After a lot of struggle with wiring my three OEM fire handles and making a suitable panel for them it is finally time to interface the unit.

My trusted buddy “The Pokeys 57E” card helped me out again. I really like the Pokeys cards they are very stable, versatile and natively supported in Prosim737. The only thing Pokeys cards not do well is acting like an output card – that is lightning up annunciators. But I found a cheap solution to that problem: The ULN2803 chip. It is a small chip that can be bought from your average china store for a few $$$. It acts like a relay board for the ground-terminals. The board it selv does not require a lot of power to be activated so it can be handled by the Pokeys card. Each ULN2803 card can handle 8 outputs and requires 8 pins on the Pokeys card.

Using this you must wire your LEDs as common cathode. I have started running both wires (GND & 5v) all the way back to the interface board. Then it is not an issue. But if you share wires between the annunciators and the interface board it is the 5v (Or whichever voltage you are using) that is the common wire.

The OEM fire handles runs on 28v. I have a 24v power supply installed where I was able to adjust the voltage to 28v. The 28v is handled by a relay-board, again keeping the power draw away from the Pokeys card. Pokeys power the relays. That is it.

It has taken 2 months of work to make this panel. That includes design, build and interface. Not full time work but still a few hours each day. But now it is ready to be installed inside the cockpit and finally I have a fire panel. And a pretty cool one if I shall say my self. Those OEM handles really look cool!