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<DIV><SPAN class=064135218-17032008><FONT face=Arial color=#0000ff size=2>Hi
Hanno</FONT></SPAN></DIV>
<DIV><SPAN class=064135218-17032008><FONT face=Arial color=#0000ff
size=2></FONT></SPAN> </DIV>
<DIV><SPAN class=064135218-17032008><FONT face=Arial color=#0000ff size=2>If you
want CHEAP then I have used discrete BJT's. </FONT></SPAN></DIV>
<DIV><SPAN class=064135218-17032008><FONT face=Arial color=#0000ff size=2>The
BC807/BC817 will run 400mA and cost 0.02NZD each</FONT></SPAN></DIV>
<DIV><SPAN class=064135218-17032008><FONT face=Arial color=#0000ff size=2>If you
can up the voltage and down the current you get a cheap H-Bridge with low
loss</FONT></SPAN></DIV>
<DIV><SPAN class=064135218-17032008><FONT face=Arial color=#0000ff
size=2></FONT></SPAN> </DIV>
<DIV><SPAN class=064135218-17032008><FONT face=Arial color=#0000ff size=2>6
BC807/817's = 0.12</FONT></SPAN></DIV>
<DIV><SPAN class=064135218-17032008><FONT face=Arial color=#0000ff
size=2>4 BAS16 diodes = 0.08</FONT></SPAN></DIV>
<DIV><SPAN class=064135218-17032008><FONT face=Arial color=#0000ff size=2>6 0805
resistors = 0.042</FONT></SPAN></DIV>
<DIV><SPAN class=064135218-17032008><FONT face=Arial color=#0000ff size=2>parts
cost = 0.242</FONT></SPAN></DIV>
<DIV><SPAN class=064135218-17032008></SPAN> </DIV>
<DIV><SPAN class=064135218-17032008><FONT face=Arial color=#0000ff size=2>the
downside is you don't get heaps of current and SMT is
the cheapest (NZ not china) way to assemble.</FONT></SPAN></DIV>
<DIV><SPAN class=064135218-17032008><FONT face=Arial color=#0000ff size=2>If you
need a bit more current the BC807 will parallel with some derating.
</FONT></SPAN></DIV>
<DIV><SPAN class=064135218-17032008><FONT face=Arial color=#0000ff
size=2></FONT></SPAN> </DIV>
<DIV><SPAN class=064135218-17032008><FONT face=Arial color=#0000ff
size=2></FONT></SPAN> </DIV>
<DIV><SPAN class=064135218-17032008><FONT face=Arial color=#0000ff
size=2>Andrew</FONT></SPAN></DIV>
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<DIV></DIV>
<DIV class=OutlookMessageHeader lang=en-us dir=ltr align=left><FONT
face=Tahoma size=2>-----Original Message-----<BR><B>From:</B>
chchrobotics-bounces@lists.linuxnut.co.nz
[mailto:chchrobotics-bounces@lists.linuxnut.co.nz] <B>On Behalf Of </B>Hanno
Sander<BR><B>Sent:</B> Friday, 14 March 2008 4:23 p.m.<BR><B>To:</B>
Christchurch Robotics<BR><B>Subject:</B> [chbot] Cheap, low voltage, high
current h-bridge<BR><BR></FONT></DIV>Hi,<BR>I'm looking for a:<BR>- cheap
(ideally <$5 with less than 5 parts)<BR>- low voltage (battery powered, so
6-8Volt)<BR>- high current (nominal ~500mA, but spikes to 1 or 2
Amps)<BR>H-bridge to drive a geared "rc car" motor. <BR><BR>This must be
a common problem for hobbyists, but I can't find a discrete component that
fits the bill. I've tried L293 and L298 which are cheap, ok on current,
but terrible for low voltage- since they eat 2 Volts- which also heats them up
over time.<BR><BR>I'm reasonably happy with the LMD18200T, but at $14, it's
not cheap, and with a minimum voltage of 12 volts, it doesn't do low
voltage.<BR><BR>Mass-manufactured items, like toy robots, seem to make their
own h-bridges using FET's - is that the
solution?<BR>Hanno<BR><BR></BLOCKQUOTE></BODY></HTML>