[Lotuswins]

Hi all,

I just thought I'd share my experiences this morning with my recently built from bits and pieces Taigen KV2.  I was having trouble keeping it going in that it would stop sometimes, the engine sound dying slowly away as it stopped responding to throttle inputs.  It would restart by pushing the start from the transmitter but if I tried to go fwd, it would die again.  Sometimes it would go forward, but if I tried reverse, it would die again.  Somewhat sporatic but in the end it simply stopped wanting to move at all.  So I tried troublshooting by:

Swapped in the following from known good sources thinking perhaps glitching or problems were in the bits and that the sound was dying slowly like the TCB was getting a command to stop:

Reciever/PWM-PPM converter
Cables to above
TCB

Then removed the Benedini sound card cables/power to the amp from the BEC of the TCB.

Still no joy, finally I swapped out the Sabertooth 5A controller, which is brand new and I thought pretty solid.....bingo.  Unfortunately I didn't have another to swap in so I put the old 45A HK ESCs in its place.  So now the tank is back in business though it doesn't quite drive as well. 

No smoke was released during the failure of the controller, which makes me think perhaps it is that the heavy tank simply overworked the overcurrent sensor in the board?  Anybody else had this happen?? This is a very recent purchase of the sabertooth, and I had to wait a while for it to finally be reproduced since I assume all stocks were out from the usual sources.

Specs on the KV2:
Taigen 380 motors on BB 4:1 steel gearboxes.
Benedini Mini with JS2 sounds and Adafruit tiny amp working off BEC 5v power (2.5w)
Turnigy 9x Xmtr and Rcvr with HK PWM to PPM converter
3000mah NiMh battery
All metal chassis, wheels, sprockets and tracks

Anyone else had issues with the recent batch of Sabertooth 5A serial controllers?

[Lotuswins]

So it always goes........wry smile.....

I just now swapped the suspect Sabertooth 5A unit into my T55A hooben, which has an earlier sabertooth and sure enough it performed flawlessly (CRAP!!).  I ran it up and down and around for a full 10 minutes and nothing, worked great.  When removing it the motors were warm, but the board was barely above ambient temperature. 

I'm now very confused.  Could it be something with the packetized serial communications??  The blue light near the serial connector seemed to be flashing when nothing was happening (on the KV2), and slowed flashing IIRC, when power was supplied to the motors.  When the TCB would shut down, the light went dead.  `

I did check voltage at the controller on the KV2, and it was solid at 8v (just recharged). 

When testing before, with the sabertooth hooked up in the KV2....  I disconnected the battery from the Sabertooth and started the tank.  The sound revved up fine with throttle.  So I reconnected the battery, and disconnected the left motor.   Started the tank, fine, tried to throttle it, and it shut down.  So I reconnected the left motor and disconnect the right motor....same thing, it shut down upon throttle. 

The packetized serial communications is one way right?? how can the TCB get the message to shut down from the serial controller??

This is really perplexing me...so I'll see about reconnecting the sabertooth up, and look into the communications issue.  Note that I never have seen the red light from the sabertooth indicating any overcurrent or other problem.

Jerry

[LukeZ]

Hi Jerry, maybe I'm imagining things but this sounds similar to an issue you had before possibly on a different model.

There clearly is an issue, but the only thing I can troubleshoot on my end is a problem that can be replicated, and this one I can not. The key to resolving it is to narrow down to the smallest possible list those things which could be the cause. You have the right idea putting the Sabertooth in another model, but if it works in the other model then that is inconclusive so keep experimenting until you have a consistent and replicable diagnosis.

The first thing I will say, is that the TCB's 5 volt supply is limited in current capacity. It can power the Benedini but I would not recommend using it to power the Benedini + external amplifier. Now a 2.5 watt amp isn't much and this may not have anything to do with your problem, but it's one thing to try eliminating and see if it helps.

It's possible you have a defective TCB, but if so, that TCB should continue to fail if moved to another model, so you should be able to determine that conclusively. If the TCB works in another model but not the KV2, there is something different about the setups between those models that you need to examine and pinpoint.

The odds of a Sabertooth being defective are very small, and it seems that you have ruled that out.

To answer your question about the serial protocol, yes it is only one-way. There is no means for the Sabertooth to tell the TCB to shut down. It is also normal for the blue serial light on the TCB to flash even when you aren't commanding anything and the model is stopped (because the communication is only one way, the TCB sends the "stop" command routinely whenever you are sitting still, in case the Sabertooth didn't get the message the first time, this is for safety). While driving the blue LED will only blink when a new command is sent, which if you are holding a steady speed may not be very often. In other words, what you describe about the blue LED sounds normal to me.

You describe this issue somewhat imprecisely. At some times you say the TCB "shuts down" by which I take it to mean it has literally lost power and rebooted involuntarily. In other cases you say the engine sound dies slowly and it's not clear to me whether you mean the TCB has shut down or else it incorrectly sent the engine stop command to the Benedini. There is no command from any source that can be sent to the TCB to cause it to "shut down," but obviously you can give it to the command to "turn off the engine." Try your experiments with the TCB hooked up to the computer in Snoop mode and figure out exactly which is happening. If your TCB is literally losing power and rebooting then you have a voltage drop issue or a short somewhere.

If I had to guess this does sound a lot like a low voltage issue but I take your word that your battery is good. Maybe check your wiring and ensure that all components share a common ground. Check your Sabertooth connections (the MOTOR SERIAL connector on the TCB should go GND to 0V, and TX-O to S1 on the Sabertooth), and make sure the dipswitch settings on your Sabertooth are correct.

Keep us posted.

[Lotuswins]

Hi Luke,

Thanks for the lengthy reply.  You make some great points. 

The first thing I will say, is that the TCB's 5 volt supply is limited in current capacity. It can power the Benedini but I would not recommend using it to power the Benedini + external amplifier. Now a 2.5 watt amp isn't much and this may not have anything to do with your problem, but it's one thing to try eliminating and see if it helps.

Yes, I thought that too so I disconnected both the Benedini and the amp from the BEC.  I restarted the tank (no sound but rear light illuminated - running light), and tried the throttle, it tried to go forward then promptly quit, serial off).  I think the amp is taking about 0.6 amps, from calcs.  Not sure about the Benedini though. 

It's possible you have a defective TCB, but if so, that TCB should continue to fail if moved to another model, so you should be able to determine that conclusively. If the TCB works in another model but not the KV2, there is something different about the setups between those models that you need to examine and pinpoint.

I swapped in another TCB, programmed it identically to the KV2, and it performed identically to the KV2 original one.  So apparently its not the TCB hardware.

You describe this issue somewhat imprecisely. At some times you say the TCB "shuts down" by which I take it to mean it has literally lost power and rebooted involuntarily. In other cases you say the engine sound dies slowly and it's not clear to me whether you mean the TCB has shut down or else it incorrectly sent the engine stop command to the Benedini. There is no command from any source that can be sent to the TCB to cause it to "shut down," but obviously you can give it to the command to "turn off the engine." Try your experiments with the TCB hooked up to the computer in Snoop mode and figure out exactly which is happening. If your TCB is literally losing power and rebooting then you have a voltage drop issue or a short somewhere.

Sorry for that, yes I did kind of wander in my descriptions.  I am referring in the whole scenerio not of a TCB shutdown, just a stop running via throttle.  All the other functions like turret, gun elevation, smoke, etc. all still work.  I can even shoot the cannon, and it will give sound and track recoil, though the track recoil will be shorter than normal as the track movement is clipped since it too comes from the serial communication.

If I had to guess this does sound a lot like a low voltage issue but I take your word that your battery is good. Maybe check your wiring and ensure that all components share a common ground. Check your Sabertooth connections (the MOTOR SERIAL connector on the TCB should go GND to 0V, and TX-O to S1 on the Sabertooth), and make sure the dipswitch settings on your Sabertooth are correct.

Yes, thought of these also, checked and double checked the serial connections, and wiring.  As for common ground?  The case for the Sabertooth is screwed down to the gearboxes, which are screwed to the aluminum frame of the chassis.  The TCB though isn't grounded to all that, nor is the benedini or amp, as those just share a common plus and minus for the BEC. 

As a side note on susceptibility to noise here is an experience that happened prior to all this:

I was running the gun elevation motor and noticed the sound was erratic, giving an 'ack, ack' noise in between the normal elevation noise.  I ran it a while, hoping it was just brush noise in the motor and with running it would break in.  Well as I continued to run the elevation motor (standard HL/Taigen elevation gearbox with cam wheel) the tank would start to buck (spiking the drive motors) and it would turn off the tank, and then restart the tank.  Since this started to become a bit more drastic than I expected, I removed the elevation motor and gearbox and found the capacitor lead for one pole lying on the other pole (intermittent short) and the other cap lead was broken but still touching the other motor pole.  So a combination short and noise generator?  In disassembling the motor I also found carbon coating the commutator indicating a lot of arcing going on.  Hmmmmmm......  I replaced the motor and now have a elevation motor that runs well, but this does show (and I have had small motor issues before) how noise from the motors can impact the operatability of the TCB and other equipment in the tank.  I'm not sure if this is generic to the issues with the Sabertooth and Serial Communications.

So, where to proceed from here?  I've established that the tank now runs well with the ESC's and the Benidini/Amp hooked to the BEC power source.  However, since the Sabertooth relies on serial communications, not the PWM that supplies the ESC's, I wonder if the serial chip is just enough of a burden to tip the scales on the BEC power?  I will reinstall the sabertooth, and disconnect the amp (the sabertooth has a 5v supply I can tie to), and see if that changes things (although I had tried disconnecting the amp/benedini before with no results - but maybe I didn't give it enough of a recovery period?).  I hope to also, if this thing repeats itself, to monitor the BEC voltage dynamically (as best I can with a DVOM with min/max).  I'll review on how to Snoop also as I haven't had success in getting that to work as yet.

Thanks again, and sorry for the winded post.....Jerry

[Lotuswins]

Hi Luke,

I just changed back to the sabertooth, and measured BEC at 4.995vdc, did not go down, but crept up to 5.153vdc. Here is the snoop dump:

Radio Ready - PPM

---------------------------------------------
FIRMWARE VERSION: 0.93.07

---------------------------------------------
RADIO INFO - PPM
---------------------------------------------
Stick       Min    Center   Max    Deadband  Reversed
---------------------------------------------
Throttle    979    1486     1994    25        FALSE
Turn        981    1488     1995    25        FALSE
Elevation  1011    1475     1959    25        FALSE
Azimuth    1006    1486     1964    25        FALSE

Aux Chan.   Min     Max     Type
---------------------------------------------
1           972     2003    Digital
2           970     1999    Digital
3           970     1996    Digital
4           1474    1507    Digital
5           IGNORED
6           IGNORED
7           IGNORED
8           IGNORED
9           NOT DETECTED
10          NOT DETECTED
11          NOT DETECTED
12          NOT DETECTED
---------------------------------------------
Channels detected: 8
Channels utilized: 8

---------------------------------------------
MOTOR TYPES
---------------------------------------------
Drive Motors:      Sabertooth Serial
Turret Rotation:   Onboard Motor Driver (A)
Barrel Elevation:  Onboard Motor Driver (B)
Mechanical Barrel: Airsoft (Enabled)

---------------------------------------------
DRIVE SETTINGS
---------------------------------------------
Vehicle Type:           Tank
Active Driving Profile: 1
Accel Ramp Enabled:     No
Decel Ramp Enabled:     No
Motor Nudge Enabled:    No
Forward Speed Limited:  No
Reverse Speed Limited:  Yes - 60%
Transmission Type:      Automatic
Shift Time:             0.0 sec
Engine Pause Time:      0.0 sec
Transmission Delay:     0.0 sec
Neutral Turn Allowed:   No
Turn Mode:              2
Track Recoil Enabled:   Yes (Kickback speed 40%, Deceleration factor 50)

---------------------------------------------
TURRET SETTINGS
---------------------------------------------
Turret Rotation Speed Limited:  No
Barrel Elevation Speed Limited: No
Recoil delay:                   No

---------------------------------------------
BATTLE INFO
---------------------------------------------
Is Repair Tank?   No
Fire Protocol:    Tamiya
Hit Protocol 2:   Taigen V1
Repaired by:      IBU Repair
Send MG IR Code:  No
Accept MG Damage: No
Damage Profile:   Tamiya Spec
Weight Class:     Heavy
(9 cannon hits, 9.0 sec reload, 10.0 sec recovery)

---------------------------------------------
SOUND CARD
---------------------------------------------
Sound card: Benedini TBS Mini

---------------------------------------------
INERTIAL MEASUREMENT UNIT
---------------------------------------------
Sensor not detected!

---------------------------------------------
FUNCTION TRIGGERS
---------------------------------------------
Turret stick functions: Yes
Turret movement delay:  0.35 sec
Turret Stick - Top Left       -> Function #1   - Engine - Toggle On/Off
Turret Stick - Top Right      -> Function #7   - Cannon Fire
Turret Stick - Bottom Left    -> Function #84  - Smoker - Toggle
Aux Channel  2 - Pos 2 (of 2) -> Function #11  - Machine Gun - Fire
Aux Channel  2 - Pos 1 (of 2) -> Function #12  - Machine Gun - Stop
Turret Stick - Bottom Right   -> Function #16  - Light 1 (Headlights) - Toggle On/Off
Aux Channel  1 - Pos 2 (of 2) -> Function #13  - Airsoft/Mech Recoil - Enable
Aux Channel  1 - Pos 1 (of 2) -> Function #14  - Airsoft/Mech Recoil - Disable
Turret Stick - Bottom Right   -> Function #22  - Running Lights - Toggle On/Off
Aux Channel  3 - Pos 1 (of 3) -> Function #98  - Start Increasing Volume
Aux Channel  3 - Pos 3 (of 3) -> Function #99  - Start Decreasing Volume
Aux Channel  3 - Pos 2 (of 3) -> Function #100 - Stop Changing Volume

---------------------------------------------
BATTERY
---------------------------------------------
Battery Detected: Yes
Voltage:          7.69v
LVC Enabled:      Yes (6.3v cutoff)

---------------------------------------------
BAUD RATES
---------------------------------------------
USB Serial Baud:   115200
Motor Serial Baud: 38400
Aux Serial Baud:   115200
Serial 3 Tx Baud:  38400

---------------------------------------------
Turn Engine On
Engage Transmission
Moving Forward
Turn Engine Off
RADIO FAILSAFE
Radio Ready - PPM
MG Stop
Airsoft - Disabled
Stopped

I didn't ask it to turn the Engine off.  I just moved the stick forward.  What is the RADIO FAILSAFE ??  thx, jerry

[LukeZ]

Radio failsafe means it has lost connection with the receiver. Whenever that happens the TCB automatically shuts down the engine for your safety, to prevent a runaway tank that you can't control.

It would appear that for whatever reason, drive motor movement is causing a radio glitch and the TCB turns off the engine in response. Once the motors stop the TCB regains the radio signal and resumes normal operation, though of course you have to start the engine again. This tells us you are not experiencing a voltage issue, and the TCB is not "rebooting", but simply turning off the engine as a safety precaution. The issue would appear to reside in your receiver or PWM-PPM converter, possibly they are picking up interference from the Sabertooth. Can you try to mount them farther away? And make sure you route your receiver antenna away from any power and motor wires.

Honestly I think it's time you ditch that janky PWM-PPM converter and invest in a quality module for your 9X, along with SBus or iBus receivers. Your models will thank you for it and you will save yourself all this headache!

[Lotuswins]

Luke,

I am SOOOOOo   offended......janky?? really 

Thanks for the explanation, that does make sense now.  The antenna was laying in the bottom, way up front under the battery, parallel to the aluminum sides of the chassis.  So I moved it to hang out the front, away from all the metal and bingo.....JOY!!! It is back working.  So I moved it to the other side, away from the battery, under the speaker but still parallel along the side of the chassis.....and it repeated the problem.  Hey, its repeatable.....oh more joy. 

So I just strapped the antenna to the top of the speaker, which is a polystyrene enclosure, and it is working great.   Tooooo easy.

Oh, and you're not going to believe this one.  The airsoft now works first time??? wtf?? so antenna placement is that critical that the airsoft switch position from the transmitter can now be received??  That is too interesting. 

Thanks so much Luke, you are the best!! 

And MAYBE I'll consider the new module.....grudgingly.......HA!! 

jerry

[LukeZ]

I'm glad we finally solved the mystery and that it turned out to be an easy fix. This may also explain similar behavior that if I recall you experience on your StugIII.

PWM to PPM is not a trivial conversion due to timing constraints, I remember when the ArduPilot team developed the first converter which I suspect Hobby King has copied. Who knows how good a job they did. Having multiple motors running inside a metal box (such as the inside of your tank) is basically the worst possible RF environment imaginable for any kind of receiver but at least the digital ones can tell if the signal is valid or not, whereas the analog receiver just passes on whatever garbage makes it to the antenna.

[Lotuswins]

Okay Luke,   I relented and ordered up an XJT module and an XSR rcvr......all off Amazon (can't wait a MONTH for HK to deliver from Hong Kong).  So we'll see how this works out.  I guess I'll start equipping all my OP tanks first (now up to seven).....omg.

Jerry