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Oct 05, 2010, 01:20 PM
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Thread OP
Help!

Mystery 20A ESC + non-conventional power source


I've obtained several 20A ESCs, but have no batteries of types usually used in RC models,


so i took a 9 volt ordinary alkaline battery and tried to power up the ESC. Accoring to the manual it shouldve beeped several times but there was dead silence,


so i eviscerated my old PC tower, pulled out a power wire (+5,g,g,+12), took a +12 combined with a pot, connected the ESC, ant still there was no reaction.

I've checked the polarity very carefully.

Notes: I'm going to use a PWM source other then an ordinary receiver,

that forms my 2nd question - that 3 wire plug (orange, red, brown) - red is for BEC which i don't need ant thus don't connect to anything, right? that leaves orange for PWM and brown for gnd?


Sorry for this messy description of the problem and sorry for possible starting a topic which has been discussed millions of times.

linky for the ESC: http://www.hobbycity.com/hobbyking/s...idProduct=9484
Last edited by Olly B; Oct 05, 2010 at 03:58 PM.
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Oct 05, 2010, 01:33 PM
Registered User
Do you have a motor hooked up?

The motor is the piece that actually creates the beep.
Oct 05, 2010, 01:52 PM
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Thread OP
I had motor attached for the 1st time with low power alkaline battery

2nd time was bare


should i have PWM as well? or the ESC+motor combo is going to beeep good enough?
Oct 05, 2010, 01:56 PM
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pmackenzie's Avatar
The 9 volt battery can't put out enough current to make the motor beep.
How did you have the pot connected when you used the 12 volt computer power supply? Unless it was a very low value (few ohms) pot, it would also prevent the ESC from functioning.
You need a low impedance source capable of a few amps.

Pat MacKenzie
Oct 05, 2010, 02:01 PM
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Thread OP
12 is a bit higher than 11.1 mentioned in the manual, the value is very low indeed.

Going to test 12 volt + motor right now..
Oct 05, 2010, 02:06 PM
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pmackenzie's Avatar
12 volts will be fine. A fully charged 3 cell LIPO battery is 12.6 volts.

Pat MacKenzie
Oct 05, 2010, 02:30 PM
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Thread OP
no, nothing.

need a multimeter to check ESC-motor soldering.. if that's not a problem than i have no idea what it is.


soldering is ok.

any ideas how to put this stuff to work?
Last edited by Olly B; Oct 05, 2010 at 03:56 PM. Reason: update
Oct 05, 2010, 04:09 PM
Registered User
meshyx's Avatar
Some escs will stay mute if they do not get a PWM signal, I am guessing this is your problem. 9 volts should be plenty for powering the ESC up, it works fine on a 2S lipo which is 7.4v nominal.

Yes, remove the red wire from the servo-type connector. You might want to look into getting a "servo tester" which will output a PWM signal (simulating a real receiver.)

And yes, escs use the motor as a speaker, so you'll need to have it attached as well.
Oct 05, 2010, 05:24 PM
Wabi-Sabi
coriolan's Avatar
Most servo driver can get their power from the bec circuit of the esc and then produce the rquired pulse to control the esc (1ms<2ms). Normally esc will arm only after being sent a low trottle pulse for safety reason. Something like this will do the trick:
http://www.hobbycity.com/hobbyking/s...y_Servo_Tester
You can use another source of pulse than a receiver or servo driver but it must be able to produce a 1ms<2ms pulse at about 50/60hz here is a typical circuit:
http://www.sentex.ca/~mec1995/gadgets/servo4.htm

http://www.sentex.ca/~mec1995/gadgets/servo2.htm
Last edited by coriolan; Oct 05, 2010 at 05:34 PM. Reason: Add circuits
Oct 06, 2010, 10:09 AM
Registered User
Thread OP
oh well

i made it beep

PWM source is made of arduino nano board, 0-255 with 8 prescaler at 8MHz (results in 4kHz - lower than 8-16kHz mentioned in ESC man)

pc +12 power supply

AND IT BEEPS 3 TIMES

firstly i didn't recognize the code - all mistake beeps are either continuous or consist of 4 beeps


but than i thought - why am i looking thruogh mistake list?

and yes, 3 beeps normally mean that the ESC is powered by 3 lipos (so it thinks)

now i need to put there a pot to control the pwm

and the question is - should this ESC operate normally with 4 kHz PWM?

added: normally it should make 2 sets of beeps on startup, 2nd which shows brake status is absent
Oct 06, 2010, 10:15 AM
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pmackenzie's Avatar
Do you mean the input signal? It is not really PWM in the normal sense of 0 to 100% duty cycle.
It should be a 1 to 2msec high pulse repeated every 20 msec.
1 msec will be motor off, 2 msec will be full power.( Might be ~1.2 for off and ~1.8 for full, but that is the general idea)

To "arm" the ESC you will need about 3 seconds at 1 msec before you can start the motor.

Pat MacKenzie
Oct 06, 2010, 10:26 AM
Registered User
Thread OP
Quote:
Originally Posted by pmackenzie
It should be a 1 to 2msec high pulse repeated every 20 msec.
1 msec will be motor off, 2 msec will be full power.
gonna implement this, shouldn't be too hard

how do i run a motor at, for instance, 37% throttle?

minpulse + 0.37* (maxpulse-minpulse) ?

what's the input resolution of the ESC?
Oct 06, 2010, 10:30 AM
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pmackenzie's Avatar
Something like that.
There are a few quirks like for example it will often only start at a higher setting/speed, and then you can get it to run slower once it is going.
Also without load the speed will not be so easy to control.

Not sure of the resolution of that particular ESC.

Pat MacKenzie
Oct 06, 2010, 10:39 AM
Registered User
Why not just find someone local who has the radio gear to borrow use for a n hour Or Gasp! spend the few $ for your own ( Look in the classifieds forum) Or even buy the $30 system from Hobby king
Gotta be more reliable than bodging up some diy workarounds?
Ohh.. the Mystery esc I have, has a few 'quirks' that the adverts and instruction sheets don't bother to mention .. That should genuinely confuse :-)
Oct 06, 2010, 11:02 AM
Registered User
Thread OP
Quote:
Originally Posted by Bare
Why not just find someone local who has the radio gear to borrow use for a n hour Or Gasp! spend the few $ for your own ( Look in the classifieds forum) Or even buy the $30 system from Hobby king
Gotta be more reliable than bodging up some diy workarounds?
Ohh.. the Mystery esc I have, has a few 'quirks' that the adverts and instruction sheets don't bother to mention .. That should genuinely confuse :-)
your way is easier, mine is a bit more interesting

buying from Hobbyking takes time, delivery ranges from 2 weeks to whatever customs decides

moreover - i don't need stock-produced (is this the right word?) receiver/remote at all.

almost forgot.. what are the quirks that you know?


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