IR Break beam wireless activated digital timer

[Alchad]

Hi all, so I'm an oap and have very little electronics experience, but am very practical. My other half is involved in judging small horse jumping events and has asked if I can come up with a sort of lap timer. Basically the horse starts it's round, triggers an IR beam which wirelessly starts a digital timer, when the horse finishes the round it breaks another IR beam which wirelessly stop the timer. These things are available on line but are horrendously expensive and come with all sorts of bells and whistles which she doesn't need (or can afford).

I've been doing a lot of Googling and a starting point would be something like this (or preferably a wireless version)

https://quasarelectronics.co.uk/.../cebek-rj-5-long-range...

First question, this receiver has a relay which is presumably tripped (excuse terminology) when the beam is crossed, what sort of kit would I need to convert this to a wireless "switch on" signal to a digital stopwatch - such as this

https://quasarelectronics.co.uk/.../3148t2-4-digit...

There would obviously be an identical system to break a beam and wirelessly stop the stopwatch.

Any advice or suggestions would be gratefully received.

Thanks

Alchad

 

[Reloadron]

If the horse is doing a lap and finishes where it starts you can use a single trigger to start / stop a timer. If the start and stop are not the same then two triggers. You can use an IR (Infra Red) beam similar to the safety beams used on garage doors or a LASER beam transmitter receiver. Anyway it starts with a trigger. You have a start and stop trigger function.

Wireless? Anytime the term "wireless" comes up the first question is distance? There are a number of ways to send data wireless but distance is always a key player. There are a number of inexpensive wireless relay cards out there good for about 100 feet (30 meters) unobstructed.

Accuracy / Uncertainty? This is where you need to call out an accuracy or uncertainty you are good with in the final count result?

Something to consider is anything with relays and relays being a mechanical device will add time, not much but none the less time.

Think of it tis way. A start signal opens a gate. Pulses of a known frequency pass through the gate. A stop signal closes the gate. Now we just count how many pulses passed through, do the math and we get the time the gate was open. It's a chronograph.

I looked at your IR transmitter / receiver modules. I can't say how well they actually work but they could serve as triggers for start stop. For the wireless I would just hack the key fob of something like this. The link is 4 channel and you only need two. Your external relay goes across a button. Not a difficult hack. That becomes the start and stop of your choice of digital timer(s).

Ron

 

[KeepItSimpleStupid]

Notice the IR receiver is "indoor only", which probably means its affected by the sun's IR light. Relays will consume power

IR remote controls are generally immune to IR interference because the IR is modulated at usually 38kHz. To conserve power, a smaller duty cycle is used.

One of my favorite ways of interfacing to buttons of your stopwatch would be either an OPTO-FET or Optomos relay. The latter requires about 1 mA to drive the LED of the solid state relay. Usually a large mount of on resistance can be tolerated for a button interface.

There are magnetic latiching relays available. They just need a pulse to set the state and they retain it after power is removed. The most useful are dual coil. One coil for set and one for reset.

Looks like someone else has the same question here: https://forum.arduino.cc/index.php?topic=358401.0

I suspect microwave and laser are the best technologies.

Here's https://info.bannerengineering.com/cs/groups/public/documents/literature/03190.pdf more information that's currently in my head.

 

[Alchad]

Guys, thank you for the replies and info.

I should have said in my original post, the horse jumping takes place in an "arena" sometimes outside, sometimes inside, normally they're about 60 metres by 20 metres and there are separate entry and exit points (where the break beams would be setup). The judging point is located just outside the arena, usually in a small caravan or hut with a large window, and this is where the timer/stop watch would be located. Normally the judge(s) use a stop watch to time the competitors as the go through the start and finish points, but an automatic system as I've described is becoming more usual. I'd guess the distance from the start/stop beams to the timer would be perhaps 30 to 40 metres max (this is wireless transmission distance).

I came across this link

DIY: How to Make the Wireless Photoelectric Beam Sensors? | Technology News (burglaryalarmsystem.com)

Which is along the lines I was thinking. Not sure if the wireless distance of the wireless shown would be adequate but it's pointing me in the right direction.

Now to figure out how to start/stop the timer.

Alchad

 

[Reloadron]

OK, reading the link something to consider. Those little RF modules as pictured need to be able to encode a Start and a Stop so with the transmitter it needs to distinguish between Start and Stop.
Your display:

The stopwatch controls are:

• START : press the START button to start timer if stopped, paused or reset
• PAUSE : press the START button when timer is running to freeze display at the current elapsed time. Timer still runs in the background, only the display has been stopped. The output pulse every minute will continue because the timer is still running. Press the START button again to re-start the display. It will jump to show the current elapsed time
• STOP : pressing the STOP button when the timer is running also freezes the display. However, the timer is stopped as well and the output pulses are also stopped. Press the START button to re-start the display. It will continue counting on from where it was stopped
• DISPLAY TOGGLING : Pressing the STOP button when the display is frozen (paused or stopped) will toggle between Seconds/Hundredths and Hours/Minutes display
• RESET : at any time you can reset the timer by shorting the hardware reset pins together. You can also reset the timer when it is stopped or paused by holding the STOP button for 0.5 seconds

The board has an active low open collector transistor output (NPN 100mA, 30V max.). This can be used with to drive our 3156 relay board or the 3141 delay timer board.

Connections: DC IN, RESET, OUTPUT, STOP and START are brought out to a 10-way header strip for easy connection.

START and STOP buttons are also provided on the board.

So in addition to the buttons on the board they allow for external signals for start and stop. I assume all that is needed is a short pulse. I would just use a board like I linked to which comes with two key fob transmitters.

Ron