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From: nahshon@vnet.ibm.com (Itai Nahshon)
Subject: Re: Efficient low-V H-bridges
Sender: news@austin.ibm.com (News id)
Message-ID: <NAHSHON.95Apr25194729@rs3bt-01.haifa.ibm.com>
In-Reply-To: evan@robix.com's message of Mon, 24 Apr 1995 10:40:24
Date: Tue, 25 Apr 1995 16:47:29 GMT
References: <3n5su1$p7d$1@mhafc.production.compuserve.com> <evan.118.000AACBD@robix.com>
Organization: IBM Israel Science and Technology, Haifa, Israel
Lines: 23

In article <evan.118.000AACBD@robix.com> evan@robix.com (Evan Rosen) writes:
... stuff deleted
>you look inside the hobby servos.  Inside the Futaba S148 is a small miracle, 
>apparently a proprietary fet hbridge ic.  The drops under load are eerie, less 
... stuff deleted

The S148 is a cheap servo and certainly not a FET device. I expect to pay
more for FET servos... RC servo chips will work in 4.5-6V and up to about
500 mA. The L293D is certainly superior in that respect.

Some companies listed RC servo IC's in their catalogs, but I could not
find any dealler which stocked any of these. Modern RC servos are probably
using proprietary chips.

My suggestion: If you need servo systems take an RC servo (or take the
electronics from one). You cannot use external power amplifiers because
these units may use motor voltage in the feedback loop.

If your power requirements do not meet the servo limits, or if you need just
the H-bridge use an H-bridge IC that meets your needs.

Itai Nahshon
Haifa, Israel
