The self-start mode is obviously useful when you want to time yourself, but it might have other purposes as well. For example, can it be used for a group of runners when there is no coach available, or when he wants to be at the finish
Apple Watch
The easiest (and coolest) setup is to start with an Apple Watch. Since SprintTimer v.
Some notes for this to work: The watch can NOT communicate while asleep (the screen is black). So the watch app must be running when you do the set up on the iPhone. Also, increasing
Sending the sound from the iPhone
Relying on the internal loudspeaker when playing the start commands and the start signal of an iPhone/iPad is unfortunately not very useful. It will be heard 10 m at most (a little more on the iPad), so it must be amplified or transferred. Some options are:
- Loudspeaker
- Bluetooth speaker or headset
- Long sound cable
- Walkie Talkie
A loudspeaker can usually work up to 30-40 m, and you will need a really powerful one to be heard at 100 m (and that won’t be very discreet :). A Bluetooth speaker/headset will also work up to 30-40 m with luck. I have tested the Apple AirPods and they work fine for a start at 30 m. There are some long-range Bluetooth adapters that might get you up to 100 m, but unless you have a use for them on other occasions, they are probably not worth the cost. Note that Bluetooth often will introduce a delay that affects the accuracy, this is discussed in this post.
A long loudspeaker cable is simple and reliable, and doesn’t have to cost much. It can also double as a microphone cable for sound triggered start. But you have to make it yourself, and it is, of course, a hassle with all that cable. See this post for some tips.
A Walkie Talkie is pretty convenient; it has a long range and a negligible delay. Place it close to the iPhone and take the other unit with you to the start. Many walkie talkies will only send a sound when the send button is pressed and you, therefore, have to come up with some mechanism that keeps the button pressed. I used a small clamp as shown in the picture. It is a bit primitive, but it works, and it is only for practice after all.
It is usually better to turn the Walkie Talkie with microphone towards the iPhone, but this gave a more desciptive picture.
Start Sender
If you have two iPhones/iPads you can, of course, use Start Sender with a self-start. It will require a network so these tips might come in handy
Reaction time
The self-start also gives an opportunity to measure the reaction time at the start. You can either use an Apple Watch or an iPhone running Start Sender. The runner must have the device on him, so the iPhone can be in a pocket or in an armband. Alternatively, you can place it on the starting blocks. In that
You don’t have to make any special setups. The reaction time will be displayed directly after the start in Start Sender and after the recording has finished on the Apple Watch. This gives a great way to practice and evaluate starts. Place an iPhone/iPad with Photo finish at 5 m or 10 m and get both the reaction and the first acceleration. Or use Video finish without motion detection and 60 fps to record the first steps.
The reaction time is measured from the moment the start sound is played until the accelerometer in the device goes above 0.1 g. You should not compare reaction times measured with the watch and the iPhone, or between an iPhone placed on different locations. Also, note that measuring reaction time requires that you have SprintTimer Pro.
