How to run an 8v setup

[Jason Chow]

so its pretty difficult to find any information regarding this so i thought id start a fresh one to get the info consolidated.

trex 600 nitro, JR 8717s, JR 9000s, how do u run them on a straight 2s lipo?

- are the servos (JR 8717s or JR 9000s) available to the public capable of 2s or is that a Team JR thing hence why there isn't much information on this.

- jason bell mentioned that spektrum receivers can handle 8v, not that i dont trust u jason, i need to hear more people say it :) can spektrum receivers or other receivers run 2s and how can we check if our receiver can run 8v or not?

- connecting the 2s lipo to the receiver, i assume you would use a switch harness, plug it into the batt port on the spektrum receiver and use that to plug into the 2s lipo. i assume this is the setup, however i want it verified.

- 99% of the gyros/tail servos out there will not work with a 2s setup, hence u would need a switching regulator for 5.1V to them. any preferance on the switching regulator for the gyro and tail servo? i know u should not use a diode like the align 5.1V. just for clarification sake, you would put this switching regulator (which looks like a servo extension i believe) in between the receiver and the actual servo wire.


thanks for the info

(reason why i am posting is b/c i want to get the supplies for this setup asap before my LHS runs out of stock on them :))

[torkboy]

can spektrum receivers or other receivers run 2s and how can we check if our receiver can run 8v or not?

I believe 99% of manufactures post Suitable Voltage limits either on the box or in the instructions for the reciever, or on the web.

- connecting the 2s lipo to the receiver, i assume you would use a switch harness, plug it into the batt port on the spektrum receiver and use that to plug into the 2s lipo. i assume this is the setup, however i want it verified.

I would think it would have to be a big switch in order to handle the amp draw. Maybe a fromeco switch would be a good idea? I liked Matts set up, 2 sets of power wires, through a dean, and plugged into Aux 3 and 4, for a very direct power source, and if one set fails, you have the other set of wires, sorta like running 2 rx packs.

[fireup]

You can use your current regulator(2 in 1 or what ever) to power just the tail gyro/servo and power the cyclic servo right off the 2s lipo.

For the gryo/tail:
Get a servo extender cable and cut the red and black (red and brown for JR). Wire the male end (receiver end) of the red and black to the input of the BEC. Then wire the output of the BEC to the female side of the servo extender. This will regulate the 8V from the receiver and step it down. You'll still need the white wire (or orange wire of JR) to send the control signal through.

Make sure the red wire on the gain channel of the gyro is also cut so it does not get the 8V from that channel.

[Jason Chow]

thanks kev, ill be sure to blame u when i blow something up :D j/k

im just about to hit the buy it now button for the 8717s :)

[fireup]

thanks kev, ill be sure to blame u when i blow something up :D j/k

im just about to hit the buy it now button for the 8717s :)

Take a picture after you done the mod and I'll let you know if it's good before you plug it in.:wink:

[Filby]

You will actually draw less current due to the higher voltage.

amps=watts/volts

For example on a system that draws 20watts on a 4.8v system will draw 4.16amps. Whereas on a 8v system it will only draw 2.5amps. This assumes that loads remain constant on the different voltages. Not sure how the speed increase of the servos due to voltage affects the load.

Fil

[Finless]

You should not break the black wire connection to the gyro from the RX! Remember that is also a reference for the signal from the RX. Just break the red wire and apply 5V power and TAP into the black wire for a common ground.

Bob

[geneween]

Here's a little diagram. Please if anybody has anything to add please let me know and I'll update the drawing.

Gene

edit: Updated the drawing

[Finless]

Nice diagram! I dont plan to use a switch as I just dont trust them... I will just use a Deans connector and plug in when ready.

Bob

[Jason Chow]

nice diagram gene. i too did plan on taking a servo extension and cutting it to put a deans on there however, the wire seems very thin....any suggestions of a substitute way to make the harness? i guess the pins in the plug that plug into the receiver are very small.

[geneween]

servo wires can take handle the load for the Gyro and Servo. It just looks like it's too thin. It's only running two components, and should be more than enough. Think of it this way...the RX has a PCB inside that has maybe 1oz, copper which is only .0014 thick ( the hair on your head is thicker) and mabey .500 wide and it handles the whole load of all the electronics. you'll be fine just using the servo wire. Maybe I should design a PCB that will do this so it's plug and play...

Geneween

[fireup]

Maybe I should design a PCB that will do this so it's plug and play...

Geneween

I had the same Idea.:YeaBaby:

I try to add to your diagram, but couldn't so...

[geneween]

I'm designing the board right now if anyone wants the design files for it they can have it...for free...then you can either make your own bath tub board or mass produce the thing for all I care....It should be ready in about a few days...

Gene

[Jason Chow]

gene, let me know, ill be very interested to test ur new board out. regarding the post, ill see what happens, i need to print it and do the wiring. the regulator is what i need to make sure of since i dont want 8v going into the 611.

i have the fromeco arizona helicopter regulator. i need to study the diagram for alittle bit but i think i can have this up very soon :)

[xStatiCa]

Have you thought about using the CC BEC? You can program it to output 8v. Since the voltage is already being regulated I have heard from an electrical engineer at work that you can put those .75v dropdowns in series to get the tail down to around 5v as long as they can handle the amperage but I have no experience on that and don't know how accurate that info is(I think someone on rcgroups mentioned that you can combine them too but can't find the post).

I was thinking about doing the above myself based on comments that they can run at higher voltages but I think even at 6v the DS8717 is way faster and stronger than what I need on a 600. I can't find the post but I remember someone got a response from JR about hooking up to a 2s lipo and they mentioned that they do not recommend any JR servo getting more than somewhere around 7.4 or 7.5 volts. Who knows what that really means though. 7.4v nominal or max. I plan to stick to 6v. There is no way I want to even take a slight chance on burning anything up because of something like this. Maybe if more guinea... I mean people start doing it I might in the future though ;). I can't afford to be the experimenter with my servos.

[Flybar-less]

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

[Pinecone]

Cool, of course Jan 08 availability means maybe March. :)

BTW Castle is having some trouble with their BEC> A bunch of reports of DOA (mine was dead out of the package) and a report of two of failures that fried servos. I am sure Castle will get it working, but for now, I would say wait a bit.

[Jason Chow]

i hate that, but that is a great solution. im currently running the 8717s on 6v and boy is it fast.