Sam Buchanan
been here awhile
The Micro-Trak 300 works like a charm in N399SB. The customary installation of this little tracker has it hidden in some out-of-the-way corner of the plane and it is very content to hide there and do its thing with no human intervention. Feed it power and data and it just keeps pumping out the beacons.
However, I decided to mod the tracker so I could have it stuffed up under the panel and still be able to monitor the two LEDs that indicate good GPS data and beacon transmission. I'm still on the steep part of the APRS learning curve and would like to be able to verify that the Micro-Trak is happy and well.
Here is the little remote panel I fabbed out of scrap 3/4" aluminum angle:
It carries a mini SPST switch (power for the tracker, may be eventually replaced with a SPDT so the tracker config can be changed for emergency beacon) and two LEDs, all from the local Radio Snack store.
The (-) leads of the LEDs are tied together and go to tracker ground.
I considered several options for getting the LED signals out of the tracker. Allen Lord (designer of the Micro-Trak) was concerned that simply paralleling the new LEDs with the ones on the board would result in dim indicators. He suggested "lifting" the downstream ends of the two 1K current-limiting resistors on the board and connecting them to the external LEDs. I attempted de-soldering the resistors and met with little success.
I decided to just cut the traces on the board between the resistors and the LED's. This is minimally invasive since all it would take to restore the onboard LEDs would be jumpers around the trace cuts. The photo below shows how I ran jumpers from the resistor pads to the DB9 so the external LEDs could receive their signals.
I also added a ground wire so I wouldn't need to ground the external LEDs to the airframe. The red wire is how I supply ship's power through the DB9. A test rig on the bench proved the new setup works perfectly and the remote indicator panel will be attached to the bottom lip of the instrument panel next to the left side of the cabin.
Obviously if someone is hooking a serial GPS directly to the DB9 these changes won't work! A custom harness would be necessary to go between the GPS connector and the tracker DB9 with the required leads for external power and LEDs.
While in hacking mode, I decided to go ahead and run a lead to the DB9 for triggering an external amplifier. Byonics has a little 8 watt RF amp that I intend to add to the APRS rig and it needs a signal to tell it when to power up. This signal comes off the same trace that powers the red "transmit" LED on the board.
Fortunately I had one more empty pin on the DB9 so this worked out just fine.
Well......guess the warranty on the Micro-Trak is now shot.....but hey....this is experimental!
However, I decided to mod the tracker so I could have it stuffed up under the panel and still be able to monitor the two LEDs that indicate good GPS data and beacon transmission. I'm still on the steep part of the APRS learning curve and would like to be able to verify that the Micro-Trak is happy and well.
Here is the little remote panel I fabbed out of scrap 3/4" aluminum angle:
It carries a mini SPST switch (power for the tracker, may be eventually replaced with a SPDT so the tracker config can be changed for emergency beacon) and two LEDs, all from the local Radio Snack store.
The (-) leads of the LEDs are tied together and go to tracker ground.
I considered several options for getting the LED signals out of the tracker. Allen Lord (designer of the Micro-Trak) was concerned that simply paralleling the new LEDs with the ones on the board would result in dim indicators. He suggested "lifting" the downstream ends of the two 1K current-limiting resistors on the board and connecting them to the external LEDs. I attempted de-soldering the resistors and met with little success.
I decided to just cut the traces on the board between the resistors and the LED's. This is minimally invasive since all it would take to restore the onboard LEDs would be jumpers around the trace cuts. The photo below shows how I ran jumpers from the resistor pads to the DB9 so the external LEDs could receive their signals.
I also added a ground wire so I wouldn't need to ground the external LEDs to the airframe. The red wire is how I supply ship's power through the DB9. A test rig on the bench proved the new setup works perfectly and the remote indicator panel will be attached to the bottom lip of the instrument panel next to the left side of the cabin.
Obviously if someone is hooking a serial GPS directly to the DB9 these changes won't work! A custom harness would be necessary to go between the GPS connector and the tracker DB9 with the required leads for external power and LEDs.
While in hacking mode, I decided to go ahead and run a lead to the DB9 for triggering an external amplifier. Byonics has a little 8 watt RF amp that I intend to add to the APRS rig and it needs a signal to tell it when to power up. This signal comes off the same trace that powers the red "transmit" LED on the board.
Fortunately I had one more empty pin on the DB9 so this worked out just fine.
Well......guess the warranty on the Micro-Trak is now shot.....but hey....this is experimental!
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