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HeliHobby . Ron’s HeliProz South . Century Helicopter

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Main Discussion > [Technical] More noob questions
 
 
paparker21
New Heliman
Location: Cookeville TN

thanks for all the help on the last thread guys; I figured i'd throw a new topic out with this next set of questions so it wouldnt get lost in the whirlwind of activity on the forums here

1) What exactly is a Battery Eliminator Circuit?
2) How many amps can i safely draw from a 4.8V LithIo battery pack?
3) How many amps can the standard servo leads handle?
4) How many amps can my wireless receiver handle?
5) Does the ESC basically limit the current to anything downstream of it? If this is the case, does this mean that for my high current draw loads (electromagnets in my case) need to be spliced in between the battery and the ESC? If this is the case, do i simply only need the signal wire from the receiver connected to the R/C On/off switch i'll be using?


And now for the tricky one of the day. A quick description of our 'submarine' is required-
Its shaped roughly like a manta ray and has two flaps (ailerons) on the on its 'wings' trailing edge. It is driven by two impellers which are off center by a few inches. What we want is to be able to switch on and off our impellers in correspondance with our flaps in order to produce a more pronounced turning characteristic.

Example: Left turn craft orientation: /
Left flap UP
right flap DOWN
ideally we would like the left impeller off and the right impeller on in this condition to aid in the turning.

Basically it needs to meet those conditions as well as the corollary for a right turn. We also need to be able to drive BOTH motors when 1) neither flap is activated (neutral positions)
2) both flaps are activated (both up or both down)


Any of you have insights on how to do this? Right now we're thinking its going to take about 4 relays and a spider web of wires to do it. My EE friend mentioned something about using a circuit board with logic gates but i dont know much of anything about that. I was wondering if you guys had any ideas or knew of a very simple and effective way to do this.

Thanks again for all your help!
10-01-2008 05:46 PM
 
 
Yug
rrProfessor
Location: UK. Herts

1) A BEC is a regulator to supply power to your receiver/servos, from a higher voltage light battery such as 4S or 10S
2) Depends on the C rating
3) With the heavier guage servo lead, you begin to get voltage drop over 5 amps or so
4) Power & Ground pins are all bussed. Limitation is on the connector and whether you use dual redundent cables to supply power.
5) There are 2 types of ESC, linear and switching. Linears are electrically quieter but cant deliver big power. Switchers are very efficient and switch the phases of the motors to establish speed control as well has using PWM.

Use a 4 channel radio and mixes to derive the control signals for the 2 ESCs and 2 servo signals.

Submarines don't fly.

Vegetable rights and Peace
10-01-2008 05:57 PM
 
 
AirWolfRC
rrProfessor
Location: 42½ N, 83½ W

If the separation between the two impellers is only about 10% of the span, I wouldn't bother trying to drive the impellers differentially.

Other wise, an off-the-shelf radio could give the "elevon" mixing you need.

If you don't want to use a standard radio, mechanical mixing can do the job also.
10-01-2008 06:03 PM
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MaxAdventure
Senior Heliman
Location: Boulder, Colorado

fist, you may also want to check these sub specific forums for information or resources:

http://www.rcuniverse.com/forum/forumid_119/tt.htm
http://www.rcgroups.com/submarines-60/

Most of the specs for the equipment you have will be listed on the manufactures site, then you can answer your questions. Without knowing the specific make/model, most of those questions are quite variable.
eg: 4.8 volts is a typical rating for four Nickle based rechargable. lithium based run 3.7 (LiPo) 3.6 (LiIon) 3.3 (Li-Phosphate)
while NiCad/NiMh are 1.2
Ah capacity is usually printed on the pack, and the discharge rate 10C, or 10 times the packs Ah rating etc)is usually printed on the Lithium based packs, but you have to check the manufacture specs for most of the Nickle based packs I've seen.

As for the coordinated turning, some computer radios have the programmable mixing built in, I've done similar with electronic mixing boards for dual steerable Kort nozzles on a tug I built.

-da (Max)
AMA 198798
issues? I have subscriptions...
10-01-2008 06:23 PM
 
 
AirWolfRC
rrProfessor
Location: 42½ N, 83½ W

Have you thought about ultra-sonic control ?
10-01-2008 06:41 PM
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Main Discussion > [Technical] More noob questions
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