Track Coach here.... My school still uses an Ultrak L10 to time meets and I am looking for a way to diy a solution to simplifying the start of a race. Currently we just have the "head timer" watch for the smoke of the starting pistol to operate a plunger that closes a contact to start the timer. I would love to put together a system that has 2 parts, transmitter (Starter pistol end) and receiver (Timer end). We have a minimal budget so I would be purchasing and building everything myself.

• Starter is wearing the Transmitter (clip on to belt, maybe wristband?)
• Receiver end plugged into Timer
  • NO Contact
• Starter fires pistol and Transmitter picks up signal
  • Max distance between Transmitter and Receiver would be 500'
  • Line of sight, no trees or other obstacles
  • Must trigger on BANG of starter pistol, not physical switch or flash
• Receiver picks up signal and closes contact
  • Momentary, not maintained
• System is ready after each shot

 

It is simple to implement until the 500 foot maximum range requirement. For closer distances, simply a directional microphone with a narrow frequency range coupled to an amplifier that triggers a 555 timer. A version of that scheme has been published by the ARRL for at least 20 years.
The difference would be in the designed frequency response of the amplifier and the microphone.
The huge issue is the delay due to the distance. Sound travels (nominally, dependent on temperature and humidity) at 1100 feet per second, so at 500 feet that is almost half a second delay.

So the system will need a sound sensor close to he starter pistol, and a radio link to the switcher part. The good news is that the wireless link only needs to be an audio link, not the trigger pulse. So an off-the-shelf FM communications pack will work. AND if the official already has such, just remembering to key the transmitter prior to the shot will be required. So suddenly the whole project gets much simpler. It could, possibly, even use a wireless microphone set to transmit the sound.

 

I was looking for a starters blank pistol with a set of contacts. Apparently, any even looking like a pistol is considered "Very Bad" these days. I do know that I have seen them in the past. Starter pistol held aloft with an internal set of contacts and cable running from the bottom of the handle to the timer. What I do find is this "thing" made to not look like a pistol with both a strobe light and cable to timer. Instead of blanks it emits an "ear safe" 90db sound that can be selected either as pistol bang or a beep if you just "Must" be politically correct!

Electronic Starting Pistol Set | FirsttotheFinish.com

Probably cheaper than the time, materials, and debugging if you DIY.

 

For the RF link a Radio Shack wireless FM intercom of the kind with the separate headset. All the signals brought out on wires ready to modify. For the actual trigger.rectify the speaker signal to trigger a 555 timer for the short pulse to the timer.For the actual sound, if you lack a starter pistol, how about a loud Cymbal Crash?? Politically correct and non-threatening and even safe for those with PTSD

 

Probably cheaper than the time, materials, and debugging if you DIY.

How will that send a signal to the timer up to 500' away?

 

How about a long-range lavalier wireless microphone to transmit the signal (example).
The large signal pulse output from the receiver due to the starter pistol sound could be then used to trigger a 555 one-shot driving a relay for the start pulse.

 

The wireless headset intercom I suggested is about a hundred dollars cheaper. AND the receiver already has the needed connections accessible.

 

How will that send a signal to the timer up to 500' away?

cable extension or a wifi pairing. Need to look at the timer it was designed to work with and see what it is capable of. Checking out the devices pdf wouldn't hurt either and it may also give some good ideas... FWIW

 

An FM radio link, as I have suggested twice, will be a better choice than wifi because there is much less probability of interference, and no communication latency issues. AND it is simpler to use because no software is involved.

 

And I don't think WIFI can actually make it to 500' without some boosting. My hearing aids to iPhone WIFI connection won't even make it 50'. Just brainstorming for consideration...

 

There are quite a few FM link products available from honest distributors. AND, here is another possibility: Use the remote control transmitter to also activate the "starting Noise" device, which could even be so original as a speech synthesis countdown: Tree, Two, One, GO! with an obvious "computer accent" so that everyone can know it is a machine. And certainly there are amplifiers that could make that loud even at 500 feet.

 

Welcome to AAC.

In principle, it is very simple but the requirements need to include some more information. Because the is a critical application, reliability is very important. It's not a health and safety issue for the runners, but it could be for the officials if the timing didn't start—and it is unlikely they would be able to run away from the angry mob that would result.

So, I think you need a supervised link. That is, the link must be definitely established and maintained, included a status light at the starting line to confirm the start will be recorded. These are the components I would use:

1. Sound Detection Module ➚—this is a ready made module with an adjustable sensitivity. With some experimentation you should be able to make it ignore everything but the gunshot.
   
   
2. (2) NRF24L01 Wireless Data Module ➚—this module, based on the very robust Nordic chip operates in the 2.4GHz band and provides reliable communications with a solid protocol. It I very widely used and there are plenty of application examples.
   
   
3. (2) Seeed Studio XIAO Development Board ➚—this MCU dev board is small, inexpensive, well made and solidly supported by the Arduino platform making it very easy to use.

Integrating these parts is a relatively simple problem for a person who has done a bit of Arduino development but will be daunting for the neophyte. None the less, it is entirely practical even for a rank beginner assuming a little persistence and willingness to learn. Good luck.

 

Welcome to AAC.

In principle, it is very simple but the requirements need to include some more information. Because the is a critical application, reliability is very important. It's not a health and safety issue for the runners, but it could be for the officials if the timing didn't start—and it is unlikely they would be able to run away from the angry mob that would result.

So, I think you need a supervised link. That is, the link must be definitely established and maintained, included a status light at the starting line to confirm the start will be recorded. These are the components I would use:

1. Sound Detection Module ➚—this is a ready made module with an adjustable sensitivity. With some experimentation you should be able to make it ignore everything but the gunshot.
   
   
2. (2) NRF24L01 Wireless Data Module ➚—this module, based on the very robust Nordic chip operates in the 2.4GHz band and provides reliable communications with a solid protocol. It I very widely used and there are plenty of application examples.
   
   
3. (2) Seeed Studio XIAO Development Board ➚—this MCU dev board is small, inexpensive, well made and solidly supported by the Arduino platform making it very easy to use.

Integrating these parts is a relatively simple problem for a person who has done a bit of Arduino development but will be daunting for the neophyte. None the less, it is entirely practical even for a rank beginner assuming a little persistence and willingness to learn. Good luck.

Thank you for the information.. I will give this a try, the price is right for the components and I have some time before the season begins.