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[DPRG] Rick's H-bridge problems

Subject: [DPRG] Rick's H-bridge problems
From: Rick J. Bickle rbickle at swbell.net
Date: Mon Sep 27 12:36:03 CDT 2004

Ian,
 
My robot is running this exact H-Bridge circuit with the PWM at 1KHz
with no problem. You could use higher speed devices in place of the
BJT's if necessary.
You will have to give me more information to determine if there is
something wrong...

Rick

-----Original Message-----
From: dprglist-bounces at dprg.org [mailto:dprglist-bounces at dprg.org] On
Behalf Of IanR
Sent: Saturday, September 25, 2004 4:30 AM
To: dprglist at dprg.org
Subject: RE: [DPRG] Rick's H-bridge problems



I'm trying to use this design to drive via PWM, but seem to be
struggling, I think the transistors are taking a very long time to
switch on and was wondering if you had any thoughts on this. I.e. Have I
probably done something wrong, do you know what frequency the Design
will work up to etc.

Thanks, 

Ian 

-----Original Message----- 
From: Rick J. Bickle [mailto:rbickle at swbell.net] 
Sent: 30 August 2004 15:45 
To: 'Farhan K.'; dprglist at dprg.org 
Subject: RE: [DPRG] Rick's H-bridge problems 


Farhan, 

One of the reasons I designed this H-bridge circuit was that it does not

have a "once only" mode. It should not be able to short the rails, 
regardless of the steady state inputs. If you leave an input floating, 
it may cause one side of the bridge to oscillate. 

As a general rule, never leave inputs floating. 
BTW: This exact H-Bridge has been running my robot drive motors at 4A 
for quite a while. 

Rick 


-----Original Message----- 
From: dprglist-bounces at dprg.org [mailto:dprglist-bounces at dprg.org] On 
Behalf Of Farhan K. 
Sent: Sunday, August 29, 2004 4:27 PM 
To: dprglist at dprg.org 
Subject: [DPRG] Rick's H-bridge problems 


Hello all. 

After having failed with trying to get two channels of L298 to work in 
parallel to give me current capacity of 4A, i abandoned that idea coz 
everything i was doing was right and still the L298 melts down :( ! . 
Has 
anyone ever really got it working practically? 

As Rick suggested, I found the h-bridge schematic in his presentation 
and 
followed it using the IRF9540 and IRF540 but still this was more pain. 
This 
solution seems to be very sensitive to any wrong input, i (accidently) 
left 
one of the inputs floating and next minute found two of the IRFs 
smoking. 
What are the considerations I should take into account when trying to 
operate that circuit? 
I am operating it at 24V. 

Back to L298, Ive heard that two L298s can also be paralleled to give 
more 
current (4A+4A), any comments on that? 

Thanks. 

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