Step-down converter for 5V (for Eachine ProDVR)

I just ordered this for use with my Little Pilot VR goggles. It needs 5V however my goggles are powered by a 2S battery (7.4V). Obviously the solution is to use a step-down converter, but i am too impatient to order from China again, and local suppliers want to charge me close to $10 to post one to me.

However i was thinking that a 12V cigarette lighter socket USB charger should contain a stepdown converter right? They are like $1, so would that work?

You got a multimeter? You could likely find a 5v source on the board of the goggles. There’ll be a regulator to take 7.4v down to 5v or even 3.3v. Not sure how comfortable you are with electronics though? You could use the cigarette charger, there’ll be a step down, not sure how elegant a solution that would be?

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Why don’t you use separate 1S lipo for ProDVR? I have one and I used ordinary 1S lipo to power it. It works fine even with 3.8V (at least the one I have)… Try…

Oh it works on 3.8V? If so that would be perfect…

The other option is to take 5v from the board of the goggles as Yets suggested (well in this case it is an FPV monitor inside the visor-x housing). I do have the multimeter/some electronics confidence; i was just trying to avoid opening up the monitor unless i had no other option. A step down converter from a dollar store USB charger seemed like a cheap and easy way to do it

But if 3.8v will do it, then a PH2.0 plug will be easypeasy!

well according to my charger’s output function, this supplies 5.2v even with an input voltage of only 6.9v (which is the lowest my goggles will go before dying) so at least my goggle battery should be able to run it too. But if it runs on 1S as well I can just take that from the balance lead of my battery, or a separate 1S

Mine works on 1S. Try it. :slight_smile:
The only drawback is that you don’t know voltage on your 1S… So, better solution is usage of battery from goggles because, I assume, you have voltage shown in goggles. But you can also try 1S…

Well the goggle battery has a balance lead, and if my understanding is correct, I can pull 3.8v off that, and the batteries will ‘balance’ themselves despite the uneven draw (correct me if I am wrong!)

They won’t balance themselves, one cell will draw slightly more as you’ve stated and the DVR draws quite a bit for such a small device of its the same as mine. If it were parallel, the cells would balance but series batts are separate cells and are only balanced through charging means. The difference when it comes to charging the battery may be negligible but you’ll have to test for yourself.

Hmm in that case I’ll use a lipo first and if I have problems with it running out of power, then the stepdown it is.

Well i finally got around to making a balance charger connector for my Goggle battery (a 1300mah 2S HV Lipo by Hyperion). Turns out that one cell is discharging a fair bit quicker than the other already. I had 3.60v and 3.22v showing on my balance charger. At this voltage (6.8v) my goggles wont even power on, even though i think the batteries have some juice left in them. Should have gone with a 3S i guess.

Still waiting on the ProDVR to be delivered…

Anyway so the ProDVR arrived, and yes you were right it powers up off a single lipo. Made a little ‘holder’ for a 300mah whoop battery on the side and was happy for a bit. But in the end I want all the lipos for my whoops, and I wasn’t happy with how messy it all was.

So I put that 5v regulator from my lighter phone charger into a little box (the top of an unused mains USB charger), ordered some new (black) wires for the little pilot and heatshrink the wires to the ProDVR

Feels cleaner, runs fine from my quick test.

One thing that annoys me is that the monitor shuts off at 6.8v, when the battery still has some juice left. According to my charger it’s only charging 800mah or so. If I was using a 3s or bigger that would let me go so much longer :-;

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Ok need some help from you electrical wizards. I am now sick of that tangled mess of wires I made in the last mod and want to get power from inside the monitor. Finally got the courage to crack open the case (held together by clips, I was scared of breaking them). So now I need to find 5v in here. I suppose I could grab it from the center pin of that AMS1117 down the bottom but I think that should go through a cap or two somewhere right?

If possible I’d like to use that 10 pin connector, or the 3 pin one, but is there any way of checking if the power is coming from the 5v rail as opposed to a pin from the chip?

If anyone has the skills to look at this pic and say, “use this” I’d be greatly appreciative (and in awe of your skill)

Ok answering my own question here, but the AMS1117 chip was only giving out 3.3v (and the other one 1.8v). However the 5.8Gghz receiver modules had 5v on the center pin ( the one on the right with that blob of solder on it). So i took my power from there, routed up through next to where the AV in/out is. Much cleaner now :slight_smile:

You’ll need to check the 5v rail regulator to see whether the amp draw is in the recommended specification with the added current requirements of the DVR otherwise you could burn it out at after prolonged use.

If it is the MP1584EN at the bottom right providing 5v that is a 3A capable buck converter. You can check if that is it by measuring voltage on the left side of the coil stamped with 100 right next to it.

(edit, swapped left and right, :upside_down_face:)

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Dammit i already closed it back up, but will check it later. That must be where the 5V is coming from though, i hadnt checked that. I checked the two AMS1117 chips and i thought that circuit was for cleaning up the input voltage for those chips. I was looking for a 5v AMS chip but couldnt find it… Didnt occur to me that there might be other types of buck converters available (duh).

Makes sense that this is the power supply for the receivers in that it has the biggest coil and components - to give the cleanest voltage to those modules (thats just my layman’s reasoning though).

Thanks guys!