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Help Needed, Acc.Power Jack Added, Switched Remote Jack FAIL!

Discussion in 'Pro/Adv Discussion' started by JonEQuest, Jun 25, 2016.

  1. JonEQuest

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    I have been trying to mimic an "extra channel" on my P3P so I can switch off and on lights or any other mods I may have on the bird. I had a mercury switch on the gimbal but was never crazy about it. My latest attempt was to add a relay to trigger off of when the front red LED's are on. Simple enough right? Well no, not really. It turns out that the front LED's run on ~4.3volts and all I had in my junk pile of parts (I have a lot of stuff) was 12v relays. Radio Shack as always didn't have anything useful, so I ordered a pack of ten 5v relays (cheap as 1, really) from Amazon and waited 2 days for them to come. It turns out that the power to the LED's is so weak it cannot even turn on the relay with the LED's connected or not. It is really weak. I don't know if I have a meter problem but the amperage of the LED's is about 0.15 milliamps. Yes .15, almost nothing. I already have a nice jack on the side of my bird now for a remote NC or NO remote plug to go in using a mini headphone jack. I also went ahead and added a battery power port using the regular sized headphone jack plug as well. So the power plug is nice but I really wanted a way to remote switch my 100watt LED, disco light, etc. remotely. I think the next thing may be a light sensing circuit but that gets complicated. Any better ideas?
     
    #1 JonEQuest, Jun 25, 2016
    Last edited: Jun 25, 2016
  2. JonEQuest

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    Added photos.
     
  3. N017RW

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    LEDs are current controlled devices.
    Most generic LEDs require about 20 milliamps (0.020 amps) to operate nominally. So I assume your readings were milliamps not microamps (.15 milliamps = 150 microamps) as that is not enough to drive LEDs.
    The drive circuitry was not intended to have available excess 'capacity' for adding accessories as this increases costs and to a lesser extent weight.
    The approach some 3rd party vendors have chosen is to use a photosensor to detect the LED illumination and use that to switch an independent circuit to drive other accessories. While this is not the only solution it is the 'cleanest' way to do it.
     
    #3 N017RW, Jun 27, 2016
    Last edited: Jun 27, 2016
  4. HWCM

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    Do you have any other RC stuff? Maybe use a second controller and a reciter to operate a switch.
     
  5. mrgoodwrench

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    Could you build a small amplifier circuit to increase the LED feed to an acceptable amount of current to trip your relays? A transistor and a few diodes should do it and wouldn't add much weight. I would think you would have to drop the original LED's from the circuit so as not to overload the driver on board the phantom.
     
  6. mrgoodwrench

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    You are using digital relays right? I've never tried to trip one with that small amount of current but I'm surprised the current you have isn't enough. What meter are you using to read the current output?
     
  7. Imabiggles

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    Use a transistor on led circuit to control relay and draw power from a tap on the board directly from battery the led circuit will burn out if u try to power anything higher in amps a transistor shouldn't upset the circuit as is very low mAmp draw
     
  8. JonEQuest

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    I have been out of town on vacation. I thank everyone for the suggestions and understood that the LED's would not need much power to drive them. I was honestly surprised that they run on so little current. (N017RW) I also understand that the current sounded way to low but that is what my meter showed. I wish I had another meter handy but I had one at home and my other one at another property I own. I didn't want to wait any longer to put the drone back together because I was going to the beach and needed it to film. (I got a shark on video BTW). I was hoping that I would have enough current to trigger a low power relay. Obviously not, so I need to find a circuit that will let me use a transistor, possibly photo sensor driven. I would like to keep the Phantom circuit isolated as much as possible. I can see a shorted transistor passing current back into the LED array and causing lots of trouble. That is why I usually love relays. They are simple and isolated. Does anyone know of a good circuit to use a light sensor or LED power to activate a relay or a transistor as a switch? I guess this one will be about as simple as it gets. I guess I need to order some more parts unless I have some stuff laying around in one of my junk boxes that will work.

    [​IMG]
     
  9. SpiderManP4P

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    Hey JonEQuest I would love to know exactly what u came up with and yes u are right about the .015 milliamperes.how many wires were run to your led? I'm guessing 2. get this ... in the p4p there is 3 wires (1)NEG. (1) 0.015milliamp and (1) 15.85volts !!!! I'm so confused. I desoldered the led and tested the wires cause I'm using the curcuit to control a servo. I was trying to build it myself after I seen this. And this should help many birds out. It's a SARbox. Go to gimbal-guard.com/sarbox. There you can get payload servos and light bars as well as other stuff and it's built for the P3s and P4s all of them. Check it out and also let me know what u did to make urs work please
     
  10. JonEQuest

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    I used a photo resistor to trigger a transistor at a certain light exposure. When the front arm LED lights up, it changes the resistance of the photo resistor that is glued near it. This change allows the current to turn on the transistor that in turn powers the coil of the relay to switch it on and off. This multi step circuit is needed because the LED lights used have very little current. Far too low to power the coil of a relay. The P3 also has 3 wires that run to the LEDs. I could have probably used power from the red LED to power the transistor but wanted something that had no actual connection to the circuitry of P3.

    Note the 3 wires going to the LED
     
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