cloudancer03

My Feedback: (22)

I recently was talking with another sprectrum user and he tried to explain about a regulator in the back of the tx.It seems that the unit draws down the battery quite quickly and indicated you can remove or modify it somehow to avoid that problem.do you know what is was saying and whether or not he was fact.??

PacificNWSkyPilot

My Feedback: (19)

I hadn't heard of it, I've been following the DX7 stuff for a long time now, particularly battery and draw-related items, since reaching a low voltage is the biggest danger with a DX7, or any other radio, in fact. I'd be interested in hearing all about it.

I just reread your post and saw you were actually talking about the TX, not the RX. I still hadn't heard about it, though, and would still be interested.

Jim

Zeeb

My Feedback: (41)

Not saying your source is mistaken, but I've not heard of anyone modifying the DX-7 in the manor you mention. The tx's do have circuitry to reduce the operating voltage from what the battery puts out, but the included 1500 mah battery in the DX-7 lasts an incredibly long period of time. I can't imagine why someone would "need" to modify it for more time but the usual course of action is a bigger battery.

Now if it's in the DSM mode to operate an AR-6000 rx, then it will draw quite a bit more battery power than when it's in it's normal DSM2 mode.

PacificNWSkyPilot

My Feedback: (19)

All of this aside, I suppose I should mention now that you can probably get a 2500 mAh Tx battery from RadicalRC.com, maybe even bigger numbers than that available. I know I've gotten 1600 size there and done well with them. Batteries always fresh, work good, last long time. Guess I'll go and check out what else they have....
Jim

cloudancer03

My Feedback: (22)

I have learned not to take everything as gospel either.I have flown the tx since summer 2008 and never encountered any issue like what I heard.I did experience a rx issue when I took off , the plane was not responding well and I darn near lost it and scared everyone on the field.after getting it back I rebound the radio did a extensive range check made sure I had a solid red light and took off and life has been good since.In that matter all I could figure was I sequenced the on and off wrong.of course a fellow flyer who hates spectrum alleged he never had any issues with his fasst futaba Insinuating the futabas spread spectrum is better and I read alot about sprectum technology and realized he is full of it as well.so far as I am aware the real danger is when voltage gets below threshold of 3.9volts (correct me if wrong) and then the signal will reboot itself.at any rate I like my radio and aree that theres no such tx problem.

PacificNWSkyPilot

My Feedback: (19)

That's below 3.5 Volts when they kick out, but you've got the right idea. Anybody who takes off with voltage anywhere NEAR that low DESERVES to crash. Since the RX lives and dies (and takes naps) by the numbers, I start out with 6 volts rather than 4.8 and I'm an extra volt or so to the good to start with. Then I up my mAh numbers to 1600 or 2500, you get the idea. A couple of extra ounces but the plane comes home every time. As long as I don't spazz out.....

Jim

cloudancer03

My Feedback: (22)

you have a great point! this past year I started upgrading my rx batteries to 6 volts.that gives me some insurance if the battery does get lower.I cant imagine ever flying on a low voltage .I am usingmor digitals too and I know they consume more power but they also hold better and center better..thanks for coreccting me I wasnt sure .as for sprectrum I know its way better than 72 though I still have it on my futaba 9C and why not I live in a fairly rural area and its a small club and the number of 2.4's is smallbut I have no competition my frequency either.

PacificNWSkyPilot

My Feedback: (19)

Woodstock is kinda rural. I'm from Chatham. Many, many years ago.
Jim

Zeeb

My Feedback: (41)

Jim is correct on the low voltage reboot happening at 3.5 volts.

One thing you may want to consider when you start running digital servos and especially bigger ones that can pull a lot of power. Just getting a battery with a high mah rating doesn't necessarily mean it'll cut the mustard. The issue is that a lot of the battery cells, especially the AA size, used to make up packs for RC use have a high impedence or internal resistance. This is because they were originally designed to operate electronic devices which don't require a lot of current (amps).

Now these cells work fine for tx's as those don't have much current draw but the higher capacity cells do have some issues one needs to be aware of regarding charging rates and self discharge rates. High impedence cells on a flight pack with a bunch of digital servos is a bad idea. If the servos pull more current than the pack can provide, the voltage temporarily drops like a rock and can cause an rx re-boot on a Spektrum/JR 2.4GHz rx.

So when you buy new rx packs, pay attention to the cell impedence numbers or at least the continous and burst amperage discharge rates. Make sure those numbers match the anticipated max load your system could pull.

cloudancer03

My Feedback: (22)

HUH???lol. could you sort of give me an example of what you just said thanks..

Zeeb

My Feedback: (41)

Well there's too much to condense into one thread reply, so I'll give 'ya a couple of links if the RCU server doesn't strip 'em out...

http://www.hangtimes.com/rcbattery_faq.html

http://www.rcbatteryclinic.com/

BuschBarber

My Feedback: (2)

If you measure the amount of current you system draws when all of the servos are under max load (stalled), it will give you some idea of what Rx battery packs to buy (mah size and max current draw capability). If the batteries can sustain the load without causing the voltage to drop, you won't have a situation where your Rx turns off and on due to a sudden low voltage.

There are inexpensive devices, from Hangar 8, for example, that let you measure the current draw of an individual servo or all the servos at once. You can use your Tx to deflect all the servos and have someone put their fingers on the control surfaces and simulate flight loads.

cloudancer03

My Feedback: (22)

thanks guys..zeeb..once you explain it as part of golf I get it very quickly lol.

PacificNWSkyPilot

My Feedback: (19)

I'll make it REAL easy for you. Call the guy at RadicalRC.com and ask him for packs that accomplish what you're looking for, high-mAh packs with the ability to crank out amps without dropping the battery voltage due to a bottleneck in the flow. That's a very simplified way of putting it and he'll know what to tell you and what to sell you. Really nice guy too. I think Saturdays used to be good to get through to him. BUT>>>>>
I honestly haven't seen this as being an issue, the wires and connectors on a standard gold RX connection are only so big and enough draw to drop the voltage in the batteries would (I believe) heat up if not start to melt wires. That's a LOT of draw. By the time you talk about getting into draw like that you're adding these big LiPos and voltage regulators and all that. That's nuts.
This is all WAY beyond, and I mean INCREDIBLY WAY beyond the modest safe setup you're looking for. We've gotten away here from the actual plane you were setting up and the fact that you're looking for some easy ways to improve DX7 cutout safety. Take it from me, a second pack "Y"d into one of the tail feather legs and the extra mAh size added to a 6-Volt setup are typically enough for anything DX7, period.

I have a 50CC Edge 540 with BIG servos (8211A's) and that is ALL I'm going to use with it. First pack has 4000 mAh, second pack 2500. I'll simply monitor the voltage every couple of flights.

Remember here that most ordinary radio setups included a 500 or 600 mAh flight pack and would fly quite a few flights. Regular servos or even 821's don't use up much more than that, if any. DX7 radios come with an 1100 mAh pack, I believe, almost twice as much. Step up only to an 1100 pack with 6 volts and for any average .60 to .90 size plane you're there, essentially. Some of the guys get crazy with the overkill.

Stop, take a breath, use common sense and remember that your wife won't appreciate your spending the retirement money. If you want to make extra sure, a 2500mAh 6-Volt battery pack is still cheap enough as your primary and use an even cheaper 6-Volt 1100 mAh pack as your backup. Two BIG double-pole switches and you've really got a very comprehensive setup there. Instead of spending 5 times the money, spend twice the time and make sure of every little thing, attention to detail in an RC plane is worth more than all the fancy setups in the world.

A flight simulator that's used to sharpen your skills is money even better spent.

Jim

Zeeb

My Feedback: (41)

Hmmm.... 8211A servos? Never heard of those, but they are BIG right?????

He never said what kind of models he was running, nobody gave him any advice about specific battery/power setups, nor recommended any particular vendor.

There's nothing wrong with learning what works and what doesn't when it comes to battery/power setups and lots of guys have their own personal preferences for setting them up. Some general rules apply and that's all we've been talking about in a thread started talking about tx batteries/power. You maybe ought to consider mentioning that your particular setup is what you like, not necessarily the only way it could be accomplished as there are lots of GS guys, who would find your setup as something less than desirable.

While some of the GS folks are still running Li-Po/Li-Ion batteries and regulators, the newer servo stuff coming out is actually rated for operation at the nominal voltage ouput of 7.4 volts which is what those batteries are rated. The rx's have been able to handle the higher voltage for some time now, but the servos had been restricted to a lower voltage.

But even that setup is being pushed aside for the new A123 batteries which are probably the best battery solution for our needs. High continous output at 30C with burst capability of 60C, no fire hazard, no regulators since they run at 6.6 volts, very little self discharge and they charge in 20 minutes. My glow stuff runs the 1100 mah size of these batteries and the gassers run the 2300 mah size with my little 50cc bird running a single 2300 with dual outputs and an 1100 on the ignition, but a number of folks are now running the ignition shared off the rx packs when running the 2.4 radios. I don't personally care for that idea right now, but who knows? Just because I don't care for the idea doesn't mean it won't work.

Oh and weight.... The 1100 packs weigh 2.9 ounces and the 2300's are 5.8 ounces. That is substantially lighter than any comparable NiMH/NiCD of a similar output capability.

JMHO, YMMV....

PacificNWSkyPilot

My Feedback: (19)

Nothing worse than telling a guy he has to spend money like crazy when he's just getting into RC.

Especially when there is no need to. He's been asking around and his plane is a regular Cessna or something similar.

The vast majority of the planes that go down with DX7 radios are due to poor connections and no backup systems, NOT voltage drop. The simple process of getting guys to pay enough attention to add that detail of a simple backup system would have prevented most of that vast majority from crashing.

RX voltage? Servo voltages restricted to? Come on. They work on 4.8 Volts or 6 Volts. Simple. DX7 RX's cut out below 3.5 Volts, so you step up to the 6 Volts and pay a little attention to not flying them when they're drained down too far. You add another battery in another leg for a backup, and use a second switch. That's it. Simple, comprehensive, and effective. Whether you care for it is irrelevent, it's a very effective use of materials and common sense. Simple, effective solutions is the primal ooze this hobby evolved from.

Not only is that all that this fella needs, that's all MOST of these fellas need. The average .46 or .60 or .90-size plane is well-covered here.

But looky here. I have a 50CC Wild Hare Edge, and as you were kind enough to point out, those 8211As are pretty BIG. And that same setup using 4000 mAh and 2500 packs is more than sufficient, has system redundancy, and it's very cost effective.

Bigger, more expensive, more advanced. That doesn't really mean BETTER. Any of those or all of those can be rendered completely ineffective by sloppy work installing them. A single bad connection.

Before I say this I should point out that I am allowed to spend all the money I wish to spend on my RC, be it hundreds of dollars or tens of thousands a year. I am in what is perhaps 5% of the modeling population out there. There's another 2% that can spend me right into the ground. It all means nothing when you don't have it and the plane is going in.

Attention to detail and careful, thoughtful installations will trump lots of money any day.

There are some really impressive systems out there, and the A123 batteries have shown promise, as have many of the regulator systems. And for that 5% or so of the new modelers out there who absolutely have money to burn there are toys galore. But for the other 95% who have wives, families, budgets, and retirements facing them (or upon them), keeping it simple and effective really is a MUST, or they could face having to abandon the hobby.

I'm going to continue to recommend simple, effective and cost-effective solutions to new pilots here. Because I didn't quite crawl out of that primal ooze with this hobby, but it was long ago enough to remember where I came from. And what this hobby is really about.

Jim