I measured the voltage coming down the leg wire while the system was "at rest" (i.e., the stick was in the neutral position). The voltage should have read zero volts, but instead it read over 12 volts.
Note that the Vantec RDFR23 speed controller uses Pulse Width Modulation, so my simple multimeter can't be used to reliably measure changing voltage over very short periods of time, but it can at least show zero or non-zero voltage. Yet, the motor would not turn.
Next, I put the motor directly on a 12 volt battery, and it ran just fine, in both directions. This would seem to indicate a contradiction of sorts, although, as I said above, the multimeter may be showing me 12 volts, when in fact that current is only present a small percentage of the time, and not enough to drive the motor.
I played with the trim on the transmitter until I got the voltage down to zero in the neutral position, and then reconnected the motor to the wire running down the leg. Lo and behold, everything started working again.
So this is still a bit of a mystery. At the moment, everything is working fine, just as it should. The motor is not dead, the speed controller is not dead. Still, I'm not yet confident that I don't have a flaky issue on my hands. Thus, I still plan to visit Mike on Sunday to troubleshoot what might have happened yesterday.
For now, I buttoned most of the foot back up, leaving the battery box off. We shall see what we discover.
9 comments:
Victor, any possibility the radio was in it's bag with the power on and the trim was inadvertantly pressed. According to your post, you reset the trim and all was well.
alan
Alan, that seemed like a plausible cause for trouble. However, today while troubleshooting at Mike's we messed with the trim in pretty much every setting, and the motors would respond to stick movements, unlike Thursday. I will need to keep a close eye on any future misbehavior, and be more careful not to "fix" the problem without knowing exactly why it's fixed.
Thanks for commenting, and if you have any other thoughts, please pass them along.
What about the tx itself? Could be the tx is having an issue? You could check that theory out by swapping out your module with Mike (Doesn't he have the identical radio to your Futaba?) You could copy your settings to his while things are good and then use his radio down the road if you experience this issue again.
alan
Tx could be the problem. If/when it ever happens again, I will want to include what you suggested in our list of troubleshooting steps. I also considered whether the Rx might be going cuckoo or perhaps battery was low, but both Tx and Rx batteries looked reasonably full.
The thing is if it were battery, all channels would be abnormal. That is the problem with inconsistant issues in rc. Imagine having a $20K rc jet in the air and the link hiccups!!!! If all else fails, there is always Spektrum. Any possiblility of a loose/marginal rc connector for that channel?
alan
Another thought, if your receiver is PCM, it could be set for failsafe. Failsafe is a user selection to cause a servo to zero out when the rx receives a spurious, outside signal. In RC, we set the throttle channel to low so as to maintain flight control surfaces. The spurious signal will cause the one servo (throttle) to go to zero/low which signals you to get on the ground asap as something is jamming the rx.
http://rcvehicles.about.com/od/glossary/g/failsafe.htm
alan
Weird failsafe behavior is a possibility, although I'm not sure if they would apply only to certain channels, or all of them.
I checked the Rx connections at the hospital. I was able to push one or two connectors in a bit further, but it didn't seem to help while on site.
I suspect whatever the problem is, it may have to do with the cross country trip to CV and back, where there were several days of near constant vibration.
Thanks,
Victor
Incidentally, I don't mean to sound like I keep ruling things out. Obviously something was/is wrong, and it may well be on the list of things we've covered. It reminds me of troubleshooting hardware and software in my job, and when we've ruled everything out, we look at each other and decide that the problem must not have happened(!).
Failsafe is only one channel if memory serves me. If your radio is set to set the one channel to zero, that could cause the problem. But I hear you, sometimes, glitches happen once and then that is it. They never appear again.
alan
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