Hi,
Please bear with me, I am not a robotics hobbyist but I do have real life application for this tech.
We sail small boats and race, for which we need a race starting system, traditionally done with flags and guns, more commonly now with lights and horns.
I know how to wire up a huge 7 segment ‘8’ display from a USB relay module, that’s easy.
But how can it be controlled? I am not a software developer but can I adapt an Android app to control the 7 segment relays and can I create a nice friendly easy to use Android front screen?
Any help appreciated
Thanks
Tim
Hi Tim,
There are many ways to go about what you are describing. Of course, most of them are not exactly simple… 
The first step would be to define your requirements further, such as:
]What method of communication is to be used? Bluetooth? WiFi? other?/:m]
]What range is needed?/:m]
]Will the display be battery powered or connected to a stable power source (like a wall adapter)?/:m]
]What kind of control do you need (simply on/off (fixed characters)? display a predefined set of characters? more control?)/:m]
In most cases, the solution will go around obtaining some kind of microcontroller and wireless interface that will control the display and abstract communications with your Android device into a virtual serial port.
From there, you can write a bit of code to control your display based on commands received.
The exact parts needed depend heavily on the questions above and any other design requirements that you may have.
If you only need to be in short range, a good option may be a Bluno microcontroller board. They are simple to use (Arduino based) and have integrated Bluetooth. The manufacturer also offers basic apps for Android support (and also some iOS support for the Bluno versions with Bluetooth 4.0 BLE). There are also plenty of generic serial port apps for Android that could be used, such as the one in this blog post. The app used in this tutorial can be found here.
If you need something longer range than regular Bluetooth, the setup will most certainly get more complex.
Sincerely,
Thanks Sebastian,
Reliability and simplicity are important so I had imagined connection via USB cable, Bluetooth sounds shaky and Wifi would rely on a router which would limit transportability. There is the potential if this works well to send this out in a boat.
Power for relays & lamps could be a 12v wall socket which could be battery again for portability.
The display operation will not be sequential numbers, only 5,4&1 will be used counting down in 5,4,1 minutes but there will be other signals by flashing alternate segments etc. So I had imagined treating the 7 segments as 7 separate lamps and finding a way to program accordingly.
I think the problem for us will be creating the idiot proof app. Lots of people will be operating this so we need to be able to create, or have created, a simple looking front screen that does all the timings etc.
Tim
If your Android device has a USB port that doubles as a host port, you could potentially connect a USB to serial device to it, such as these:
USB To Uart 5V/3.3V Serial Adapter
CP2102Micro USB to UART Adapter Board
You can find more here.
Of course, you may also be able to simply connect directly and Arduino or other similar microcontroller board, which would be responsible for driving the display directly.
Is the Arduino similar to the Rasberry Pi?
Do these devices have onboard relays or relay drivers?
And what would form the user interface?
Hi,
The Arduino and Raspberry Pi are actually quite different, both in hardware/software and intended use. Please see this blog post for more details.
Neither of those boards have any relays or relay drivers directly (at least not the official boards).
This will be up to you to decide. The amount of potential solutions is great and the choice will mostly come down to what you need & can implement yourself.
You can find many relay and LED controllers available here: robotshop.com/en/relays-led-controllers.html
Sincerely,
Thanks for all your help Sebastian,
It sounds like I need to talk to a software developer. the hardware is obviously the easy bit.