SC16A noise issue

Autonomous Robot, Manual Robot, DC Motor Driver, Stepper Motor Driver, Servo, Multi PWM chip.....

SC16A noise issue

Postby Leom » Sun Aug 14, 2016 3:39 pm

Hi all,

Previously I thought my project having data streaming issue from laptop -> bluetooth -> Xbee bluetooth -> SC16A.
After some long time debugging and probe here and there even try change to ESP866 WIFI module to try. I didn't even success the use of UART from ESP8266 some senior in this forum advice it shouldn't be a problem if just use Xbee bluetooth.

So I went back to try the bluetooth module again. I found that if I not connect the servo the UART link actually work well without any issue. But after connect servo the servo work weird. After probing the SC16A servo signal found that the signal actually keep on reset when the servo position change made by me from the SC16A GUI.

To verify this I try probe the servo signal at other channel which not connect to servo, change that channel position so that I can monitor there is constant signal from SC16A, then try jog the servo position for another channel which connected to servo. Now the servo signal that I'm probing is gone.

There is reset button for the SC16A PIC to reset when pull low, I try probe it. It show about 4V when working normally without servo connected. When connected to servo the voltage seems fluctuated when there is servo movement.
I wondering is this the root-cause that keep on reset the SC16A.

For the hardware setup on power source:
6V batt direct to servo supply
6V batt -> 5V regulator to main board supply (with IN-OUT capacitor)
5V -> 3.3V regulator to Xbee power supply (with OUT ceramic cap)
Xbee UART signal -> logic level shifter to SC16A Rx pin
All share common 0V.

Anyone have any advice?
Leom
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Posts: 19
Joined: Tue Aug 09, 2016 10:48 pm

Re: SC16A noise issue

Postby Leom » Mon Aug 15, 2016 7:07 pm

To be be specific:

Noise issue only happen when using bluetooth with servo plug in.
No problem if no servo plug in.
If use USB and plug in servo also no problem.
Leom
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Posts: 19
Joined: Tue Aug 09, 2016 10:48 pm

Re: SC16A noise issue

Postby Leom » Sat Aug 20, 2016 1:41 pm

Finally found the rootcause, is because 6v batt voltage drop easily and cause 5v regulator min V-in not enough and during servo draw current it even worst untill it reset the controller. Using Usb no problem because circuit using pc 5v so no problem.
Leom
Novice
 
Posts: 19
Joined: Tue Aug 09, 2016 10:48 pm


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