Addon Light Going Out In Flight

[Sevyn13]

I purchased an addon light for my P3S and it worked for maybe five slights but now it's giving me problems. When I turn my drone on and turn the light on with the switch on the converter the light works fine and will continue to work indefinitely on the ground. When I turn the rotors on the light will still work indefinitely at idle. Once I give it full throttle and start climbing the light will go out around 4 seconds.

I tested the volts from the battery going into the converter and its around 16-17 volts, coming out of the converter going to the light is 12 volts, I held it in my hand and gave it full throttle to make the lights go out and tested everything again. Same voltage from battery but the converter output has dropped to 7 volts. Turning the switch on the converter off then on again makes the light come back on but full throttle will make it go out again. I also ran it without the light hooked up so there was no load on the converter then ran at full throttle for ten seconds and tested output and sure enough the output still dropped to 7 volts.

I thought it was the converter so I ordered a new kit. I replaced everything, converter, light and battery connector. But the problem still persist. Anyone have any ideas?

Here is the link to the light I ordered
DigiPower - Re-Fuel LED Headlight for Select DJI Phantom 3 Drones - White

Here's a pic from the site.

 

[Waylander]

Hi
It sounds to me like a volts drop at the input to the converter, where have you picked up the input supply voltage from.
You say in the second paragraph that on full throttle the output voltage dropped to 7 volts, and the input voltage was the same, did you measure the input voltage at full throttle, or did you assume it .
Waylander

 

[Sevyn13]

Hi
It sounds to me like a volts drop at the input to the converter, where have you picked up the input supply voltage from.
You say in the second paragraph that on full throttle the output voltage dropped to 7 volts, and the input voltage was the same, did you measure the input voltage at full throttle, or did you assume it .
Waylander

I am getting input power directly from the battery using the little connector that comes in the kit, it just slides on to the battery prongs in the battery compartment. I throttled up until the light turned off, throttled down then tested everything. That is when I see the voltage drop to 7 volts and the input voltage the same. I did not check any volts while at full throttle, I'll have to get someone to help me do that and hold everything.

 

[Waylander]

I am getting input power directly from the battery using the little connector that comes in the kit, it just slides on to the battery prongs in the battery compartment. I throttled up until the light turned off, throttled down then tested everything. That is when I see the voltage drop to 7 volts and the input voltage the same. I did not check any volts while at full throttle, I'll have to get someone to help me do that and hold everything.

Yes I understand the difficulty doing it yourself, cant you simply weight the Phantom down, with something through both legs...

Take the input voltage measurement at the terminals on the converter, and not at the battery terminals, it may be that there is a volts drop at the battery connector terminals.

Another way to check this, ( although this takes a bit of messing around and some soldering ), Get a 12v tail light from a car, solder some wires to it and solder those cables to the solder pads where the wires connect to the converter, if there is a volts drop across the battery terminals you will see the lamp dim when you Rev up to full throttle, that way you can still hold the Phantom in your hand.
Waylander

 

[Sevyn13]

Yes I understand the difficulty doing it yourself, cant you simply weight the Phantom down, with something through both legs...

Take the input voltage measurement at the terminals on the converter, and not at the battery terminals, it may be that there is a volts drop at the battery connector terminals.

Another way to check this, ( although this takes a bit of messing around and some soldering ), Get a 12v tail light from a car, solder some wires to it and solder those cables to the solder pads where the wires connect to the converter, if there is a volts drop across the battery terminals you will see the lamp dim when you Rev up to full throttle, that way you can still hold the Phantom in your hand.
Waylander

I was taking the measurements directly at the solder pads on the input. I was assuming it to be a voltage drop from the source, I wanted to see what someone else thought first.

So lets assume that a voltage drop from the source is what is causing this problem. Then why after I let off the throttle and input voltage return to normal the output voltage does not return to normal unless I turn the converter off and on again?

Also how would I keep the voltage from dropping? It used to work just fine and then this started happening. This light kit is made specifically for the Phantom 3.

 

[Waylander]

Hi
Well my initial assumption was a volts drop from the source, however there could be other explanations.
You say that the output voltage still drops off to 7 volts even without the load (LED array) connected, perhaps therefore it is not a Volts drop from the battery connector, thus the problem appears to be on board the converter.
Connect the converter directly to a fully charged battery external to the Phantom, power it on and then gently tap all of the semi-conductors on the converter, it could be that there is a "Dry joint" somewhere in the circuit, and at low RPM there is not a lot of vibration from the drones motors, but at high throttle the vibrations increase and cause a problem only at that time.
Gently tapping the converter circuit board could potentially show up a dry joint.
The way we test for this kind of thing on circuit boards at work is to use a freeze spray and a small heat gun to alternately heat up and rapidly cool the semi conductor devices, which often shows up a dry joint.
Good Luck
Waylander

 

[Sevyn13]

Ok, so I turned it on and tapped on all the different components and no change. Also remember this is the second converter I have tried.

 

[Waylander]

Hi Mate
OK understood.. but you have to eliminate something from the equation, ideally we need to create the fault externally from the Phantom.
Do you have a means to vary the voltage to the converter, for example do you have a 3 cell LIPO battery, whose output voltage is nominally 11.1 volts, but fully charged would be around 12.6 volts, connect the converter to a 3 cell, or for that matter to your cars battery, this will check how sensitive the converter is to fluctuations in the input voltage, if it works OK then its not an input volts drop problem.

Waylander

 

[Sevyn13]

So you are just wanting me to hook it up to a lower voltage to see if it works? The aircraft battery is 16 volts, you're saying hook it to a 12 volt source and see if it works?

 

[Philltayl]

I personally would Never hook anything external to the flight battery...........that is just looking for issues. Have you tried an external battery????

 

[Waylander]

Hi Sevyn13
So Ok yes I am asking you to do something out of the ordinary, and the reason is that we are trying to trouble shoot the problem.
So without benefit of a circuit diagram we have to make an assumption about how the circuit works, on board the regulator PCB ( Converter ) there will be an op amp and a comparator circuit, which monitors the changes in the input voltage and compensates for any voltage reduction in order to keep the output voltage at 12 volts. This is generally how a DC to DC converter works, and generally if the compensation circuit is well balanced and designed the converter will work OK even if the Input voltage drops down to almost the same voltage level as the output.
So unless the converter has a large on board capacitor, ( and I can't see one from the photo), when the input voltage falls below the output voltage threshold the output voltage will drop off accordingly.
In the workshop I would use a variable power supply, but I would not see a problem connecting to a battery provide there are no short circuits in the wiring.
Waylander

 

[Sevyn13]

So it was a bad connection. The connector that slides on the battery would briefly lose contact. I put a tad bit of solder on it to make the connection better and so far no problems. But I did break one of the mounts for the battery connector while doing all my troubleshooting. I ordered a new connector for $10 bucks, once I get it I'll just solder my leads directly to the battery input to the board to assure good contact. Thanks for all the help!

 

[Waylander]

So it was a bad connection. The connector that slides on the battery would briefly lose contact. I put a tad bit of solder on it to make the connection better and so far no problems. But I did break one of the mounts for the battery connector while doing all my troubleshooting. I ordered a new connector for $10 bucks, once I get it I'll just solder my leads directly to the battery input to the board to assure good contact. Thanks for all the help!

Hi Sevyn
Glad you sorted out the problem..
Happy Flying
Waylander

 

[Sevyn13]

Yeh I guess any slight voltage drop makes that board mess up somehow and you have to turn it off then back on to reset it.


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