(21-Apr-2022, 11:44 AM)iFly4rotors Wrote:       Just a note here, many FC boards do NOT have a 3.3 volt
      rail, so 5 volts is the only option unless one wants to add an
      external 3.3 volt BEC. 

All FCs have a 3.3v rail because this is what the MCUs run off of, and almost all also have a 3v3 pad broken out . Some Spektrum receivers require 3.3v instead of 5v, so the 3v3 pad is usually near the UART meant for the receiver.

Hi V,

Thanks for that clarification. Even though they all might have a 3.3 volt rail, there are some 
FC boards that I just don't see any break out pads for 3.3 volts. Now, I will say that I am getting old 
and I don't see as well as I once did...plus some of the imprinting is hard to read. I have went back 
through all of my FC boards and done a little additional research. However, there are still some FC's 
that I can't find any 3.3 pads.  Some boards may have a 3.3 volt pad, but it is either not imprinted 
and not shown in any relevant wiring diagram. 

Maybe you can find the 3.3 volt pads. Thanks.

See if you find any 3.3 volt pads on the ones listed below. Thanks.

I can't seem to find the 3.3 volt pads on this JHEMCU GHF405 board 





 
     I can't seem to find the 3.3 volt pad on this NamelessRC FC. 
   





The CLRacing FC lists the 3.3 Volt BEC, yet says it is for the "system".
  



Now, I will say that these are ALL whoop format AIO boards 
where space is at a premium. We are now in a Brave New World. 

(21-Apr-2022, 08:02 PM)iFly4rotors Wrote: Hi V,

Thanks for that clarification. Even though they all might have a 3.3 volt rail, there are some 
FC boards that I just don't see any break out pads for 3.3 volts. Now, I will say that I am getting old 
and I don't see as well as I once did...plus some of the imprinting is hard to read. I have went back 
through all of my FC boards and done a little additional research. However, there are still some FC's 
that I can't find any 3.3 pads.  Some boards may have a 3.3 volt pad, but it is either not imprinted 
and not shown in any relevant wiring diagram. 

See if you find any 3.3 volt pads on the ones listed below. Thanks.

     I can't seem to find the 3.3 volt                                   The CLRacing FC lists the 3.3 Volt 
     pads on this JHEMCU GHF405 board or                        BEC, yet lists it for the "system".
     the NamelessRC board below it.                                  I could not find the 3.3 volt pads.

Hello

so better if i will buy a 3.3 bec ?

This could be fine right ? https://it.aliexpress.com/item/400071472...mainSearch

I'm also not sure about my fc, if there are 3.3v pads...but i haven't seen if im not wrong, are 5v or a bit more.

(17-Apr-2022, 05:09 PM)iFly4rotors Wrote: Hi Rosssiii,

Well, I have been giving some thought    to this whole thing of powering the GPS.

I think this approach might end up being the best for your particular needs. In fact, I
am thinking that I might also use this same method. There are advantages and 
disadvantages to using the method and each option. I will consider the situation 
and determine the most appropriate method for powering the GPS.

The advantages to this method are that it is self contained, you only need the primary
battery, size doesn't matter since it uses a buck converter, it eliminates the need for
external batteries & all that goes with that, and it is easy to use in the field. 

The disadvantages are that it will add some weight, it also adds 2 battery connectors 
(XT30 or XT60), it involves an extra circuit board that needs to be fitted somewhere, 
and you have extra power cables to be managed.

I have also included two situations: 

1) direct wiring to the new power cable which makes it integral to the quad and 
2) option such as you and I have where we have a connector between the GPS & quad.
    {this is the option that I will use as I view it to be the most flexible}

The basic concept is to have a method to plug the primary quad battery into the GPS,
wait for Sat Lock, then plug into the quad without disconnecting the GPS from the battery.
Since, the battery has a higher voltage than the GPS will support, a +5V BEC is used to
reduce the voltage for the GPS.



=============================================




=============================================





=============================================

I will use this second method as I believe it to be the most flexible. First, it will
allow use of this new Power Adapter, an independent battery, or simply connected 
to the quad's wiring harness. 

Yeah, I like using connectors since it keeps my options flexible without the need for
additional soldering. It also allows a single "Power Adapter" to be moved and used
on multiple craft. Plus, it can also function as a +5V power supply for use on the
bench. Wow, all kinds of options. 

In fact, I will construct one of these for use with Surveillance-1 and Rescue-1.

Hello 

it's long time since you wrote that guide and finally i have all the components to can do that test:

i understand the scheme and how I should do it, but i still have some questions:

1)  On the drone i have alredy these JST PH 2.0 that i have used in the past to do hot start using lipo 1s, but i have see that it will not work because every time i unplug the lipo 1s that require long time to do sat fix, so i could leave these two cables i think and use the cable that carry power to the gps that is a JST 2.0 female where i will plug a JST 2.0 male that will came out from the BEC;

2) on the bec you have show in the scheme there are 4 pads of course, but i don't see other 4 pads on my BEC, i will show you some pictures:
https://i.imgur.com/ryflSeY.jpg
https://i.imgur.com/6zuCBGT.jpg

where i have to solder the cables (+/-) that carry the high voltage in the BEC from the lipo and where i have to solder the cables (+/-) that carry the 3.3v output (because that BEC should be 3.3v if i don't remeber bad) ?

because before to give the 3.3v to the gps i would like to test if that BEC really give 3.3v using a multimeter.

Quote:I have also included two situations: 

1) direct wiring to the new power cable which makes it integral to the quad and 
2) option such as you and I have where we have a connector between the GPS & quad.

3) considering that i will use the Ph 2.0 connectors that are alredy on my drone, i will be in which of these two cases ?
and what connector should be that one : https://i.imgur.com/zhbYGWC.png ?

Hi Rosssiiii,

Yeah, it has been a while. What I am doing these days is to use a small battery and
just plug it into the quad and wait for sat fix. After I get the satellites, then I just
disconnect the small battery and plug in the one that I want to actaully fly with.

The BEC that you have uses a common ground. That is, the ground connects to both
the battery and the GPS. It is only the positive (+) that is separate; one for the battery
and one for the GPS.  

I think that the top method might work best for you. That way, the GPS always has power
and is not disconnected to plug in the quad.

(22-Oct-2022, 01:05 AM)iFly4rotors Wrote: Hi Rosssiiii,

Yeah, it has been a while. What I am doing these days is to use a small battery and
just plug it into the quad and wait for sat fix. After I get the satellites, then I just
disconnect the small battery and plug in the one that I want to actaully fly with.

The BEC that you have uses a common ground. That is, the ground connects to both
the battery and the GPS. It is only the positive (+) that is separate; one for the battery
and one for the GPS.  

I think that the top method might work best for you. That way, the GPS always has power
and is not disconnected to plug in the quad.

Hello

i have completed with the work on that new connector, but now i have some question on how to check that it erogate 5v without have any issue using the 4s lipo.

here some pictures of the connector:
https://i.imgur.com/ZyRTfiv.jpg
https://i.imgur.com/F1TDrQe.jpg
https://i.imgur.com/xH9nPUo.jpg

i have alredy did some check with multimeter and looks like there is no continuity when i test between positive and negative, there is continuity just when i check between positive and positive or negative and negative.

Only the positive 3.3v output have no continuity with other positivie and i think it is normal because is solderend on a different pad of the board and should receive a reduced power.

while the negative are all connected eachother.

1) should be fine right ?

2) now i wait even for advices from some of you, what is the best way to check in safe using the 4s ? 

SOLUTION: plugin the lipo in the smoke stopper and connecting it to that circuit that i have made, in this way it should indicate me if there is a shortcircuit or not right (my fear is to fire the 4s lipo) ?


3) after the use of the smoke stopper i will use the multimeter to check how much voltage there is, so i will just have to check using the tweezers of the multimeter the values on the jst PH 2.0 connector being careful not to short-circuit them by touching them.

should be all safe that right ? it should indicate 3.3v

i wait for some confirmation and advices because with the lipo better be carefull ;

Hi Rosssiiii,

First, the device looks FINE.   GOOD JOB. 

WELL DONE     

As for testing, I would plug a battery into it and then check
the BEC output at the PH2 connector. If it reads 3.3 volts
then you are good to go. 

When you get ready to fly, Plug the battery in and connect
the PH2 to the GPS lead. Wait. Since the quad is not getting
power, you will just have to "guess" how long to wait. In
time, you will know how long it takes. Finally, plug in the
battery lead to the quad. Check your satellites...and FLY.

(23-Oct-2022, 01:50 PM)iFly4rotors Wrote: Hi Rosssiiii,

First, the device looks FINE.   GOOD JOB. 

WELL DONE     

As for testing, I would plug a battery into it and then check
the BEC output at the PH2 connector. If it reads 3.3 volts
then you are good to go. 

When you get ready to fly, Plug the battery in and connect
the PH2 to the GPS lead. Wait. Since the quad is not getting
power, you will just have to "guess" how long to wait. In
time, you will know how long it takes. Finally, plug in the
battery lead to the quad. Check your satellites...and FLY.

Hello  

Thanks 

yeah but before to plug in the battery i would like to have a bit more safety, maybe i could use the smoke stopper between that device i made and the battery, could be a good idea ?

Hi Rosssiiii,

Yes, you could use a smoke stopper...for an initial test...like when you are checking the
voltage at the PH2 connector. I wouldn't hurt anything.

in my personal tests, 3,3v as better voltage seemed a myth, finding sats was worse, for sure not better.
i believe its just a question about product quality.

as original spektrum receivers are very expensive and huge, it doesnt make sense to use them for fpv anymore. i beleive its not requested anymore, therefor they save 3.3v pads in the board design.

my personal experience is, all additional gear is an additional risk. add a bec doesnt match saver for me. i would aim an additional lcfilter befor a separate bec

Hi Bat,

The reason he is adding a BEC is to step down the battery voltage. If you connect a GPS straight to
any battery that is bigger than 1S, the GPS unit will COOK. Consequently, a BEC is required so that
the GPS won't be damaged. Now, the difference between using a 3.3 volt and a 5 volt is just personal
preference. Personaly, I would use a 5 volt, but that is just me.

The concept here is to power the GPS without powering the quad, then keep the battery connected
to the GPS, and then connect to the quad after enough time has past to acquire the sat fix. The device 
that he has created is EXACTLY what is needed for what he is doing. It had previously been determined
that the battery on the GPS was dead.

Note: The power leads for the GPS are connected to the device, NOT to one of the quad's power rails.

Yes, he might be better served just buying a better GPS unit, however, he wants to still use the GPS
that does not hold the sat fix...probably the little battery inside is dead and he doesn't want to try
to change it.

Anyway, the concept is correct for what he wants to do and 
the device that he built is appropriate and very well done.

i didnt read the whole thread, didnt understand the battery between. i thought the whole work is to get 3.3v instead of 5v.

i use the 5v rail on the fc, the one powered by usb, use a powerbank.

(24-Oct-2022, 01:20 PM)hugnosed_bat Wrote: i didnt read the whole thread, didnt understand the battery between. i thought the whole work is to get 3.3v instead of 5v.

i use the 5v rail on the fc, the one powered by usb, use a powerbank.

Hi Bat,

That is a good idea as well; as long as there is a USB powered rail. 

Rosssiiii checked the 5 volt rails and nothing gets power from the USB connector.  Post #21 
Consequently, the USB idea doesnt' work for him. Likewise, the 5 volt rail is not powered by 
the USB connector on many of my FC boards either. 

Also, different methods of using a secondary battery were offered, but all of these seemed
to be more complicated than the method selected. I, myself, have tried many of the "alternate"
battery methods of powering the GPS for "hot" starting and I will say that most of them ended
up being more of a PITA than just plugging the main battery into a connector, waiting a few
minutes, then plugging that harness into the quad's battery connector. As a side benefit, this
method is all plug and play. If a different GPS unit is used later, this plug together harness
can be easily removed. 

aaah :-) sorry for confusing, thank you for explain ifly.

(25-Oct-2022, 09:53 AM)hugnosed_bat Wrote: aaah :-) sorry for confusing, thank you for explain ifly.

Hi Bat,

No worries, mate. 

It all might be helpful to others who read the thread. 

Cheers, iFly