[Top][All Lists]

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

[Paparazzi-devel] Hitec Spectra (PLL) Module and Eclipse 7 Radio

From: Matthew Currie
Subject: [Paparazzi-devel] Hitec Spectra (PLL) Module and Eclipse 7 Radio
Date: Sun, 13 Sep 2009 01:32:00 -0700
User-agent: Thunderbird (Windows/20090812)


I have been away for some time. I am back and on track to get airborne within a week or two. The changes within the project since I last left off are tremendous. Great job developers. The Pyrenees flight is inspirational.

I have spent most of the day trying to stomp out a serious and unexplainable "RFI" nightmare in Funjet today. I have a Tiny 13 v1.1 onboard complete with LEA-4P GPS, XBee Pro (2.4GHz 100mW), and PPM-tapped Berg 4L receiver. The problem was simple, or so I thought. The servos would chatter endlessly and the motor would turn on/off without command (in manual mode). It was more obvious when I ran the motor at 1/4 throttle. It would actually cut out, speed up, slow down, etc. My motor/esc are quite acoustically entertaining so it was easy to "hear". I went through a dozen different scenarios trying to resolve. I added a ton of ferrite chokes, routed all wires to the bottom of the fuse with metalized tape, covered the receiver in metalized tape, rerouted the antenna, removed servos, ESC, even soldered up/hacked another FM dual conversion receiver. Nothing would remedy it. Then I realized I had "NEGATIVE" in my pulse_type of my aircraft config file. I changed it to positive, reconfigured my setup and voila! or so I thought. For about 10 minutes the Funjet didn't glitch a single bit. It was so quiet and silent I forgot it was even powered on. I was bragging about this "simple" fix in IRC but moments later the plane began violently shaking, throttling, etc. It was back!

During the "RFI silence" I bumped my Eclipse transmitter and the episode ceased as quickly as it started. I began suspecting at this time it might be the radio but it wasn't so obvious. I carefully disassembled my radio. I had previously modified it internally to have a 3 POS mode switch conveniently located on the top. I decided to give the radio power to see if I could wiggle wires, etc. Within moments I smelt an evil scent... I turned to see a puff of smoke leave the back of the radio. Heart sunk, I figured I just ruined my radio. Through some careful poking around and following my nose I discovered something that I should also warn the others about. The Hitec Eclipse 7 is a rats nest of 30 AWG wires (literally, many dozens) all passing under and over circuit boards. What I discovered is that all of the through-hole components on the multiple different boards have razor-sharp leads remaining and one of the wires, likely from my last modification attempt had been pierced by a components lead! I figured the least I could do is trim ALL of the through-hole leads on all of the boards flush to the PCB to prevent this from happening again and so I did. I carefully removed EVERY piece of debris and finally blew out the transmitter with compressed air. Although I was convinced I destroyed the radio I put it all back together and powered it up. It worked... glitches and all!

Stumped, I began searching the web. I was not happy with the craftsmanship I saw in the radio so began suspecting a larger overall problem. It turns out there is a widely known problem with the Hitec Spectra PLL synthesized RF module I was using. Many even made reference to a date code of "507". Mine has 507 stamped on a little green sticker on the back. The problem is described as two fold. Some are saying its simply the electro-mechanical mating which occurs when the module is placed into the back of the radio. Hitec has added tape to all repaired spectra modules to make them fit tighter in the back of the radio. Apparently this snug fit has been enough for most people and solving an intermittent electrical mating problem with the radio. Another group is complaining about an overall faulty design with "glitching" building the longer the radio is left on as if it may be thermal. While some say static buildup, I am skeptical.

I disassembled the spectra module and carefully reflowed each pin on the electrical connector. It should be noted the female connector on the spectra module is tin plated and the male header on the radio is gold plated. I sprayed some heavy duty flux cleaner in the connector and on my solder job. I reassembled the module and also wrapped its sides in fibre-reinforced (thick) tape. I fit the module into the back of the radio snuggly. It has been 30+ minutes of my tx left on. All is quiet. I have to keep getting up and wiggling the sticks, as it is so calm and motionless I have no way of telling it is powered on.

Apologies for the small novel but there were a few points I wanted to get out. It sounds to me that the spectra module is not generally trusted in the RC community and a common recommendation is to replace it with a fixed frequency RF module. I may do exactly this. The glitching was so severe, I am convinced it would have been a plane killer.

Matthew Currie  VE7MJC
British Columbia, Canada

reply via email to

[Prev in Thread] Current Thread [Next in Thread]