What's new
Van's Air Force

Don't miss anything! Register now for full access to the definitive RV support community.

KY-97A schematic details request

az_gila

az_gila

Well Known Member
Could anyone send me a copy of just the lamps portion of a KY-97A schematic?

I need to see if it will work with my PWM lamp dimming circuit.

I think it might be just two short, isolated strings of lamps that can be wired in parallel for 14V and series for 28v, but I need to confirm that the lamp circuitry is truly isolated.

The installation manual isn't too clear on the internal workings...:)
 
Gil,

Sorry I didn't see your post sooner. While it will take a couple extra components, we can still make the PWM work with the KY97A. I also am installing a KY97A so I have a vested interest.

As a plus, King has already drawn up the schematic for what we need. On the schematic posted:
ky97ainverter.png


The output the the microcontroller in the KY97 is the same as the dimmer unit. In order for them to use that signal with their own lighting circuit, they had to invert the signal and then ampliify with a PNP transistor so it will work with the common-ground lighting. We just need to duplicate this simple circuit and connect it to the output of the PWM. They probably made it this way to be compatable with the old rheostat-type dimmers. They should have just had a separate ground pin that would be connected aircraft ground for voltage-based dimming or connected to the external controller for PWM dimming...ohh well.

I'll try to make some time this weekend to test out a circuit. I don't have my radio installed at the moment (working baffles and other things), so I won't be able to test on the actual radio.
 
On a side note if anyone has a more complete schematic, I would love to see it. I really want to know what PIN 1 (14v lighting low) connects to internally. The install manual doesn't say anything about that pin. I also looked up the Icom 200 manual (since it is a drop-in for the 97) and it calls it out as ground for the lighting pin, but shows no connection.
 
Gil,

I put together a quick test circuit last night. I realized that I don't need to invert the signal since I'm not trying to drive something complicated like a servo. I just used the output of the dimmer to drive a PNP transistor connected to the + side of some diodes that are then bussed to ground.

In the picture below, the white wire comming from the connector in the (-) output of the dimmer and in connected to the (- , blue) buss in the breadboard. The (+, red) buss is connected to battery power. The second (-, blue) buss on the lower part of the picture is connected to battery ground. The gate on the transistor is connected to the dimmer output buss via a resistor (to limit current) and the collector is connected to the + battery buss. one leg of the LEDs is connected to the emitter of the transistor (via some resistors to work with the 12v output). The other leg is connected to the ground buss.

cimg6204y.jpg


The LED array in the background is connected to the dimmer normally. The LEDs in the forground are connected in reverse so they now use a common ground rather than a common +. All the lights dim in unison. This setup should work just fine to dim the radio lights. I have no idea what the current draw on the lights in the radio are, but lokking at the schematic they should be less that 1watt.

I'll stop by radioshack this weekend and find a PNP transistor good to at least 5w for some margin and we will have a solid solution. Once I'm done I will post up the part numbers and schematic for you.
 
Very strange, I posted this yesterday, but it was gone today. Ohh well, here it is again:


Gil,

I stopped and picked up a more suitable transistor capable of handling the current for the lights. I made a prototype unit and bench tested it. Everything seems to be working as it should.

Here is the scematic for the new PNP transistor to drive the lights on the radio. The diodes are there to prevent the inverter from interfering with the rest of the lights and to prevent the radio from doing the same (or damaging the inverter). The transistor is capable of more that 1A, so if you need more output, you could use a larger diode on the output, but then the transistor may need a heatsink.

dimmercircuit.png


Here is a completed assembly. If you PM or e-mail me your address, I can send it to you. Please take note that I have bench tested this only. I don't have my radio wired up to test it in service.

cimg6212.jpg
 
WingsOnWheels said:
Very strange, I posted this yesterday, but it was gone today. Ohh well, here it is again:


Gil,

I stopped and picked up a more suitable transistor capable of handling the current for the lights. I made a prototype unit and bench tested it. Everything seems to be working as it should.

....

Here is a completed assembly. If you PM or e-mail me your address, I can send it to you. Please take note that I have bench tested this only. I don't have my radio wired up to test it in service.

cimg6212.jpg
Click to expand...

Whoa... fantastic. Address coming via e-mail.

I wired my comm radios up with short jumber cables to a "standard" 15 pin D-Sub I defined to enable future upgrades. This will work out well since your little assembly can just go in the jumper cable to the KY-97A. Works out well.

Again, thank you...
 
az_gila said:
Whoa... fantastic. Address coming via e-mail.

I wired my comm radios up with short jumber cables to a "standard" 15 pin D-Sub I defined to enable future upgrades. This will work out well since your little assembly can just go in the jumper cable to the KY-97A. Works out well.

Again, thank you...
Click to expand...

Gil,

I never received your address, so you may want to resend.

-Colin
 
You must log in or register to reply here.
Back
Top