No hardware specified yet and no code written. This is just a sanity check and request for input to clarify my thinking (and perhaps point out things I have forgotten).
This is my second Arduino project, so I am not a total novice. My first was a display box for a 5-axis motor-controlled stage on a big scientific instrument. (UNO with Ethernet shield. Fairly simple messaging through UDP for updating any axis display and some commands for configuring the box, stored in EEPROM. Each axis display made from 2 4-digit 7-segment display driven with SPI).
I am looking to put together a flexible archery timing system. There are others out there but they are very expensive. I do not begrudge people making money on these as they are fairly niche and the companies have development costs to cover. However for small clubs we can not afford this and I would like to give this a go for my own interest too.
I have a number of design major decisions to make, and this is where I would like some feedback. Penny pinching is not needed, though I don’t want to be spending mega-bucks.The basic system will likely be as follows.
A central control unit (required)
Used by the judges to start and stop timing. Timing sequences can vary depending on the tournament. The actual programming of this will be somewhat complicated, but I think I can handle this (programming is my day job). Typically there will also need to be a number of buttons (up to about 10) for various start/stop/abort functions and possibly some menu functionality to pick timing sequences (hence some form of display like a 20x4 LCD). I will also use the display to show the count down on this box for the director of shooting. While at some venues mains power may be available that can not be guaranteed, so the system must have a battery option and ideally be able to run for at least 12 hours and preferably 2 days of 12-hours a day. (I will come on to communication in a moment).
Various Display/sound units
Similar commercial systems are supplied with a 2 or 3 different displays which need to be visible from about 60-80m. These display
a. count-down in seconds and a set of traffic lights (this may be optional but would be nice),
b. which groups should be shooting (alternates) (could be on the first display as instead)
c. a set of loudspeakers for audible start/stop. Could be part of the main display but for flexibility a seperate box would be good.
The main commercial system runs off 24v (2 car batteries strapped together) which can power for 2 days. It is cabled with some form of serial connection which also carries power (24v I believe) for all the display boards and speakers. This means a number of daisy-chained 30m cables which the archers regularly trip over thus disabling the timing displays!!
I am wondering about going to Wireless communications (Ciseco radios I think as they should happily do 300m with line of sight and they look quite nice in the way they work. http://shop.ciseco.co.uk/rf-module-range/). Then perhaps locating smaller batteries with each unit.
I guess my questions are these.
Anyone have experience with the Ciseco radio devices (positive or negative)?
Can anyone give me good reasons to stick with a wired approach (including power distribution)?
I am likely to put some form of arduino (or similar) in the remote units. I would like to ensure that several time display boards stay in step. Would I be better just starting the time with a single radio command and assuming the clocking is accurate enough for display to stay in synch (I am only looking for a maximum of 240 seconds). Alternatively would I be better sending out a change each second from the controller. The Ciseco devices could be set to all listen on the same command broadcast? I will probably play with sketching each approach, but thought there might be some exiting experience of this sort of issue. My feeling is that over 240 seconds I shouldn’t see any drift between displays.
I have spent a lot of time trying to locate supplies to make large LCD displays. I am looking for the equivalent of 7-segment digits at least about 4 inches tall, maybe bigger. Something like this (these are 4 inches tall).
My googling skills have let me down. I can find any number of small 16x2, 8x2, 20x4 etc LCD modules, and up to 6 inch single digit 7-segment LEDs. However these would probably take more power than I would want to run off a battery (unless some else can tell me differently).