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Nov 27, 2014, 03:15 PM
Registered User
RPinCA's Avatar
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Chi Town
I missed this earlier. Hello from afar! Nice of you to look to us for advice, even though we don't eat Vienna Polish Sausage!

I used to live near Barrington, worked near Wrigley Field and rode the CNW from Arlington Park to work every day. If you know the scene, we were one of the groups of card-players near the back. "Chicagoland" was home for a year or two. FWIW, Pizzeria Uno would be astonished at what CA calls Chicago-Style Pizza.

Edit: The Bonanza in my avatar landed at Palwaukee field a half-dozen times at least. Even after I moved back to CA, Chicago still played a big role in my life. As in Seeburg, Williams and Taito.
Last edited by RPinCA; Nov 27, 2014 at 03:20 PM.
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Dec 01, 2014, 01:32 PM
Windy City Flyer
Brian Kloft's Avatar
HA! Vienna Sausage is OK. Italian beef is the BEST! :-)

So guys when I say small.. It is a plane called the lightning bug. 34" SAL or DLG. Going to use it for some light wind slope action locally.

I was hoping that there might be a "component" solution to get the battery output down to 5v. Using 2 analog servos so this is not only a small plane the current draw will be very small.

I can try turnigy or dualsky for a bec/ubec solution. The goal here is to keep the GRAMS to a minimum!

if there are other ideas out there I am all ears! Thanks for everyone comments!

Brian
Dec 01, 2014, 02:04 PM
NorCal Electric Soaring (NES)
SoaringDude's Avatar
Thread OP
Okay Brian, yeah that is small . How about trying a string of four (4) 1N4001 diodes? They can take 1A of forward current and each weigh 0.3 grams. Pretty sure it will work even tho' the engineer in me says it's not elegant. If you don't live near an electrical parts store you could buy them at Digi-key, Mouser, or Jameco (Google for details).

Let me know how it works.

Chris
Dec 01, 2014, 02:15 PM
Registered User
RPinCA's Avatar
Quote:
Italian beef is the BEST! :-)
You have a point there!

Quote:
The goal here is to keep the GRAMS to a minimum!
That's why I mentioned the Smart Lipo. 11.4g total, including battery and 5v regulator. A NanoTech 180mAh 2S 25C Lipo Pack weighs 11.5g by itself. A string of diodes won't work as well as a true regulator, and as mentioned earlier, the low current draw is a bit problematic for diodes.

Good luck, whatever you choose.

Hey - how are you gonna fly that lightweight in The Windy City??? I hope you live in Palatine or Crystal River. :-)
Dec 01, 2014, 02:23 PM
NorCal Electric Soaring (NES)
SoaringDude's Avatar
Thread OP
I selected the 1N4001 diodes (datasheet, see Vf - If curve on page 2) to have a low enough "knee current" where you won't have problems. At room temp they should always drop ~0.7v each at the idle current of your plane (2 servos + rcvr).

And Randy's solution will work fine too!
Dec 02, 2014, 03:54 AM
Windy City Flyer
Brian Kloft's Avatar
Based on my dimension constraints.. the Shred RC Smart LiPo will not fit! If I could find one that did, I would buy it!

SoarDude~
OK.. I am not an electrical engineer, but my soldering skills are excellent! Can you put together a quick sketch on what you are proposing? I will gladly give it a try. Might be best to just PM me the details, or if you want the info for all to see then post it here. I can post pictures/progress here. Soldering iron is warming up!

Brian
Dec 02, 2014, 12:58 PM
NorCal Electric Soaring (NES)
SoaringDude's Avatar
Thread OP
Okay Brian, attached is a quick sketch. You need to "splice" the 4 diodes in series with your existing power wiring and receiver power connector.

As far as soldering goes there is nothing critical about the length of the diode wires: you can make them as short as you want as long as you don't make a really sharp bend right at the diode case. Try to let a few mm of wire come straight out of the diodes before you do any bending.

Good luck and check back with q's or how it's working.
Last edited by SoaringDude; Dec 02, 2014 at 02:15 PM. Reason: Updated diagram with switch
Dec 02, 2014, 02:00 PM
Registered User
RPinCA's Avatar
Quote:
Based on my dimension constraints.. the Shred RC Smart LiPo will not fit! If I could find one that did, I would buy it!
Ah... I was not able to find your plane in the time I had to search. In that case, the diode solution worked well for me, and Chris knows what he's doing. I'm sure you'll get the help you need.

In case it hasn't been mentioned, remember you must charge the pack directly, as you can't charge it through the diodes. They are one-way gates, so to speak. Might be wise to solder in a charging lead between the battery and the first diode as you go. . . . (I hope I'm not repeating here, time is short for the self-employed)
Dec 02, 2014, 02:16 PM
NorCal Electric Soaring (NES)
SoaringDude's Avatar
Thread OP
Randy is absolutely right, I did not show a switch or charging jack! I just updated the diagram with both.
Dec 02, 2014, 04:30 PM
Windy City Flyer
Brian Kloft's Avatar
yep. I did catch that.. thanks for the updated drawing! waiting for parts to arrive from Mouser! should only be a couple of days. I already know how I will add in a switch! Something I used on a DLG. Pics and testing sooon!

Thanks guys for the help!

Brian
Dec 08, 2014, 03:31 PM
Windy City Flyer
Brian Kloft's Avatar
ok. Mouser parts are in the house! Did a quick mock up and have some questions about the results! So the battery is fully charged, and I get a DC reading of 7.54V. I added in the diodes into the circuit and I get a reading of 6.35V DC. Is that correct? I was expecting a result of something closer to 5V. I know there is no load with these tests, so not sure if this test is really valid...

The part I ordered is: 1N4001

Appreciate some input here before I do any further testing and have something go POOF!
Dec 08, 2014, 04:11 PM
NorCal Electric Soaring (NES)
SoaringDude's Avatar
Thread OP
Hi Brian,

Yes with no load (i.e. not connected to your receiver or servos) the voltage will not drop much. There has to be at least a few mA of current for the drop to happen. If you have any resistors in your electronics parts bin you could simulate a plane's idle load by connecting a 1k ohm resistor across the receiver side of the diodes to ground. That will cause ~5mA of current and should bias the diodes enough to do their job.

If I understand how you're measuring the voltage now (hooking a voltmeter across the output side of the diode string) ) then the only terminating resistance you have is the input impedance of the voltmeter. That is usually about 1Mohm.

Chris
Last edited by SoaringDude; Dec 09, 2014 at 12:14 AM. Reason: sp
Dec 09, 2014, 05:53 AM
Windy City Flyer
Brian Kloft's Avatar
That is what I was thinking.. I will add in the receiver and retest. Thanks!

brian
Dec 11, 2014, 06:35 AM
Windy City Flyer
Brian Kloft's Avatar
OK. Had a chance to do a test with a receiver in the circuit... Much better results! So the unloaded voltage from the battery as still 7.54V DC. With the receiver the measured voltage was 4.98V DC at the receiver! Woohoo!

I guess now I need to do some additional testing and run the battery down and track the supplied voltage to see where it drops off to an unacceptable level.

As I get further along I will post some install pictures of the switch, etc. Right now it is just bare components and wires on the bench.

Thanks for all the help on this, as it is just what I needed for this plane and installation! I am sure others might find it useful in their applications too!

Brian
Jun 23, 2015, 09:15 PM
Registered User
AlteredState's Avatar
Hey Guys,
Just wondering if there is any benefit to installing an on/off switch between my battery and my regulator. Is it true that by doing this I can leave my 2s lipo's connected indefinitely without the worry of current drain over time? Many Thanks


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