Here you can see the PCB that I have made. All is controlled by a ATmega328P microcontroller that got a program from Arduino. It has 4 outputs at the bottom, that are switched in sequence, but when only 3 are needed, just leave the last. Note that each output can be grounded with a jumper near the relay.
To the left are 3 input terminals. At the top is power plus 12V and minus. The circuit can function on 5V when the 5V regulated is bypassed. In the middle is PTT input and at the bottom left you have relay return input. My relais input needed a 1K resistor in parallel to ground to work correct.
The top left are jumpers. First 4 from left are: Delay D-A.
A: 30 mSek, B: 40 mSek, C: 50 mSek, D: 75 mSek
The 5 jumper is for enable reverse status input from relay and number 6 is enabling status from relay.
Last connector in lower right corner is for TX inhibit that I now have added. Programming socket is the smal 6 pin header near the microcontroller.
On the picture, are all light diodes mounted on the PCB top. But instead on the PCB I would add some wires instead to the front of that box you can place it in. It’s good to see action status on the front of your case where it is mounted 🙂
Hope it gives sense how it works – else contact me.
P.S. – The four transistors in the schematic is of the MMBF170 N-Channel FET type or equlent type BS170 and component placing picture can be found down under.
Note that the 4 FET transistors and the 4 diodes near relays – are SMD types, and are placed on the solderside.