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Author Topic: Newbie question  (Read 2340 times)

hazmat

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Newbie question
« on: May 26, 2010, 12:40:46 AM »

Don't yawn yet please.
 I'm new to using multiple batteries so help much appreciated.

12 volt 5AH battery to esc. Fujitsu 6ex receiver. Do I need to cut the red wire from the esc to the receiver?
Or, can I just do away with the rx battery pack?



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poddy

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Re: Newbie question
« Reply #1 on: May 26, 2010, 12:49:02 AM »

If the esc has a bec (battery eliminator circuit) then you don't need a seperate rx battery pack
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FullLeatherJacket

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Re: Newbie question
« Reply #2 on: May 26, 2010, 08:13:45 AM »

Can you tell us exactly what type and model of speed controller you have there? (I think you'll find it's a Futaba receiver.)
FLJ
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hazmat

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Re: Newbie question
« Reply #3 on: May 26, 2010, 01:57:27 PM »

Hi FLJ
Yep, Futaba not Fujitsu (always get the names the wrong way round).

Dunno what make of ESC , generic Chinese one.
No markings except for max DC volts 15, max current 40 amps, colored a sort of pale blue.
No documentation (pretty dumb really buying it without paper) BUT when I tried it out on 7.2v it works a treat.
My worry is that 12 volts could blow the receiver.
As for a BEC thingy ???
I get the wife to work the dvd remote as she has more technical knowledge than me so easy questions only please!



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FullLeatherJacket

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Re: Newbie question
« Reply #4 on: May 26, 2010, 03:19:53 PM »

Have you got a digital multimeter? If so, then connect the ESC to the 12v battery and put the multimeter - set to the 20V DC scale - across the red and black wires which go into the receiver plug. If you get a reading of around 5v then the thing includes a regulator (BEC) and you shouldn't use a separate Rx battery. If there's a small on/off switch connected as part of the ESC wiring harness then try this test with the switch in both positions.
If you don't have a DMM then connect a small (6v) bulb  across those red and black wires to see if there's a voltage there.
For the gen about BEC read this stuff:
http://www.action-electronics.co.uk/pdfs/BEC.pdf
FLJ
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hazmat

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Re: Newbie question
« Reply #5 on: May 26, 2010, 10:41:59 PM »

For " shouldn't use a separate Rx battery", does that mean 'BANG'!

DMM---- no but a 6.3 volt bulb blew on connecting up so I'll assume that the BEC thingy isn't fitted.
no switches either.
 
so, me thinks that I need a RX battery as no BEC thingy appears to be fitted (or have I got it all wrong) :embarrassed:!

paul


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FullLeatherJacket

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Re: Newbie question
« Reply #6 on: May 26, 2010, 11:34:26 PM »

If what you're saying is that over 6.3v appears across the red and black wires which feed into the receiver plug then it looks like the ESC is supplying an unregulated voltage from the main motor battery to the receiver. This is not a good idea.
Unless someone out there knows what type of ESC this beast is; has a set of instructions and can copy them to you then my advice would be to sideline it and use one which does have some documentation.
FLJ
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hazmat

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Re: Newbie question
« Reply #7 on: May 27, 2010, 07:04:06 AM »

FLJ
Seems like the best and safest option.
Thanks for your help
Paul
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malcolmfrary

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Re: Newbie question
« Reply #8 on: May 27, 2010, 12:42:00 PM »

I would guess that the ESC does have a BEC, but a broken one if it is letting full battery voltage out on the red wire. 
The BEC does two jobs - one is to supply the internal control circuits of the ESC from the main battery, and the other is at the same time to supply a regulated 5 volts to the rest of the system. 
Some "rest of system" items can live with 7.2 volts, and this is what might have been happening to allow them to live through it.  Use of 12 volts might well kill off the ESC internals, and will almost certainly kill off the rest of your electronics. 
Mr Jacket's suggestion to sideline it and saving up for a proper one of known parentage is probably best.  You could always sell it to someone you didn't like.
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hazmat

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Re: Newbie question
« Reply #9 on: May 29, 2010, 06:52:23 AM »

Sell it on! No chance, I don't hate anyone that much. So my options are:-

I needed something to level the shed workbench

Another attractive idea involves the hammer and bin!

Anyway, sat here, I have just stripped the beast down (only 4 torx screws holding it together and a ton of heat sink compound) and found INSIDE THE  CASE  a  Q.A stamp with the funny word "FAILED". <:(

"Ex friend" >:-o who supplied it will be  politely informed later today. <*< <*<

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malcolmfrary

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Re: Newbie question
« Reply #10 on: May 29, 2010, 11:40:44 AM »

Since you managed to get inside, it might be possible to repair - I suspect that there will be 5 three legged lumps, if they have numbers, two pairs and an odd one.  The odd one is likely to be the voltage regulator, and since volts are getting out, it might be something as simple as a dry joint on the ground leg, just needing a dab of solder.  Anything more, it becomes a bin jobbie, after removing any leads for use in the goodies box.
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hazmat

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Re: Newbie question
« Reply #11 on: May 29, 2010, 07:04:25 PM »

7805 giving 12 volts out according to brainy son.
still going to level my  workbench though and buy new.

Paul
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malcolmfrary

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Re: Newbie question
« Reply #12 on: May 30, 2010, 10:44:57 AM »

Last time I looked, a 7805 was about 65P at Maplin.  Probably worth a dibble.  Or just dig it out and see if the system works with an RX battery.
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FullLeatherJacket

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Re: Newbie question
« Reply #13 on: May 30, 2010, 05:14:36 PM »

7805 giving 12 volts out according to brainy son.
Nope - 7805 him give 5.0 volts (according to Fairchild's datasheet anyway). This um one him maybe go to great ESC tip in sky? Me with Doc Frary - him say buy new. ACTion P80 plenty good; 100% QC and no BEC to confuse!
Chief Broken Digit
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malcolmfrary

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Re: Newbie question
« Reply #14 on: May 30, 2010, 09:18:11 PM »

Quote
Nope - 7805 him give 5.0 volts (according to Fairchild's datasheet anyway).
7805 him give 5 volts only when him not knackered. 
A working one should be fine.  If the ground line gets disconnected, the thing has nothing to refer to, so the voltage can rise to the supply voltage.  Now it gets technical - not all 7805s are identical between manufacturers or even batches.  Some can turn into a disconnection (no volts out), others might well turn into a direct connection (full volts out).  When working properly, they all behave like the data sheet says, under fault conditions, either inside the plastic or in the circuit around them, its toss a coin in the air time.  Maybe best of three.
Digging the 7805 out will show whether the supply volts will stay where it belongs or whether there is another path giving the trouble.
The thing is though, even if it was bought on the strength of a vendors specification, without anything to actually identify it, it is a box of unknown capability, so a known replacement is the safest bet for a valuable model.
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787Eng

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Re: Newbie question
« Reply #15 on: May 31, 2010, 01:46:01 AM »

7805 giving 12 volts out according to brainy son.

I think you will find its a 7812 if you need 12V
But for a receiver you will need the 7805 and that outputs 5V
all above ahve a 1 Amp limit, OK for one or 2 servos due tos startup surge currents on the servos....
dont for get to put some decoupling caps on the input and Outputs...

Mark
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