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K8004 problem with PWM controller noise

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Chippie

Member
You need to change the components in the oscillator section...C3 and R3....try making C3 around 22nf

Making the frequency around 18khz will make it inaudible
 
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Chippie

Member
So I should change C3 from 100nF to 22nF. And the resistor change to what?
Won't it bother my cat?
Make one change at a time....Change the capacitor first and see if that makes it better....Leave the resistor as is for now...

Put the cat outside...:D
 
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smilem

Member
Make one change at a time....Change the capacitor first and see if that makes it better....Leave the resistor as is for now...

Put the cat outside...:D
Well, changing the capacitor improves it but I still can hear it a bit myself, don't know about the cat:confused:

What lower value I can try because the higher the frequency the lower the torque of the motor, I mean it has less power right?
 

Chippie

Member
You'll have to experiment unitl you find a cap that doesnt affect your hearing.....or else change the value of the 2k2 resistor by half...The effect of that would be to reduce the charging time for the cap so the RC time constant is shorter and the frequency should go up...

You could always wear earmuffs....:)
 
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smilem

Member
Thanks, is it normal that the FET is dead cold, and SG IC chip is a bit warm, doesn't it require a heatsink?
 

Chippie

Member
Thanks, is it normal that the FET is dead cold, and SG IC chip is a bit warm, doesn't it require a heatsink?
The fet may warm up depending on the load current it is switching...

as for the chip....shouldnt get too hot...You could add a small dip heatsink if you wanted...
 

smilem

Member
To get stable motor speed do I need to use LM338 or can I just use A diode bridge with transformer as power source?

Also isn't is possible to calculate the required frequency?
 
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smilem

Member
So do I need to feed this circuit from LM or it will work fine simply by using diode bridge with capacitor?
 

smilem

Member
Have a look at figures a,b, and c in the manual
The manual lists: 8-35VDC unregulated and figure A shows a simple diode bridge with capacitor as power source. But since I use configuration C that shows internal reference voltage used as control coltage. This means if my DC current is unstabilized by LM338 the motor speed will change as voltage changes right?

I will use slowest motor rotation mode possible so that means that LM338 is a must no?
 
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Chippie

Member
If you use figure C, just connect a potentiometer value 1k as per the drawing, using Vref,
connect your dc power supply as shown, the motor speed is then controlled by the new 1k pot....:)
 

kimjessen

New Member
sory that i bomb in here, i just have a question conserning the power of the k8004, i have a DC motor (24VDc 14A) fedet vit 24DC care bat.
I like to controle the motor with the kit it just sems that it are loosing power.... schoud i ad on a nother fet, an hau?????
it works fine until i ame puting some balast on it then it daies out.... and it can not be the curent ther ise plenti..... I have a der that it might bee the Diod acrose the fet.???
 

Chippie

Member
The controller is current limted at 6 amps.

This is probably why your motor isnt running at its full load capability...

You ned to change the current limiting resistor and add more mosfets to handle the power hungry motor
 

kimjessen

New Member
thank you for the quic reply.... i asume you meane the resistor r8+r9+r10....

hau dou you put in more fet???? just in paralel????
 

smilem

Member
My C3 is 22nf but I still can hear very high freq slight motor noises. Decided to fix it after all.
I got frequency measured and it's 29.333khz

So should I now lower to like 15nF or change resistor POT from 2k2 resistor by half ?
The cap change is more easy and cheaper :)

Thanks.
 
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smilem

Member
It seems I need to use bypass cap for the motor, what value would be better?
I read to use ceramic, but why not polyester they are cheaper, would 0.47uf work?

Furthermore I read about adding a diode, but my controller has one at the controller side.
 
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