servo motor resets 16f877a

[skimask]

When servo rotates,brightness of lcd changes (getting brighter or darker)...I think thats another weird thing...

Doesn't that right there tell you something about the quality of your power supply?
Let's see...if I'm driving down the road, and my headlights change brightness, does that tell me anything about the electrical power in the car? If I'm sitting in my living room at night reading a book and the room's lights either dim or get brighter, would that tell me something about the local power grid?

I don't see ANY capacitors in there, either across Vdd and Vss or across your servo's power supply. I don't see what kind of power you are supplying this circuit with. I don't see a lot of anything.

Ya know, for that matter, we haven't seen your code yet... Who knows...maybe it is actually a firmware problem...

[Archangel]

I would agree with Skimask re: the capacitors and your power supply, I would add, disable Brown Out Reset in your config statement so PIC does not reset, I would further suggest you change your reference to God Blessed servo, just remembering something Moses said to Pharoe, "by your own words . . ." Cause if he Damns it, it's toast.

[aratti]

Hi, Burak from your schematic and your explanation I understand that is just a power supply problem! Add 10nF capacitor to the Vdd pic pin. Since surely you are using battery, my suggestion is that you use a two 9 volts batteries in parallel to a 7805 and use its output as power supply for your project. One way to check quickly that current failure is your problem, can be achieved simply removing (disconnect it) the backligth of your lcd, and very likely the problem will disappear as long as the present battery will be able to supply the required energy

[burak450]

i should repeat that=Lcd brightness doesnt change at normal work. when servo moves than it goes high or low...
my power supply is that.

switching adapter
input:ac 100-240V-50hz 0.36A
output:dc 5v--2.5A

and my program is that

DEFINE LCD_DREG PORTB
DEFINE LCD_DBIT 0
DEFINE LCD_RSREG PORTB
DEFINE LCD_RSBIT 4
DEFINE LCD_EREG PORTB
DEFINE LCD_EBIT 5
DEFINE LCD_BITS  4
DEFINE LCD_LINES 2
DEFINE OSC 4                                                                       
DEFINE ADC_BITS     8      
DEFINE ADC_CLOCK  3     
DEFINE ADC_SAMPLEUS 100
SYMBOL F=PORTA.0
SYMBOL G=PORTA.1
alta var byte
usta var byte
altb var byte
ustb var byte
ADCON1=2
TRISA=3
TRISB=0
PORTB=0
TRISC=0
LCDOUT $FE,1 
pause 4000
adcin  0,ALTa
ADCin  1,usta

t var byte
i var byte
T=150

yap:




adcin  0,altb
ADCin  1,ustb






if  ((((usta+10)*100)/(ustb+10)))>135 then 
T=T+15
endif

if (((alta*100)/altb))>135 then 
T=T-15
endif


gosub motor





  

LCDOUT $fe,2,#usta," ",#ustb," ",#altA," ",#altb   

goto yap

motor:
for i=0 to 25
PULSOUT PORTC.2,T
PAUSEUS 20000-(T*10)
next
return

end

[aratti]

Check power supply wiring, especially the connector, install 1000 uF 16V electrolytic capacitor and 10 nF on your pic power pin

[skimask]

For grins, try changing your BYTE values to WORDs and see what happens.
Might be overflowing the byte values somewhere killing the program somehow someway.

[Acetronics2]

Hi, Burak

I'm curious to know which testboard you use ...

16F877A , LCD on PortB ... that sounds quite familiar.

So, the question is ... Where do you ( geographically ) take the servo 5v supply from ???

Alain

[Bruce]

Use a separate power supply for your servo.

[burak450]

Bruce thanks for advice,i tried million times but couldnt connect separate supply correctly.I think you mean opto-isolotor circuit.Do you suggest any opto-isolator circuit??
Some guys said i dont need this circuit.I am confused now.

Acetronics,I took 5v supply to servo from same source where I took power to pic.I mean servo and pic is feed same source...

[sougata]

Hi,

16F877a has got a Power Control Register (PCON). Section 14.10 page 151 in the datasheet.

In the top of your code just after you initialize the LCD. Read the PCON into some variable and display it on the LCD for say 5 seconds. Note it down just after a reset. This may help decide the cause of the reset---> Brown Out, WDT, MCLR etc.

Also make sure that your RB3 (Pin 37) is not floating. It is the LVP pin and noise on that can trigger the ICSP mode.

Just for information on the opto part you can use a TLP250 optocoupler (works upto a few khz) which has got a totem-pole output. So you drive the LED and get a 0-1 on the output. I use it mainly for my IGBT driver needs.

[Bruce]

You should not need an opto, but you may want to include the series resistor shown in the .PDF Alain linked to.

A separate power supply for the servo is a good idea, but you need a common ground connection between the two power supplies.

Most hobby type servos will work fine with a DC supply of ~4.8 to 6Vdc. I normally use a set of 4 x D cells. Just connect the ground leg from your batteries to the ground leg of your regulated supply for the controller.

If you use another regulated supply for the servo, make sure it can handle the servo load current. A servo can draw quite a load. Some up to 1A or more. Having this load on your primary supply can drop voltage and cause a device reset. With separate supplies you shouldn't have this problem.

[Acetronics2]

Ok, Folks

I've got it ...

Servo driving values on C.2 go out of the nominal 0.8 - 2.2 ms range OR Pause between pulses goes wrong.

Servo bumps on its mechanical stops ... or the amp doesnt like the pause !!!

That's all !

Alain