BD3SX, SATS & Brownouts

[woodsta888]

Hi all,

I'm mid build on an E820 and wanted to use the 3SX as the FBL due to the rescue.

I have Low voltage servos as I don't fly 3D. I have an ESC with no BEC and have been reading that the 3SX wants a minimum of 5.5v to power RX sats which I have and want to use. All BECS I have been recommended by shops have a default of 5.2V on the RX part of the BEC - but this means that when you use a a BEC and SATS from the 3SX it causes brownouts and tyhis is fairly well documented.

I flew big gassers 10 years ago and just getting back into the hobby and the electrics side is a bit new and full of pitfalls.

What solution do I need to get the right voltage to 3SX and it's SATS whilst running 6V align 615 & 655 servos?

Pleae dont reply with 'get another FBL unit, get HV servos, or get a seperate reciever UNLESS these really are the only options.

Can I run a 7.4V 2S Rx Lipo into the 3SX and put a voltage regulator in between them to 6V. THE 3SX happily takes upto 10V but does the 3SX have the programming to select the voltage to the servos, negating teh need for a seperate voltage regulator.

Thanks in advance for any help/advice

[r4nd0m]

hi, this is actually known - yes you can run a 2S lipo straight in - I actually built a cable to have 2 servo leads going in - on the battery and the usb port when no programming lead is connected - though I dont run Spektrum

edit: oh just read further - I actually run HV servos ... let me review what the option was without HV servos

I believe the only option for you would be to run a full size receiver rather than SATs only

[Guest]

For example this would suit plus other types out there:

Gryphon QUASAR Hyper 75V 20A HV Switching BEC GSR-7075 LMT

Western Robotics Ltd. - Hercules Super BEC G2, 20 Amp Peak, 14s LiPo

All BEC are not equal check the spec, grab one capable of minimum 10amps and run at least 2 rx power cables.

MJ

[Ian_R]

You can run a voltage reg, Castle BEC or, better still a 2s "LiFe" Rx pack. These are 6.6v and in both my opinion & experience (my 700e runs with 610/650 servos, 3SX, Spektrum DSMX sats, & a Hyperion 2s 2100mah 25c LiFe rx pack) your servos will be fine.

[Guest]

LiFe is also a great choice as above and got one in ads.

MJ

[Bob H]

Most voltage regulators will have switchable output voltages. The CC BEC Pro certainly does and can output 5.6V or 6.0V to everything with enough grunt to supply the necessary current needs. There are, of course other BECs and VRs available and most of the decent ones will have switchable outputs. I merely used the BEC Pro as an example unit.

The alternative is to use a 2s LiFe battery direct into the electronics bus. Such a battery will provide a relatively constant 6.6V. The servos should be able to cope with the extra 0.6V with no problems. Many folks power Align 610s/650s and the like in this way with no voltage issues. The main problem with LiFe batteries though is that although their voltage output is fairly constant through out their discharge their current output can drop significantly after about 50% discharge which can, in itself, cause brownouts and servo stalls. Something to keep aware of if you do decide on the LiFe path.

[iceuk]

I run a Caste creations BEC pro, Castle Creations BEC PRO - 20A Voltage Regulator, 50V with two sats DS510 cyclic servos and DS655tail servo all at 6volts, my Trex 500 is my basher and do fly it hard at times and I have never had a brown out,

[woodsta888]

Thanks very much for the advice guys. I'm gonna take Maj's LIFE pack and go with that. Thnaks for the options and helping me understand a 'bit' more about electronics.

Thnaks guys

[Mike Sanders]

LIFE pack is the way to go. It will provide 6.5 volts, which will be no problem for your servos. You can't really tell by the voltage when they are about to lose their charge because they do so suddenly.

The answer is to do a couple of flights and see how many MAHs you put back in when you charge. You will then be able to calculate how many flights you can do before you need to recharge.

That's what I do anyway but I do know one chap who charges up his LIFE battery after every flight. It only takes a few minutes.

[james_2k]

i know you dont want hv servos, but if you have servos already then just find out their max voltage. even if you set 7v on your bec you will be fine. and its less hassle/weight than an extra battery

[Grumpy]

LIFE pack is the way to go. It will provide 6.5 volts, which will be no problem for your servos.

A fully charged 2s LiFe pack is 7.2v... That could conceivably be a problem for 6v servos, though i know if practice they usually tolerate it.

[Mike Sanders]

Align 610 and 650 tolerate it. I have no reason to believe that 615 and 655 would have problem with it.

[BenScoobert]

MY Dune is on the 3SX with LV servos, fed by the Jive BEC, it is now on 6v, but fo rthe 1st 12 months it was on 5.5v and had no issues at all.

The looks the daddy
SGH5690 | Scott Gray Products Reactor HVX Voltage Regulator
multiple voltages

[woodsta888]

I'm happy with the servos being powered by a BEC.

The main issue is that the BECs I was recommeneded by retailers had RX supplies of 5.2V. The 3SX recommends when using SATS a minimum of 5.5V supply otherwise Brownout for loss off transmitter connection with SATS. I was at a loss as to which BEC to use and whilst heavier with a 6.6V LiFe the E820 is relatively light for an 800 heli and weight is really only an issue when you are a full 3D pilot requiring most power/weight ratio. My flying style certainly wont be needing that as I'm running lower headspeeds for longer flight times ~1400rpm. I fly more big air soft 3D.

The 3SX can handle upto 10V input but I don't think the 3SX regulates voltages to the components.

I couldnt get a 3SX in UK this week after being sent a bashed one from a popular heli retailer. (Spent £1k in 2 weeks and had damaged items in both deliveries ((not impressed)). So I've had to go outside UK mainland and even after euro conversion and delivery is was £395. Actually delivery was free.

radiocontrolledshop.ie

service and comms was second to none.