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Rx, battery, and servo setup - for a noob, please help

#1
Hi guys,
New to the forums and everything but come from the fpv drone world... I had an old, partially built, dlg glider in my attic and decided to build it completely. Everything went fine but I'm stuck a little with the electronics. So with drones, I'm used to there being a pdb that you plug your battery into but with the dlg, there's no flight controller and no esc(because there's no motor) so do you plug the the battery directly into the receiver and the servos get the power from there? And the receiver controls the servos? I know, noobie question but your help is appreciated!
 

The Hangar

Well-known member
#2
Welcome to the forums! You're going to need a BEC for the servos. The thing is, most esc's have a BEC built into them and these days you can find esc's for so cheap, it's best just to buy an esc for like $5-10 from ebay. If you want to spend a little more, you could find a dedicated BEC that would be lighter than an esc. It all comes down to how concerned you are with the weight and how much you want to spend on electronics. Here's a cheap esc I've been using that I've been happy with: https://www.ebay.com/itm/Simonk-30A...166247?hash=item5d8418a567:g:THQAAOSwdrdcAgHu
 

FDS

Well-known member
#3
As above for power, in planes the receiver does all the servo control, you set the model up on the TX like normal, there’s lots of options for gliders, then bind the receiver, then it should just work.
 
#4
As above for power, in planes the receiver does all the servo control, you set the model up on the TX like normal, there’s lots of options for gliders, then bind the receiver, then it should just work.
Awesome! I got confused for a second with the BEC thing... So, do I need an external BEC if my servos already have them built in and also, how do know if your servos have them built in? The servos I'm using are brand new but old date wise, the product code is gwspic/std/j. Thanks for your help!
 

The Hangar

Well-known member
#5
Awesome! I got confused for a second with the BEC thing... So, do I need an external BEC if my servos already have them built in and also, how do know if your servos have them built in? The servos I'm using are brand new but old date wise, the product code is gwspic/std/j. Thanks for your help!
Servos never have a built in BEC.
 

makattack

Winter is coming
Moderator
Mentor
#9
Old gliders used to be powered by nimh rechargeable batteries that output 5v (eg 4 AA batteries in series.) So that's another option. Gliders (older ones especially) sometimes are built for heavier batteries in the nose, so if you use a light one or two cell lipo, you might need more nose weight for the cog to work out.

Other options if you use lipos is to use a 1 cell with a buck booster (that can output enough amperage for the servos and rx or a step down converter / Bec with a 2S or larger lipo.
 
#11
Old gliders used to be powered by nimh rechargeable batteries that output 5v (eg 4 AA batteries in series.) So that's another option. Gliders (older ones especially) sometimes are built for heavier batteries in the nose, so if you use a light one or two cell lipo, you might need more nose weight for the cog to work out.

Other options if you use lipos is to use a 1 cell with a buck booster (that can output enough amperage for the servos and rx or a step down converter / Bec with a 2S or larger lipo.
I'm actually using 2s Nimh packs, but it says that outputs 7.6V and I know we're looking for 5V.
 

sprzout

Knower of useless information
Mentor
#13
Not to add confusion... but it it possible for a lot of receivers to run on a 1s battery. The last few gliders I did I just used a 1s battery with a the little red JST lead and stuck it on an unused set of (+)(-) pins in the receiver.
As Hondo said, you can definitely can run some receivers on 1s batteries; there are some gliders that use a 1s battery to power them, and I've got a little (and I mean LITTLE, like 19" wingspan little) balsa Taylorcraft that uses a 1s battery for power. :)
 
#14
2s nimh are built as receiver batteries and that's what most people directly plug in to power rx and servos. They are 6v
I see what you're saying but on the heatshrink around the battery, it says 7.4V - I know I said 7.6 but I just checked and its 7.4... Just scares me a little bit.
 
#15
As Hondo said, you can definitely can run some receivers on 1s batteries; there are some gliders that use a 1s battery to power them, and I've got a little (and I mean LITTLE, like 19" wingspan little) balsa Taylorcraft that uses a 1s battery for power. :)
Appreciate the response! I have 4 2s 360mah nimh that I'm trying to use because I have them and I'm not trying to go buy even more stuff haha. I'm wondering if the output of the listed 7.4V is too much for my receiver and servos without a BEC.
 

sprzout

Knower of useless information
Mentor
#16
Appreciate the response! I have 4 2s 360mah nimh that I'm trying to use because I have them and I'm not trying to go buy even more stuff haha. I'm wondering if the output of the listed 7.4V is too much for my receiver and servos without a BEC.
Me personally? I wouldn't try to connect it without a BEC, as 7.4v is the voltage of a 2S battery and has the potential to short out a receiver. I'd recommend getting a BEC to connect up.

The good news is that they're not too expensive; I paid $8 for 2 of them through Amazon:

https://www.amazon.com/dp/B01GHMW0C0/?tag=lstir-20
 

makattack

Winter is coming
Moderator
Mentor
#17
Agreed... it's probably safer to go with a BEC / step down circuit if you aren't sure the receiver and servos can handle 6/7v... but a lot of glider rx/servos tend to work ok with 6V. The problem I have with BEC's is that it's another thing to watch for... you need a BEC (or a buck step up for that matter) that can deal with the amperage draw of all your servos... and ... they still can fail.

BTW, I don't think you have a NiMH 2S battery if it's listed as 7.4V... each cell of those is about 1.25V, so you would need 4 of them (hence my 4 AA comparison) for 5/6V... anyway, it is old tech, and as Bruce from RCModelReview suggests, probably not a great idea to use NiMH for newer models... if your glider came with those batteries, and the servos are original, they are probably ok / fine with those batteries, depending on how old. they are.

If you have a 2S battery, and it's listed as 7.4V, that's a 2S LiPo battery! You definitely will need a BEC for that... when in doubt, get a volt meter and measure it!

Here's a good video on batteries and powering receivers/servos:
 
Last edited:

Hondo76251

Well-known member
#18
I've used the balance lead on 2s batteries before too, like this:
20200218_175656.jpg

Just make sure the red wire is on the center pin and whatever you do, do not put all three pins onto the receiver or it will let the magic smoke out!
It will unbalance the battery as its only running on the one cell but as long as you have a good charger it's not a big deal...
 
#20
Agreed... it's probably safer to go with a BEC / step down circuit if you aren't sure the receiver and servos can handle 6/7v... but a lot of glider rx/servos tend to work ok with 6V. The problem I have with BEC's is that it's another thing to watch for... you need a BEC that can deal with the amperage draw of all your servos... and ... they still can fail.

Here's a good video on batteries and powering receivers/servos:
Hahaha, just got done watching this video. Thanks