ESC or Receiver

[SeanD]

Some part of the electronics on my WK cr#pped out this weekend and I am trying to determine which it is. Its all stock. Here's the gist:

Thursdsay night - motor stopped working properly. It would stick and humm. I am thinking that it was held in a stall (not by me) with low batteries and that perhaps this burned the winding. I thought maybe a run in a cup of water would work (I have a new 55t coming in so I thought "what the heck".) The motor ran great - better than ever before - after that but it appears too great. It must have pulling more amps than nomal

Sunday Morning (Happy Father's Day!!!) my son took the WK for a drive around the living room and then informed me that it was not working right - it was jerking backwards. I felt the ESC and it was very hot (I normally run a separate fan on the ESC when crawling but as this was just driving around the house it was not turned on) I manged to get the motor running again but it was arcing REALLY bad and smoking. So naturally I stopped.

Here's what the thing does now:

turn on ESC and transmitter and the steering servo jerks and the motor cuts in out at full throttle.

turn off the transmitter and the motor beeps - like normal.

Voltage off the ESC to the motors jumps all over the place - even without the throttle pressed.

The steering servo will respond to the transmitter but slowly and with no power and only in between jerks described above.

I hooked up a similar motor and it behaved the same way.

Should the steering servo respond to the transmitter with the ESC leads to the motor disconnected. I can only get the servo to move when the motor is hooked up. Is this normal?

I am really at a loss here so any suggestions would greatly. Would this be an ESC or transmitter problem - or both!

I don't mind buying a new ESC as breakage is always a good excuse for an upgrade but I like to know that I'm replacing something that HAS to be replaced at this time. Its unlikely that my LHS will have a ESC so I'll be looking at a two week downtime. Of course, my 55t motor and 96t and 15t gears should be here later this week so I'll have to just look at them and not get a a chance to try them!!!

Sean

(yes I posted this in the Electronics Forum but I think those of you with WKs may have some better insight)


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[heyok]

"Should the steering servo respond to the transmitter with the ESC leads to the motor disconnected. I can only get the servo to move when the motor is hooked up. Is this normal?"

My steering servos work when the ESC in unplugged.

It sounds like you need to divide and conquer a little more.

First, take your volt meter and check that the Battery Eliminator Circuit (BEC) part of the ESC is working. Connect your meter to the red lead and black leads on a servo plug. These are all connected in parallel on the receiver so any pair will work, but check each pair anyway just in case. My stock WK ESC put out about 6 volts. If this is screwy, suspect the ESC, but to be sure, unplug the steering servo just in case it is loading down the circuit.

If the ESC is working without the steering servo plugged in, you have found a bad servo.

It would be nice to test the steering servo without the ESC plugged in. To do this, you need to supply the receiver with 6 volts. Can you rig up something to do this?
The steering servo should work plugged into either the CH1 or CH2 socket on the receiver as long as you are able to power up the receiver (the servo will operate when you work the throttle control if you plug it into where the ESC was).

I hope that was clear enough - I was up really late!

Please write if I can make things clearer.

Al

 

[SeanD]

First quick answer - 3300 maH.

Darn - I should've taken my WK to the office with me today to try these things!!

I did check the voltage at the receiver plugs and was getting nothing for the steering servo (the only one I checked) at least. I did this while turning the steering control on the transmitter as well.

Certainly don't recall the ESC running the motor without the steering servo plugged in.

How do I supply the receiver with 6 volts - what connection do I use?

Sean

 

[heyok]

Connecting power to a receiver:

There are three wires on the servo plugs.
Black which is connected to the negative of the battery, Red which is positive (normally 5 to 6 volts) and usually comes from the BEC portion of the ESC.
The third lead is the signal lead which is an output from the receiver that tells the servo or ESC what position to move to . This is a modulated signal and reading it with a volt meter won't really tell you much.

To power the receiver without using the ESC's BEC, you would connect 5 to 6 volts to the same place as where the red and black wires from the ESC connected. You can get yourself something called a receiver pack that will power the receiver or something called an external BEC to do it or if you are comfortable around electronics, you should have enough info now to rig something up.

Once you get the receiver powered up, your steering servo should work normally. Also plug the servo into the other channel (where the ESC was plugged in) and see if you are able to position the servo using the throttle control. If those things work, the problem seems to be the ESC.

 

[DaViolentOne]

This seems to be a common thing with the WK's... I've heard that swapping the Tamiyas style plugs for Deans will cause this, also... Too much current being let out of the pack...

I know someone will try and correct me 'cos I said the same in another thread with the same issues and got told I was wrong.. But...

Others have had issues right off just from swapping out to Deans ends... Deans have FAR less resistance than Tamiya's do and will allow more current to get thru to whatever component they're on...

However, after reading these issues, I'm glad that I didn't get a WK... But then, I'd only use the axles from the whole thing anyways... Just seems the ESC isn't up to the task it's been given...

Putting a 55 or so on it should help alleviate some of the hard draw, but, I still think a better ESC would be a good improvement for the truck 'cos how many ppl will keep the stock motor in if they're gonna use it as a wheely machine? Not many.. Most would go to a 19 or so to get wheelies on command...

 

[SeanD]

heyok:

I ran 6 volts through the receiver. With the transmitter turned off, the servo will turn in both directions if you switch the leads, e.g red to red and black to blacks turns the servo all the way to the right while red to black turns the servo all the way to the left. If you turn on the transmitter the servo does not respond to the steering control.

Does this have to do with the fact that the white wire is not connected - that I am only running a black and red power wire to the receiver?

Can anybody help here? I have noone in my area to help with this so I am depending on your expertise.

Sean

 

[heyok]

Sean,

I'm not sure what to say.

When I described how to connect 6 volts to the receiver, I was careful to describe that where the red lead is going connects to positive and the black lead goes to negative.

I have to ask why you would connect the power up in the opposite polarity?

The circuits inside the servo, receiver and electronic speed controller have polarity sensitive components. If a part wasn't broken before, it most likely is now.

I think you need someone local to you to help you with this.

Let's hope things turn out okay.

 

[SeanD]

I guess I did the polarity switch because the servo would only turn one way (via the transmitter control) with them hooked up the correct way. Curiosity, perhaps bad in this case, made me switch the polarity to see if I could make the servo go the other way and it did. So I guess , while the servo motor may still work, the circuits are probably fried!

 

[DaViolentOne]

The white wire in a servo lead is the signal lead.. The lead that the servo gets it instructions from as which way to turn and hold or return to center... Put that on the positive RX lead and you have one fried servo...

Curiosity can be a good thing.. But when dealing with sensitive electronics, well, things usually don't end up with the best of results... Trust me on this one... I have my share of fried components and burns on my hands n fingers from learning the hard way...

If the servo's not turning at all with everything hooked up right, yer RX is toasty... It could be the TX, but, I suspect the RX now... Do you have another RX or a friend with an RX that runs on the lower 27 AM band? That way you could swap out the RX's and see if that helps... If the servo works, then yer RX is toast... If the ESC don't work with the other RX, then you'e cooked the ESC, too...

I'm not exactly impressed with the WK's ESC as it is.. It looks rather wimpy.. Even for the 27t in the WK.... That'd be the first thing I changed out... To an XRS or something with a lower turn limit to give a bit of a buffer zone for playing with different motors and such...

 

[SeanD]

I am pretty sure that my ESC is toasted. Now I think my RX is and I'm not sure about the servo.

Traxxas TQ3's (radio and receiver) can be head on ebay for 25.00. I assume that these would work with my new ESC that I ordered yesterday - I am taking my chances on the Moped. I was also contemplatlng finishing off with the Hitec 645 steering servo. Can you comment on whether this should all work together?

I laready have a 55t motor and and a 96/15 gear combo on the way.

Sean

 

[DaViolentOne]

That should work well together, yep... The TQ3 is not a bad radio.. I use one in my super... And I also use an HS645MG servo up front for steering.. I only have 2WS for the time as I have a dig setup for the rear right now... But I use an EVX ESC for dual motors... The MoPed's a good deal for the $$ but has a reverse delay...

If you want to spend less on a servo, look into the TP945 or 995 serov's.. One of those 2 is far=irly cheap compared to a 645MG.. Up here, the 645MG is about $50 and the 995 or 945, which I can't recall, is less than $30...

 

[SeanD]

I did some rechecking on this problem:

I am getting 1.5 volts directly off the ESC BEC. Voltage to the motor jumps from below 1 to above 5 with no pattern - even with the TX turned off.

I ran 5 volts (correctly this time) through the old RX. 5 volts showed up on the servo connection as well but the servo will only slowly move - via pulsing - in one direction with no control from the TX. I get similar results from the TQ3.

It sounds like a fried ESC and servo, right?

How can I check that the RX and TX are "talking " to each other? I am using the WK crystals in the TQ3 and I can only assume they are compatible.

Thanks,

Sean

 

[SeanD]

Tested my RX and with another servo. The stock WK RX did not work (fried) but the TQ3 was fine.

So I fried both the stock servo and the RX. Luckily I have the new TQ3 RX and a Tower Pro mg965 on the way.

Mystery solved. Thanks to all who offered suggestions/assistance.

Next step - check my Moped when it arrives soon.

Sean