How to run 8717's on 8v?

[magicmalik19]

What is needed to run the servos on 8v? Can someone list the setup and how everything is connected?
Is it like this:
You connect the cyclic servos to the receiver. Connect a 2s lipo directly to the receiver. Then between the throttle servo (if its not an 8v servo) and the receiver, you connect a step down regulator. Also between the gyro and receiver you connect another step down?
I have 3 8717's for the head, a spartan gyro and 8900g servo for the tail. I will be running a 9252 futaba on the throttle (through a multigov). Also a hs81 with a carbsmart.
If anyone could describe how to hook this up on 8v, I would appreciate it.

[george0079]

Borrowed this from anotheRR site...

This is how you want to run it

[magicmalik19]

thanks alot bro. I appreciate that. Im guessing the regulator used for the gyro and throttle is that spectrum dual output regulator?

[george0079]

You are correct.

[q8hobbytime]

can the DX7 reciver handle that

[Stolpe]

If you mean the AR7100 it can handle voltage between 3,5 - 9,6 volt.

http://www.spektrumrc.com/Products/TechnicalSpecs.aspx?ProdID=SPM6070

/ Stolpe

[TooLy]

A friend of mine running his heli on 2S lipo with 8717, but with 6 amp diode on each ccpm servo, so it's about 7.7V and a small 5V regulator for the tail and throttle.
Works great.

[geneween]

wait a few weeks and get this thing.

http://www.spektrumrc.com/Search/Default.aspx?SearchTerm=ar7100&SortBy=LatestRelease

gene

[Bobbyk]

How is does the sensor works attach to the bottom of the engine?

[wingswest328]

It reads the crank rotation I believe. You can also use an existing sensor, like the ones that read magnets. There is a Rev max in that receiver so any compatible sensor will work. The backplate mount will also clear all the popular pumped engines.

Cameron

[Duke600]

I am running a 2cell directly into my ar7000 receiver to power my 8717's in my 600. I am also using a spektrum vr5203 voltage reg. for my tail. I have been running this way for about a week with no problems.:thumbup:

http://www.spektrumrc.com/Products/Default.aspx?ProdID=SPMVR5203

[rasjax]

I've heard some people say on other various forums, including this one...in other threads, when I was doing research on setting up a 8717 8V setup and some have said that that lipos tend to not hold a constant voltage and that if you don't use a BEC with the 8717 you risk not having the power available when you need it. If that is the case, that a direct 8V setup to the receiver is a problem, why not use something like the Castle Creations CC BEC 10 Amp Switching Regulator which can handle an 8V system?? that way you dont have to use a 6V BEC, and you get all the benefits a BEC might provide to a 8V setup (ie: Regulated constant Voltage).

CC BEC SWITCHING REGULATOR
Current Output: Peak: 10 amps
Continuous: <12 volts input = 7 amps*
<24 volts input = 5 amps**Ratings are determined with a 5mph airflow on the BEC. Servo connectors are not rated for current in excess of 5 amps. Users are encouraged to replace the connectors if more than 5 amp currents are anticipated.
Output Voltage: Output 5.1 volts out of the package, user may set output voltage from 4.8 to 9 using the Castle Link (sold separately).
Input Voltage: 5v to 25.2v (2S to 6S LiPo)

[geneween]

well it doesn't hold a constant voltage but if you start with a 2S lipo that fully charged is 8.4V and 7.4V is the nominal voltage under load and a cell dies at anything under 3V per cell, you will never fall under 6V, so you electronics running at 8V at a fully discharged 2S lipo will never run under 6V and at the very least it will run at 7V based on how many flights you log.

Your getting much better eff. running the lipo straight to the RX. When you use any kind of regulator you will loose mah to heat, because the remaining voltage over the regulated voltage gets transfered to heat.

So a 2S lipo fully charged at 8.4V that gets knocked down to say 6V, your burning up 2.4V that's going into heat and wasted, it's not much, but why not use all the voltage.

So if you use a regulator that regulates to 8V you need to start off with a 3S lipo (12.6V fully charged / 11.1V under load) because 2S under load falls to 7.4V below the 8V regulated. now your burning up 3.1V again not much, but you add in the weight of an addtional cell.

Your right though the voltage does not stay current, but my two points are this, one, if you run the lipo down that far where your not seeing at least 7.4V, the lipo is going to have a short life, two, you will not notice the speed diff. between 8.4V fully charged and 7.4V.

Personally I run an Align 2 in 1 (6V) becasue it has everything built in. When they come out with a 8V 2 in 1 I'll switch over to that.

gene

[layinitdown]

I have a simple maybe stupid question,, but how is everyone connecting the 2cell LIPO to the receiver,, what switch are you using etc,etc,, what I mean is all the lipos I have seen has the deans connector,, you know what I mean,, do you put a deans on the switch,, or what

[Steel Butcher]

Is the AR7000 bus amperage rating known? Nothing is listed on Spektrums site.

[LoveMyTrex]

I would use an ar7100r and plug the pack directly into that, and run the tail of the built in 5.2 voltage reg, run a switch glow for the glow plug, throttle and cyclic would run off 8v, and maybe run the switch glow of gear aswell as the gyro gain, because the 7100 has two gear ports. not sure if channel 7 will be needed to run the govenor because it is built in.

http://www.horizonhobby.com/Products/Default.aspx?ProdID=SPMAR7100R

[layinitdown]

But how exactly are you talking about plugging it straight in to the ar7000,, with a 2S Lipo you have a deans coming off of the pack, would you get a male deans adapter with 2 JR(regular servo ends) on it,, you could plug the two servo ends into the receiver and then plug the Lipo into the male deans,, am I making any sense, I don't know ,, to put it simple how to you plug the Lipo with deans battery end, into the AR7000 receiver,

[geneween]

some RX lipo packs come with a RX connector on it, looks like a servo connector, that you plug into the batt. port. so you can plug it drectly into the RX. the newer Spektrum RX's have connectors out the back that you plug you Lipo to. or you can use a switch, which I don't reccomend, I've had a few switchs go bad in flight and that's not good.

gene

[layinitdown]

What are some of the Lipo receiver packs that have the end already on them,,

[lakespinner2]

I'm curious too. I'm pretty sure folks have been running the 8.4 to the receiver for a few months now; but I'm curious if they're mostly using some type of heavy duty switch, or else removing the canopy to plug in the battery for each flight. I guess I'm lazy but I'm really not wanting to deal with 4 canopy screws every flight if there's a better way.

I know lots of regulators come with failsafe switches but I'd like the failsafe switch without the regulator. :P

Is adding some length to the battery-to-receiver wires along with a pair of deans connectors reasonable ? If the deans connector is positioned outside the canopy it might work.

Lots of people have figured this out but I can't get my head around it. I know the new spektrum receivers would solve this problem when they come out but I'm impatient. ;)

[LoveMyTrex]

layinitdown did you click on the link to horizon if you did you would see that the ar7100R not ar7000 has large gage wiring coming directly out of the back of it, and I would not be using deans or EC3 connectors I would be using power poles.

http://www.qsradio.com/Powerpoles%20for%20Dayton%20Banner.jpg

[geneween]

inagine this
http://www.helidirect.com/product_info.php?cPath=31_565&products_id=7226
but with a lipo insted of round cells...I can't find the lipo picture I was looking for, but it's the same concept.

gene

[layinitdown]

Yes I looked at the receiver but it is not out yet, and it is 170 dollars,, I was looking some way to run my regular ar7000,,, and my buddy lakespinner pm'd me this link http://www.espritmodel.com/index.asp...OD&ProdID=6138 (http://www.espritmodel.com/index.asp?PageAction=VIEWPROD&ProdID=6138) which is what I was looking for the whole time,, it is a flightpower lithium with dual leads, this will work with what I was going to do,,

[geneween]

that's the one...

gene

[Steel Butcher]

Is the AR7000 bus amperage rating known? Nothing is listed on Spektrums site.

I emailed Spektrum. "The receiver itself is rated 30 amps, the limiting factor is the battery connector at 6 amps"