Linking secondary ground wires from 3 dc/dc convertors

[collectors]

Hi, i have a 6amp 20v power supply that also runs a 20v to 12v convertor & a 20v to 5v convertor, so 3 voltages on the lay out from 1 power supply.
Now i have some 5v IR sensors that i wanted to use to switch a 12v relay panel using a low signal. So i connected everything up & the 5v IR,s would not trip the 12v relays with a low signal. So i tried linking the ground wires on the secondary side of the 5v & 12V convertors & hay ho all worked fine.
But is this ok to do & should i think of connecting all grounds together on the secondary side of all 3 voltages. Thanks

[Flashbang]

So long as the power supplies are separate or each supply comes from a separate winding or as in your case all three supplies come from one source then linking all the Ov together is fine.
Its normal to do this on most electronic circuits and especially those that use active low switching.

[collectors]

Many thanks Brian. Wasn't sure if i needed a diode or similar to keep them apart.

[Flashbang]

No, no diodes needed