In my car I have the Federal Signal SS2000 (SmartSiren) a unit that controls lights and sirens for emergency vehicles. It has a keypad controller that's connected via an RJ11 wire to a control head / amp / "brain" unit. The keypad has numerous buttons that do things like turn on and off individual lights, blow the air horn, activate the siren, etc.
I wanted to add my own buttons to trigger some of these functions, separate from the keypad. My first thought was that the easiest path would be to simply unplug the RJ11 from the "brain", plug it into my own circuit board, have an RJ11 output from my circuit board that goes into the "brain" and basically I will pass through any signals that come from the keypad and relay them onto the "brain," along with triggering my own functions when needed.
Given the number of wires in the connector (assuming voltage, ground, then two more for data), is it naive of me to think that I'll be able to read/decode the signals that come from the keypad? Could it be using some proprietary communications methodology/signaling and I won't have any hope of decoding it for the purposes of redirecting the commands / sending my own commands?
Any guidance would be appreciated.
Here's a link to the product manual:
https://www.fedsig.com/resource-document/file/8043
Thanks!
Did you notice that the device is programmable already?
You'll have to find out where the "intelligence" resides, in the control head or amp/relay unit. I'd guess that it's all in the amp/relay unit, so that you have little chance to add functionality from the RJ11 connector.
But of course you can try to find out the physical connection (purpose of the wires) of the RJ11 connector, the logical connection (signal levels and protocol), and the meaning of the transferred bits.
If this is fitted to an emergency vehicle and it goes wrong, and someone gets hurt , what about the insurance/liability aspects... ?
I'd not touch it myself.
regards
Allan
- This is my personal vehicle, it is NOT used to transport patients
- The modifications I'd like to make are meant to be used in non-emergency situations
- I'd like to do this project to learn more about electronics, not necessarily a long-term modification to this system.
What do you mean by "little chance to add functionality"? Why not?
If this is a 4-wire interface, is it likely that it's power, ground, rx, and tx? If so, is it still more likely that I'd be able to simply hook up the "brain" to my computer (via an arduino) and see what data is being sent on the rx line?
If you left the lines connected and monitored them with a scope, you'd get an idea of data rate.
If 2 lines had inverted signals it's a rs485 differential interface.
In either case use a terminal programme on your pc to a rs232 input and see what you get...Putty for example...
regards
Allan
ok, i'll give that a shot, thank you!
osmosis311:
What do you mean by "little chance to add functionality"? Why not?
If the control head is only a dumb keyboard, the controller in the amp/relay unit will act upon keys as programmed. Then you'll have to replace the controller in the amp/relay unit, if you want to add functionality.
If the programmable controller sits in the control head, you'll have to find out which commands it sends to the other unit, before you can start sending your own command sequences.
Just to be clear, I'm not looking to add functionality, I'm simply looking to hook up my own buttons that do the exact same things as the existing buttons on the keypad.