Alt-BEAM Archive
Message #06014
To: beam@sgiblab.sgi.com
From: SG Sparkyg@seark.net
Date: Fri, 10 Sep 1999 00:21:33 -0400
Subject: [alt-beam] I see now... was: 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 11:29 PM 9/9/99 -0400, you wrote:
>Thanks guys!
>I'll try the 4 mosfets
>but i'll have to do some research on the "pinout"
>not clear on which is base, collector, and emit.
>or equivilant.... never worked with them before
>and not sure of the specifics of the component in regard to
>the schematic....
>Thanks though!
>-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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