# 30 Second timer shutoff

Thread Starter

#### PattyT

Joined Nov 7, 2019
5
Hi circuiters,

I'm am a scout leader and am working on designing a handful of trip wire alarms for use on an upcoming camp.
The basic plan is to have teams of kids playing nerf stealth combat simulations around the very large bushland campsite. Teams score points for eliminating opposing team players (they are only eliminated for a short time before respawning) whilst sneaking around to find resources and equipment to help them for the weekend.
In an effort to make this more challenging, we want to place tripwire alarms around the bushland where we can expect teams to traverse through so if they trip the alarm, all the other teams will know where they are and theoretically come and attack them with their nerf blasters.

I already have several alarms, either purchased or built, but am wanting to make a final one using a 12v truck horn, flasher relay (to sound the horn intermittently) and a timer circuit to automatically shut the alarm off as the horn is 150db and an accidental trigger by wildlife overnight would be deafening for 20mins or so until I could get to the trap to turn it off.

I have a fair amount of electrical knowledge and am comforbuilding circuits but have no experience with creating timer circuits so am chasing some help in how to go about setting it up.

I would be super happy with a timer circuit that energises the flasher relay for 30 seconds then powers off.

Hope someone can help!

#### dl324

Joined Mar 30, 2015
8,877
Welcome to AAC!
I would be super happy with a timer circuit that energises the flasher relay for 30 seconds then powers off.
Sounds like a 555 timer would suffice. What is the coil resistance on the flasher relay?

Here's a schematic I had handy:

The time period is 1.1*R1*C1. About 11 seconds as drawn.

Depending on coil resistance, you may not need Q2. Or you could need something that can handle more current.

Don't know how you plan to trigger the one shot, but that's what Q1, R3, and C3 are for. Don't remember why I included D4.

#### danadak

Joined Mar 10, 2018
3,577
Consider using one of the Arduino boards and an IDE that programs in
block language, mBlock, ArduBlock, Scratch for Arduino, Sanp4Arduino.

The boards range from $2 to$ 6, the IDE is free, coding is done by drag
and drop functional blocks, setting in them things like pin number or
delay. You then hit upload button and the IDE generates Arduino C code
(you can look at that if you want) and programs the board.

Here is mBlock example that approximates what you are trying to do -

Regards, Dana.

#### danadak

Joined Mar 10, 2018
3,577
This is what a breadboard of it would look like -

The button simulates the trip wire. The transistor drives the relay, the diode protects
board and transistor from relay turn off transients. Cap to give board "clean" power.

Regards, Dana.

#### djsfantasi

Joined Apr 11, 2010
5,585
Danadak thinks that his favorite software will solve all the worlds problems. But I’d like to ask a couple of questions first, if you’ll indulge me.

Do you or anyone in your troop have programming knowledge? If not,even block programming may not help you. That still requires an understanding of programming constructs, albeit making consideration of the grammar and syntax of programming much easier.

A foreign language translator doesn’t work when fed non-grammatical input.

But perhaps someone in your group is familiar with programming skills. Then, Danadak’s approach may be of value to you. IMHO, he never asks that question. When you have an immediate objective, it’s not the time to learn a whole new language. Even if some of the translation is done for you.

I propose that you need to understand at least the concepts of microprocessor timers, conditional execution, external inputs/outputs, loops and boolean expressions. Even when using block programming.

IMHO, by the time you are familiar enough to use block programming, you can learn to program yourself, without the crutch of block programming. But I also recognize that for some people, this may not be true.

Danadak and I have different viewpoints. And we both know it.

I think that you can execute what you want with a couple of 555 sub-circuits and perhaps a transistor flip flop or two.

Good luck.

#### AnalogKid

Joined Aug 1, 2013
8,102
Assuming you are in the US, try this:

Adding an electrolytic cap in parallel with the one already on the board will extend the max time to 30 s. Accuracy and repeatability will not be great, but should be good enough for your application.

As above, building a circuit from scratch gives you more control over the performance and eliminates the relay in favor of a power transistor. With a CMOS 555 the standby current will be very small.

What are the voltage and current ratings for the horn?

ak

Thread Starter

#### PattyT

Joined Nov 7, 2019
5
Danadak thinks that his favorite software will solve all the worlds problems. But I’d like to ask a couple of questions first, if you’ll indulge me.

Do you or anyone in your troop have programming knowledge? If not,even block programming may not help you. That still requires an understanding of programming constructs, albeit making consideration of the grammar and syntax of programming much easier.

A foreign language translator doesn’t work when fed non-grammatical input.

But perhaps someone in your group is familiar with programming skills. Then, Danadak’s approach may be of value to you. IMHO, he never asks that question. When you have an immediate objective, it’s not the time to learn a whole new language. Even if some of the translation is done for you.

I propose that you need to understand at least the concepts of microprocessor timers, conditional execution, external inputs/outputs, loops and boolean expressions. Even when using block programming.

IMHO, by the time you are familiar enough to use block programming, you can learn to program yourself, without the crutch of block programming. But I also recognize that for some people, this may not be true.

Danadak and I have different viewpoints. And we both know it.

I think that you can execute what you want with a couple of 555 sub-circuits and perhaps a transistor flip flop or two.

Good luck.

Thanks for your comment and questions.
I already have block programming experience with android and am fairly confident I can apply this to the arduino logic as it doesn't seem all that difficult.

Consider using one of the Arduino boards and an IDE that programs in
block language, mBlock, ArduBlock, Scratch for Arduino, Sanp4Arduino.

The boards range from $2 to$ 6, the IDE is free, coding is done by drag
and drop functional blocks, setting in them things like pin number or
delay. You then hit upload button and the IDE generates Arduino C code
(you can look at that if you want) and programs the board.

Here is mBlock example that approximates what you are trying to do -

View attachment 190823

Regards, Dana.

I've been looking to get into some arduino so this seems like as good a time as any...... thanks!

Assuming you are in the US, try this:

Adding an electrolytic cap in parallel with the one already on the board will extend the max time to 30 s. Accuracy and repeatability will not be great, but should be good enough for your application.

As above, building a circuit from scratch gives you more control over the performance and eliminates the relay in favor of a power transistor. With a CMOS 555 the standby current will be very small.

What are the voltage and current ratings for the horn?

ak

I'm in Australia but this is also a good option.
30seconds was an arbitrary timeframe, if this board does 15seconds that would be fine.

Horn is a truck air horn so power is for the brushed motor air compressor.
12v, 10A startup current, 5A constant

Thread Starter

#### PattyT

Joined Nov 7, 2019
5
Assuming you are in the US, try this:

ak

Just found this on Ebay and by the item description, it looks like I can power it up, set it for 30seconds then power it down and connect it to a tripwire switch. Upon power on it should start and run the timer then power down on it's own as long as I don't program it to start again......
Is my assessment correct?

Thread Starter

#### PattyT

Joined Nov 7, 2019
5
Just found this on Ebay and by the item description, it looks like I can power it up, set it for 30seconds then power it down and connect it to a tripwire switch. Upon power on it should start and run the timer then power down on it's own as long as I don't program it to start again......
Is my assessment correct?

I have found some detailed instructions for this board and it is VERY versatile!

It can be programmed from 0.1sec to 999minutes for both delay before power on AND delay before power off.
It can be triggered by sensors or power on on the board and has 4 operating modes
-timer to power on by sensor/trigger
-timer to power off by sensor/trigger
-timer to power on by board power on
-timer to power off by board power on

This is pretty much what I was after and plenty more!

I'm just gonna buy it.

I'll be sure to test it and let you all know how it goes when I finally get it from china......

#### danadak

Joined Mar 10, 2018
3,577
@PattyT

When you get back into Arduino there are several block languages out
there with different (and similar) capabilities. Some even support ESP8266
for WiFi applications

mBlock, two versions 3.x and 5.x

Ardublock, also 2 versions, one a lot more capability

Sbnap4Arduino this you can tether a board to a PC and make talking
applications, and other capabilities due to tethering

Flowcode, the license free version

Scratch for Arduino

Regards, Dana.

Thread Starter

#### PattyT

Joined Nov 7, 2019
5
@PattyT

When you get back into Arduino there are several block languages out
there with different (and similar) capabilities. Some even support ESP8266
for WiFi applications

mBlock, two versions 3.x and 5.x

Ardublock, also 2 versions, one a lot more capability

Sbnap4Arduino this you can tether a board to a PC and make talking
applications, and other capabilities due to tethering

Flowcode, the license free version

Scratch for Arduino

Regards, Dana.
Cheers mate!