Hacking into a 196

Toobuilder · #1 10-01-2009, 01:45 PM

Forgive me if this is a little vague... Is there any way to pull data from a Garmin 196 to provide steering for an autopilot? I have an 80's vintage single axis autopilot (forget the brand at the moment) that used to be able to follow a LORAN driven course. I removed this unit the second I got the airplane home, but now I'm thinking of reinstalling it even if it only acts as a wing leveler driven from the head unit. It would be nice if there was some way "MacGyver" the 196 into talking to the autopilot and driving the airplane along the flight plan.

Any possibility here?

rich · #2 10-01-2009, 02:11 PM

Garmin sells a Power/ Data cable for the 196.

This power and data cable has bare wires at the end so you can hard wire your GPS directly to a DC power source or some other electronic device. This allows you to send speed and position data to devices such as a chartplotter, computer, auto pilot, radar, etc.
Part Number: 010-10082-00

https://buy.garmin.com/shop/shop.do?pID=519

w1curtis · #3 10-01-2009, 02:32 PM

You will need more than a power data cable. In addition to the power data cable, you will also need a device such as this. It will convert the GPS digital signal into the analog signal required by older autopilots.

http://www.porcine.com/gps/sc/sc_frameset.html

Toobuilder · #4 10-01-2009, 04:07 PM

Thanks guys! This looks like exactly the ticket!

Now, has anyone on the board done this, and if not, why not? Seems it adds a lot of new functionality to some of the older analog autopilots using handhelds that most of us own. I know it's hardly a replacement for a 2 axis TT, but...

Neal@F14 · #5 10-01-2009, 08:37 PM

I've hooked up several Garmin x96 portable GPS's to autopilots that can accept serial RS-232 digital gps inputs (Trio & TruTrak autopilots). It's actually pretty trivial to do that with the power/data combo cable from Garmin. The above mentioned Porcine Smart Coupler adapter for analog autopilots says it wants GPS serial data in NMEA format same as the Trio and TruTrak digital autopilots, which the Garmin 196 (all the x96 models) is happy to output. Selecting NMEA is just another choice on the interface setup menu of the Garmins. On the 296/396/496 models, you might also need to select the "advanced" NMEA option and make sure the output rate (different thing than the baud rate, which is 4800) is set to normal instead of "fast" since some of the autopilots can't handle the "fast NMEA output" setting which the color screen Garmins tend to have as their out-of-the-box factory default setting, and the Porcine coupler is likely the same way about the output rate setting.

Toobuilder · #6 10-01-2009, 09:21 PM

Well this is indeed good news! I dug through my boxes of removed "stuff" and found the AP - it's a Navaid (AP-1 head unit, S-1 servo) circa 1990. I have all the assembly and install manuals, and as I said, it was working when removed, so I guess I just need to get my hands on a Porcine coupler and start soldering.

The Hiperbipe needs constant attention going cross country, so this will be a welcome relief. All it took was one trip in the RV-8 to understand the value of an AP.

Thanks a million!

dan1376 · #7 10-11-2009, 10:33 PM

Long time lurker here, but just had to contribute to this one...

I purchased the Porcine unit (and had a 196) and it does drive my single axis AP but there is one problem that I could never overcome; the Garmin196 doesn't provide any turn anticipation, so the plane didn't begin to turn until after the (current and next) coarse line intersection had passed. If the next coarse line was less than about 5 degrees from the current coarse, the plane would oscillate (damping was adjustable) and would eventually settle-in (sort of) until the next coarse adjustment. If the next coarse was greater than 5 degrees the oscillation was ridiculous. The damping adjustments helped but it still wasn't acceptable IMO.

By no stretch of the imagination am I an experienced AP user so there may be some settings I never got dialed in right, but I gave up on the Porcine and went back to driving my relic AP with the VOR. YMMV

Dan H.

BTW this was a C172 not an RV.

sprucemoose · #8 10-12-2009, 02:36 AM

Michael,

The Navaid unit is a familiar one in the RV world, with many of them flying around for years. Navaid did manufacture the AP-1 with the Porcine unit built into the A/P head, not sure if yours is one of those or not, but might be worth looking in to. FWIW- I drive the AP-1 from my 196 so I have exactly the setup you are trying to build, feel free to contact me directly with any questions.

Now, if you want to put speedbrakes on the AP-1, you're on your own

Toobuilder · #9 10-14-2009, 03:28 PM

Thanks for the input Dan, I will be looking out for that.

Jeff,

My unit does not have the Porcine built in. It's SN# 82, so it's a fairly early unit. I bought the coupler and am in the process of installing the whole mess right now. I very much appreciate the offer of assistance - I might be taking you up on it. I promise to leave the term "speedbrakes" out of the conversation.