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Author Topic: Servo start and then just stop  (Read 1754 times)

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Offline guru_iTopic starter

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Servo start and then just stop
« on: October 04, 2009, 08:20:30 AM »
Hi

Im beginner in this world and as hobbyist taken up $50 robot project and enjoyed it thoroughly !!.
I got most of the electronics done (after 2nd try!) and working on Photo-resistors part. But Meanwhile I was checking up with my servo (http://robokits.co.in/shop/index.php?main_page=product_info&cPath=2_5&products_id=187) and how its function but now have a doubt/problem(?) with its behaviour and mainly on my circuit or power supply (battery pack).

Before that ...I programmed my robot using USB Programmer (http://robokits.co.in/shop/index.php?main_page=product_info&cPath=12&products_id=54)  and it doesn't require any external voltage (take it from PC/Laptop) so Im using direct ~5V supply for servo (recommended is 5 to 6 V).

When I apply ~5+ V supply (1.2 V * 4 Ni-Mh 2100maH batteries) my servo motor start once and then no response.

1) I checked the voltage on servo supply and it reads as 5v same as input).

2) I also checked for loose connection but its not...(i think so)

3) I also checked connectivity using multimeter (buzzer) and everything looks fine.


Also I have not understood the LED's use in circuit as it is getting power from output ping of Voltage Regulator but my input volaage is merely above 5 V so should I not worry about it?

Can anyone help me with troubleshooting

Thanks
Guru

Please see the circuit  image attached



Offline blackbeard

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Re: Servo start and then just stop
« Reply #1 on: October 04, 2009, 12:30:12 PM »
ouch >.<! no offense but you NEED to practice your soldering. make sure you tin your iron and have a sponge ready to clean it often! that asside usually when they jump a bit but don't move it's because they arn't getting a signal. allot of the time they do that as soon as when power is applied. can you set it up on a solderless breadboard and show us?

edit: it also looks like there are allot of solder bits that could be shorting out your circuit, DEFINITELY lay it out on a protoboard to start and tell us the results

edit edit: if your iron tip is really fuxord or you want to tin it fast get one of these

http://www.dealextreme.com/details.dx/sku.7207

also get good solder. bad solder is extremely hard to work with and can dirty/rot your tip very fast. you don't need anything more then a basic soldering iron but do try to get the best one you can. even a $20 weller stick is great for starts
« Last Edit: October 04, 2009, 12:38:02 PM by blackbeard »
"sure, you can test your combat robot on kittens... But all your going to do is make kitten juice"

First step: Build androids with AI
Next step: Give them vaginas

Offline guru_iTopic starter

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Re: Servo start and then just stop
« Reply #2 on: October 05, 2009, 07:17:54 AM »
Thanks Yes i need practice with soldering. I will also give a try with prototyping board and let you know. Meantime are there any good link on buying good iron..I saw some on YouTube but didnt find much interesting.

Thanks again
g

Offline blackbeard

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Re: Servo start and then just stop
« Reply #3 on: October 05, 2009, 10:39:05 AM »
weller is a good brand. i have one from a college basement sale and it was made in the 1960s! the ones they sell at radio shack arn't too bad but they are overpriced. as a general rule i go for between 45w and 60w for through hole lead soldering and between 60w and 80w+ for lead free. a flat tip is useful for through hole since it transfers more heat too. if you can afford a station (a stick attached to a box) then get that because it's well worth it. if not then make sure to at least get a proper stand and cleaning sponge. a tip refresher is good too. for technique make sure to heat up the component and pad NOT the solder directly since it's the component you want the solder to bond with. make sure to clean your components too to get it even better.
"sure, you can test your combat robot on kittens... But all your going to do is make kitten juice"

First step: Build androids with AI
Next step: Give them vaginas

Offline guru_iTopic starter

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Re: Servo start and then just stop
« Reply #4 on: January 01, 2010, 01:38:27 AM »
Hi

Im back after a while. As you suggested i tried to build $50 robot on prototype board and facing some strange issue. Before that please see my cabling on breadboard..I also modified code little bit (to debug the issue)..

if(sensor_left > sensor_right && (sensor_left - sensor_right) > threshold)
{//go left
LED_off();...rest of the code
 ...
 }
else if(sensor_right > sensor_left && (sensor_right - sensor_left) > threshold)
{//go right
LED_off();
....
}
ELSE
{
LED_on()
......
}

I purposely made LED_on in last("go straight") else condition and LED_Off in "turning conditiion" to check the circuit and code. I found that when im not attaching survo but just "on" the circuit to run the code..my LED shines in normal light condition (i.e. when light is equal on both the sensors) but when i move my hand on one of the sensors..(I tried both left and right) LED turns off that is to prove that my circuit is correct and so is the code in ATMEG8.

But as soon as i attach my servos (modified for full rotation) nothing works..servo just makes strange noise and thats it..sometimes one of the servo rotates and then stops...i am having no clue what is wrong here but my servo looks ok..

and one more thing to mention is when I attach even one of the servo voltage drops straight from 5.02 to 2.2~ Volts and im not sure why its happening

Can somebody help me debug the issue?

Im using 2.2Kohm resistor for my photoresistors and i calculated them using the method you mentioned and also using the excel sheet to see voltage drop difference..

You tube video of my running circuit is here (w/o servo attached)
MVI_1001.AVI


 


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