Brushless speed controller problem - Page 1
Forum section: electronics / general

author: Bibiricat
author_rank: Contributor
timestamp: September 18, 2013, 09:14:13 pm
content: Hello.I was playing with the Hobbyking SS 30A ESC and managed to connect the battery with the wrong polarity. I didn't break it, but managed to damage it. Now , if i connect a motor, a servo tester and a battery, it will provide the 5V to the tester, but won't spin the motor correctly, just jiggle it around.What can i test (and replace) ?My ESC :http://www.hobbyking.com/hobbyking/store/__6460__hobbyking_ss_series_25_30a_esc.htmlImages:http://postimg.org/image/uhi93o0jl/http://postimg.org/image/nt5y1ah07/PS: the microcontroller is an Atmel MEGA8L , and i tested the regulator voltage, and it's good.

author: Rerouter
author_rank: Super Contributor
timestamp: September 19, 2013, 02:36:11 am
content: you either cooked the micro, or you blew up one or more of the switching fets, and definitely did a number on the capacitors,now it could just be my eyes, but the fets towards the capacitors look like they have gotten quite hot,best way to identify the fault would be with a scope, or atleast a multimeter with AC voltage measurement,you hook it up as per normal, stick the negative of the meter to battery negative and positive to each output looking for which have a difference,though in my own opinion at $8 a pop short of a learning experience your not going to cut costs by repairing it,

author: Bibiricat
author_rank: Contributor
timestamp: September 19, 2013, 04:11:37 am
content: Yes, i know it's not worth it repairing it, but i want to learn to debug faulty electronics and this was a chance to learns a thing or two.Regarding the ESC, can i still test them with a multimeter , in they are in parallel ?

author: Bibiricat
author_rank: Contributor
timestamp: September 19, 2013, 09:36:45 am
content: Hello.I managed to get some wave forms of the control signal.The first one is for the N Channel mosfets , and the second one is for the P channel mosfets. I have no idee if they are what they should, but at least the micro works...N channle mosfet signalP channle mosfet signalNote that because i used the pickit 2 logic analyzer, there were some problems with getting the correct second signal, so there are no gaps between when the signal starts and when it ends.

author: Rerouter
author_rank: Super Contributor
timestamp: September 19, 2013, 10:15:56 am
content: you will notice how the middle channel on the p mosfets is not changing, there is your faulted channel,also i am confused by the n-channel output but believe its an artifact of one of the p-channels not working (would not spin motor)next hook up your analyser to the p-channel gate signals to identify if the source/drain is open circuit or if the micro output isn't workingif all 3 gate signals look similar then that implies all 3 parallel fets for that channel need to be replaced

author: Psi
author_rank: Super Contributor
timestamp: September 19, 2013, 10:29:04 am
content: Yep, one channel is fried. The fet driver might also be damaged.You can check this by removing all the fets on the dead channel and retesting with the logic analyzer but this time test the gate pins.If all channels look good the driver is ok.Unsolder some of the good fets from other channels and use them to fix the missing fets.It will work with less fets per channel.But the max current will be less, 15A maybeI'm not sure why there's only 15 fets total, i would have expected multiples of 6.Seems like they just used whatever fets they had laying around, quite a mix there.Replacement fets will probably cost more than a new ESC, or close to it.

author: Bibiricat
author_rank: Contributor
timestamp: September 20, 2013, 08:59:25 pm
content: The wave forms i posted there were the gate pins of the FETs. The transistors were already removed.However, keep in mind that the ESC have some 'motor is blocked' protection, and will close motor control.I tried getting the signals while the FETs were on the board, but managed to short them (the logic analyzer had 4.5k pull down resistors), and they caught on fire.And regarding the second channel, i managed to get some waveforms if i was triggering off that channel, but it was looking like the others 2.