H-bridge suggestion for this type of DC motor?

[lloydi12345]

Never thought these big motors are hard to run and maintain. *sigh

 

[lloydi12345]

Hi again, I've finalized my decision and I'll go for MOSFET H-bridge. I think this is now a good chance of learning about max usage of H-bridges. I've changed some parts and now its pretty running in my Proteus ISIS simulation. Sorry, I didn't have any formal education regarding MOSFETs. I just read this article and somehow it enlightened me.
**broken link removed**

It improved my 1st design of MOSFET to a better one since I can see the dc motor in my simulation is now turning fast. I hope you can let me understand the essential things about constructing H-bridge by MOSFETs with P-channel and N-channel. Please do consider also Panasonic 6v 4Ah / 20h lead acid battery as my power source for my MOSFET H-bridge and Mabuchi RS-380PH motor for my load. I'll be driving the motors using PIC16F877A.

I used IRF4905 as P-channel and iRF3704 as N-channel. I designed my H-bridge by only using the available MOSFETs on ISIS and I only considered the max current it can handle. I also don't have any idea if these components are common that it is available on any local electronics market. I would love to know how to design efficiently so that there would be no wastes that would take place at the end.

I think this one is a good idea to use:
**broken link removed**

But I don't know what to choose on VGS, RDS and so on. Can you help me again?

 

[lloydi12345]

I think it's wrong. I'll modify it to this one. Anyone there?

 

[4pyros]

Never thought these big motors are hard to run and maintain.

Its all in the stall current. If you run into a wall and can not move any farther than the motors will draw full current and the controls must be capable of handling it. They're two ways to handle this to reduce the stall current and thus the amount of current the controller has to handle.

1 a mechanical slip clutch, so that if you run into a wall the clutch slips and the motor keeps turnning and never reaches stall current.
2 Electronic current limit, so that if you run into a wall and current starts to go up the electronics will limit the current to a safe level for the controller.

Using a high current controller with out limiting, mechanical or electronic is a brute force method and may break stuff.

You should consiter some sort of limiting anyway so nothing breaks and you will have a side benift of the ability of using a smaller controller.

Andy

 

[audioguru]

A brake slows down or stops something that is moving. A moving object might break something it runs into. The difference is in the "spelring".

I brought home a case of 24 beers. It as very heavy so I used brute force to carry it. Spelrying again.

Somebody else can teach the simple basics of the spec's for Mosfets.

 

[4pyros]

audioguru; You picking on my "spelring"?

Somebody else can teach the simple basics of the spec's for Mosfets

??
Andy

 

[hypersnapper]

Hi, I would like to ask in this thread. If I use PWM, Can it reduce the current flow that the motors will ask from the battery like on his case the LEAD Acid battery? Im not sure if did.

 

[lloydi12345]

I haven't thought about this one. Maybe others can tell us if it does affect the current flow from H-bridge?

 

[4pyros]

I haven't thought about this one. Maybe others can tell us if it does affect the current flow from H-bridge?

Yes thats what PWM is for, and you can set high and low limits. Andy

 

[lloydi12345]

I see. So we can avoid then the desired stall current?

 

[audioguru]

PWM is used for motor speed control. When the motor runs slowly then its unloaded current is low.
But if it is almost stalled then its peak current is high. The PWM has narrow pulses when the speed is slow so the average current is fairly low.

 

[4pyros]

Yes you can limit the max current in software using PWM control.