Just dipping my toes into this project. It is essentially a rebuild of a commercial unit that has had the remote control misplaced and there is no source for a replacement.
I have decided to go with an arduino based system to build the remote and link these with the Nordic radio module with antenna to 'mesh' the receivers form one transmitter (remote control).
The remote will have a dual line LCD display allowing for event round time setting. It will then countdown the 'waiting time' (10 secs) to the main timer start and then into the preset timer with a green indicator lamp. A warning to the archers will be given via an amber light with 30 secs to go and finally a red light to show event completion along with a sounder.
There are other designs out there but I have selected this way as it seems the best solution to interface to the existing displays I have.
The receivers will need to be rebuilt in the displays and modified to accept another arduino acting as a slave of the remote to display the time, lamps and run the sounder. All powered from a 12V 7Ah battry.
The remote will be powered from 4 x AA cells.Or possible a LiPo battery.
So far I have had a single line 16 character LCD which I have discarded after I found that
1. I needed more characters to display tidily.
2. The 16x1 (1601A display) line to character layout is really messed up.
The 1601 displays appear to chop the display into 2 halves that are addressed in different locations making text longer than 8 characters very interesting to try and display.
I opted for a 1602 display to overcome this issue. It works great and is very easy to address with the standard LCD library for the arduino.
So now that I have the display going I will be attacking the keypad data entry next. I hope to have the remotes software pretty much nailed after this and then I can concentrate on reverse engineering the displays to rip out what I do not need and convert them for my use.
This will be a longer term project when I can find the time to spend on it, but I Hope that I will end up with a very usable result.