T Rex build question

[R A]

Forgive me if this is a stupid question, I'm just putting together a T Rex
450 and was just starting to connect the radio gear to test the servo
movements, when if dawned on me I haven't set up a power supply for the
receiver which is a JR R770, but when I plug in the esc it appears to power
up the receiver, is this correct or should I be connecting in a separate
power direct to the batt port of the receiver ?.

Rob

[R A]

A bit of a blond moment as I should have realised its must be controlled via
the esc for the voltage to be ok I assume :-/

"R A" <mgroverelectronics(remove)@btinternet.com> wrote in message
news:BZadndNWsrvLyTPbnZ2dnUVZ8q2dnZ2d@bt.com...
> Forgive me if this is a stupid question, I'm just putting together a T Rex
> 450 and was just starting to connect the radio gear to test the servo
> movements, when if dawned on me I haven't set up a power supply for the
> receiver which is a JR R770, but when I plug in the esc it appears to
> power up the receiver, is this correct or should I be connecting in a
> separate power direct to the batt port of the receiver ?.
>
> Rob
>

[Steve R]

"R A" <mgroverelectronics(remove)@btinternet.com> wrote in message
news:BZadndNWsrvLyTPbnZ2dnUVZ8q2dnZ2d@bt.com...
> Forgive me if this is a stupid question, I'm just putting together a T Rex
> 450 and was just starting to connect the radio gear to test the servo
> movements, when if dawned on me I haven't set up a power supply for the
> receiver which is a JR R770, but when I plug in the esc it appears to
> power up the receiver, is this correct or should I be connecting in a
> separate power direct to the batt port of the receiver ?.
>
> Rob
>

The receiver will get it's power through the ESC when you plug the ESC into
the main battery that provides power to fly the helicopter.

If you just want to power up the RC systems for setup purposes, just plug in
a standard 4.8v pack to any open channel on the receiver. It doesn't
necessarily have to be the one marked "battery." That way you can play with
all you want without having to worry about the main drive motor taking off
on you.

Fly Safe,
Steve R.

[GAZLAZ]

yes its fine with just the flight battery!


"R A" <mgroverelectronics(remove)@btinternet.com> wrote in message
news:R4mdncz_fqU-xzPbnZ2dnUVZ8qqlnZ2d@bt.com...
>A bit of a blond moment as I should have realised its must be controlled
>via the esc for the voltage to be ok I assume :-/
>
> "R A" <mgroverelectronics(remove)@btinternet.com> wrote in message
> news:BZadndNWsrvLyTPbnZ2dnUVZ8q2dnZ2d@bt.com...
>> Forgive me if this is a stupid question, I'm just putting together a T
>> Rex 450 and was just starting to connect the radio gear to test the servo
>> movements, when if dawned on me I haven't set up a power supply for the
>> receiver which is a JR R770, but when I plug in the esc it appears to
>> power up the receiver, is this correct or should I be connecting in a
>> separate power direct to the batt port of the receiver ?.
>>
>> Rob
>>
>
>

[R A]

Thanks for your help on that, sometimes things are not as clear as they
could be, again I wasn't aware that I could plug the standard battery into
any of the ports, It feels like your putting power into the receiver through
the back door :-).


"Steve R" <srhodes13@comcast.nospam.net> wrote in message
news:46ae8029$0$4679$4c368faf@roadrunner.com...
>
> "R A" <mgroverelectronics(remove)@btinternet.com> wrote in message
> news:BZadndNWsrvLyTPbnZ2dnUVZ8q2dnZ2d@bt.com...
>> Forgive me if this is a stupid question, I'm just putting together a T
>> Rex 450 and was just starting to connect the radio gear to test the servo
>> movements, when if dawned on me I haven't set up a power supply for the
>> receiver which is a JR R770, but when I plug in the esc it appears to
>> power up the receiver, is this correct or should I be connecting in a
>> separate power direct to the batt port of the receiver ?.
>>
>> Rob
>>
>
> The receiver will get it's power through the ESC when you plug the ESC
> into the main battery that provides power to fly the helicopter.
>
> If you just want to power up the RC systems for setup purposes, just plug
> in a standard 4.8v pack to any open channel on the receiver. It doesn't
> necessarily have to be the one marked "battery." That way you can play
> with all you want without having to worry about the main drive motor
> taking off on you.
>
> Fly Safe,
> Steve R.
>

[Swiss Tony]

Ooooo, power through the back door!I like the sound of that ;-)



"R A" <mgroverelectronics(remove)@btinternet.com> wrote in message
news:Q_SdnQn3wo-7bzPbRVnygAA@bt.com...
> Thanks for your help on that, sometimes things are not as clear as they
> could be, again I wasn't aware that I could plug the standard battery into
> any of the ports, It feels like your putting power into the receiver
> through the back door :-).
>
>
> "Steve R" <srhodes13@comcast.nospam.net> wrote in message
> news:46ae8029$0$4679$4c368faf@roadrunner.com...
>>
>> "R A" <mgroverelectronics(remove)@btinternet.com> wrote in message
>> news:BZadndNWsrvLyTPbnZ2dnUVZ8q2dnZ2d@bt.com...
>>> Forgive me if this is a stupid question, I'm just putting together a T
>>> Rex 450 and was just starting to connect the radio gear to test the
>>> servo movements, when if dawned on me I haven't set up a power supply
>>> for the receiver which is a JR R770, but when I plug in the esc it
>>> appears to power up the receiver, is this correct or should I be
>>> connecting in a separate power direct to the batt port of the receiver
>>> ?.
>>>
>>> Rob
>>>
>>
>> The receiver will get it's power through the ESC when you plug the ESC
>> into the main battery that provides power to fly the helicopter.
>>
>> If you just want to power up the RC systems for setup purposes, just plug
>> in a standard 4.8v pack to any open channel on the receiver. It doesn't
>> necessarily have to be the one marked "battery." That way you can play
>> with all you want without having to worry about the main drive motor
>> taking off on you.
>>
>> Fly Safe,
>> Steve R.
>>
>
>

[Chuck]

There are potential issues with receiver and servo power from an esc.
Voltage-- Some servos don't like 6 vdc, and are happiest on about 5 vdc
High servo current draw when there are more than 3 servos, or one or more of
the servos is a high speed version (example gyro servo).
The max current draw can exceed the safe current capability of the esc
(usually about 1.5 amp for the receiver and servo voltage)
If a LiPo battery is used for power, and has a built in safety shutdown, you
may loose control if it actuates due to low battery voltage or high current
draw.

"R A" <mgroverelectronics(remove)@btinternet.com> wrote in message
news:BZadndNWsrvLyTPbnZ2dnUVZ8q2dnZ2d@bt.com...
> Forgive me if this is a stupid question, I'm just putting together a T Rex
> 450 and was just starting to connect the radio gear to test the servo
> movements, when if dawned on me I haven't set up a power supply for the
> receiver which is a JR R770, but when I plug in the esc it appears to
power
> up the receiver, is this correct or should I be connecting in a separate
> power direct to the batt port of the receiver ?.
>
> Rob
>
>

[Kevin]

Chuck wrote:
> There are potential issues with receiver and servo power from an esc.
> Voltage-- Some servos don't like 6 vdc, and are happiest on about 5 vdc
not all ESC's are 6V
> High servo current draw when there are more than 3 servos, or one or more of
> the servos is a high speed version (example gyro servo).
I have 4 servos in my T-Rex and have no issues
> The max current draw can exceed the safe current capability of the esc
> (usually about 1.5 amp for the receiver and servo voltage)
> If a LiPo battery is used for power, and has a built in safety shutdown,
no model battery has a built in safety shutdown,satety shutdown as you
put it is all done my reducing the motor power to warn you, in one of
two ways complete cut off as in an aircraft or in the case of my t_rex
it reduces the power
you
> may loose control if it actuates due to low battery voltage or high current
> draw.
>
> "R A" <mgroverelectronics(remove)@btinternet.com> wrote in message

how many electric models that use the ESC to power the model do you
think are are in use? it is the far greater % and all my models use the
ESC to power them and I have never had an issue.
All the T-rex (450 size) in my local club use the ESC its only when you
get to 4 cell + LiPo's and the big boys that the standard system will
not work
I think your post is just scare mongering for the sake of it and some of
it is just hot air

[R A]

:-) :-) I'll wait for a comment from Beav now on the back door issue :-)
"Swiss Tony" <daveyruss@btinternet.com> wrote in message
news:ttOdnRYOMoYPCjLbnZ2dnUVZ8tyqnZ2d@bt.com...
> Ooooo, power through the back door!I like the sound of that ;-)

[Doug McLaren]

In article <9CVri.18777$rH6.8404@newsfe22.lga>,
Chuck <Chuckk2nospam@cox.net> wrote:

| There are potential issues with receiver and servo power from an
| esc. Voltage-- Some servos don't like 6 vdc, and are happiest on
| about 5 vdc

Actually, all (except maybe a few of those that go with 1 cell lipo RX
packs) servos are *perfectly* happy with 5 or 6 volts. The reason
that 6 volts has a bad rap is that when you take 5 NiCd cells and put
them in a pack, if you multiply 1.2 volts * 5, you get 6 volts, but in
reality when the pack is fully charged you get 1.4 volts * 5, or 7
volts, and that's when some servos have problems. Most are fine, but
a few have problems right at seven volts.

Now, the vast majority of ESCs out there that provide power to the RX
have a voltage regulator that drops the voltage down to 5 or 6 volts.
The only exceptions are a few car ESCs that assume that your radio
gear can handle the 8.4 volts (1.4 volts * 6) that the battery can put
out. But I've never seen an airplane/helicopter ESC that provided
power to the radio gear that didn't have a voltage regulator or
something else to drop the voltage if it actually did provide power to
the radio gear. I guess it would be possible for something designed
for 5 or 6 cell NiCd/NiMH or 2 cell LiPo packs, but I've never seen
one.

| High servo current draw when there are more than 3 servos, or one or
| more of the servos is a high speed version (example gyro servo).

.... or one of the servos is stalled. Stiff linkages are very bad
things for BEC circuits!

| The max current draw can exceed the safe current capability of the
| esc (usually about 1.5 amp for the receiver and servo voltage)

That varies from ESC to ESC. It's mostly a matter of cooling.

| If a LiPo battery is used for power, and has a built in safety
| shutdown, you may loose control if it actuates due to low battery
| voltage or high current draw.

That actually has nothing to do with LiPos, unless you've actually
found some used for R/C usage where the shutoff is actually in the
battery itself -- which is very rare. Many ESCs do have shutdown
circuits that will cut power if the temperature goes too high, but as
far as I know they all cut power only to the motor, not to the RX. If
your servos are drawing too much power and that causes the BEC part to
emit too much heat, then the motor will shut off as that heat affects
the rest of the ESC, but the BEC will not, and eventually it may
release it's magic smoke. Yes, a protection circuit could be added,
but turning off your RX generally means a crash, so they'd rather push
the ESC a little too hard and risk damaging it than cause a certain
crash.

The reason that most BECs have so much trouble with high voltages and
high currents is the way they work. Most BECs use simple voltage
regulators and waste a lot of power. If your servos are drawing one
amp, and your pack puts out 12 volts, and your BEC puts out 5 volts,
then you're drawing 1 amp from the battery, and (7 volts * 1 amp) of
heat is being generated in the BEC, which is a lot for something so
small.

Things like the Ultimate BEC use a DC-DC converter and are a lot more
efficient. In the case given above, if the servos draw 1 amp at 5
volts, the UBEC will draw about 0.4 amps from the battery at 12 volts
and create little heat.

| > Forgive me if this is a stupid question, I'm just putting together
| > a T Rex 450 and was just starting to connect the radio gear to
| > test the servo movements, when if dawned on me I haven't set up a
| > power supply for the receiver which is a JR R770, but when I plug
| > in the esc it appears to power up the receiver, is this correct or
| > should I be connecting in a separate power direct to the batt port
| > of the receiver ?.

It's not a stupid question at all.

The ESC's BEC may be adequate as a power supply for the RX and servos.
But if it gets too hot, you might want to cut the red wire from the
ESC to the RX pack, and either use a separate RX pack or get something
like a UBEC. The UBEC is only one of many different brands of DC-DC
converter meant for R/C use. Really, it's a little switching power
supply, like the one in your computer.

Of course, a separate RX pack is more weight, and another battery that
needs charging and one you can easily forget to charge, especially
since it won't need charging after every flight. I'd suggest just
getting something like a UBEC if you need to go this route. But your
ESC's built in BEC may very well be adequate for a smaller helicopter
like a Trex 450 -- but it's going to be close.

--
Doug McLaren, dougmc@frenzied.us
You can only live once, but if you do it right, once is enough.

[The OTHER Kevin in San Diego]

On Wed, 01 Aug 2007 07:06:20 GMT, Kevin <dontemailme@ntlworld.com>
wrote:


>how many electric models that use the ESC to power the model do you
>think are are in use? it is the far greater % and all my models use the
>ESC to power them and I have never had an issue.
>All the T-rex (450 size) in my local club use the ESC its only when you
>get to 4 cell + LiPo's and the big boys that the standard system will
>not work
>I think your post is just scare mongering for the sake of it and some of
>it is just hot air

I think that statement is a bit harsh. Some ESC's BEC circuits don't
have enough capacity (output amperage) to run the gear. I run (like
most folks seem to do around here) Hitec HS65s on the swash of both of
my 450s, a GY401 gyro and a Futaba S9650 digital servo on the tail.

The 450SE runs a Futaba 146iP PCM receiver and the Align "G" ESC. The
450SEV2 runs on a AR6100 2.4GHz receiver and the Align "X" ESC.

The SE has never had an issue with glitches or lockout due to lack of
power from the BEC circuit. The SEV2's BEC power isn't enough to
drive the gear and will reset the Rx on occasion. If you've ever
worked with a DX7 and it's gear, you'll know a Rx reset takes about 2
seconds. Makes for some good pucker factor when it happens in the
air. I'm going to have to pick up an ESC with higher BEC output to
resolve this issue.

On my Trex600, I won't even convert it to 2.4GHz until I get the 6A
voltage regulator installed. Too many people having receiver resets
with the 3A regulator.

[The OTHER Kevin in San Diego]

On 01 Aug 2007 14:56:04 GMT, "Doug McLaren"
<dougmc+usenet-20070801@frenzied.us> wrote:

>In article <9CVri.18777$rH6.8404@newsfe22.lga>,
>Chuck <Chuckk2nospam@cox.net> wrote:
>
>| There are potential issues with receiver and servo power from an
>| esc. Voltage-- Some servos don't like 6 vdc, and are happiest on
>| about 5 vdc
>
>Actually, all (except maybe a few of those that go with 1 cell lipo RX
>packs) servos are *perfectly* happy with 5 or 6 volts. The reason
>that 6 volts has a bad rap is that when you take 5 NiCd cells and put
>them in a pack, if you multiply 1.2 volts * 5, you get 6 volts, but in
>reality when the pack is fully charged you get 1.4 volts * 5, or 7
>volts, and that's when some servos have problems. Most are fine, but
>a few have problems right at seven volts.

hehe, a few have issues at 5.8v - namely the Futaba 3154 micro. Even
though the docs say it's rated for 6V, it doesn't like 6V and they
burn up.

>Now, the vast majority of ESCs out there that provide power to the RX
>have a voltage regulator that drops the voltage down to 5 or 6 volts.
>The only exceptions are a few car ESCs that assume that your radio
>gear can handle the 8.4 volts (1.4 volts * 6) that the battery can put
>out. But I've never seen an airplane/helicopter ESC that provided
>power to the radio gear that didn't have a voltage regulator or
>something else to drop the voltage if it actually did provide power to
>the radio gear. I guess it would be possible for something designed
>for 5 or 6 cell NiCd/NiMH or 2 cell LiPo packs, but I've never seen
>one.

The new Spektrum servos in development for 50+ sized helis will run on
8.4V and have over 200oz.in. of torque and 0.04 sec/60 deg speed..

>That actually has nothing to do with LiPos, unless you've actually
>found some used for R/C usage where the shutoff is actually in the
>battery itself -- which is very rare. Many ESCs do have shutdown
>circuits that will cut power if the temperature goes too high, but as
>far as I know they all cut power only to the motor, not to the RX. If
>your servos are drawing too much power and that causes the BEC part to
>emit too much heat, then the motor will shut off as that heat affects
>the rest of the ESC, but the BEC will not, and eventually it may
>release it's magic smoke. Yes, a protection circuit could be added,
>but turning off your RX generally means a crash, so they'd rather push
>the ESC a little too hard and risk damaging it than cause a certain
>crash.

All the ESCs I've got, whether they've got BECs or not act like this.
When you hit the low voltage cutoff, they pulse the motor and if you
keep sucking electrons, they'll kill the motor outright and let
whatever power is left drive the electronics.

[Chuck]

I see there are the usual web yea and nay sayers expressing their views at
various points in the thread.

When all is said and done--
Make sure that the ESC you are using can provide the current needed for the
number and type of servos you are using.
Some servos just do not like ~ 6Vdc (Even the mfrs note this in the specs.)
Operating such servos at ~6vdc is just asking for trouble.

There are Lipos out there with safety circuits that momentairly cut the
battery off if the cell voltage drops too low. (I have 3 7.4 Vdc 800ma packs
myself that have the safety circuits in them. The safety circuits do cause
problems with some balancing chargers, and since I'm using one, I may
eliminate them. (Or just get replacements without the circuits.) I noticed
that Megatec still uses the safety circuit, and the same or similar small
helios from Walkera and others such as E-Flite use cells without the safety
circuit and these cells have balance connectors.

Seems that some ESCs use a switching regulator for the 5-6 v output, and
others use an analog regulator.
(I believe that older and less expensive ESCs use an analog regulator.)

You'all do whatever you please-- If you are using 6v on the servos and have
trouble, or an ESC with too low a current capability for the servos, it's
your A/C that may crash, not mine. I have enough crashes as it is, and
really don't need help from the electronics to cause more.

The other day for instance-- an unexpected gust caught my helio and I had no
choice but to add power to clear a bush. Unfortunately, I forgot about a
tree branch. (replace bent parts in rotor head & blades.) (And it was a
brand new set of blades.)

A couple of months ago, I was disconnecting a helio battery after setting
the transmitter on the ground. Managed to knock over the transmitter, which
advanced the throttle on the helio while I was holding on to it and the main
blade. Before I got the battery disconnected, the ESC quit due to over
current. (I know, add a fuse next time) Classic case of fried FETs when all
was said and done. The motor survived.



"The OTHER Kevin in San Diego" <skiddz "AT" adelphia "DOT" net> wrote in
message news:9b14b3d1ohlt742vib0uppthgi055ebpae@4ax.com...
> On 01 Aug 2007 14:56:04 GMT, "Doug McLaren"
> <dougmc+usenet-20070801@frenzied.us> wrote:
>
> >In article <9CVri.18777$rH6.8404@newsfe22.lga>,
> >Chuck <Chuckk2nospam@cox.net> wrote:
> >
> >| There are potential issues with receiver and servo power from an
> >| esc. Voltage-- Some servos don't like 6 vdc, and are happiest on
> >| about 5 vdc
> >
> >Actually, all (except maybe a few of those that go with 1 cell lipo RX
> >packs) servos are *perfectly* happy with 5 or 6 volts. The reason
> >that 6 volts has a bad rap is that when you take 5 NiCd cells and put
> >them in a pack, if you multiply 1.2 volts * 5, you get 6 volts, but in
> >reality when the pack is fully charged you get 1.4 volts * 5, or 7
> >volts, and that's when some servos have problems. Most are fine, but
> >a few have problems right at seven volts.
>
> hehe, a few have issues at 5.8v - namely the Futaba 3154 micro. Even
> though the docs say it's rated for 6V, it doesn't like 6V and they
> burn up.
>
> >Now, the vast majority of ESCs out there that provide power to the RX
> >have a voltage regulator that drops the voltage down to 5 or 6 volts.
> >The only exceptions are a few car ESCs that assume that your radio
> >gear can handle the 8.4 volts (1.4 volts * 6) that the battery can put
> >out. But I've never seen an airplane/helicopter ESC that provided
> >power to the radio gear that didn't have a voltage regulator or
> >something else to drop the voltage if it actually did provide power to
> >the radio gear. I guess it would be possible for something designed
> >for 5 or 6 cell NiCd/NiMH or 2 cell LiPo packs, but I've never seen
> >one.
>
> The new Spektrum servos in development for 50+ sized helis will run on
> 8.4V and have over 200oz.in. of torque and 0.04 sec/60 deg speed..
>
> >That actually has nothing to do with LiPos, unless you've actually
> >found some used for R/C usage where the shutoff is actually in the
> >battery itself -- which is very rare. Many ESCs do have shutdown
> >circuits that will cut power if the temperature goes too high, but as
> >far as I know they all cut power only to the motor, not to the RX. If
> >your servos are drawing too much power and that causes the BEC part to
> >emit too much heat, then the motor will shut off as that heat affects
> >the rest of the ESC, but the BEC will not, and eventually it may
> >release it's magic smoke. Yes, a protection circuit could be added,
> >but turning off your RX generally means a crash, so they'd rather push
> >the ESC a little too hard and risk damaging it than cause a certain
> >crash.
>
> All the ESCs I've got, whether they've got BECs or not act like this.
> When you hit the low voltage cutoff, they pulse the motor and if you
> keep sucking electrons, they'll kill the motor outright and let
> whatever power is left drive the electronics.
>
>