Girish

If I'm not wrong when the regulator on Vrx (78M05) is supplied 5v, it would be supplying 3v theoretically to the Vrx because drop out voltage of that regulator is 2v. How would that effect the Vrx other than the reduced current draw.
Similarly would the decreased current draw have any effect on working of the Vrx itself? Whether that would have any effect on range/quality/sensitivity since its not emitting any signal itself.

Anyways having a cutoff voltage on the Vrx would have saved the lipos, which right now sucks the life out of them.

SideWinder,

Linregs need that minimum supply voltage, below that voltage, the output voltage will sag in a non deterministic fashion. The linreg will try to compensate by increasing the current pull (V=IR) from the source (for constant power P= VI) and that's what's happening here most likely, the rc305 is rated for 130mA but is pulling 200mA... the current would increase rather than decrease with a lower voltage..

Yes having a cutoff mechanism would save the lipos for sure, a low voltage alarm or a lipo voltage checker comes in handy


From wikipedia:

All linear regulators require an input voltage at least some minimum amount higher than the desired output voltage. That minimum amount is called the dropout voltage. For example, a common regulator such as the 7805 has an output voltage of 5V, but can only maintain this if the input voltage remains above about 7V, before the output voltage begins sagging below the rated output. Its dropout voltage is therefore 7V − 5V = 2V. When the supply voltage is less than about 2V above the desired output voltage, as is the case in low-voltage microprocessor power supplies, so-called low dropout regulators (LDOs) must be used.

When the output regulated voltage must be higher than the available input voltage, no linear regulator will work, (not even a Low dropout regulator). In this situation, a switching regulator of the "boost" type must be used.

http://en.wikipedia.org/wiki/Linear_regulator


PS:
Almost all ESCs use 7805 for the BEC, (not the LVC - thats separate circuitry)

But Chils observations shows otherwise 214mA@3S; 200mA@2S and 138mA@5V

And the Datasheet you mentioned earlier is for the transmitter not for the receiver in question. You can find the specs @

http://www.hobbyking.com/hobbyking/store/uploads/109500705X727853X35.pdf

which states 150mA as supply current at 6.5 to 12V.

However my question is, if reduction in current draw would effect range/sensitivity and quality of video feed from receiver?

RC 305 all use the same chipset, bought from made-in-china or Boscam, the quailty of other parts, supply chain, value added services etc is generally what brings the price variations. Its like Intel Core i5 inside a Dell Vs Asus

Yes the reduction in current draw would affect the range, and most likely quality of feed... flickrs would be apparent. A field test would give better insight on what is the best range possible.

PS: The earlier spec sheet I posted was from a chinese vendor, so E&OE   Probably they meant Transceiver

PPS: I stand corrected in my observation, it is indeed pulling more current on 3S, there have to be some other factors in play

Yeah, Chinese are good in mass manufacturing and stuff but there documentation most of the times needs to be taken with a grain of salt.

If Chils has successfully bypassed the regulator on Vrx, then everything should fall in place. The Vrx could be powered from Screen which inturn would be powered by Lipo. Bypassing regulator on Vrx should also help in reducing heat generated by the system(how much needs to be seen?). Best part ground station becomes portable and easier to carry around.

 

That'd mean pulling up a +ve and ground line from the 5v source and soldering it to the Vout and Gnd of the linreg in the Vrx and good to go

Guys ur forgetting one more thing. No matter from where he is taking the power, but there is another regulator in the vrx ckt as well. So even this regulator has got some drop. We ve to consider this drop as well.

Mig, SideWinder is suggesting to bypass the one in the Vrx... so 5 volt goes directly to the video circuitry

Alri8 guys, so after reading all those comments , these are the tests I am going to run.

1. First I am going to use BEC and bypass the 5vReg on Rx. and check the Current Drawn.
    Since BEC is able to supply upto 2A, this will really tell how much current Rx draws.

2. Power Rx with 5vReg from Screen ckt(w/ 5vReg on Rx bypassed) and check the Current Drawn.
    In my last experiment I dint bypass the 5vReg on Rx.

I brought all the stuff to work today, so if I get enough time to play around, will post some results soon.

PS: are you guys aware of some super cheap solution to record AV out from Rx? Or some simple DIY DVR ?

ok so I dint get much time to play around, but I made one very interesting discovery.

> As I mentioned in earlier post, there is 25v out on screen to power the backlight.
   Its actually not right, wait Kind of??!!!?!
   - it measures 25v only when you disconnect the screen.
     when connected it measures ~9.45v and ~5.08v when TURNED OFF using front power button.

Now that is pretty interesting cause, now I can power Rx w/o bypass 5vReg or any ohter modification.

so i will let u know how that works out, and how much it get hot stepping down tht ~9.5v and how much current it draws.

A compliant TV Capture card with video capture software...  It's not realtime, a slight lag always but alright for recording... The 305 has two video outs, useful to dedicate one to recording.

Oh we shd start a company. So many research orientated people.

ok so here is the quick update.
we are BACK TO SQUARE ONE  , kind of.

first sorry as I couldn't post any updates for a few days, got so bz with work.

Anyway I got my new 60W Soldering Iron, and I am loving it.
you can see I did pretty good job this time compared to previous solders with 30W iron.



Any way let me cut to the chase here

>  Powering Rx from that 9.5v/25v supply [which also powers back light of TFT screen] DID NOT WORK.
    It dose provide enough power but not current(~106mA) and as soon as I connect Rx, it shuts off the screen Back lights.
    So to say, 25v drops to 9v when you power on the screen, but its not sufficient to power both Rx and screen at the same time.



>  So again we are back to power the Rx with that 5v regulator AMS1117, but this time bypassing the 5v regulator on Rx.
    Nope that dose not work either. It shuts off the screen as soon as you power the Rx with it.




>  So as before I powered Rx with 5v AMS1117 through the on board regulator, and again it draws ~139mA as we already know.


   

So this gives new objective here, TO DO THE RANGE TEST!
which I plan to do this Sunday.

One thing for sure is Rx needs or it draws ~200mA when powered up using 2S(dosent get too hot) , and a bit
more ~215mA with 3S(gets pretty hot), so ~200mA is ideal current required.

IMO best bet is put a tiny BEC/UBEC inside the Screen casing, where the holes are, and that will do the trick.
BUT THE RANGE TEST WILL BE REALLY NECESSARY BEFORE THROWING EXTRA STUFF ON THIS MOD.


PS: crashed another one last night,(I am complete noob  but will get there) and that 30Amp ESC
      dose not seem to be working. I dose powers up 6ch Rx and the control servos but not motor. 
      so I can use tht as BEC and do the LAST test!!!

<peace>

I'll do that as soon as I am back home.
I have an easycap, it should work just fine

check this out,
Better option than dealing with video capture software, n computer n stuff on the go.

LINKY

chils it will be easier to get one of these as a dedicated power supply for your rx...rush to the closest walmart and get rid of your worries. No messing with the screen... one bad connection and poof it goes

http://www.walmart.com/ip/INSTEN-Black-USB-Mini-Car-DC-Charger-Adapter-2in1-Micro-USB-Cable-For-Cellphone-Mobile/36616147

Chils, also the C-DVR is a lovely option... its hard to get locally in India.. capture cards are available at every round the corner store...

Prateek, some of those need external power supplies via USB hubs to work properly.. It took me three days realising that with the raspberry pi.

chils, howz this going on? still onto it or have I spread my half completed endeavors disorder to you ....lol

i have cdvr for sale if interested let me know

Hey guys, its been long time since I have been here. Got so busy with work and family.
But I was still working on this project little bit at a time. And I guess I figured out pretty good way to integrate everything in one compact package.

Check out the video below, of the complete build.
If any suggestions please let me know. Thnx.

Here is some pics!





Back



Internals

Nice mod  . Could you post some internal pics after final assembly.

Thnx. Uploaded more pics!

So the power supply to Video Rx is from 2S lipo or from the 5V regulator on the monitor pcb as shown in earlier pics?

No, now 2S lipo is connected straight to both Monitor and the Receiver. Say in parallel.
The entire system is drawing about ~540 mA.
If you run just the Monitor it draws ~320 mA and if you run only the receiver by it self draws about ~260 mA.

I am trying to find the picture of the Connections Diagram I made.
If you get chance, take a look the YouTube Video that I posted.

had to get outta bed and take a picture again. here you go