Alt-BEAM Archive
Message #06013
To: beam@sgiblab.sgi.com
From: SG Sparkyg@seark.net
Date: Thu, 09 Sep 1999 23:43:20 -0400
Subject: [alt-beam] Re: motor driver: h-bridge or IC?
ok, i see now.
Source, Gate, Drain..
not B,E,&C .
on the schematic, the sources of two are conected
together, the left and right connect to the gate,
and drain goes to the motor.
now, if i can just find these little doo-dads
-Sparky
At 05:48 PM 9/9/99 -0700, you wrote:
>I don't like the big voltage drop (~2V) on the L293 and L298 chips. They run
>hot and are really too inefficient to be used applications below 12V. On the
>other hand a mosfet h-bridge is perfect for 5V applications. The mosfets
>have high input resistance and low forward voltage drop depending on the
>"on" resistance. Only 4 components are needed for a full h-bridge and these
>are available for free if you are resourceful and willing to de-solder
>components. A dead 80M Conner and similar IDE harddrive typically has
>6-10 complementary IR mosfets often in 4 pin DIP packages. I have found some
>with part numbers IRFD123 (N-channel) and IRFD9020 (P-channel). The specs
>for those parts are approximately 0.2 ohm "on" resistance and max current of
>1.2A @30V. They can comfortably drive hobby servos with minimal losses.
>Attached is a schematic of the mosfet h-bridge ready to be attached to a
>Bicore or microcore.
>
>enjoy
>
> <>
>
> Wilf Rigter mailto:wilf.rigter@powertech.bc.ca
> tel: (604)590-7493
> fax: (604)590-3411
>
>> -----Original Message-----
>> From: Dan Larson [SMTP:dlarson@citilink.com]
>> Sent: Thursday, September 09, 1999 2:54 PM
>> To: beam@sgiblab.sgi.com
>> Subject: Re: motor driver: h-bridge or IC?
>>
>> If you want a real h-bridge for battery powered
>> applications, get an L293D (SGS Thompson).
>> It is rated up to 600mA, *dual* hbridge,
>> and has back emf diodes built in.
>>
>> There is also the L298N which is good up to 3A.
>>
>> You can get them at Mouser http://www.mouser.com
>> for US $2.12 each (The L293)
>>
>> 74HCT245s might be fine for smaller current
>> motors, but anything bigger cries out for
>> a real h-bridge chip. Making your own h-bridges
>> from discrete transistors (I've done it) is
>> too much trouble.
>>
>>
>> Dan
>>
>> On Thu, 09 Sep 1999 14:47:39 -0400, SG wrote:
>>
>> >Hi all,
>> >I think one of my 6 transistor h-bridges burned
>> >out (i hope thats what the problem is anyway)
>> >and rather than solder some more transitors together, i thought i might
>> try
>> >two 74HCT245's stacked.
>> >Does anyone know if this will be enough to power standard servo's?
>> >Thanks!
>> >-Sparky
>> >
>> >
>>
>>
>>
>
>Attachment Converted: "c:\pipeplus\eudora\attach\FETBRIDGE.gif"
>
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