I have the flying down pretty good with about 2 dozen successful manual flights and missions, but one thing that's been bothering me in the build manual is this section on 'backup power'.
One the one hand it says the zener diode is best but not required. Should I connect the backup power and is it necessary to use the zener diode? I'm no electronics wizard so any detailed explanation of what's the best route to take is appreciated. I'm sure I followed the assembly instructions closely with the exception of this section as it does give options for the backup power wire which is currently not plugged in.
Thanks
http://3drobotics.com/wp-content/uploads/2014/05/3DR-DIY-Y6-Build-Manual-vA.pdf pg 18
Replies
I had trouble last year installing two strobes in parallel to my pixhawk. They worked fine (switch by rc channel 9) when the drone was not armed and motors Not engaged however, when they were the strobes were erratic with what looked like trace voltage causing them to flicker constantly.
Are you suggesting I run a ground from the front side (flight battery) connected to the signal pin on the backside rail?
(Which pin exactly should this reference ground be connected )
Note: my ESC are opto, no power, also I apply 5 volts to backside rail with separate 3s battery and BEC
A zener is a diode that works at what's called it's "Breakdown voltage", and is designed to do that. They are found in all kinds of power supply devices, the word "regulated" basically means it has a zener in it to keep the output voltage constant.
A normal diode has about a 0.7v drop, and only allows current to flow in one direction (think of the striped end as a wall). LED's are diodes, but use the extra voltage to produce light (normally run around 2v).
A zener, here the 1N5339, works backwards. It will maintain the voltage at 5.6v by eating current (Volts = Current * Resistance). Normally in a regulated power supply circuit you have a current limiting resister in series with the zener, so you don't let the magic smoke out of the zener.
Mouser link to the 1N5339B:
http://www.mouser.com/ProductDetail/Micro-Commercial-Components-MCC...
The part specified is a 5 watt zener, so using watts law (Watts = Current * Voltage) you can use up to 0.89 amps at 5.6v supply, or 0.41 amps at 12v before failure, though it will get very hot running at that current level.
Backup power can be a good thing, but it will add a bit of weight for the extra components. Do you value redundancy, or more flight time? To me, redundancy is very important so I would connect up the backup power components.
Murphy's Law is a constant companion in our RC vehicles, so anything I can do to slow it down is a good thing in my book!
Thanks Joel. We had the right zener diode at work, and will put it on. The instructions really weren't clear and one would think 3DR would supply a connector with it.
One more question. What settings are normally used for Low Voltage warnings and Failsafe? I have it set at 14 for 4S battery. I calibrated the voltage in MP but will have to redo the current test because I reset everything a week or so ago.
DG,
The safest answer I can give is "it depends". Someone with more Y6 experience I hope will chime in here.
A quick google search turned up this article on LiPO batteries, it's a long read but you don't need to be an electrical engineer to understand it all:
http://www.rchelicopterfun.com/rc-lipo-batteries.html
If you don't want to read through it all, jump to the heading "OVER DISCHARGING - THE NUMBER ONE KILLER OF LIPO'S" and you should be able to do some calculations and testing. Start conservative, and keep good notes, you'll start to see a pattern over time.
I have mine set for 14v for 4S with auto land as the immediate action but would suggest this is your final backstop. I have similar alarms on my helis and they have come in very handy, especially if a pack has gone bad on you.
My main failsafe is actually the current where I set it to 4800mA, I have a 6000mAh pack so this is 80%, which again does an auto land. I guess you could set the current lower and set the action to RTL so it comes back to you but this would then depend on how far away you fly as you need to allow enough for it to get back to you without falling out of the sky.
I tend to always fly close to or to the failsafe although the timer on my radio gives an even earlier warning which I use to bring the Y6 back to a reasonable landing area if flying far out or high before the auto land would happen.
PS I've not been flying the Y6 for long, couple of months, so others may have a better idea, but I have flown helis for a number of years.
Did you calibrate the current and voltage before using those settings? I found both to be off by quite a bit in MP. What is the "reserved mah" for?
Sorry DG, my bad, I set the reserve to 1200mAh which meant I would hit the failsafe after using 4800 mAh.
I did do some basic calibration on the voltage, simply took the pack voltage from my charger and corrected the pixhawk measured voltage to that. Once done the current was reasonably accurate. Again simply took the current added from my charger which was within a 100 mAh compared to the failsafe which is close enough for me.
It pays to have a good charger, I have an iCharger 306B which is great.
Thanks.
I have an iCharger 206b and use a power supply from a retired PC (500w).
What battery are you using? Mine are Tiger Power 6000 mah (3DR recommended, not bought through them) and right now I'm not having warm fuzzy feelings. It looks like one cell will not go above 4.13v in one battery. It was not over discharged.
I contacted Thunder Power for a 6600 4s and they are not cheap ($204), but like anything else you get what you pay for I suppose; have read accounts of some not having much good to say about the Tiger Power. Of course that was after I bought them in early June, and they no longer sell them.
A lot of people buy the Turnigy Nanotech, but have heard both good and bad. Anyone feel free to chime in.