ptulmer

My Feedback: (5)

I received this email today in response to a past email asking for just the pcb version. He now offers it separately.

Patrick,

I have great news for you. And please spread the words out to your community of RC hobbyists.
I am offfering the VPack PCB version now. It can be integrated to your LiPo battery to give you the 5V output. And best of all, you can just change the resistor RF2 to get any voltage < 6V, (due to the rating of the capacitors). It is truly versatile, and you can use it the way you see fit.

http://www.bodhilabs.com/vpackbare.html

Good luck,

Bic

hfenn

Size and weight? Looks interesting. How many series cells will it regulate, if any? Or, is it for use with a single cell? That would be great in a 1/2A model because a single cell 250 LiPo is pretty darned small and light.

Sneasle

Looks interesting. I wonder if it is worth the cost to buy the separate part.

BMatthews

I gather this works with one cell by stepping up the output using a DC chopping and additive capacitor output. The specs shown are a little fuzzy but I gather that it's good for up to 300 ma. That doesn't seem high enough to me. Or did I miss something?

ptulmer

My Feedback: (5)

Bruce, that should be ok for two channel half-a, right? I've got an .020 airplane with hs-50's that started this search. At a 300mah surge peak, this definitely has a ceiling, but where would you guys draw the line? Oh, yessir. One cell.

BMatthews

For the smaller stuff with only two servos I suspect you'd be OK but just barely. Even the small servos can esialy suck 100 to 150 ma if loaded.

small_rcer

Hello:

I re-read the specs several times to try and see the output rating and I could not find any. Typical current load at 3V input is 200ma. If that is the input current from the 3v at 80% efficiency that would be about 160ma output current at 3 volts or 60% of this at 5 volts. If that is correct then 100mah output at 5volts is not going to be enough for most uses.

The maker is going to have to present more accurate and complete information to satisfy most purchasers.

For 2 channel use, you have 220ma running current with no load for each HS81 plus receiver, tells me that 450 ma at a minimum is needed. If using HS55 which Hitec says have running current of 150ma at no load, then 320 to 350ma is needed. No figures are given in the Hitec specs for current at maximum rated torque. So the real need may be higher.

Now if the output of the voltage regulator is 200ma at 5 volt with a 3v input, ( it does not say this is the case ) then its' use with 2 HS55 and a receiver would be risky at best or not advisable or unuseable at worst. Note the standby current for the servos is minimal, so if you use only one channel at a time (!!!!!) then you can likely get away with it.


But ....... I do stand corrected if my reading of Hitec specs and the vendors specs for the regulator, is somehow flawed.

Jim H


edit to correct typos that I found

ptulmer

My Feedback: (5)

HAH! I finally figured out where you guys are finding these specs. Gotta click on the spec sheet link up top. The HS-50 is 8ma idle and 100ma running, no load. Micro 05 receiver is 9mah drain. At a glance, even this is running close. The servos will have a bigger load on them when deflected while flying. So that's even more current needed. Too close for me. I'm back off the bandwagon again...[sm=bananahead.gif]

chevy43

Well that is pretty cool. I wish they gave the weight. As far as the current; it would be easy to just try it out on the ground and see if it will handle say 4 servos fully loaded for a short period.


It is not clear that it will STEP UP voltage though. When I looked at all the specs before I remember they would only lower voltage on a 2 cell lipo. Lowering voltage is one thing but it is another story RAISING it.

PS... I does look like it will raise voltage as well! It might be worth a try for that price!

chevy43

Well I just bought one of those regulators.

I'm going to try it with a two cell 200 ma lipo that weights .3 oz sold here: http://www.batteriesamerica.com/newpage8.htm

I hope it can handle 2 cell input. They don't give the input voltage specs. I've sent an email asking about that. If not I'll run a pair of single cell 200 ma in paralell.

This will give me 230 mah at 5V and be somewhere around .5 oz I'm guessing. I'll do some tough ground testing and see if it can handle the loads of HS55's.

Treven.

Bipe Flyer

Geez Patrick, it looks like they made a product specially for you!

chevy43,
It's not a regulator, it's a DC to DC step up converter. The output voltage is higher than the input.

ptulmer

My Feedback: (5)

Bipe, that kind of bothered me. All he had to go on was my guesses? At least Chevy43 can be our guinea pig. Just keep in mind that this doesn't have a low voltage cutoff. (you wouldn't want one on the receiver!)

Bipe Flyer

Patrick,
I'm sure that he just saw an opportunity and decided to sell the board separately as an option. I'm thinking about getting one for some electronics projects instead of using a 9V and a 7805 regulator.

chevy43

Here is an email I got:

Treven,

I will get back to you on the weight issue, once I get my hands on a good scale.
Input range:1-4.3V (Vout=5V)
Switch peak currrent limit: 1.8A (input side)
This is a booster with small components, so don't plan on using for heavy loads.
Let me know if you need more info.

Good luck on your project

Bic


If the input really is 1.8 amps at 4.3 volts then it seems that output at 5v could be as high as 1.2 amps or 1200ma but something doesn't make sence or they wouldn't rate it at 200 ma.

The fact is, it is almost never that all 4 servos would be maxed out and if they were it would be a really short moment!

chevy43

Another email:

Treven,

If you are using a 3.7V LiPo, which I assume you are using, you can achieve a sustainable current of 200mA easily. Remember:
Efficiency: .7 = (VoutxIout)/(VinxIin).
Maximum Iin = 1.8A, so
Iout=.7x3.7x1.8/5=.9A
I am not sure it can hit .9A , but definitely over 200mA.
Remeber iNput range : 1 - 4.5V
Please let me know the results of your experiment.

Thanks
Bic


It is advertised at 80% effieciency but now he says 70%.

It looks like it will work though with two 200ma lipos in paralell and come in under 1/2oz. I guess saving a 1/2 oz is worth it...

Bipe Flyer

These things are really designed to run 5V TTL and CMOS circuits, not motors.

chevy43

Bipe Flyer, Do you mean servos? I'm only talking reciever battery....

ptulmer

My Feedback: (5)

Chevy, He just sent me a response to the weight question. He says an even 2 grams. You're right about the servos not being maxed out at the same time, but just moving they suck 100ma. I doubt like heck that they are under a significant load with the average sport flier, but still, I'd do some testing before tossing it in the air. And yes, 1/2oz is worth it! On a Blink I'd pay more than that to get another 1/2oz. Think of the possibilities! 3D'ing a Surestart! It boggles the mind.

Bipe Flyer

Yes, I meant servos. It should run a receiver fine, but how can you use a receiver with nothing else?

rrragmanliam

My Feedback: (1)

You have to love this line in the ad...


"This is for the advanced user who knows what she/he is doing. You assume full responsibility."

Well that leaves me out, Ill stick to the safer Nicads and Nimh batteries.


Darren

chevy43

So at 900ma peak output why wont it run servos? Well I guess I'll find out anyway.....

Bipe Flyer

chevy43,
You'll have to stay under 200mA for 99% of the time with occasional peak of up to 900mA; burn that baby out and the whole works is a comin' down. Also a switched mode power supply, which is what this unit is, generates EMI that may interfere with the receiver. It just seems a little too risky for me when you can use a 150mAh NiMH pack that weighs under .5oz, or a 2s1P LiPo with a regulator (el-cheapo speed control).

Just my opinion. You can report back with the empirical data.

chevy43

I was a little worried about interference from the chopped current....... Current draw will be no problem to test on the ground though - just tape up four servos and torqe on them all at once If it survies that then[8D]

Bipe Flyer

Yup, there's no better way to find out than to test it. Maybe you should use 4 standard servos for the testing - if it works with them...

ptulmer

My Feedback: (5)

Ok, Chevy and I just received an email. Bic poked his head in to see what we were up to and helped out with these tests. Now I gotta find the best battery to meet these specs.

Here is what I got from my test on the VPack_PCB, using a bench supply:
Vin : 3.7V
Iin : 1.39A
Vout : 5V
Iout : .8A
Efficiency: 78%
The PCB can get hot, so DONT mount it on the back of the battery.
So the answer is if the LiPo battery can deliver 1.4A @ 3.7V without dropping, the VPack can supply .8A @ 5V continously. The circuit will get HOT.
Let me know if you need more test results.