AVR-Chat

Do you Yahoo!?
Yahoo! Small Business - Try our new resources site!

At 07:36 PM 3/28/05 -0800, kc wong wrote:
>good day everyone.
>
>i have build a hbridge cct with 2 IR2110 MOSFET driver to control a linear 
>motor.
>my main function of this ct is to generate an AC squarewave output 
>continuously to the linear motor(3phase motor).
>
>i have attached two photo below. this photos shows one phase output but in 
>reality i will use three set of this cct to generate 3phase output.
>
>my questions are:
>
>1)  when i  measure the output from the hbridge(motor voltage) with 
>oscilloscope, i found that there is spikes in the waveform.(as shown in 
>the figure if compare between the desired and actual output waveform) this 
>spike occur when the voltage change from high to low state.why?is this 
>because of the back EMF from the motor?

Inductance.

>2) what can i improved my cct for protection, faster response because i 
>found that the actual timing is longer from my setting timing?

Beg pardon?  You will have to explain this better.

>
>3) i feel confuse with this cct because when i use it to control 
>rotational motor, it cant work because the high side output of IR2110 cant 
>hold long enough?
>
>PS: i m not using PWM to control this cct.i only use normal on/off 
>commands in the BASCOM AVR (AtMega8535 chip) to control the POWER mosfet 
>for this time.

Unless you have a floating power supply for the high side gate drive you 
will need a PWM on the high side.  A high frequency ceramic cap wouldn't 
hurt either.  Also your gate drive voltage is way too low to start 
with.  The 2110 should be in UV lockout at the 5V you indicate on the 
schematic.

Robert


" 'Freedom' has no meaning of itself.  There are always restrictions,   be 
they legal, genetic, or physical.  If you don't believe me, try to chew a 
radio signal. "  -- Kelvin Throop, III
http://www.aeolusdevelopment.com/