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Receivers and Servos

Old 10-05-2010, 07:19 AM
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_brad_
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Default Receivers and Servos

Hi All,

Iam in the process of building my second plane and Iwant to get the electronics for it. Ihave a Spektrum DX7 transmitter.
The plane is a standard 4ch setup with nothing fancy.

Ihave no idea on what to look for in servos or receivers. Icannot seem to find Spektrum 4ch receivers and Ido not know if Ican use other brands of receivers with the Spektrum transmitter. Iknow that I can plug a futaba servo into a spektrum receiver if I cut off the tag, but can Ibind a futaba receiver to my Spektrum transmitter?

Does anyone know where Ican look for 4ch spektrum receivers? What servos should Ibe looking for? The plane is a Goldberg Super Tiger 60 so nothing fancy at all. Should Ibe looking at different receivers?

Thanks in advance for any help.
Brad
Old 10-05-2010, 07:32 AM
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Default RE: Receivers and Servos

The DX7 is a great radio. You might as well get the AR 7000 RX. They cost around $80.00 on RCU. It is a 7 channel RX and you have a 7 channel TX . The Futaba Receivers will not bind to the DX7, only spektrum or JR receivers will work. The choice of servos is up to you, depending on what type of aircraft you are building. The Spektrum DS-821 is a very good all around servo.
Old 10-05-2010, 08:47 AM
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Default RE: Receivers and Servos

Ditto that, but you can also get one of their 5 channel receivers if you wish. And as far as servos are concerned, well, you've built and flown your first plane, I assume, so you are going into a more advanced plane. But, that does not mean you have to spend a lot of bucks for servos.

The basic Futaba, Airtronics, Hitec (other brands too) will work just fine. For instance, a good example is the Airtronics 94102Z which is a basic standard torque servo that serves as a good choice for most of the first or second level planes. It's nothing fancy, works with any receiver, and is cost effective.. around $10.00 from Tower Hobbies. The Futaba basic servo is about the same cost and qualiity.

CGr.
Old 10-05-2010, 09:24 AM
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Default RE: Receivers and Servos

An AR500, that CGr referred to, will set you back about $50-$60. I had one in my trainer and had no problems with it.
HobbyKing is now selling what they call OrangeRx's. They state that they are Spektrum DSM2 compatable but, at only $14.95, (back ordered) I'd be quite skeptical.
Bob

Old 10-05-2010, 11:33 AM
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Default RE: Receivers and Servos

Standard servos in most 60 size planes is pretty normal. I use a lot of hitec servos but I do have a lot of other brands. The only thing about the standards I ever mention is to buy the servos with bearings, they last longer, are smoother and don't wear out the case.
Old 10-05-2010, 11:53 AM
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Default RE: Receivers and Servos

ORIGINAL: AB Bob

HobbyKing is now selling what they call OrangeRx's. They state that they are Spektrum DSM2 compatable but, at only $14.95, (back ordered) I'd be quite skeptical.
Bob

I got one a few months ago and they are not what I would call a reliable reciever for a valuable airlpane. They bind right up to your spektrum receiver beautifully but the range on the one I got is its biggest down fall. I pluged a battery into and a servo in one of the ports and started walking away from it to range test it. I wasnt even holding the bind button in and at around 50 feet the signal seemed to cut out completely. The only thing I would put this receiver in is a small park flyer that I cared nuthing about.
Old 10-05-2010, 05:36 PM
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Default RE: Receivers and Servos


ORIGINAL: AB Bob

HobbyKing is now selling what they call OrangeRx's. They state that they are Spektrum DSM2 compatable but, at only $14.95, (back ordered) I'd be quite skeptical.
Bob
I would be very careful with these types of receivers. Think of it.. $14.95? This may be ok with 72 MHz systems, but 2.4 GHz with the proprietary software that these things use, it is very specific to Spektrum/JR, Futaba for their receivers, and so on.

CGr.
Old 10-05-2010, 08:13 PM
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Default RE: Receivers and Servos

Thanks to everyone for your advice.
Old 10-05-2010, 08:47 PM
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Default RE: Receivers and Servos

Re the 5 channel Spectrum receivers, you might want to do a search re issues with some of them (faulty batch of chips in one of the series), I know it cost at least one crash at our local club (there when t happened), as I'd hate to see it happen to anyone else! (the guy at the club had his entire plane replaced by the LHS as a result - the crash was that bad)
As an option, the AR7000 someone mentioned are great, AR6200 receivers 6CH are two, and from what I know, neither have had any reported batch issues like the 5 channel ones are. They also come with a satellite receiver, which will lessen any risk of a lost signal, and are both FULL RANGE receivers, so as long as you can see the plane clearly, you'll not have any range/signal issues either!
As for servos, my 65" 0.61 powered trainer works just fine with common old standard Futuaba 3003's (just had to trip the flap bit off the plug to get them to fit). As an alternative, I use "Ino-Lab" branded digital servos on my .50 nitro heli, and so far they are proving faultless in performance after 10 months use, and were half the cost of other alternatives I looked at locally (nitro heli's need some seriously grunty/fast/EXPENSIVE servos for their size re cyclic control)

PS - as I'm pretty sure your Spectrum AR6200's can handle up to 9 volts on the RX (can't find my manual right now to confirm 100%), so you get high voltage servos as well, you can then run a larger 7.2 volt LiPo battery pack without the need for a voltage regulator, and get more grunt and speed from that given servo as a result of the higher RX voltage!
Old 10-06-2010, 05:16 AM
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Default RE: Receivers and Servos

DSM2 AR6200 6-Channel Receiver Ultralite Product Specifications
Type: Full Range Aircraft Receiver
# of Channels: 6
Modulation: DSM2
Band: 2.4GHz
Length: 30.1mm
Width: 21.6mm
Height: 12.3mm
Weight: 10 g
Voltage Range: 3.5–9.6V
Antenna Length: Main Rx: 30mm (2); Remote Rx: 30mm (2)


Pay particular attention to that lower voltage in the voltage range spec, especially if you are going to use 4 cell NiMh or NiCd packs.

CGr.
Old 10-06-2010, 05:40 AM
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Default RE: Receivers and Servos




ORIGINAL: _brad_

Hi All,

Iam in the process of building my second plane and Iwant to get the electronics for it. Ihave a Spektrum DX7 transmitter.
The plane is a standard 4ch setup with nothing fancy.

Ihave no idea on what to look for in servos or receivers. Icannot seem to find Spektrum 4ch receivers and Ido not know if Ican use other brands of receivers with the Spektrum transmitter. Iknow that I can plug a futaba servo into a spektrum receiver if I cut off the tag, but can Ibind a futaba receiver to my Spektrum transmitter?

Does anyone know where Ican look for 4ch spektrum receivers? What servos should Ibe looking for? The plane is a Goldberg Super Tiger 60 so nothing fancy at all. Should Ibe looking at different receivers?

Thanks in advance for any help.
Brad
Is your DX7 a PCM or 2.4Ghz DSM2 transmitter?

I assume that because you use the word "bind" that yours is 2.4Ghz DSM2.

SO if its a 2.4Ghz Tx then no you cannot bind a Futaba Rx to a JR/Spektrum Rx. Their mode of operation is very different.

If it is a PCM system i.e with the long telescopic aerial, then as long as the Rx is on the same frequency and says "Futaba" compatible then you can use it with your DX7.

Servo's. Any of the JR 500 series i.e 539, 577, 591 and i guess many more, in this series is more han adequate.
IF you prefer Futaba then the S3001, S3003 or S3004 servo's are excellent.





As far as channel son the Rx goes, Most of the 2.4 Rx that are less than 6 channels are park flyer Rx and not really suitable for a methanol plane. Range MAY be an issue with theseas well as Vibration.

Old 10-06-2010, 02:46 PM
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Default RE: Receivers and Servos

There's no such thing as a 72mhz PCM DX7

All DX radios are DSM 2.4ghz
Old 10-06-2010, 02:48 PM
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_brad_
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Default RE: Receivers and Servos

I ended up with the Spektrum AR6200 and Spektrum DS821 servos.  I am excited to receive them, and more excited to get the plane done so that I can install the electronics.

Thanks once again for all the advice and help.  This forum rocks!!!
Old 10-06-2010, 03:43 PM
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Default RE: Receivers and Servos

Good luck and let us know how it all goes Brad!
Old 10-06-2010, 03:52 PM
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Default RE: Receivers and Servos

ORIGINAL: TimBle .........As far as channel son the Rx goes, Most of the 2.4 Rx that are less than 6 channels are park flyer Rx and not really suitable for a methanol plane. Range MAY be an issue with theseas well as Vibration.

Myself and a person at my LHS looked up the range on one of Specktrum's 6ch 'parkflyer' RX's a few months back, and was shocked that it was actually good to 1000meters, and that would be further than I could see any of my models, yet that vibration concern combined with the lack of a satellite RX was enough to stop me form getting it.
Old 10-06-2010, 04:01 PM
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Default RE: Receivers and Servos

"range" isn't the issue with the park flyer recievers.

The single reciever design is subject to shadowing, if the motor or a battery passes between the transmitter and the signal you could lose signal.

Thats why they are designated (and should be used as) park flyer recievers
Old 10-06-2010, 05:16 PM
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Default RE: Receivers and Servos


ORIGINAL: _brad_

I ended up with the Spektrum AR6200 and Spektrum DS821 servos. I am excited to receive them, and more excited to get the plane done so that I can install the electronics.

Thanks once again for all the advice and help. This forum rocks!!!
Good choice, Brad. I have several of those servos, but I've reserved them for something a bit larger. They will do well with your plane, I'm sure. I also have two of the AR6200 receivers and they too have worked out just fine.

CGr.
Old 10-06-2010, 05:51 PM
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AB Bob
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Default RE: Receivers and Servos

Good choices. I've had real good service from the DS-821 servos I have.
I'd go with at least a 5 cell (nominal 6.0V) nimh battery of at least 1100 mah capacity.
Old 10-06-2010, 07:50 PM
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_brad_
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Default RE: Receivers and Servos

AB Bob, batteries are an area I know nothing about and need to learn.

Could you please explain your recommendations? 
I know the higher the mah capacity, the longer the battery life.  What is the significance of the 5cell (nominal 6.0v)?
Old 10-06-2010, 09:05 PM
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Default RE: Receivers and Servos

ORIGINAL: _brad_

AB Bob, batteries are an area I know nothing about and need to learn.

Could you please explain your recommendations?
I know the higher the mah capacity, the longer the battery life. What is the significance of the 5cell (nominal 6.0v)?

Sorry to butt in, higher voltage will increase the torque of your given servo, as you normally see ratings for a servo's power and speed on the side of the box they came in quoted for both 4.8 & 6volts (provided it's a 6 volt capable servo of course), with the 6volt power option delivering more speed and power than the 4.8volt option - i cut and pasted the spec info off the Specktrum site below, and you'll notice that the torque at 4.8 volts is only 72 oz/in, while at 6 volts that same servos torque rises to 88 oz/in, a torque increase of 22% over the 4.8v level..
I use a 5 cell 6volt NiMh 2700mah pack's on my plane and heli for that very reason - I'd rather have too much power and speed than not enough.
A point of interest, that quoted 6volt level is also just the discharged voltage level of a 5 cell NiMh, the actual charged voltage level is a fair amount higher than that!


DS821 Sport Hi-Torque Digital Servo
Product Specifications
Size Category: Standard
Type: Digital
Torque: 72 oz/in @ 4.8v, 88 oz/in @6v
Speed: .19 sec/60 deg @ 4.8v, .15 sec/60 deg @ 6v
Old 10-07-2010, 05:29 AM
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Default RE: Receivers and Servos

ORIGINAL: _brad_

AB Bob, batteries are an area I know nothing about and need to learn.

Could you please explain your recommendations?
I know the higher the mah capacity, the longer the battery life. What is the significance of the 5cell (nominal 6.0v)?

Brad:

To follow up on what kiwibob stated, there was a time when some of the 2.4GHz receivers would re-boot due to low input voltages. This happened when pilots allowed their receiver battery voltage to drop below a threshold that caused the receivers to reboot, thus losing connection - bind with the transmitter. This was notable in the 7 channel Spektrum.

Since then, Spektrum made changes in how the receiver dealt with the low voltage. I believe they changed the time to reboot but not the threshold. So, when it happened, it might take a couple of seconds for the reboot which may not be noticed by the pilot. The alternative, before the change that is, the reboot time caused crashes.

As I said, the problem has been addressed but many users are skeptical about using 4 cell packs (nominal 4.8 volts). Of course, if the pilot didn't push the envelope and recharged when it was prudent to recharge, this would have never happened. However, many of us have moved to 5 cell, (nominal 6 volts) packs. This provided two distinct advantages. 1. as pointed out by kiwibob, more torque and faster servos. 2. there is practically no chance you will reach the threshold voltage with a 5 cell pack thus making them safer to fly.

It has been noted that for a 6 volt pack, the system uses up the charge a bit quicker. Well, that has never really been proven to my satisfaction.. Ohm's law provides some proof of that.. power = voltage X current so if voltage goes up, with a constant current, power goes up.

Anyway, this is not a debate on Ohm's Law. The main point is that you can move up to a 5 cell pack and get the benefits.

I use 5 cell NiMh 1200 mah packs and have had great success with them. The weight difference is negligible, although they are slightly larger... one more cell in length for the ones I use.

One more recommendation... and I'm sure someone will read this and say "Oh boy.. here he goes again".. but I use a device called Voltwatch2. It plugs into a vacant receiver channel, or can be Y connected to an in use channel or to the battery plug in slot. This gives you an instantaneous look at the battery condition before you fly. I usually check mine before and after each flight.

It has a series of LED's that glow according to the voltage of the battery pack. What's nice about it is that because it is active when the system is active, you get a true "system loaded" reading of the battery charge condition. And, by it's design, it also great to seek out a binding servo or servo connection to the control surfaces, and especially the throttle, which is where many linkage binds originate - exceeding end stops of the throttle arm by the servo linkage will cause the servo to try to continue moving.. binding it up and drawing excessive current. You can find the binds, fix the problem, and optimize your system for the least amount of current flow for your operation.

Best of luck!

CGr.
Old 10-07-2010, 06:02 AM
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Default RE: Receivers and Servos


ORIGINAL: BarracudaHockey

There's no such thing as a 72mhz PCM DX7

All DX radios are DSM 2.4ghz

ah! thanks for that. Iwas under the mistaken impression that there was an early version that was FM PCM but I went back and checked teh emails and specs I was sent a year ago while iwas looking for a radio. th bloke said it was a DX7 and had a 35.14 MHz crystal blah blah..
It was not a DX 7 in fact.
Old 10-07-2010, 07:52 AM
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Default RE: Receivers and Servos

Ohm's law is great if the load is constant, which our systems aren't.

Actual consumption increase by increasing from 4.8 to 6v systems is about 5 percent. (proven with reliable testing), essentially a non-factor.

As for the 821s, they have some warnings associated with them so be careful how big of a plane you put them in.
Old 10-07-2010, 02:23 PM
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Default RE: Receivers and Servos


ORIGINAL: CGRetired ........One more recommendation... and I'm sure someone will read this and say ''Oh boy.. here he goes again''.. but I use a device called Voltwatch2. It plugs into a vacant receiver channel, or can be Y connected to an in use channel or to the battery plug in slot. This gives you an instantaneous look at the battery condition before you fly. I usually check mine before and after each flight..........
Sounds like great advice to me, better than guessing or hoping that your battery is up to the task!
Old 10-07-2010, 06:11 PM
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Default RE: Receivers and Servos

I won't hijack this thread with a discussion about voltwatch. There are many previous to this that discuss pro's and con's about their use. For NiMh and NiCd, in my opinion, you can't go wrong. With the new LiFe packs, well, it's not such a good idea.

Do a "search" on Voltwatch and Voltwatch2 and see what there is on these devices.

I highly recommend them, as stated, for NiMh and NiCd pack use.

CGr.

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