Garmin 430W, KT76, and Dynon Encoder

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dahugo
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Garmin 430W, KT76, and Dynon Encoder

Post by dahugo »

Gentlemen, I am wiring a KT76 with a Garmin 430W and a Dynon FlightDEK 180 which uses an "encoder."

I paid to have a wiring harness done, and the manufacturer said "There are isolation diodes needed between the transponder and the 430W. This is becauwe the transponder does not have internal diodes while the 430 does."

Tihs makes NO SENSE TO ME. It seems the my harness manufacturer SHOULD have written "there are isolation diodes needed between the transponder and the 430W. This is because the transponder has internal diodes while the 430 does not."

Bottom line is, I am CONFOOSED!!!. Do the diodes go on the 430W side or the KT76 side before being fed into the dynon encoder?

I have already wired the approprate diodes in the Garmin 430W side. Assuming I am wrong and the diodes go on the KJ76 side, can I just leave the430W side diodes where the are with no ill effect and then add the diodes to the KT76 side?

Hep me! Hep Me!

Thanks,

HUGO

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bullojm1
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Post by bullojm1 »

Hugo,

Just curious -- what information does the KT76 feed the 430W? From looking at the installation manual for the KT76 (http://www.aeroelectric.com/Installatio ... T76-78.pdf), it takes a power input plus the parallel encoder input from the Dynon encoder. I don't see any provisioning for any interfacing to a 430W.

If you can give me the pin's this data is going to on the 430W and KT76 I might be able to help more.
Mike Bullock
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Brantel
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Post by Brantel »

The Dynon outputs serial ALT Encoder data. This data can be converted to Parallel Grey Code data that the KT76 needs by using the Dynon Serial to Parallel converter.

The 430W can use serial or parallel data.

One could split the Dynon serial output between both the 430 and the converter but you will need to make sure that the 430 can be set to understand the same format as the Dynon converter requires because you will be forced to use that format since it is required to get the converter to work.

Most transponder signal lines are active low which means the encoder typically is an open collector output that pulls the line to ground when active.

The diodes are required to prevent one device or the other from becoming a problem if one unit fails or if one unit is turned off. The diodes prevent one device from falsely pulling the other device's inputs low.

The KT76 install manual shows that it must use external diodes if used in a system where you have two devices connected to one encoder output. Therefore the KT76 most likely does not have internal diodes.

The 430 install manual confirms that it has internal diodes so none will be required for it.

Looks like you have the diodes on the wrong device. Having double diodes on the 430 may not be a problem but they are not needed and I would remove them.
Last edited by Brantel on Wed Aug 11, 2010 10:22 am, edited 1 time in total.
Brantel (Brian Chesteen),
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Spike
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Garmin 430W, KT76, and Dynon Encoder

Post by Spike »

Wow you have some smarts!

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Wed, Aug 11, 2010 14:18:43 GMT+00:00
Subject:
Garmin 430W, KT76, and Dynon Encoder



The Dynon outputs serial ALT Encoder data. This data can be converted to Parallel Grey Code data that the KT76 needs by using the Dynon Serial to Parallel converter. The 430W can use serial or parallel data. One could split the Dynon serial output between both the 430 and the converter but you will need to make sure that the 430 can be set to understand the same format as the Dynon converter requires because you will be forced to use that format since it is required to get the converter to work. Most transponder signal lines are active low wich means the encoder typically is an open collector output that pulls the line to ground when active. The diodes are required to prevent one device or the other from becoming a problem if one unit fails or if one unit is turned off. The diodes prevent one device from falsely pulling the other device's inputs low. The KT76 install manual shows that it must use external diodes if used in a system where you have two devices connected to one encoder output. Therefore the KT76 most likely does not have internal diodes. The 430 install manual confirms that it has internal diodes so non will be required for it. Looks like you have the diodes on the wrong device. Having double diodes on the 430 may not be a problem but they are not needed and I would remove them.Brantel RV-7/TU, #72823, N159SB O-360Carb, 2 Slicks, FP Metal Prop D100,D120,HS34,AP74,SV32Roll,SV42Pitch, Aera 510, A210 Com, KT76A xPonder, Zaon XRX PCAS, PM3000, LS Zulu Headsets Phase I completed 06/12/10 Dynon AP Alpha/Beta tester rivetbangers.com - Discussion topic http://www.rivetbangers.com/forums/viewtopic.php?p=34644#34644
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dahugo
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Post by dahugo »

Thank you, Brantel. Your explanation and instructions were MUCH simpler than those provided by the guy that built the harness.

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