Jittery Servos Need Help

[motion55]

Of course, WriteUSART(1234) sends a byte 0xD2. If you want to send a string of bytes then use putsUSART()

[xyzled]

Sir, I got another question.

Is it okay to use the pins of vref+ and vref- as output pins when the Vref+ is Vdd? Or should I free those pins for vref purposes?

[xyzled]

I tried to separate the supply terminal of the servos and MCU and it works fine now. It seems that the voltage drop is affecting the Vref+ configured as Vdd and affecting the final results of the conversion.

[rdpzycho]

^ always remember to put capacitors very close to the Vref pin. same situation din kung merong separate analog Voltage pin.

[motion55]

To avoid the dependency on the quality of the supply, you should tie the reference not to PIC's supply but to a voltage derived from the supply of the flex sensors. If the supply of the flex sensor is greater than the PIC's supply, you can drop the voltage down using a voltage divider. If the flex sensor's supply isn't stable/clean, at least Vref will vary with it at the same time. That is one purpose of having a separate Vref. Another is to tie Vref to a precision voltage reference.

[xyzled]

To avoid the dependency on the quality of the supply, you should tie the reference not to PIC's supply but to a voltage derived from the supply of the flex sensors. If the supply of the flex sensor is greater than the PIC's supply, you can drop the voltage down using a voltage divider. If the flex sensor's supply isn't stable/clean, at least Vref will vary with it at the same time. That is one purpose of having a separate Vref. Another is to tie Vref to a precision voltage reference.

Noted sir. I just wired a separate power supply used by the Servos since I use a PC power supply it has several terminals and upon observing the voltage supply or Vdd, it becomes stable. The flex sensor shares the supply with the Vdd and servos have separate one so it becomes more stable now.

Now I'm going to program my accelerometer. Thanks for the help, pogi points for sir motion55 and rdpzycho.

[xyzled]

I got another problem, I have 2 PICs in a circuit, the problem is solved last time when I only plug in one pic, but when 2 pics are plugged in the jitter starts again but only slight. What could be the other factor?

[rdpzycho]

^ para saan 'yung isa pang PIC?

[xyzled]

bali 8 lang po kase yung kaya i control ng 1 Pic for servo, yung isang pic may extra 3 servos na i cocontrol po.

[rdpzycho]

subukan niyong i-separate ng supply at 'yung reference ayusin din. posibleng grounding issues ang problem. dapat multipoint 'yung ground para walang masyadong effects 'yung bounce ng ibang parts ng circuit.

[motion55]

Malamang noise related ang cause ng jitter. Pwede bawasan pa ang jitter using more filtering but best is to good PC layout techniques and a clean power supply + reference to reduce noise. Isolate the power supply to the servos from the PIC's and sensor's power supply.

[rdpzycho]

mas maganda siguro kung i-post niyo dito 'yung picture ng mismong hardware niyo. since you are dealing with multiple motors with medium current, malaki ang effect ng layout diyan plus 'yung wiring papunta sa servo.

[xyzled]

Mga sir, I tried to separate the supply, bali dalawa yung ginamit ko na supply from the PC PSU and ganun pa din po ang naging epekto. I think sa pcb layout na talaga yung mali ko kasi shared yung supply ng dalawang pic and ground nila iisa lang.

Since 9 motors yung gagamitin namin, I modified the program to control 9 servos, buti umabot yung timing nia. Hindi ko na po ginamit yung isang MCU to solve at least the jitter problem. Medyo may slight movement sya pero hindi na po masyadong noticeable.

I already finished our project and I'm gonna post the output after we present it again to the panel. Maraming salamat po sa mga tulong niyo. God Bless !

[rdpzycho]

^ ang next na magandang gawin diyan, ayusin mo 'yung layout kahit may grade na kayo sa complete project. preparation na rin kasi 'yan for real life applications sa work kung sa design ka mapupunta.