Hello guys,Iam trying to build a quadcopter,and Iam using a kk2.1.5 filghtcontroller and I couldnt arm it.Help please!.

Just ignore the frame,I will replace it with a glassfiber frame.

I can't see anything in the image.
However what is the error you are getting?
You need to switch on transmitter first and then your quad.

Sorry i will upload again

I moved my throttle up and down thrice and finally i moved it to right.Iam just getting series of beeps.

Upload the pic again

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Unlike multiwii or APM or pixhawk, the kk2.1.5 arms at throttle down and yaw left amd disarms for yaw right.

Thanks,I was able to arm it,but one of my motors is not spinning.When I connected all the motors to a servo tester,that motor is spinning very slowly and stops suddenly.

You can try re-calibrating your ESCs with servo tester directly and then check if the problem persists. If the problem still persists then problem could be motor or ESC. Lets say this combination to be XX. Wroking combination of motors be YY.
To verify this you can swap your non-working motor--XX with working motor--YY. If the working motor spins slowly then problem is with ESC--XX and vice-versa. You can try putting motor --XX with ESC--YY to cross check.

I swaped the motors and when I coonected the working motor and esc to servo tester,it worked for a while and it stopped suddenly.So,I connected the motor to flightcontroller along with two other motors and I have set the controller to tricopter layout and I armed it,and it worked.It did not stop spinning.I think the problem is with motor,it is not working with other escs.Looks like I have to build a tricopter instead of a quad  .