Building a PWM circuit

[mbrownn]

OK guys, I need your help. I need to build a DC PWM with variable frequency that will run a motor at 220 to 240v. The mosfets at either side of the motor have to open and close at the same time, don't worry about the inductive spikes as I know what to do with that. The pulse has to be from 5 to 50% duty cycle and the frequency from 100 to 500000Hz if possible. It has to be as simple and cheap as possible as funds are limited, I don't even know if that is doable.

It is for testing inductive kickback in DC motors. Any assistance would be appreciated.

[leo48]

Perhaps this circuit will help
you search in to google datasheet UC 3845
Leo48

[mbrownn]

I was thinking something a little simpler like this Circuit Simulator Applet

But I dont know what mosfets or transistor to use

I should say that my expected power will be less than 1kw

[Guest]

Here's one... you may be able to adapt it to some use. Also look for Forrest Mims Op Amp IC book, including a 'Square Wave Generator' with pwm.

[nueview]

i am looking into a driver mechanism as well and the high power required seems to effect allot of circuits so i am looking to go as simple as possible with as few parts as possible.
these are astable class D flip/flops and some are used as SCR drivers for heavy loads you may want to check them out.

Astable Flip-flops

Martin

[mbrownn]

Thanks guys keep em coming

[Bizzy]

PWM circuits

Good morning
Now that our harvest is done and the wine is made I have more time for tinkering. I am still working on my Watson machine and have been experimenting with several types of methods of pulsing. The one I like best is using mosfets however the pulses are so quick the mosfets stay open and quickly burn out.
On the motors and mosfets thread Bits mentioned using 555 circuits unforfutantely I didn't have the time nor the knowledge to delve into it deeper.
But your thread as well as Bit encouraged me and I am glad I did look into 555 circuits more. Currently I am simply trying to understand them better and how they operate by pulsing a simple LED.
However with pulsing a motor in mind I have also been researching as well. So that is why I really find this thread and your website recommendations usefull.(especially the circuit simulator site)
I also have found several other circuits I was wondering if you have tried.
They look promising. Let me know what you think
Thanks
Bizzy

[Bizzy]

attachements

For some reason I am having issues attaching the circuits I found....
Ok I think I finally have it now
Bizzy

[Bizzy]

I was thinking something a little simpler like this Circuit Simulator Applet

But I dont know what mosfets or transistor to use

I should say that my expected power will be less than 1kw

mbrownn
I was exploring your circuit last night as well as the site in general.
Is there a way to save a circuit design after you build it?
thanks
Bizzy

[mbrownn]

Yes, go to file then export and copy and paste the text into a text editor.

I cant open the doc file can you save it in an earlier version?

[Bizzy]

Yes, go to file then export and copy and paste the text into a text editor.

I cant open the doc file can you save it in an earlier version?

Ok great I cant wait to try that when i get home tonight.
I cant down load the older doc version I have onto the thread. that was the problem I was having originally, so i went to a newer doc version which did down load.
Bizzy

[mbrownn]

I have sent you a PM with my email you can send it there

[Bizzy]

555 motor

Good morning
Last night I was able to pulse a small motor from a 555 chip using a mosfet.
The gate was supplied by the 3 pin and the drain attached directly to the positive rows.
I attached the motor between the mosfet and the negative rows. There this test I used only a small 9 volt battery and got great pulsing results, I was also able to change the speed of the pulsing using othjer capacitors.
I do have a question:
Normally I ran my motor between the the positive terminal of the battery and the mosfet but it wouldn't work there this time it would only run between the mosfet and the negative terminal of the battery, is that normal?
Thanks
Bizzy

[mbrownn]

Im not good with semiconductors so I,m not sure

[Bizzy]

555 mosfet and motor

Good morning
After looking at my notes this morning I think I was able to answer my own question ( used a pdf this time so hoepfully everyone can see it)
Since I was using a small 9 volt battery to run the 555 chip as well as the battery there was not enough current to run the motor once the power was "split" between the chip and the motor if the motor was in position A
However if i put th emotor in postion B the power from the drain combined with the power from the gate so that when it left the source there was enough current to run the small test motor.
I am not as advanced as some in the forum are, in regards to electronics such as Bit and Caroll. So if I am on the wrong track please feel free to correct me.
But for now that is what I am observing and the conclusions i am coming to.
Thanks
Bizzy