skaliwag

My Feedback: (1)

Has any one tried the Novak Smart -Stop cut off Gizmo #5472 for e-control line?


http://www.teamnovak.com/products/li...ule/index.html

da Rock

From the description, it doesn't sound suited to control line.

It is described as a warning device, not a shut-off. What you need for a CL model is a shut-off.

Do you have further information that explains how to turn it into a switch?

skaliwag

My Feedback: (1)

The switch is the big Boogga Boo. This thing plugs into Channel 3. Need a way of tricking it into thiinking a switch is a Rx.

mikeainia

My Feedback: (1)

You've lost me here -- Every ESC that I'm aware of will act as a
low-battery cut-off. What is it about this device that looks like
it might be useful?

Mike A

skaliwag

My Feedback: (1)

Yes Mike you are right...
I am looking for a way to fly E-C/L.. and not use a timer.
A timer can go on until after you have reached the point of no return for a battery.. I want the motor to cut when a set (low) voltage has been reached.

mikeainia

My Feedback: (1)

Well, there are two issues - first, you must use an ESC, at least for a modern
Brushless motor. Since you have to use an ESC, you have to have some
device to tell the ESC whether or not to run the motor. These are commonly
called timers - but probably should be called sequencers - as they do more
than just run the motor for a certain amount of time.

Like I said, every ESC has a battery monitor which will stop the motor if
the voltage goes below a certain level - usually about 3.0 v. / cell, or 9.0 v
for a 3s Lipo. Most can be set for NiMH/NiCd cell too and then they stop
the motor at about .8 v. / cell. In any case, this is the Cut-Off voltage.

If you don't have a timer or some other circuit to drive the ESC, it will just
sit there and never run - it needs to have the throttle pulse from a Receiver
or something that mimics that throttle pulse. You can use a servo
exerciser - a small device that allows an RC servo to be moved without
turning on the transmitter. You could carry this in the plane, set the knob
for the desired RPM, then fly until the ESC hits CutOff voltage - but I can
tell you that this will not be very satisfactory, and will actually be kind of
hard on batteries. You are left with the option of using the "Timer" - and
since they only cost between $15 and $30, they aren't any more expensive
than the servo driver. They are programmable in several ways:
1st - You can precisely set the run time from very short to very long
2nd - You can make it wait before the motor starts and choose how long
than wait is - this gives you time to walk to the handle and get ready
3rd - You can set the motor RPM from slow to Full speed, and most that
I am aware of will slowly increase the speed, to minimize the effects of
a battery that is running down.
4th - They all have some method of warning you that the time is about
up and they are about to shut down, so you don't get halfway through
a loop and lose power.
And lastly, they have a clean and total shut down, so you don't have to
fly around on nearly dead batteries that will barely keep the plane
moving.

I'm not sure what it is that you are trying to avoid by not using a timer -
I've got several different ones and they are all slightly different, but all
are a great asset to C/L flight. With the programmability of the timer,
you can dial the flight in to exactly what you want, and still have the
auto-cutoff of the ESC as a safety back up, in case the timer somehow
runs too long.

Mike A

skaliwag

My Feedback: (1)

I fly 1/2A and it's a little annoying that you have to have $50 worth of electronics to turn the motor off when the juice runs out.

mikeainia

My Feedback: (1)

Are you talking about brushed motors ? If so, then yes, you only need some kind
of switch.

Any brushless motor though, needs the same $50 worth of electronics to
turn the motor ON.

(Actually, you can get a "1/2A size" ESC for under $20, a motor for under $20
and a "timer" for $15).

mikeainia

My Feedback: (1)

I don't know if you guys are still interested in this thread or not, but I thought I'd show some pix of what it triggered - I decided that I'd just build something so anyone would be able to have a starting point -

This one will be flying on 2-cell packs. All up weight should be right at 8 oz. It was originally going to be a modified Sig 1/2A Skyray, but I decided to just build a new one - the built up wing is one I've built before for glow powered Skyrays. The full fuselage was just kind of a whim.

The motor and ESC cost $16 (as a combo)
The battery packs cost $7 @
The Timer circuit cost $15

The two motors shown both need fairly large props, but there are others available that would turn smaller props at higher speeds. The packs I'll be using are 900 mah, 2 cell lipo's and I expect 5 - 6 minute runs. The timer lets me break that into 2 or 3 short runs if I wish, for training beginners etc.

If anyone wants more information, I'll gladly send or post a list of sources for this stuff.

Mike A.

ekotil

Good looking plane Mike!

da Rock

Yes, it would be nice for you to post the source for the parts.

mikeainia

My Feedback: (1)

Re-posted below - Quoted the wrong message.

mikeainia

My Feedback: (1)

Go to Lightflightrc.com - he has the "Suppo Cheap Combo" for about $18 - this is a motor and speed control. Get the motor with the highest Kv (a motor constant that kind of describes how it can run) - I think there is one with a Kv of 1450 and one with a Kv of 1800.

The speed control is an 18 amp one, has NO options to set. It auto-senses how many cells you have and turns the motor off at a safe low voltage.

The timers that I use come from Will Hubin ([email protected]). I will attach his price sheet to this post. You will only need his $15 unit - it allows you to set the run time, the RPM, and the "Idle Time" (How long it waits after you start the sequence before it starts the motor - allows you to walk out to the handle).

The plane is a Sig Skyray (1/2A) 'spiffed up' with a full fuselage and a full-airfoil wing. ANY plane with about 150 square inches will probably work, the built up wing may be very helpful. The successor to the plane in the pix is a little larger and I went back to a profile. The battery just straps to the outboard side of the fuse, about over the high point of the wing, like a fuel tank. I don't know why a slab wing wouldn't fly OK either - I know of a couple of guys who managed it - if you have a smooth flying area and wheels or a helper who can be trusted to "assist" the takeoff, once you have a little flying speed it would be fine.

The power system I have described will fly pretty well with a 7-6 prop and 2 cell Lipo's.

I get Lipo's from hobbyking.com - 2s1p 1200 mah - you can probably do as well on ebay from one of the Hong Kong re-shippers = many of them have free shipping. You will also need a charger - the cheapest 2-3 cell balancing charger is adequate. You can also get the batteries and charger from a place called www.dealextreme.com - The charger is about $10, a power supply for it is about $10 and the batteries are about $15 each ( from memory - 2s1p 1000 mah 'emax' brand, I think).

That is about all you really need to get started in this - if you have to buy everything new you'll be well under $100. There isn't anything special to know - just follow the instructions when charging (it really isn't as dangerous as many would have you think). Watch your balance - the weight distribution is quite different from a glow engine and tank.

This outfit is easily capable of the beginners stunt pattern on 35 foot lines. The Mk2 that I've mentioned spins a 6-4 prop at almost 13000 RPM - I set the timer for a 2min 45 sec. flight and I can get two patterns out of a battery charge (with 1300 mah battery). Total weight is about 9 ounces.

So I walk over to the park and fly four patterns off the basketball court and walk home again - I don't even need to take a flight box.

Happy to answer any other questions you may have.

Mike@

OK- the board won't let me upload a pdf - so I'll go screen-cap it and upload it as a jpg.

(edited for formatting)

mikeainia

My Feedback: (1)

Here is some info on Will Hubin's Flight Managers - there are other options, but you need more expensive esc's to take advantage of them, so I've only shown the two that are "plug and play" for the simplest systems.

If you want to see the whole sheet, PM me or say so here and I'll email it to you - it's a .pdf
of ~ 600 Kb.

Mike @

cutaway

How about something like a 555 timer set up as a one-shot working a contactor? If you know your battery is good for 5 minutes at full power, just select the 555's parameters accordingly.

mikeainia

My Feedback: (1)

These are brushless, 3 phase motors. You can't just connect power to the leads and have them run. They need an Electronic Speed Control (ESC) in order to turn at all - the ESC normally recognizes signals from an RC receiver, but we use a "Timer" (Flight manager, flight programmer, sequencer) to mimic a receiver throttle output.

There is also a method of sending speed control pulses from a different kind of controller - called a U-tronics unit - down the lines, and this unit can be controlled by a pot mounted on the handle. This gives you throttle control without the 3-line bellcrank and handle.

There are also a few who have mounted a receiver and control speed with a transmitter, usually hanging around the neck, but one guy I know of made a control line handle out of a pistol grip transmitter, so he flies control line but uses the throttle channel to control the motor. Note: any system that uses radio control for any function cannot be used at a contest, but for sport flying is perfectly fine.

Mike@

cutaway

3-phase motor? What converts the battery's D/C to A/C then?

mikeainia

My Feedback: (1)

The ESC -

The motors have three windings, connected to 3 leads and no commutator or brushes. All the commutation and "logic" of applying power to those windings takes place in the Electronic Speed Control (ESC) - it is basically a microcomputer and a bunch of MOSFET power transistors.

cutaway

3-phase has a very specific meaning. Having three windings doesn't mean something is necessarily 3-phase. Ones I've seen anly use two of the three leads in actual operation.

The only practical (electrical) reason I can see for an ESC is to provide the equivalent of a soft-start for the motor to limit startup currents to reasonable levels.

mikeainia

My Feedback: (1)

I know what 3-phase power is and how a 3-phase motor works - These are three phase motors. There are 3 distinct windings, connected internally in either delta or Y configuration. Either way, there are 3 output leads and 3 leads from the ESC. The windings are stationary and the magnets (and the outer 'can') rotate around the windings; this is referred to as an "outrunner" configuration. They will not run on DC and they have no commutator or brushes, so the ESC provides all the logic to commutate the current to the different windings at the correct time. It also provides a Brake function, a battery monitor function, sometimes a "Governor" function, and usually a few other programmable options.

For more information, I'm sure that this board has some RC Electric forums pertaining to motor and electronics design.

da Rock

For those of you who're speculating about different ways to do a "LiPo battery cut off" keep in mind the two requirements that're needed for LiPo's in a C/L environment.

You will need the basic requirement this thread is about, a cut off.

Also remember that the nature of a LiPo requires that you have a backup cutoff that responds to the voltage level and shuts the system down to keep from destroying the LiPo. The special switch mentioned earlier and most ESCs both have this functionality.

So whatever you brainstorm, keep both those ideas in mind.

mikeainia

My Feedback: (1)

That is the "battery monitor" function that I was talking about - should also mention that although MOST people use Lipo's these days, some still use NiCd or NiMh and the ESC's will most often have a method of setting to those chemistry's. And without going into a long-winded side post about A123 cells, if you use those (and I sometimes do) you can set the ESC to the NiCd/NiMh setting and they will work well with A123's.

mikeainia

My Feedback: (1)

That is the "battery monitor" function that I was talking about - should also mention that although MOST people use Lipo's these days, some still use NiCd or NiMh and the ESC's will most often have a method of setting to those chemistry's. And without going into a long-winded side post about A123 cells, if you use those (and I sometimes do) you can set the ESC to the NiCd/NiMh setting and they will work well with A123's.