What is your skill set for assembling a small circuit on perf-board?

ak
I was going to base my led selection on what type of output I could get. They don't need to be super bright, with night vision a lit cigarette is as bright as day.
 

AnalogKid

Joined Aug 1, 2013
8,540
A piezo beeper loud enough to affect performance is going to pretty much kill a 9 V battery in 30 minutes. You might not need a timer circuit. OK, that was semi-kidding. A Duracell 9 V is around 550 mAh new, just under 5 Wh (watt hours). That's less than 550 mA for one hour (rating is derated at higher discharge currents), enough for several 30-minute cycles. Really loud piezo beepers usually need more than 9 V. When perusing vendor websites, pay attention to the SPL rating *and the distance*. Huge difference between the same value at 1 m and 3 m. The one on my alarm system will make your fillings fall out, but it is pretty hungry.

Here is the Digi-Key listing, sorted by loudness. You can select other sort parameters.
https://www.digikey.com/products/en/audio-products/alarms-buzzers-and-sirens/157?FV=7680028,768002e,8e80009,15d80006,1f140000,ffe0009d&quantity=0&ColumnSort=-397&page=1&stock=1&k=piezo&pageSize=500&pkeyword=piezo

ak
 
Top