Question

i 需要测量两点之间的时间。我无法使用简单的手表, 因为我没有免费的手。 (“ 坚固的” mountainbike - downhill )

我的第一个想法是设置两个GPS点,并测量这两个点之间的时间,但我认为这样做是不准确的。

我的第二个想法是将一个蓝牙装置设置到每个点, 测量从我到蓝牙装置的距离, 检查最短的距离并节省时间。

但比起我意识到我需要三个蓝牙装置来计算距离,这有点烦人

Any idea how i can measure the time between two points with an accuarcy <1sec ? I want to control this via smartphone.

编辑 :

Okay i have another idea. Maybe i could set one bluetooth device to each point. I set the signal strenth to <=1m. Than i could easily start and stop the time until i receive the bluetooth signal on my android. Do you think this would be the best approach ?

Answer 1

It seems you re trying to take total and split times for a course. Definitively, forget of using bluetooth for other things that are not constant transmissions, with slow connection time... (I speak from experience). Of course you want to do it in the cheap, because there already professional solutions for that (e.g.). From my point of view, if you want something accurate and been able to integrate it with you phone, you ll need the following:

DIY photocell sensors. Maybe involving simple chip (e.g. msp430), phototransistor-diode pair, cheap 433mhz transmitter and batteries.
DIY 433mhz receiver for your phone. There already many boards that supports android open accessory library, (e.g. 49$ from sparkfun), so you only have to connect it to a 433mhz receiver and to your phone.
Custom code programming in your android phone. To be able to receive the signals from the split signal senders and keep track of all times.

这个计划在250-200美元以下(如果你自己做了:P),

Answer 2

不需要任何特殊硬件的一个可能的解决办法就是在终点线使用智能手机。您只需要有网络连接的专用智能手机和一些软件。

SP sends the start signal to your phone. You start when you hear the signal.
SP uses its camera to detect when you reach the finish line.
SP calculates the time between start and stop and displays it, and possibly sends the info to your phone, too.

也许你甚至可以录一段带时间邮票的录像

(当然,低成本的解决方案是让其中一人在终点线使用手表。 )

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