university project - advice welcome.

[Dansi1315]

Hi all,

just to introduce myself, I'm Simon and am currently training to be a Design and Technology teacher at brighton University. However my experience is all in automotive and abrasive materials rather than electronics so would appreciate any advice given.

My current project is to design a pistol firing range, so that one person can practice for competition shoots.

the shoot runs like this;

firer presses start on control panel,
10 second pause,
buzzer sounds,
random pause between 3 - 10 seconds,
buzzer sounds to start shoot.

at this point I would like a stopwatch to start, displaying seconds, 1/10ths and 1/100ths.

Firer must fire at five targets up to 25 metres away.

i would like each target to illuminate an LED on control panel when hit, and the fifth target should illuminate an LED but also stop the stopwatch.

My Ideas so far:

Have found some code on random here already and am happy with the outcome for the second pause.

was thinking of using a digital stopwatch and somehow using picaxe to start/stop/reset the clock, as I have looked around and figured it is very difficult to time to 1/100th sec, especially when you need the pic to be doing other stuff at the same time.

I was going to look further into using electret mics on each target and have borrowed Hippy's ideas for a circuit on that.

Sorry for the long post but wanted to give you as much info as possible. I would welcome advice on any issue's I may have, and would dearly like to hear peoples oppinions on which hardware would be best suited to this project.

Oh and feel free to criticise my initial thoughts as I am a novice, however my Shiny new picaxe Dice works a treat

Thanks in advance, all advice and info will be acknowledged in any work I produce as it will be for my final assessment

 

[Andrew Cowan]

What is being fired? How will you know when the target has been hit - could an electret mic be triggered by the gun firing? What are the targets made of?

Have you found any digital stopwatch chips? Using a digital stopwatch would work, but it may look a bit messy, and be hard to fit into a case.

Otherwise, sounds like a good idea.

Andrew

 

[Dansi1315]

wow quick response!!

The range is designed for air pistol, so a metal target will be hit by a pellet, I will be playing with the target design to produce an acceptable noise, but it will be equal to if not greater than a handclap, and I am intending to have the mic circuit a few centimetres behind the target plates.

Am I making a simple error in thinking that the five circuits behind the targets can be connected by external wiring to a main circuit in a control panel on the firing point?

i haven't found a stopwatch yet. and haven't designed the case to hold the control/interaction hardware either. i am intending to build a panel that will have the following componnents for user interaction;

Start button.
Reset button.
5 x LED's
Stopwatch display.
Power supply switch.

The panel will also hold the batteries/power supply connections and a little storage area for the target plates in transit, so it isn't going to be a small unit.

 

[Andrew Cowan]

You would want the amplification of the signal to be in the target, so it is a strong dignal that travels to the main control panel. You'll have to do some tests, but I think that if the mic is touching the metal plate, the noise should be loud enough to make a recognisble signal.

Andrew

 

[Dansi1315]

Just FYI

I have access to VSM and editing software as well as Crocodile technology and a few others.

I have endless supply of breadboards and components for try-outs and have already played with Picaxe components in the form of the dice set and a flashing LED's component setup.

Monday next week I will be trialing the Electret mic set-up as shown here;

http://www.reconnsworld.com/audio_electretamp.html

What sort of output should i be looking for from this circuit in order for it to be a suitable input signal to say, an 18x? Which would be 25m away.

and my coding for the random pause at the beginning is looking to be as follows;

random b0
	             b0 = b0/36
		w1 = b0*1000
		w1 = w1 + 3000
		pause 5000
		sound 0, (50,50)
		pause w1
		sound 0, (199,50)
		high 1

It does create some issues with replicated patterns, when starting the program on different occasions, but works suitably enough for these purposes.

 

[bgrabowski]

Several years ago one of my students sucessfully produced an intelligent target for a soft pellet airgun. The target face was four separate concentric plastic rings and attached to the back of each one was a piezo sounder. Each piezo, when it's ring was hit, generated a pulse which was stretched using a 555 timer monostable and fed to a picaxe to calculate and display the score. The rings were fixed to a backing board using a sheet of plastic foam as accoustic insulation to prevent the triggering of piezos adjacent to the one struck.

Piezos could be used this way for your project. They respond very well to impact vibration but are not easily triggered by sound waves through the air.

 

[Dansi1315]

Using Piezo

Sounds like a nice setup, although more than I actually need. The targets for my range only need to detect hit or not, there will be no scoring for closer to centre etc....

I have considered piezo for this, but feel it may be too fragile for a transportable setup. Most other devices for this purpose use Piezo electronics as a trigger and they all come with handling warnings such as.....do not tilt targets forward as this will damage the piezo.....

It is a very good suggestion and something i intend to trial alongside the mic idea. But I am leaning heavily towards the mic for durability.

I have made a note of accoustic foam though as this may help to reduce external noises in my setup, thank you.

 

[Michael 2727]

I think the piezo disc option may be a better solution than an Electret Mic.
The microphones can be damaged by high SPL levels (Sound Pressure).

Some Targeting systems use piezo sensors in a triangulation array to detect
the bullets shock wave, decode the info then display it on an LCD display.
( I had to repair/refurb some once )

If you mount a piezo sensor directly on a metal plate which is struck by a bullet you will probably get a voltage output 1000 x what you would get by yelling at the same sensor.
This is how electronic cigarette lighters work, a piezo crystal is slammed by spring loaded
hammer, albeit a very small one, they produce 3 to 4 KV.

A soft rubber mounted, piezo sensor nearby your target will probably work fairly well.

 

[eclectic]

Simon,
A few thoughts.

1. "Am I making a simple error in thinking that the five circuits behind the targets can be connected by external wiring to a main circuit in a control panel on the firing point?"

What about using a simple and cheap 433 MHz radio link?
Tons of info on the forum. And no tripping hazards!

2. Random. From Hippy's thread
http://www.picaxeforum.co.uk/showthread.php?t=7799

RANDOM w0
b2 = w0 // 8 + 3

3. Timer
Use a second Picaxe.
The “pause 100” is not perfect, but can be altered by
varying between say 97 – 103 or by using “calibfreq”
This picaxe could then provide a “background” tick.
Using SETINT and interrupts are then possible.

e.

 

[MBrej]

As for timing how long until the target is hit, you could use a real time clock (RTC) which gives the time down to 100ths of a second. At the start you read the time, and when the target is hit read the time again and calculate the difference, then display the time however you want.

Look here, and click "HH-MM-SS-hh" under time format to filter those who can output 100ths.

As for detecting a target being hit I also agree piezos like this would work well

Matt

 

[Dansi1315]

loads of options

Thanks guys, lots of options for me to look at, keep 'em coming.


Micheal I will do more research into Piezo discs, I did intend to anyway.

Eclectic. I had thought of counting ticks at pause 100 then inserting a decimal point to create the correct display, but hadn't thought of usig another chip to do the pauses, so that is a good thought and I shall research it more.

Radio Tx for the targets would be good, but would I be able to use 5 different frequencies (1 for each target?) otherwise this could cause confusion, 1 target being hit more than once for instance, which I do not want to count, as each of the five should only be hit once, and missing one but hitting another twice should be a disqualification in competition.

MBrej,

I shall have a look at the options listed, but right at this second my sausage in onion gravy and yorkshires is ready.

Thanks all this is really helping me get some ideas

 

[eclectic]

Simon.
433 radio. Simply send a different serout value.
On reception, two of the same is a penalty.
e

 

[manuka]

Those uncased piezo's are VERY rugged- a typical party trick is to flick or flex them, causing an attached LED to flash. We've used them for all sorts of work & I'd say they'd be the automatic choice for your air pistol needs.

 

[Dansi1315]

Piezo

would i be looking at a circuit like this?

http://members.shaw.ca/novotill/PiezoVibrationSensor/index.htm

 

[alband]

Are the mic's for working out if a target has been hit or just record the sound?
I've done some shooting with real and air rifles; not much, but enough to know the sounds.
Are the targets next to each other or physically connected?
If so I really cannot see how mic's are going to know which target was hit - the sound will be very similar at adjacent targets and if the targets are in the same box or frame, the noise will flow through it like a river in spring.

I may have missed something, but this just sounds like a very unreliable way of detecting a hit.
Can you give and pictures of the targets. I've used some air rifle targets before and if I was to ware those up I'd use light gates. It is very dependent on the target design and I'm sure the accumulated minds of this forum would be able to think of something much more reliable.

 

[Dansi1315]

types of targets

Hi Alband,

Prior to this course I spent 12 years as an Army vehicle technician and soldier, so am not unfamiliar with the sound of guns and targets being hit etc...

The targets are 100mm dia of (probrably) sheet steel. and each target would have either Piezo or electret mic (or any other solution) board mounted directly behind it. This would be encased to both protect the board and to reduce any external noise.

the targets could be anything from 500mm to 25m apart. As I understand it the mics wouldn't really pick up anything from those distances, and the piezo's work on energy displacement rather than pure sound.

I will be carrying out tests next week, and can include external influence tests just to satisfy my (and anyone else's) minds..

Thanks all, keep it coming......

Concentrating on displaying the time it takes from starting the shoot to the fifth target being hit.

So far I am looking at using a 2nd PIC to count loops of a pause circuit, then displaying the ticks via cmos 4026b's and seven segment displays(with a rogue SSD after 2 digits displaying a decimal point). Is this a viable option? would doing this per tick (1/100th sec) cause too much delay?

 

[boriz]

This is what I’d prolly do…

Hot-melt glue the piezo disk directly to the back of the metal target plate. Connect this directly (un-amplified) to the trigger of a 555 monostable pulse-stretcher. The monostable delay should be long enough for reliable detection by a Picaxe and short enough for there to be no possibility of crossover with another target’s signal. Start with something like 2mS. Test it.

If it works reliably, build 4 more and use the 555 outputs as inputs to a Picaxe. The Picaxe monitors the 5 inputs and when one goes HIGH, it transmits the ID of that target over the RF link to the receiver Picaxe which controls the external timer. Then it wait’s until the input’s are all LOW again and then continues monitoring.

Or something like that.