2.4 mhz low voltage problems

[rcers]

Originally Posted by celticflyer

OK group, I have Spektrum DX7, what should the min. cutoff voltage be on my esc be set? CC ICE 50 (5 amp bec) preset to 3volt per cell.
I guess the real question would be, what is the min. power for Spektrum RX

You are confusing two things that are unrelated. One is LVC = low voltage cutoff and one is BEC voltage out.

To directly answer your questions - some of the older Spektrum RX's would start to show issues near 3.8v cutoff most now are 3.5v or below. You should not even come close to those numbers. I never use a value below 5v. In fact I use 5v to 6.5v depending on your servos. The higher the voltage the better - as long as your servos can handle it.

The "LVC" cutoff has NOTHING to do with the BEC. That depends on your cells. Most high "C" cells (anything above 20c) I set in the Castle controllers to cut at 3.2v. However I NEVER fly to LVC rather I use a timer that I know brings my cells down between 3.7-3.8v/cell resting voltage. This saves batteries...

On another side note - the Castle BEC's in the ICE controllers are over-rated IMHO. I lost a valuable ship to an ICE 75 with a 5 AMP switch mode bec. It only had 4 digital servos in it - but it was too much for the Castle BEC. Due to that loss - I now run only separate SBEC's or my preference 2s LiFe battery packs.

Just a warning on the Castle BEC! I have watched others go in as well. I normally have great confidence in my Castle stuff but the ICE BEC's are not worth it IMHO.

Mike

[kyleservicetech]

Originally Posted by celticflyer

OK group, I have Spektrum DX7, what should the min. cutoff voltage be on my esc be set? CC ICE 50 (5 amp bec) preset to 3volt per cell.
I guess the real question would be, what is the min. power for Spektrum RX

My Spektrum AR7000 receivers all reboot at 3.2 Volts DC. So, in theory, that would be the minimum allowable voltage. The CC ICE BEC is normally programmed to about 5.0 Volts DC, I'd just leave it there.

But in the real world, if you allow your multicell LiPo packs to drop down to 3 or 4 volts DC output voltage, you'll likely damage the LiPo cells, permanently.

Question, how many series cells do you have in your LiPo packs, or what is their voltage rating?

[celticflyer]

OK guys, First of all I really appreciate all of the input. My setup is:
42" AJ SLICK
Omega 103 gr. motor
4 12 gr. servos (MG) (NOT DIGITAL)
2200mah 30c 3 cell

I've been using an EMAX value 50 and have noticed some strange issues.
After two separate rough landings, no plane damage, just flops in the grass,
My motor sounded like it didn't want to run, kind of the same sound as you would get with a loose prop. After cycling the throttle a couple of times it was OK.

As far a battery goes, I never let it go down beyond 10.9 volts
6 1/2 min flights usually keep it 11.1 to 11.3 volts and that is my timer set.

John

[rcers]

I am so leery of the ICE BEC I am not sure I would use it even on 4 standard servos!

But suspect you should be fine especially since it is a small model. Some of those no-name budget servos really suck the juice!

[kyleservicetech]

Originally Posted by rcers

I am so leery of the ICE BEC I am not sure I would use it even on 4 standard servos!

But suspect you should be fine especially since it is a small model. Some of those no-name budget servos really suck the juice!

That's interesting.
Do you have any information about field problems on the ICE switching power supply type of BEC?

Two club members have this CC ICE on their models, and they've had zero problems.

[rcers]

Originally Posted by kyleservicetech

That's interesting.
Do you have any information about field problems on the ICE switching power supply type of BEC?

Two club members have this CC ICE on their models, and they've had zero problems.

Two of us lost models within a week both on ICE 75's and 4 mid size digitals. I was curious so used my servo sense and measured those servos in flight. I was never able to get above 3 amps of peak usage. I measured those servos on the ground at stall they pulled around an amp each. So that's 4 amps - well within the 5amp limit. Besides in flight - I never peaked more than 3 amps.

I was running 5s and my buddy was running 6s. AGain well under the 8s capacity of the ESC.

I have the Hitec A9 and watched as my telemetry voltage alarm went off (5.5v). Startling considering I was running it at 6.5v!!!!

As soon as the alarm kicked - I prepped for landing and never made it - well I did "land" but it was not pretty.



I am a bit at fault - as I had another telemetry warning the week before and thought it was a fluke. Ummmm NO....

Enough "field" tests for me. Search RCG - I am not alone.

Mike

[celticflyer]

Originally Posted by rcers

I am so leery of the ICE BEC I am not sure I would use it even on 4 standard servos!

But suspect you should be fine especially since it is a small model. Some of those no-name budget servos really suck the juice!

Is the ICE ESC at question or the on-board BEC
If it is the BEC that's an easy fix.

[kyleservicetech]

Originally Posted by rcers

Two of us lost models within a week both on ICE 75's and 4 mid size digitals. I was curious so used my servo sense and measured those servos in flight. I was never able to get above 3 amps of peak usage. I measured those servos on the ground at stall they pulled around an amp each. So that's 4 amps - well within the 5amp limit. Besides in flight - I never peaked more than 3 amps.

I was running 5s and my buddy was running 6s. AGain well under the 8s capacity of the ESC.

I have the Hitec A9 and watched as my telemetry voltage alarm went off (5.5v). Startling considering I was running it at 6.5v!!!!

As soon as the alarm kicked - I prepped for landing and never made it - well I did "land" but it was not pretty.



I am a bit at fault - as I had another telemetry warning the week before and thought it was a fluke. Ummmm NO....

Enough "field" tests for me. Search RCG - I am not alone.

Mike

Good info
That's why on my two giant scale models, the primary receiver power is a CC 10 Amp uBEC, and the backup power is a two cell 2300 Mah A123 battery pack. Two 10 Amp silicon diodes are inserted in the A123 pack to drop the voltage down below the set voltage of 6.5 Volts on the uBEC.

So far after two years of flying, its been flawless. I do have an on board alarm that flashes if the battery drops below 6.0 Volts DC. This alarm also shows just how low the battery voltage dropped. The little microcontroller checks the battery voltage some 4000 times per second.

[rcers]

Yep that was the crash that caused me to go to LiFe cells....

Mike

[John C]

I'm a bit surprised no one has mentioned the use of a capacitor to bufffer the BEC for transient low voltages. Spektrums are 47 mf IIRC. I've just added one to a GP Stearman with a Castle Thunderbird 36 and four HS65s with which I believe has been subjected to two browouts (but no crashes).

The same setup in an electrified Herr Lil Extra and 9 gram servos has had no issues, but I added a capacitor to it as well. Both are using AR500 Rx's.

Haven't flown with the capicators yet, but hope to Friday.

John C

[CNY_Dave]

It will protect against a very short transient, but not against, say, a stalled servo drawing a lot of power.

[rcers]

Here we go again - caps will solve your issues!

Sorry man - but caps DO NOT solve low voltage issues.

While they likely do no harm - they simply do NOTHING for improper voltage supplies. Period.

The Spektrum caps are intended for use in cars who race on carpet. Not made for solving low voltage issues.

Mike

[Neko]

So i'm re-entering the sport after a long break. I have a DX7 that's about 4 years old. Should I worry about it? Are the newer ones more reliable?

[kyleservicetech]

Originally Posted by Neko

So i'm re-entering the sport after a long break. I have a DX7 that's about 4 years old. Should I worry about it? Are the newer ones more reliable?

I HAD two DX7's that were about 5 years old. Got one new in box DX7 for $175 including a receiver. That NIB DX7 was my spare for five years. So, this year I bought a DX8, and sold the NIB DX7 to a club member.

Still have the original DX7, it has never had a problem. FYI, I sent in that original DX7 along with six Spektrum receivers to Horizon Hobbies last winter for a "check over". Horizon completely tested them, returned them, indicating all was OK. The very unexpected item, Horizon returned them at NO CHARGE, they even paid return shipping!

A club member did have an issue with his DX7 this past summer, the throttle stick pot inside the transmitter got a little noisy. HH repaired it at N/C. But, the club member wanted next day return, so that cost $25.

So, if you have any concerns about your DX7, you can send it to HH for a check over, "Just in case".

[kyleservicetech]

Originally Posted by rcers

I am so leery of the ICE BEC I am not sure I would use it even on 4 standard servos!

But suspect you should be fine especially since it is a small model. Some of those no-name budget servos really suck the juice!

Uh Oh
Don't know how I missed that one. I've got two giant scale models that use a pile of Hitec 645MG servos. Also have a $350 Fluke 87V digital meter that can measure peak currents with one millisecond response time. Accuracy of that meter is better than 0.1% on DC current. I've also double checked those results on my Tektronix 2236 oscilloscope with a precision current shunt.

Each of those 645MG servos pulls a peak current of 2.1 AMPS, while just moving the transmitter stick back and forth. All seven servos pulled a peak current of 14 Amps, just by moving the transmitter sticks back and forth. So, it's quite possible your four digital servos pulled more current than the CC 5 Amp ICE BEC was rated for.

One very good option would be to use both the ICE 5 Amp BEC, and, the Castle Creations 10 Amp uBEC. They need to be isolated from each other with a 9 Amp Schottky diode. If you don't do this, the two BEC's might interact and cause problems. That will give you dual DC supplies to your model with very little added weight. And, it also eliminates maintaining the receiver battery.

The wiring would look like this:
http://www.wattflyer.com/forums/showthread.php?t=67094

Schottky diodes are not available from Radio Shack. Here is one supplier of them. Digikey sells to anyone with a credit card. I've ordered a LOT of stuff from them over the years.
http://www.digikey.com/product-detai...Q035-ND/358618

The current rating of this diode is not an issue. It's rated at 9 amps continuous, and is also rated for repeating peak currents of less than 10 milliseconds duration at over 100 Amps.

(PS, that club members BEC setup with dual 100 Amp CC ICE ESC's performed flawlessly. Only problem is the two fans were pulling near 150 Amps each at full throttle. A full 90 Amps over the fans specifications. Third flight, the ESC's overheated, shut down, causing an off field crash. The CC ICE ESC's showed a peak internal temperature of near 300F at the end.)

[Neko]

Originally Posted by kyleservicetech

So, if you have any concerns about your DX7, you can send it to HH for a check over, "Just in case".

Thanks, much. Good to know.

Neko

[kyleservicetech]

Originally Posted by Neko

Thanks, much. Good to know.

Neko

No problem, check out this thread:
http://www.wattflyer.com/forums/showthread.php?t=65573

[celticflyer]

I bought a CC Phoenix Ice 50 with a 5 Amp Bec
I took notice of the comments and warnings(thank you all) but it was on its way and I thought I'd still like to try it.
One thing I noticed was that the literature that came with it said that I could go up to an 8 cell lipo. BUT-- DO NOT USE THE ON-BOARD BEC with anything larger than a 3 cell.
Advice that I will remember.

John

[kyleservicetech]

Originally Posted by celticflyer

I bought a CC Phoenix Ice 50 with a 5 Amp Bec
I took notice of the comments and warnings(thank you all) but it was on its way and I thought I'd still like to try it.
One thing I noticed was that the literature that came with it said that I could go up to an 8 cell lipo. BUT-- DO NOT USE THE ON-BOARD BEC with anything larger than a 3 cell.
Advice that I will remember.

John

Don't understand the 50 Amp CC ICE ESC. It doesn't appear that CC makes a 50 Amp ICE ESC.

The older Phoenix ESC's (NOT ICE) did use a linear voltage regulator, and their BEC can't be used on more than two or three LiPo cells.

Take a look:
http://www.castlecreations.com/suppo...User_Guide.pdf

[celticflyer]

Originally Posted by kyleservicetech

Don't understand the 50 Amp CC ICE ESC. It doesn't appear that CC makes a 50 Amp ICE ESC.

The older Phoenix ESC's (NOT ICE) did use a linear voltage regulator, and their BEC can't be used on more than two or three LiPo cells.

Take a look:
http://www.castlecreations.com/suppo...User_Guide.pdf

http://www.headsuprc.com/servlet/the...nix-ICE/Detail
Sorry to disagree, I have one with a switching 5 amp bec

[kyleservicetech]

Originally Posted by celticflyer

http://www.headsuprc.com/servlet/the...nix-ICE/Detail
Sorry to disagree, I have one with a switching 5 amp bec

OOOOOPPS!

I was looking at the Phonix HV ICE's.